AGROEKOLOGI SAWAH Diabstraksikan oleh: Soemarno, PSL-PPSUB 2013 KOMPENDIUM KAJIAN LINGKUNGAN DAN...

AGROEKOLOGISAWAH

Diabstraksikan oleh: Soemarno, PSL-PPSUB 2013

KOMPENDIUM KAJIAN LINGKUNGAN DAN PEMBANGUNAN

SAWAH - PADDY FIELD

A paddy field is a flooded parcel of arable land used for growing rice and other semiaquatic crops.

Paddy fields are a typical feature of rice farming in east, south and southeast Asia. Paddies can be built into steep hillsides as terraces and adjacent to depressed or steeply sloped features such as rivers or marshes. They can

require a great deal of labor and materials to create, and need large quantities of water for irrigation. Flooded paddies provide an ideal environment for rice

cultivation and discourage the growth of many weeds.

The Oxen and water buffalo are one of the most important working animals adapted for life in wetlands, and are used extensively in paddy field farming.

During the twentieth century, paddy field farming became the dominant form of growing rice. Paddy field farming is practiced in Cambodia, Bangladesh, China, Taiwan, southern France (in the Camargue), India, Indonesia, Japan,

North Korea, South Korea, Malaysia, Myanmar, Nepal, Pakistan, the Philippines, Sri Lanka, Thailand, Vietnam, and Laos, as well as Piedmont in

Italy, the Camargue in France, the Artibonite Valley in Haiti, and Sacramento Valley in California.

Paddy fields are a major source of atmospheric methane and have been estimated to contribute in the range of 50 to 100 million tonnes of the gas per

annum. Recent studies have shown that this can be significantly reduced while also boosting crop yield by draining the paddies to allow the soil to

aerate to interrupt methane production.The word "paddy" is derived from the Malay word padi, rice plant.

Diunduh dari sumber:... http://en.wikipedia.org/wiki/Paddy_field …….. 12/1/2013

http://en.wikipedia.org/wiki/Rice

http://en.wikipedia.org/wiki/East_Asia

http://en.wikipedia.org/wiki/South_Asia

http://en.wikipedia.org/wiki/Terrace_(agriculture)

http://en.wikipedia.org/wiki/Marshes

http://en.wikipedia.org/wiki/Manual_labour

http://en.wikipedia.org/wiki/Camargue

http://en.wikipedia.org/wiki/India

http://en.wikipedia.org/wiki/Nepal

http://en.wikipedia.org/wiki/Piedmont

http://en.wikipedia.org/wiki/Italy

http://en.wikipedia.org/wiki/Camargue

http://en.wikipedia.org/wiki/Sacramento_Valley

http://en.wikipedia.org/wiki/California

SAWAHA paddy field is a flooded parcel of arable land used for growing rice and

“PALAWIJA” crops.

Diunduh dari sumber:...foto smno-madiun-jan 2013

http://en.wikipedia.org/wiki/Rice

SAWAH

Flooded paddies provide an ideal environment for rice cultivation and discourage the growth

of many weeds.

Diunduh dari sumber: Foto smno-sawah.mdn-desember 2012

Rice paddy fields are also one of the typical agricultural ecosystems in Monsoon Asia. Among them, single rice cropping

paddies that dominates in northeastern Asia are characterized by two contrasting periods, a flooded growing period and dry fallowed period which lasts two thirds of a year. From the

analyses using stable isotopes of water and carbon, the largest carbon input was CO2 fixation by photosynthesis of rice, where

64-65% of the fixed carbon was harvested in autumn. Inflow and outflow of dissolved carbon accounted for 5-9% of the total input

and output

Diunduh dari sumber:.. http://www.niaes.affrc.go.jp/annual/r2003/html/no52.html.…….. 10/1/2013

SAWAHSawah adalah lahan usaha pertanian yang secara fisik

permukaan BIDANG OLAHNYA rata, dibatasi oleh pematang, serta dapat ditanami padi, palawija atau

tanaman budidaya lainnya.

Diunduh dari sumber:.. Foto smno-sawah.mdn-desember 2012.…….. 12/1/2013

AGROEKOSISTEM SAWAH

Paddy field ecosystem is composed of surface water, plowed soil layer and subsoil, and the plowed soil layer is divided into two layers;

thin oxidized soil layer and reduced soil layer. These soil layers are connected by percolating water. In addition, rice roots are developed and plant residues such as rice straw and stubble

after rice harvest are incorporated into the plowed soil layer. These microsites are different habitats for microorganisms, and

unique microbial communities inhabit depending on the microsites.

Diunduh dari sumber: http://www.agr.nagoya-u.ac.jp/~soil/Soil_Biology_and_Chemistry-e/Researches.html ……..

28/10/2012

SAWAHSawah adalah lahan usaha pertanian yang secara fisik permukaan BIDANG

OLAHNYA rata, dibatasi oleh pematang, serta dapat ditanami padi, palawija atau tanaman budidaya lainnya.

Biasanya sawah digunakan untuk bercocok tanam padi. Untuk keperluan ini, sawah harus mampu menyangga genangan air karena padi

memerlukan penggenangan pada periode tertentu dalam pertumbuhannya. Untuk mengairi sawah digunakan sistem irigasi dari

mata air, sungai atau air hujan. Sawah yang airnya berasal dari hujan dikenal sebagai sawah tadah hujan,

sementara yang lainnya adalah sawah irigasi. Padi yang ditanam di sawah dikenal sebagai padi lahan basah (lowland

rice).

http://id.wikipedia.org/w/index.php?title=Lahan&action=edit&redlink=1

http://id.wikipedia.org/wiki/Pertanian

http://id.wikipedia.org/w/index.php?title=Pematang&action=edit&redlink=1

http://id.wikipedia.org/wiki/Padi

http://id.wikipedia.org/wiki/Palawija

http://id.wikipedia.org/w/index.php?title=Tanaman_budidaya&action=edit&redlink=1



http://id.wikipedia.org/wiki/Padi

http://id.wikipedia.org/wiki/Irigasi

http://id.wikipedia.org/wiki/Mata_air

http://id.wikipedia.org/wiki/Mata_air

http://id.wikipedia.org/wiki/Sungai

http://id.wikipedia.org/wiki/Hujan

EKOSISTEM SWAHDalam usaha budidaya padi harus diketahui faktor-faktor yang

mempengaruhi pertumbuhan tanaman secara ekologi, baik faktor biotik dan abiotik di lingkungan tumbuh tanaman tersebut.

Pertanaman padi sawah adalah monokultur, selain itu terdapat beberapa flora dan fauna di sekitar pertanaman yang akan mempengaruhi

pertumbuhan tanaman padi. Organisme yang ada di sekitar tanaman padi adalah mikrofauna dalam tanah, mesofauna, makrofauna dan vegetasi (gulma) yang ada di sekitar

persawahan.

EKOLOGI PENGENDALIAN HAMA

HUBUNGAN AIR-TANAH-TANAMAN

Diunduh dari Sumber: …..30/10/2012

Hidrologi lahan sawah

Pengetahuan tentang hidrologi lahan sawah sangat diperlukan dalam merancang strategi pengelolaan air.

Karakteristik hidrologi lahan sawah sangat ditentukan oleh kondisi biofisik lahan.

Hidrologi sawah beririgasi berbeda dengan sawah tadah hujan maupun sawah rawa. Oleh karena itu strategi pengelolaan air pada

lahan sawah beririgasi akan berbeda dengan pada lahan sawah tadah hujan maupun sawah rawa.

Diunduh dari sumber: http://fftc.imita.org/library.php?func=view&id=20110722052543………. 30/10/2012

Types of Response to

Water Scarcity

Sumber: Irrigation

Management in Rice-Based

Cropping Systems: Issues and

Challenges in Southeast Asia .

Randolph Barker and Francois

Molle.

Diunduh dari sumber: http://www.knowledgebank.irri.org/rkb/1-the-water-balance-of-lowland-rice.html ………. 30/10/2012

THE WATER BALANCE OF LOWLAND RICE

Because of the flooded nature of lowland rice, its water balance and water productivity are different from those of other cereals such as wheat and

maize. Water inputs to lowland rice fields are needed to match the outflows by seepage, percolation, evaporation, and transpiration (Figure 1). Seepage is the lateral subsurface flow of water and percolation is the down flow of water

below the root zone. Typical combined values for seepage and percolation vary from 1-5 mm d-1 in heavy clay soils to 25-30 mm d-1 in sandy and sandy loam soils. Evaporation occurs from the ponded water layer and

transpiration is water loss from the leaves of the plants. Typical combined evapotranspiration rates of rice fields are 4-5 mm d-1 in the wet season and

6-7 mm d-1 in the dry season, but can be as high as 10-11 mm d-1 in subtropical regions before the onset of the monsoon. Total seasonal water

input to rice fields (rainfall plus irrigation) varies from as little as 400 mm in heavy clay soils with shallow groundwater tables to more than 2000 mm in

coarse-textured (sandy or loamy) soils with deep groundwater tables. Around 1300-1500 mm is a typical value for irrigated rice in Asia. Outflows of water by seepage and percolation account for about 25-50% of all water inputs in heavy soils with shallow water tables of 20-50 cm depth, and for 50-85% in

coarse-textured soils with deep water tables of 150 cm depth or more.

http://www.knowledgebank.irri.org/rkb/1-the-water-balance-of-lowland-rice.html

KARAKTERISTIK HIDROLOGI LAHAN SAWAH

Lahan sawah Pluvial 1. Sumber air berasal dari air hujan 2. Kelebihan air hilang melalui perkolasi dan aliran

permukaan 3. Terdapat di daerah landai sampai lereng curam 4. Air tanah dalam, drainase baik, tidak ada gejala

jenuh air dalam profil tanah 5. Padi ditanam sebagai padi gogo

. Hydrological processes in a paddy field. (a) Hydrologic Characteristics of a paddy field. (b) Outline of runoff simulation model

in paddies.

Simulations of storm hydrographs in a mixed-landuse watershed using a modified TR-20 model

T.I. Jang, H.K. Kim, S.J. Im, S.W. Park.Agricultural Water Management. Volume 97, Issue 2, February 2010, Pages 201–207.

KARAKTERISTIK HIDROLOGI LAHAN SAWAH

Lahan sawah Phreatik 1. Sumber air berasal dari air hujan dan air tanah 2. Air tanah (phreatic) dangkal, paling tidak pada

waktu musim tanam 3. Kelebihan air hilang melalui aliran permukaan 4. Tidak pernah tergenang lebih dari beberapa jam 5. Dalam profil tanah ada gejala jenuh air (gley

motting)6. Bila tanpa perataan (leveling) dan pembuatan

pematang, akan lebih baik ditanami padi gogo 7. Bila dengan perataan dan pembuatan pematang

dapat dikembangkan untuk padi sawah .Schematics of water balance components in a paddy field.

Model development for nutrient loading from paddy rice fieldsSang-Ok Chung, Hyeon-Soo Kim, Jin Soo Kim.

Agricultural Water Management. Volume 62, Issue 1, 19 August 2003, Pages 1–17

Karakteristik hidrologi lahan sawah

Lahan sawah fluxial 1. Sumber air seluruhnya atau sebagian berasal dari aliran

permukaan, air sungai dan air hujan langsung 2. Dalam keadaan alami tergenang air selama beberapa

bulan yaitu selama padi ditanam3. Terdapat di daerah lembah, dataran aluvial sungai dan

sebagainya 4. Drainase permukaan dan drainase dalam (perkolasi)

lambat sehingga genangan air mudah terjadi 5. Padi ditanam sebagai padi sawah .

Schematic diagram of a paddy field. (hmin, hmax and Hp denote the three critical depths; Ecan, Epot and Es denote the three kinds of evaporation from the free water in canopies,

the water body surface and the soil water respectively; Ep denotes the crop transpiration.

Development and test of SWAT for modeling hydrological processes in irrigation districts with paddy rice

Xianhong Xie, Yuanlai Cui.Journal of Hydrology. Volume 396, Issues 1–2, 5 January 2011, Pages 61–71.

TRANSPOR AIR: Tanah – Tanaman - Atmosfir

Air bergerak dari tanah, melalui akar, batang, daun, memasuki atmosfer

Laju aliran air ini merupakan fungsiF (selisih potensial, resistensi)

Potential unit name Corresponding value

Water height (cm) 1 10 100 1000 15850

pF (-) 0 1 2 3 4.2

Bar (bar) 0.001 0.01 0.1 1 15.85

Pascal (Pa) 100 1000 10000 10000 1585000

Kilo Pascal (kPa) 0.1 1 10 100 1585

Mega Pascal (MPa) 0.0001 0.001 0.01 0.1 1.585

TEGANGAN AIR

Potential air bernilai positif dalam kondisi “free liquid water”Potential dalam sistem tanah-tanaman-atmosfir bernilai negatif

(dalam tanah sawah tergenang, potential air positif)Air bergerak dari potential tinggi (top of hill) menuju ke potential

rendah (bottom of hill)Tegangan adalah – potential: air bergerak dari tegangan rendah

menuju tegangan tinggi

Diunduh dari sumber: http://www.knowledgebank.irri.org/ewatermgt/courses/course1/modules/module02/m02l03.htm ………. 30/10/2012

Rice plants take up water from the soil and transport it upward through the

roots and stems and release it through the leaves and stems as vapor in the atmosphere (called transpiration). The movement of water through the

plant is driven by differences in water potential: water flows from a high

potential to a low potential (imagine free water flow over a sloping surface: water flows from the top, with a high potential, to the bottom, with a low

potential). In the soil-plant-atmosphere system, the potential is high in the soil and low in the atmosphere. Therefore water moves from soil to plant and to

the atmosphere.

Potential = 0

Potential is +

Potential = -

Potential = 0

Potential = +

POTENSIAL AIR DALAM TANAMAN DAN TANAH

-140

-120

-100

-80

-60

-40

-20

0

20

-60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60

ponded water

muddy suspension

impermeable layer

subsoil

ground water table

Pressure head (cm)

Depth (cm)

Water potential in the flooded rice soil

The unsaturated soil“pulls” at the water and

potential is negative

Potential during the growing season in an aerobic soil

(aerobic rice, Changping, China, 2002)

0

10

20

30

40

50

60

70

80

90

100

175 200 225 250 275 300Day number

Soil moisture tension (kPa)

Panicle initiation Flowering Harvest

TEGANGAN LENGAS TANAH SELAMA PERTUMBUHAN TANAMAN

Tanah liat mampu menyimpan banyak air, tetapi dengan tegangan yang tinggi, sehingga akar tanaman sulit

menyerapnya Tanah berpasir menyimpan sedikit air , tetapi dengan

tegangan rendah , sehingga akar tanaman mudah menyerapnya

A medium-textured, loamy soil, holds intermediate levels of water at intermediate tensions, so there is relatively

much water for extraction by rootsTidak ada masalah pada tanah sawah tergenang, tetapi menjadi masalah serius kalau tanah mengering selama

periode kering

Potential air di atmosphere (di atas tajuk daun) mendorong laju transpirasi potensial, yang merupakan fungsi dari: F (radiation, wind speed, vapor pressure, temperature).

Siang hari yang cerah dan panas => menarik dengan kuat air dari tubuh tanaman

Potential air dalam tanah dipengaruhi oleh sifat-sifat tanah dan kadar air tanah:

Tanah liat mengikat kuat air • Tanah pasir mengikat longgar air • Banyak air tanah : Potensial tinggi

• Air sedikit : Potensial rendahTanah liat yang kering mengikat kuat air (Air tanah sulit

diserap akartanaman)

Kekeringan Landa Pemalang, Lahan Sawah Jadi Retak-retak

Sabtu, 21 Juli 2012 00:57 WIB

Diunduh dari: http://www.lensaindonesia.com/2012/07/21/kekeringan-landa-pemalang-lahan-sawah-jadi-retak-retak.html ….. 31/10/2012

Para petani tanaman padi di daerah Pantura (Pantai Utara), Jawa Tengah, kesulitan mendapatkan air irigasi di musim kemarau.

Akibatnya, ribuan hektar tanaman padi di daerah Pemalang terancam gagal panen. Untuk menyelamatkan tanamannya, petani terpaksa harus membuat sumur bor yang disedot dengan mesin pompa air

diesel. Kondisi ini menyebabkan biaya produksi meningkat.

Bahkan, akibat kurangnya air irigasi ke sawah para petani, tanah sawah mengering dan retak-retak, membuat kondisi tanaman padi

tidak maksimal. Jika tanah sawahnya tidak mendapatkan air, dikhawatirkan petani mengalami gagal panen.

Dampak kekeringan pada tanaman padi muda

Irigasi Kering, Puluhan Hektar Sawah Kekeringan(Post date: 05/07/2012 - 20:19 REPORTER: ab. EDITOR: mdika

Lebak - Sedikitnya 30 hektar lahan persawan di desa Talaga Hiang, Kecamatan Cipanas, Kabupaten Lebak, kekeringan. Dinas Pertanian

Kabupaten Lebak masih terus melakukan upaya mengairi sawah warga tersebut dengan cara melakukan penyedotan air di Leuwi Herang untuk

disalurkan ke saluran irigasi Leuwi Dolog.Kepala Bidang Sarana Dinas Pertanian Lebak, Rahmat Yuniar didampingi Kabid Produksi, Yuntani, mengatakan, saat ini lahan tanam petani di Desa

Talaga Hiang yang luasnya mencapai 30 HA dilanda kekeringan akibat kemarau, bahkan sarana irigasi yang ada di daerah setempat yaitu Irigasi

Leuwi Dolog tidak jalan sehingga tidak dapat membantu memenuhi kebutuhan air yang dibutuhkan para petani desa setempat

DIUNDUH DARI: http://mediabanten.com/content/irigasi-kering-puluhan-hektar-sawah-kekeringan

….. 31/10/2012

http://mediabanten.com/content/irigasi-kering-puluhan-hektar-sawah-kekeringan

http://mediabanten.com/content/irigasi-kering-puluhan-hektar-sawah-kekeringan

. 5100 Hektare Sawah di Bekasi Terancam KekeringanPosted by korantrans pada Agustus 22, 2009

Diunduh dari: http://korantrans.wordpress.com/2009/08/22/5100-hektare-sawah-di-bekasi-terancam-kekeringan/….. 31/10/2012

. Trans, Bekasi : Akibat bencana alam yang menimpa bangunan bagi sadap (BKG/4) di daerah irigasi (DI) Kedung

Gede, Desa Cipayung, Bekasi, maka seluas 5100 dari 13.000 hektare lahan sawah di daerah itu akan terncam kekeringan. Apabila tidak diatasi segera maka sejumlah petani di daerah tersebut, atau yang berada di saluran Rengas Bandung tidak

bisa menggarap sawahnya karena tidak tersedianya air.Menurut Kusmana, untuk mengantisipasi agar tidak terjadinya kekeringan, maka pihaknya bekerjasama dengan Perusahaan Jasa Tirta Jatiluhur akan membuat saluran pengelak (kisdam) dengan cara pemasangan cerucuk bambu dan karung pasir.

Hal ini dalakukan untuk menaikan debit ar pada saluran. Sementara untuk penanganan jangka panjangnya harus

dilaksanakan pembangunan baru yang biaya fisiknya saja diperkirakan antara Rp 1 sampai Rp 2 miliar.

Masalah bencana alam di BKG/4 ini sudah dilaporkan ke pusat melalui Balai Pengelola Wilayah Sungai (BPWS) Citarum di

Bandung. Selain itu pihak PPK Irigasi 1 sekarang sedang melakukan koordinasi dengan pihak kecamatan dan Pemkab Bekasi,

terutama dalam masalah jika ada pembebasan lahan apabila adanya pembangunan saluran baru. “ Akibaat bencana alam

itu, BKG/4 ini memang perlu segera diatasi dengan pembangunan baru. Namun sebagai orang lapangan, saya

usulkan pembangunannya lebih baik dilaksanakan dalam dua tahap. Hal ini mengingat waktu yang sudah mepet ke akhir

tahun anggaran,” (Kusmana).

SMJDampak kekeringan parah pada tanaman padi sawah

SAWAH BER-TERAS-BANGKUAnalysis of percolation and seepage through paddy bunds

Han-Chen Huang, Chen-Wuing Liu, Shih-Kai Chen, Jui-Sheng Chen.Journal of Hydrology. Volume 284, Issues 1–4, 22 December 2003, Pages 13–25.

Diunduh dari sumber: http://www.sciencedirect.com/science/article/pii/S0022169403002282…….. 29/10/2012

This study investigates percolation and seepage through the bunds of flat and terraced paddies. Field experiments were conducted in Hsin-Pu of Hsin-Chu County, Taiwan, to measure the soil water content of various types of bund.

Measurements revealed that the soil was unsaturated along the sloped surface of the terrace.

Experimental results also indicated that seepage face flow did not develop even after 2 days of heavy rainfall. A three-dimensional model, FEMWATER, was adopted to simulate percolation and lateral seepage under various bund

conditions. In a flat paddy, the rate of percolation of bunds under which a plow sole was located, was 0.40 cm d−1, close to the average infiltration rate of

a flooded paddy. The percolation of the bund without plow sole was 0.85 cm d−1, or double the average infiltration rate of a flooded paddy.

Infiltration in the central area of a terraced paddy is mainly vertically downward, whereas flow near the bund is predominantly lateral. The paddy field near the bund has a high hydraulic gradient. The simulated infiltration flux into the bund (1.47 cm d−1) after 85 days of rice cultivation exceeded that

into the central area (0.54 cm d−1) by a factor of 2.72. The final percolation flux from the bund (1.24 cm d−1) also exceeded the final percolation from the plow sole (0.68 cm d−1) by a factor of 1.82. The lateral seepage fluxes through

the bund, downward and upward along the slope surface, are 2.01 and −2.12 cm d−1, respectively. However, the lateral seepage flux does not fully

saturate the surface of the hillside soil. A simulation clearly shows that the seepage upstream of the paddy field does

not move water downstream and is reused as subsurface return flow. Both experimental and simulation results clarify the mechanisms of water

movement in the terraced paddy and reveal the existence of an unsaturated seepage face along the sloping surface of the terraced field.




Two types of lateral seepage flow through bunds




Schematic representation of a cross-sectional view of terraced rice field and the terminology used herein. Open arrows indicate soil

water sampling locations and directions

SAWAH BER-TERAS-BANGKUAnalysis of percolation and seepage through paddy

bundsHan-Chen Huang, Chen-Wuing Liu, Shih-Kai Chen, Jui-Sheng Chen.

Journal of Hydrology. Volume 284, Issues 1–4, 22 December 2003, Pages 13–25.


Cross-section in the vicinity of the bund of a typical flooded rice field




Model of terraced rice paddy

Darcy velocity flow field for lateral seepage in the terraced paddy (cm d−1).

Jaring-jaring Makanan dalam Ekosistem Sawah

Trophic relationships in a rice ecosystem showing the importance

of detritivores and non crop vegetation components.Source: The three planks for ecological engineering

(Heong et al 2012)

Diunduh dari sumber: http://allplantprotection.blogspot.com/2012/05/cultivating-flowers-on-rice-

field-edges.html …….. 28/10/2012

http://4.bp.blogspot.com/-EnkKNA7q_3c/T60oSuo8UVI/AAAAAAAAAdc/lwO2ryVhOok/s1600/Rice+ecosystem+food+web.gif

HASIL-HASIL PENELITIAN

AGROEKOLOGIAGROEKOSISTEM

SAWAH

Ecological Sustainability of the Paddy Soil-Rice System in Asia Kazutake Kyuma

Department of Environmental ScienceThe University of Shiga Prefecture

2500 Hassaka-cho, Hikone CityJapan 522, 1995-09-01

Nutrient Status of Paddy Soils General Redox Transformations under Waterlogged Conditions

The most characteristic management practice in paddy rice cultivation is waterlogging, or submergence of the land surface. This brings about

anaerobic conditions in the soil, due to the very slow diffusion rate of oxygen through water. Biologically, after the oxygen reserve in the soil is exhausted

and aerobic microorganisms have all died, facultative anaerobes dominate for some time. As the anaerobioc conditions continue, these microorganisms are

gradually replaced by obligate or strict anaerobes.

The biological changes are accompanied by a very characteristic succession of chemical transformations of materials. Following the disappearance of molecular oxygen, nitrate is used as a substrate for denitrifiers. Manganic oxides are solubilized as a result of reduction to manganous ions, likewise orange yellow to reddish colored iron oxides are reduced to soluble ferrous

ions, decolorizing the soil.

Many fermentation reactions based on various organic substrates proceed along with these mineral transformations, producing carbon dioxide,

ammoniacal nitrogen, low molecular weight organic acids, and so forth. As the soil becomes even more reductive, sulfate reducers, which are strict anaerobes, produce sulfides; and methanobacteria, also strict anaerobes,

produce methane.

Diunduh dari sumber: http://www.agnet.org/library.php?func=view&id=20110721171053&type_id=4 …….. 28/10/2012




All these biochemical changes occur vigorously for the first month after submergence, when readily decomposable

organic matter, the energy source for microorganisms, is abundantly available. Past this stage, there will be a period when the supply of oxygen by diffusion, though extremely slow, exceeds its consumption at the soil/water interface.

As all the oxygen is trapped by such reduced substances as ferrous and manganous ions at the interface, a thin oxidized,

orange colored layer (normally a few millimeters thick) is differentiated from the underlying bulk of the strongly

reduced, bluish-gray plow layer.


Successive Chemical Transformations in Submerged Soils




Supply of Basic Cations through Irrigation Water

At least 1000 to 1500 mm of water is used to irrigate paddy fields during one rice cropping season. Nutrients dissolved in water, particularly basic cations such as calcium, magnesium

and potassium, as well as silica, are supplied to rice in the water. If we assume that 1000 mm of water is used for one crop of rice, 1 mg kg -1 or 1 ppm of a substance dissolved in

water amounts to 10 kg/ha. According to the mean water quality of Japanese rivers,

irrigation of 1000 mm of water brings to a paddy field 88 kg/ha of Ca, 19 kg/ha of Mg, 12 kg/ha of K, and 190 kg/ha of

SiO 2. Usually more than 1000 mm of water is used for irrigation, so the amount of nutrients supplied to rice is

larger.


Water Quality of Japanese and Thai Rivers




Supply of Nitrogen through Biological Nitrogen Fixation

There are paddy areas where rice has been cultivated for hundreds of years without receiving any fertilizer, but where yields are

sustained at 1.5 to 2 mt/ha. It is estimated that about 20 kg of N is required to harvest 1 mt of paddy. Thus, it is difficult to explain how rice yields can be sustained for so long without any application of N.

The greater part of N in paddy soils exists in soil organic matter. This tends to be conserved more in paddy soils than in upland soils,

because of the anaerobic conditions. Microbial decomposition of the organic matter gradually releases ammoniacal N (NH 4

+-N). As NH 4 +-

N is stable under anaerobic conditions, it is retained as a cation on negatively charged soil mineral and organic particles, until the time when rice roots take it up. Thus, the leaching of NH 4

+-N from paddy fields into the environment is not significant.

Besides soil organic matter, there is another important source of N, i.e. biological N fixation. In paddy soils there are many microbes that

are capable of fixing atmospheric N, such as blue-green algae, Clostridia, photosynthetic bacteria, and many of the heterotrophic

bacteria in the rice rhizosphere. Estimates of the amount of biologically fixed N per crop of rice vary quite widely, but 30 to 40

kg/ha would be a reasonable figure. This amount of N is two or three times higher than the amount of N fixed in ordinary upland soils

planted in non-leguminous crops. Interestingly enough, this amount of fixed N can explain the average yields of paddy obtained in

unfertilized fields in southeast Asia (1.5 to 2 mt/ha) on the basis of 20 kg of N for 1 mt of paddy.





Paddy soils are equipped with an excellent N cycling mechanism, with an input through biological N fixation and an output through denitrification.

This appears to set the basis for sustainability of rice cultivation as an efficient food production system.

Schematic Diagram of Nitrogen Cycle in Paddy Soil Ecosystem





Negative Aspects of Soil Reduction

Rice is known to suffer some physiological disorders under strongly reduced conditions. The best known is a root rot, caused by

hydrogen sulfide evolved in soils that are poor in readily reducible iron oxides. These soils are often derived from pale colored, sandy,

granitic sediments. They are poor, not only in iron oxides, but also in some other plant nutrients such as Mg, K and SiO 2. It is now known that root rot due to hydrogen sulfide is an acute case of the more

general "akiochi" phenomenon observed in these "degraded paddy soils", as characterized above.

In Japan, a nationwide project was carried out during the post-war period to ameliorate degraded paddy soils by dressing the soil with

Fe-rich, more juvenile materials. With the aid of a government subsidy, the project was successfully completed, so that "akiochi" is

no longer seen in Japan.

There are large areas of paddy fields in southeast Asian countries that are characterized by the very low inherent potentiality of the soil. In fact, some of these deserve the name of "degraded" paddy soils. However, because of the generally low levels of both fertilizer

inputs and rice yields, at present they may not be clearly differentiated from "normal" soils.





Advantages of Paddy Rice Cultivation Comparison of Paddy Soils and Upland Soils

The high level of resistance of paddy soils to erosive forces is even more important, from the viewpoint of sustainability. Upland soils tend to be eroded away unless they are properly protected. This is particularly true in the tropics, where the erosivity of rainfall is very

high, and where upland soils usually have poor resistance to erosion. Paddy soils are most resistant to erosion when they are terraced and

there are ridges around the field, as measures to retain surface water. In addition, paddy fields in the lowlands receive new

sediments deposited from run-off that carries eroded topsoil down from the uplands, thus perpetuating soil fertility and productivity.

Paddy soils have other advantages. In upland farming, crop rotation is a necessity to avoid a decline in yield due to diseases and pests that arise from a monoculture situation (soil sickness). In paddy

fields, on the other hand, rice can be grown year after year without any clear sign of yield decline, over a considerable length of time.

The alternation from aerobic to anaerobic conditions in a yearly cycle of rice farming is the best measure to remove the causes of soil sickness. No pathogens or soil-borne animals can survive such a

drastic change in the redox environment.





Intensification of Paddy Rice Cultivation and the Environment

Rice is the staple food for more than two billion people, most of whom live in developing countries where the population is still

rapidly increasing.

A study conducted by the International Rice Research Institute (IRRI 1989) reveals that to meet the projected growth in the demand for

rice, the world's annual rough rice production must increase from 458 million mt in 1987 to 556 million mt by 2000 and to 758 million tons

by 2020. This represents a 65% increase. For the leading rice-growing countries of south and southeast Asia, the same study

indicates that the increase needed in rice production by 2020 is even higher, at about double the present level.

The potential for expanding the area planted in rice seems to have become very restricted in south and southeast Asia. Most land

resources have already been exploited to their fullest extent, and most of the readily manageable water resources also have been developed

to irrigate paddy fields. Therefore, any further increase in the production of rice depends heavily on intensification in existing rice

lands.





Impact of Irrigation/Drainage and Chemical Inputs

Intensifying rice cultivation could have various impacts on the environment. If good irrigation and drainage are provided, improved rice cultivars may be introduced, along with better management of

fertilizer, weeds and pests. The construction of dams, and of irrigation and drainage canals, would normally bring more benefits than disadvantages to the regional environment, as long as they are

properly planned and implemented. It improves water use efficiency, regulates floods and droughts, and, through these, improves the

environmental quality.Increased use of chemical preparations, such as fertilizers, pesticides

and herbicides, could be more hazardous. It is possible that they might pollute irrigation water and soil, and sometimes cause human

health problems. This must, however, also be evaluated in comparison with the upland cultivation of other crops.

Generally speaking, paddy rice cultivation could be less hazardous to the environment if it is intensified, with a high level of chemical

inputs, than upland crop cultivation.





Impact of Gas Emissions from Paddy Fields

In relation to the global environment, air pollution from soil emissions is receiving more and more attention. The production of

nitrous oxide (N 2O) from N fertilizers and manures is now considered to have an environmental impact. The gas is evolved in

both nitrification and denitrification processes. The former is considered more important at present. It affects the destruction of

ozone to oxygen, and also acts as a greenhouse gas. However, N 2O emissions from paddy fields are considered to be very low (De Datta

and Buresh 1989).

Paddy fields have been emitting methane since time immemorial. Therefore, the issue at the present time is the reason for the recent

rapid increase in the atmospheric methane concentration of about 1% annually. Certainly, there was a large increase in the area planted in rice during the early postwar period, but if we take the most recent

decade, 1980 to 1990, the world-wide annual rate of increase in rice area has been only 0.23% (IRRI 1993).


.. Methane emission from a simulated rice field ecosystem as influenced by hydroquinone and dicyandiamide

Xingkai Xu, Yuesi Wang, Xunhua Zheng, Mingxing Wang, Zijian Wang, Likai Zhou, Oswald Van Cleemput.

Science of The Total Environment, Volume 263, Issues 1–3, 18 December 2000, Pages 243–253.

A simple apparatus for collecting methane emission from a simulated rice field ecosystem was formed.

With no wheat straw powder amended all treatments with inhibitor(s) had so much lower methane emission during rice growth than the treatment

with urea alone (control), which was contrary to methane emission from the cut rice–soil system.

Especially for treatments with dicyandiamide (DCD) and with DCD plus hydroquinone (HQ), the total amount of methane emission from the soil

system and intact rice–soil system was 68.25–46.64% and 46.89–41.78% of the control, respectively.

Hence, DCD, especially in combination with HQ, not only increased methane oxidation in the floodwater–soil interface following application of urea, but

also significantly enhanced methane oxidation in rice root rhizosphere, particularly from its tillering to booting stage.

Wheat straw powder incorporated into flooded surface layer soil significantly weakened the above-mentioned simulating effects.

Regression analysis indicated that methane emission from the rice field ecosystem was related to the turnover of ammonium-N in flooded surface

layer soil.

Diminishing methane emissions from the rice field ecosystem was significantly beneficial to the growth of rice.





Relationship between CH4 emission from rice field ecosystem amended with wheat straw and NH4

+-N concentration in the floodwater (mg N l−1).





Relationship between CH4 emission from rice field ecosystem without applying wheat straw and NH4

+-N concentration in the floodwater.


SAWAH = WETLANDS

Atmospheric methane (CH4) is an important greenhouse gas. On a scale of 100 years, it is approximately 20 times more effective than carbon dioxide (CO2). The total annual

CH4 emission both from natural and anthropogenic terrestrial sources to the atmosphere is about 580 Tg (CH4) yr-1. The contribution of natural and man-made wetlands (e.g. rice paddy) to this global total varies between 20 and 40%. Thereby, natural wetlands

are the major non-anthropogenic source of methane at present and rice agriculture accounts for some 17% of the anthropogenic CH4 emissions. This is because of the

prevailing anaerobic conditions in these ecosystems, their high organic matter contents and their global distribution. Northern wetlands (>30° N) for example constitute about 60% of the global wetland area and emit a quarter to a third of the total CH4 originating

from wet soils.Microbial turnover of methane and transport pathways of gases in wetlands.

Diunduh dari sumber: http://www.ibp.ethz.ch/research/environmentalmicrobiology/research/Wetlands …….. 28/10/2012

Valuating ecosystem services is crucial for making the importance of ecosystem functioning explicit to the public and decision makers as well as scientists.

Investigations of the value of agricultural ecosystems have focused mainly on value food and fibre production and been carried out at relatively coarse scales. However, such studies may have underestimated services provided by agricultural ecosystems because they did not consider additional services such as gas regulation, pollination

control, nutrient transformation, and landscape aesthetics.

We present the results of a field experimental study of gas regulation services and their economic values provided by rice paddy ecosystems in suburban Shanghai, China. Two major components of gas regulation by paddy fields are O2 emissions and greenhouse

gases (GHGs) regulation (including the uptake of CO2 and emissions of CH4 and N2O). Seasonal emissions of O2 from experimental plots with different urea application rates

ranged from 25,365 to 32,612 kg ha−1 year−1, with an economic value of 9549–12,277 RMB ha−1 year−1 (Chinese currency; 1 euro = 10.7967 RMB, Jan 18, 2005).

The net GHGs regulation ranged from 705 to 2656 kg CO2C ha−1 year−1, with an economic value ranging from 531 to 2000 RMB ha−1 year−1. Thus, the overall economic value of gas regulation provided by the rice paddy ecosystems ranged from 10,080 to

14,277 RMB ha−1 year−1.

Our results refined, and in some cases, modified previous estimates of agricultural ecosystem services based mainly on coarse-scale studies.

Our study also demonstrated a systematic method to valuate the gas regulation services provided by rice paddy ecosystems, which will be useful for understanding regulation

of atmospheric chemistry and greenhouse effects by other agriculture ecosystems..

The value of gas exchange as a service by rice paddies in suburban Shanghai, PR China

Yu Xiao, Gaodi Xie, Chunxia Lu, Xianzhong Ding, Yao Lu .

Agriculture, Ecosystems & Environment. Volume 109, Issues 3–4, 1 September 2005, Pages 273–283


. Illustration of the static chamber used to measure gas fluxes in the rice paddy fields..





The estimated economic values of CO2 uptake, CH4 emission, N2O emission, and overall GHGs regulation from the rice paddy ecosystems during the

growing season with different urea application rates in suburban Shanghai, China.

The bars are the means of eight measurements ± S.D., each of which is the average of three reduplicate plots.

Letters a, b, and c beside the same legend denote the significant difference in Duncan's multiple range test (at the 5% significant level) across four N

treatments for CH4 emissions, or N2O emissions, or CO2 uptake or integrated CHGs regulation.





DINAMIKA NITROGEN EKOSISTEM SAWAH

A coupled soil water and nitrogen balance model for flooded rice fields in India

V.M. Chowdary, N.H. Rao, P.B.S. Sarma.Agriculture, Ecosystems & Environment. Volume 103, Issue 3, August 2004, Pages

425–441.

Diunduh dari sumber: http://www.sciencedirect.com/science/article/pii/S016788090300433X …….. 29/10/2012

In the present study a simple model for assessing concentration of nitrate in water percolating out of the flooded rice (Oryza Sativa) fields is presented.

The model considers all the important nitrogen (N) transformation processes that take place in flooded rice fields such as urea hydrolysis, volatilization,

nitrification, mineralization, immobilization, denitrification, crop uptake and leaching. It is based on coupling of soil water and N-balance models.

The coupled model also accounts for weather, and timings and amounts of water and fertilizer applications. All the N-transformations except plant

uptake and leaching are considered to follow first-order kinetics.

The simulation results show that urea hydrolysis is completed within 7 days of fertilizer application.

It was also observed that the volatilization loss of N varies from 25 to 33% of the applied fertilizer and 75% of the total volatilization loss occurs within 7

days of urea application. The modeled leaching losses from the field experiments varied from 20 to

30% of the applied N. The N-uptake by the crop increased immediately after the application of fertilizer and decreased at 60 days after transplanting.

The model is sufficiently general to be used in a wide range of conditions for quantification of nutrient losses by leaching and developing water and

fertilizer management strategies for rice in irrigated areas.




425–441.


. Schematic representation of the N-transformations in flooded rice field.




425–441.


. Zoning of ideal paddy field for N-balance studies.




425–441.


Schematic representation of nitrogen balance model.




425–441.


Nitrogen uptake in rice at Pantnagar, Uttar Pradesh, India. (a) Basal application (80 kg N ha−1) and (b) split application (40+20+20 kg N ha−1).

AIR DAN PADI SAWAH

Rice and WaterB.A.M. Bouman, E. Humphreys, T.P. Tuong, R. Barker.

Advances in Agronomy. Volume 92, 2007, Pages 187–237.

Diunduh dari sumber: http://www.sciencedirect.com/science/article/pii/S0065211304920044 …….. 29/10/2012

.Rice environments also provide unique—but as yet poorly understood—

ecosystem services such as the regulation of water and the preservation of aquatic and terrestrial biodiversity. Rice production under flooded conditions is highly sustainable. In comparison with other field crops, flooded rice fields produce more of the greenhouse gas methane but less nitrous oxide, have no to very little nitrate pollution of the groundwater, and use relatively little to

no herbicides.

Flooded rice can locally raise groundwater tables with subsequent risk of salinization if the groundwater carries salts, but is also an effective

restoration crop to leach accumulated salts from the soil in combination with drainage.

Water scarcity is expected to shift rice production to more water‐abundant delta areas, and to lead to crop diversification and more aerobic (nonflooded)

soil conditions in rice fields in water‐short areas. In these latter areas, investments should target the adoption of water‐saving technologies, the

reuse of drainage and percolation water, and the improvement of irrigation supply systems.

A suite of water‐saving technologies can help farmers reduce percolation, drainage, and evaporation losses from their fields by 15–20% without a yield

decline. However, greater understanding of the adverse effects of increasingly aerobic field conditions on the sustainability of rice production, environment, and ecosystem services is needed. In drought‐, salinity‐, and

flood‐prone environments, the combination of improved varieties with specific management packages has the potential to increase on‐farm yields by

50–100% in the coming 10 years, provided that investment in research and extension is intensified.

AIR DAN PADI SAWAH




. Water balance of a lowland (paddy) rice field. C, capillary rise; E, evaporation; I, irrigation; O, overbund flow; P, percolation; R,

rainfall; S, seepage; T, transpiration.

AIR DAN PADI SAWAH




. Emissions of CH4 (A) and N2O (B), and combined global warming potential (C) of rice fields under continuous flooding (control), under plastic film with

unsaturated soil underneath, and under straw mulch with aerobic soil conditions underneath, at three sites in China. Source: Dittert et al. (2002).

http://www.sciencedirect.com/science/article/pii/S0065211304920044



AIR DAN PADI SAWAH




Surface and subsurface water flows across lowland rice fields. D, drainage (overbund flow); I, irrigation; P, percolation; S, seepage.

NERACA AIR SAWAH TADAH-HUJANWater balance simulation model for optimal sizing of on-farm

reservoir in rainfed farming systemDipankar Roy, Sudhindra N. Panda, B. Panigrahi.

Computers and Electronics in Agriculture. Volume 65, Issue 1, January 2009, Pages 114–124.


. The on-farm reservoir (OFR) is used to harvest the surplus water from the diked crop field and recycle the stored water as supplemental irrigation to rice in monsoon (rainy) and non-rice (dry) crops in winter season under rainfed farming system. A user-friendly software, using Visual Basic 6.0 program, is developed to find out the optimal size of the OFR in terms of

percentage of field area (here in called as OFR sizes throughout the manuscript) by simulating the water balance model parameters of the crop

field and the OFR. The software is meant for all the concerned including the engineers, planners and farming community for any monsoon influenced cropping area, which uses rainfed agriculture. The menu driven system is flexible enough to simulate the OFR sizes for various combinations of the

OFR geometry, field sizes, and the cropping systems. The user has to specify the crops to be grown in the fields, irrigation management practices of the crops, types of OFR (lined or unlined), side slope, depth of OFR, and field sizes. Evapotranspiration sub-model is embedded with the main model to compute the ET from the meteorological data. As model application, the

developed model is used to simulate the OFR sizes for the rice–mustard and rice–groundnut cropping systems using the experimental observed and

meteorological data of the study area located at Indian Institute of Technology, Kharagpur in eastern India. The water balance model parameters

of the crop field are validated with 2 years of observed data from the experimental field of above mentioned study area. The study reveals that

rice–groundnut cropping system requires higher OFR sizes than rice–mustard cropping systems. Moreover, it is observed that as the field areas increase,

the OFR sizes for each cropping systems is found to decrease.





Schematic presentation of water balance parameters of the rice field and the OFR with their respective control volumes.





Flow chart for computation of OFR size.





Variation of actual evapotranspiration, AET in rice field.





Variation of deep percolation in rice field.

KEHILANGAN AIR DARI SAWAH

. Causes of high water losses from irrigated rice fields: field measurements and results from analogue and

digital modelsS.H. Walker.

Agricultural Water Management. Volume 40, Issue 1, 1 March 1999, Pages 123–127.


In places where rice is grown in paddy fields with permanent bunds, considerable quantities of water are lost through lateral seepage of water into the bund and from there vertically to the

groundwater.

Lateral percolation losses increase with increases in field water depth, bund width, aquifer thickness and depth to groundwater.

These losses do not occur in systems where the bunds are reformed every year.

The paper discusses the areas of research required to quantify the magnitude of these `losses' at a scheme level and suggests

management interventions to improve the efficiency of water use.

KEHILANGAN AIR DARI SAWAH. Causes of high water losses from irrigated rice fields: field measurements and results from analogue and digital models

S.H. Walker.



Hypothesis: lateral percolation into and down through the bunds greatly exceeds vertical percolation through the impermeable bed of

the rice fields.


S.H. Walker.



Field observations verify inflow to the bund from both the adjacent fields.


S.H. Walker.



Analogue model result for flows in vertical section.

CO2 & PANAS PADA EKOSISTEM SAWAH. CO2/heat fluxes in rice fields: Comparative assessment of flooded and

non-flooded fields in the PhilippinesMa. Carmelita R. Alberto, Reiner Wassmann, Takashi Hirano, Akira Miyata, Arvind Kumar, Agnes

Padre, Modesto Amante.

Agricultural and Forest Meteorology. Volume 149, Issue 10, 1 October 2009, Pages 1737–1750.


The seasonal fluxes of heat, moisture and CO2 were investigated under two different rice environments: flooded and aerobic soil conditions, using the

eddy covariance technique during 2008 dry season. This study was intended to monitor the environmental impact, in terms of C

budget and heat exchange, of shifting from lowland rice production to aerobic rice cultivation as an alternative to maintain crop productivity under

water scarcity.The aerobic rice fields had higher sensible heat flux (H) and lower latent heat

flux (LE) compared to flooded fields. On seasonal average, aerobic rice fields had 48% more sensible heat flux while flooded rice fields had 20%

more latent heat flux. Consequently, the aerobic rice fields had significantly higher Bowen ratio (0.25) than flooded fields (0.14), indicating that a larger

proportion of the available net radiation was used for sensible heat transfer or for warming the surrounding air.

The total C budget integrated over the cropping period showed that the net ecosystem exchange (NEE) in flooded rice fields was about three times higher than in aerobic fields while gross primary production (GPP) and

ecosystem respiration (Re) were 1.5 and 1.2 times higher, respectively. The high GPP of flooded rice ecosystem was evident because the photosynthetic capacity of lowland rice is naturally large. The Re of flooded rice fields was

also relatively high because it was enhanced by the high photosynthetic activities of lowland rice as manifested by larger above-ground plant

biomass. The NEE, GPP, and Re values for flooded rice fields were −258, 778, and 521 g C m−2, respectively. For aerobic rice fields, values were −85,

515, and 430 g C m−2 for NEE, GPP, and Re, respectively. The ratio of Re/GPP in flooded fields was 0.67 while it was 0.83 for aerobic rice fields.

CO2 & PANAS PADA EKOSISTEM SAWAH. CO2/heat fluxes in rice fields: Comparative assessment of

flooded and non-flooded fields in the PhilippinesMa. Carmelita R. Alberto, Reiner Wassmann, Takashi Hirano, Akira Miyata, Arvind

Kumar, Agnes Padre, Modesto Amante.



Solar radiation (SR), rainfall, and ambient temperature during the 2008 dry season from 11 January to 15 May.






. Mean diurnal variations of air temperature, T air, in the rice canopy (0.75 m above the soil) during 2008 dry season. Student's t-test was applied to

compare the difference in the average daily means of flooded and aerobic rice fields. Values were averaged over the growth stage. (DAT—Days after

Transplanting; DAS—Days after Sowing).






Mean diurnal variations of soil temperature, T soil, in the rice canopy (0.75 m above the soil) during 2008 dry season. Student's t-test was applied to compare the difference

in the average daily means of flooded and aerobic rice fields. Values were averaged over the growth stage. (DAT—Days after Transplanting; DAS—Days after Sowing).






Mean diurnal variations of vapor pressure deficit, VPD, in the rice canopy (0.75 m above the soil) during 2008 dry season. Student's t-test was applied to compare the

difference in the average daily means of flooded and aerobic rice fields. Values were averaged over the growth stage. (DAT—Days after Transplanting; DAS—Days after

Sowing).






Mean diurnal variations of half-hourly net ecosystem CO2 exchange, NEE, during 2008 dry season. Student's t-test was applied to compare the difference in the average daily means of flooded and aerobic rice fields. Values were averaged over the growth stage.

(DAT—Days after Transplanting; DAS—Days after Sowing).






Relationship between daily sum of ecosystem respiration (Re) and soil water potential (SWP) at 15 cm soil depth in aerobic rice fields during 2008 dry

season. Daily Re was grouped into 24 bins and averaged with equal number of data points per bin. Vertical bars denote standard error. Triangles denote values during vegetative to panicle initiation stage; squares denote values during reproductive to ripening stage; circles denote values during harvest

stage.






Relationship between daily sum of gross primary production (GPP) and soil water potential (SWP) at 15 cm soil depth in aerobic rice fields during 2008

dry season. Daily GPP was grouped into 24 bins and averaged with equal number of data points per bin. Vertical bars denote standard error. Triangles denote values during vegetative to panicle initiation stage; squares denote values during reproductive to ripening stage; circles denote values during

harvest stage.






Relationship between net ecosystem CO2 exchange (NEE) at photosynthetic active radiation (PAR) larger than 1000 μmol m−2 s−1 and vapor pressure

deficit (VPD) in (a) aerobic fields when soil water potential (SWP) at 15 cm depth was <−100 kPa and (b) flooded rice fields during 2008 dry season.

Half-hourly data were sorted by VPD and bin averaged with equal number of data per bin. Vertical bars denote standard error.






Seasonal variations in daily NEE, Re, and GPP in flooded rice fields during the 2008 dry season from 21 January to 12 May. The vertical bars show the different growth stages of the flooded rice (vegetative, tillering to panicle initiation, reproductive, heading to flowering, ripening, and harvest). The shading of the horizontal bar denotes flooded (black), saturated (grey) and

dry soil conditions (white).






Seasonal variations in daily (a) NEE, Re, and GPP and (b) soil water potential (SWP) at 5 cm and 15 cm soil depths of aerobic rice fields during 2008 dry

season from 21 January to 12 May. The vertical bars show the different growth stages of the aerobic rice (vegetative, tillering to panicle initiation,

reproductive, heading to flowering, ripening, and harvest).

NERACA KARBON EKOSISTEM SAWAH

. Rice paddy fields are also one of the typical agricultural ecosystems in Monsoon Asia. Among them, single rice cropping paddies that dominates in

northeastern Asia are characterized by two contrasting periods, a flooded growing period and dry fallowed period which lasts two thirds of a year. From the analyses using stable isotopes of water and carbon, the largest

carbon input was CO2 fixation by photosynthesis of rice, where 64-65% of the fixed carbon was harvested in autumn. Inflow and outflow of dissolved

carbon accounted for 5-9% of the total input and output

Diunduh dari sumber: http://www.niaes.affrc.go.jp/annual/r2003/html/no52.html …….. 29/10/2012

http://www.niaes.affrc.go.jp/annual/r2003/png/060500zf1.png

Management-induced organic carbon accumulation in paddy soils: The role of organo-mineral associations

Livia Wissing, Angelika Kölbl, Werner Häusler , Peter Schad, Zhi-Hong Cao, Ingrid Kögel-Knabner.

Soil and Tillage Research. Volume 126, January 2013, Pages 60–71.

Iron (Fe) oxides strongly interact with organic matter in soil and play an important role in the stabilization of organic matter. These processes are often influenced by soil

cultivation, including tillage, crop rotation and irrigation.

We assessed the effect of Fe oxides on organic carbon (OC) accumulation during the development of soils used for paddy rice production in comparison to non-irrigated cropping systems. Soil samples were taken from two chronosequences derived from

uniform parent material in the Zhejiang Province (PR China). Bulk soils and soil fractions were analyzed for OC concentrations, soil mineralogy and soil organic matter

(SOM) composition was determined by solid-state 13C NMR spectroscopy. Paddy soils were characterized by increasing OC concentrations, from 18 mg g−1 to

30 mg g−1, during 2000 years of rice cultivation, but OC concentrations of non-paddy soils were low in all age classes (11 mg g−1). SOM composition revealed from Solid-

state 13C NMR spectroscopy did not change during pedogenesis in either chronosequence. Selective enrichment of lignin-derived compounds, caused by long-

term paddy rice management, could not be confirmed by the present study.

The management of paddy soils creates an environment of Fe oxide formation which was different to those in non-paddy soils. Paddy soils are dominated by poorly

crystalline Fe oxides (Feo) and significantly lower content of crystalline Fe oxides (Fed − Feo). This was in contrast to non-paddy soils, which are characterized by high proportions of crystalline Fe oxides. The paddy-specific Fe oxide composition was

effective after only 50 years of soil development and the proportion Fe oxides did not alter during further pedogenesis.

This chronosequence study revealed that the potential for OC accumulation was higher in paddy versus non-paddy soils and was already reached at earliest stages of paddy soil development. Changes in paddy soil management associated with redox cycle

changes will not only affect Fe oxide composition of paddy soils but most probably also OC storage potential.


Management-induced organic carbon accumulation in paddy soils: The role of organo-mineral associations

Livia Wissing, Angelika Kölbl, Werner Häusler , Peter Schad, Zhi-Hong Cao, Ingrid Kögel-Knabner.

Soil and Tillage Research. Volume 126, January 2013, Pages 60–71.

Relation between oxalate (Feo) extractable iron (Fe) oxides and the organic carbon (OC) concentrations of the paddy (P) and non-paddy (NP) soil

fractions (20–6.3 μm = medium silt; 6.3–2 μm = fine silt; 2–0.2 μm = coarse clay; <0.2 μm = fine clay) with standard errors.


PLoS One. 2012; 7(5): e34642. Published online 2012 May 4. Effects of Tillage and Nitrogen Fertilizers on CH4 and CO2 Emissions and Soil

Organic Carbon in Paddy Fields of Central ChinaLi Cheng-Fang, Zhou Dan-Na, Kou Zhi-Kui, Zhang Zhi-Sheng, Wang Jin-Ping, Cai Ming-Li, and

Cao Cou-Gui.

Quantifying carbon (C) sequestration in paddy soils is necessary to help better understand the effect of agricultural practices on the C cycle.

The objective of the present study was to assess the effects of tillage practices [conventional tillage (CT) and no-tillage (NT)] and the application

of nitrogen (N) fertilizer (0 and 210 kg N ha−1) on fluxes of CH4 and CO2, and soil organic C (SOC) sequestration during the 2009 and 2010 rice

growing seasons in central China.

Application of N fertilizer significantly increased CH4 emissions by 13%–66% and SOC by 21%–94% irrespective of soil sampling depths, but had no effect on CO2 emissions in either year. Tillage significantly affected CH4 and CO2 emissions, where NT significantly decreased CH4 emissions by 10%–

36% but increased CO2 emissions by 22%–40% in both years.

The effects of tillage on the SOC varied with the depth of soil sampling. NT significantly increased the SOC by 7%–48% in the 0–5 cm layer compared with CT. However, there was no significant difference in the SOC between NT and CT across the entire 0–20 cm layer. Hence, our results suggest that

the potential of SOC sequestration in NT paddy fields may be overestimated in central China if only surface soil samples are considered.

Diunduh dari sumber: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3344821/…….. 31/10/2012



Cao Cou-Gui.

The entire process of CH4 emission from rice fields, including production, oxidation, and transport into the atmosphere is influenced by agricultural

management practices, such as tillage and N fertilizer use [1]–[3].

Tillage affects a range of biological, chemical, and physical properties, thereby affecting the release of CH4 [4]. No-tillage (NT) has been reported to

reduce CH4 emissions from paddy soils because rice straw is placed on the soil surface under NT and the soil conditions are more oxidative than those of

conventional tillage (CT) [3], [5]. CH4 emissions from paddy fields are reportedly affected by the form and

amount of N fertilizer applied [6].

1. Chu H, Hosen Y, Yagi K. NO, N2O, CH4 and CO2 fluxes in winter barley field of Japanese Andisol as affected by N fertilizer management. Soil Biol Biochem. 2007;39:330–339.

2. Guo J, Zhou C. Greenhouse gas emissions and mitigation measures in Chinese agroecosystems. Agric Forest Meteorol. 2007;142:270–277.

3. Harada H, Kobayashi H, Shindo H. Reduction in greenhouse gas emissions by no-tilling rice cultivation in Hachirogata polder, northern Japan: life-cycle inventory analysis. Soil Sci Plant Nutr. 2007;53:668–677.

4. Oorts K, Merckx R, Gréhan E, Labreuche J, Nicolardot B. Determinants of annual fluxes of CO2 and N2O in long–term no–tillage and conventional tillage systems in northern France. Soil Till Res. 2007;95:133–148.

5. Liang W, Shi Y, Zhang H, Yue J, Huang GH. Greenhouse gas emissions from northeast China rice fields in fallow season. Pedosphere. 2007;17(5):630–638.

6. Minami K. The effect of nitrogen fertilizer use and other practices on methane emission from flooded rice. Fertil Res. 1995;40:71–84.


http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3344821/








Cao Cou-Gui.

Tillage practices can affect soil biochemical and physical properties, consequently influencing the release of CO2 [8]. However, there is no

consensus on the differences in the soil CO2 emissions between NT- and CT-treated paddy fields. Some authors have reported similar soil CO2 fluxes

from NT- and CT-treated paddy fields [7]. However, Liang et al. [9] reported higher soil CO2 emissions from CT-treated paddy fields than from the NT

paddy fields. Nitrogen supplied by commercial fertilizers can be expected to affect soil CO2 flux by increasing the C input from enhanced plant

productivity and crop residues returned to the soil [11]. However, studies on the effects of N fertilizer on soil CO2 emissions reveal diverse results [12].

Within the past few years, Iqbal et al. [13] and Xiao et al. [14] observed increased CO2 emissions from paddy soils because of a positive effect of N

fertilization on plant biomass.

1. [7]. Harada H, Kobayashi H, Shindo H. Reduction in greenhouse gas emissions by no-tilling rice cultivation in Hachirogata polder, northern Japan: life-cycle inventory analysis. Soil Sci Plant Nutr. 2007;53:668–677.

2. [8]. Oorts K, Merckx R, Gréhan E, Labreuche J, Nicolardot B. Determinants of annual fluxes of CO2 and N2O in long–term no–tillage and conventional tillage systems in northern France. Soil Till Res. 2007;95:133–148.

3. [9]. Liang W, Shi Y, Zhang H, Yue J, Huang GH. Greenhouse gas emissions from northeast China rice fields in fallow season. Pedosphere. 2007;17(5):630–638.

4. [11]. Paustian K, Collins HP, Paul EA. Management controls on soil carbon. In: Paul EA, Paustian K, Elliot ET, Cole CV (Eds.) Soil Organic Matter in Temperate Agroecosystems - Long-term Experiments in North America, CRC Press, Boca Raton, FL, 1997;15–49

5. [12]. Lee DK, Doolittle JJ, Owens VN. Soil carbon dioxide fluxes in established switch grass land managed for biomass production. Soil Biol Biochem. 2007;39:178–186.

6. [13]. Iqbal J, Hu RG, Lin S, Hatano R, Feng ML, et al. CO2 emission in a subtropical red paddy soil (Ultisol) as affected by straw and N fertilizer applications: a case study in Southern China. Agric Ecosyst Environ. 2009;131:292–302.

7. [14]. Xiao Y, Xie G, Lu G, Ding X, Lu Y. The value of gas exchange as a service by rice paddies in suburban Shanghai, PR China. Agric Ecosyst Environ. 2005;109:273–283.











Cao Cou-Gui.

Land management practices are increasingly thought to affect soil carbon levels and may partially ameliorate CO2 emissions and climate change [17], [18]. Studies have

indicated that NT can increase C sequestration in paddy soils compared with CT [19]–[21]. In 2007, Tang et al. [20] indicated that the NT could sequester 112.3 kg C ha−1 yr−1 in the top 20 cm of purple paddy soil in the Beipei district of Chongqing City, China. In a 12-year study, Gao et al. [21] reported that NT could sequester 26.68 kg C ha−1 yr−1 in

gray fluvoaguic paddy soils to a depth of 30 cm in Zhangjiagang City, Jiangsu Province, China.

However, Six et al. [22] and Su [23] indicated that the effects of NT on SOC sequestration depend on the soil type. In a 5-year study, He et al. [24] indicated that NT did not increase the SOC sequestration of paddy fields in the 20 cm layer of sandy silty

loam in Ningxiang country, Hunan Province.

1. [17]. Lal R. Soil carbon sequestration impacts on global climate change and food security. Science. 2004;304:1623–1627. [PubMed]

2. [18]. DeLuca TH, Zabinski CA. Prairie ecosystems and the carbon problem. Front Ecol Environ. 2011;9:407–413.

3. [19]. Lu F, Wang XK, Han B, Ouyang ZY, Duan XN, et al. Soil carbon sequestrations by nitrogen fertilizer application, straw return and no-tillage in China’s cropland. Global Change Biol. 2009;15:281–305.

4. [20]. Tang XH, Shao JA, Gao M, Wei CF, Xie DT, et al. Chin J Appl Ecol 18: 1027–1032. (in Chinese); 2007. Effects of conservational tillage on aggregate composition and organic carbon storage in purple paddy soil.

5. [21]. Gao YJ, Zhu PL, Huang DM, Wang ZM. Soil Environ Sci 9: 27–30. (in Chinese); 2000. Long-term impact of different soil management on organic matter and total nitrogen in rice-based cropping system.

6. [22]. Six J, Feller C, Denef K, Ogle SM, Moraes Sa JC, et al. Soil organic matter, biota and aggregation in temperate and tropical soils – effects of no-tillage. Agronomie. 2002;22:755–775.

7. [23]. Su YZ. Soil carbon and nitrogen sequestration following the conversion of cropland to alfalfa forage land in northwest China. Soil Till Res. 2007;92:181–189.

8. [24]. He YY, Zhang HL, Sun GF, Tang WG, Li Y, et al. J Agro-Environ Sci 29(1): 200–204. (in Chinese); 2010. Effect of different tillage on soil organic carbon and the organic carbon storage in two-crop paddy field.


http://www.ncbi.nlm.nih.gov/pubmed/15192216









http://www.ncbi.nlm.nih.gov/pubmed/15192216



Cao Cou-Gui.

Changes in CH4 emission fluxes from paddy fields under different management practices during the 2009 and 2010 rice growing seasons.


The pattern of seasonal CH4 emission fluxes was similar across NT and CT treatments during the 2009 and 2010 rice growing

seasons . In both years, the CH4 emission fluxes in the four treatment groups were all initially low, increased gradually, and

then peaked in mid-July (about 4–5 weeks after sowing). Thereafter, the CH4 emission fluxes declined gradually and

remained relatively low until harvesting when the CH4 emission fluxes were lowest.

http://www.ncbi.nlm.nih.gov/core/lw/2.0/html/tileshop_pmc/tileshop_pmc_inline.html?title=Click%20on%20image%20to%20zoom&p=PMC3&id=3344821_pone.0034642.g001.jpg



Cao Cou-Gui.

Changes in CO2 emission fluxes from paddy fields under different management practices during the 2009 and 2010 rice growing seasons.


Tillage treatments exhibited clear seasonal variations in soil CO2 fluxes in the 2009 and 2010 rice growing seasons . The soil CO2

fluxes remained relatively low for the first two weeks after tillage, increased rapidly, stayed relatively high until about the middle 10 days of July, and then decreased to relatively low levels. Just one day after tillage (June 9, 2009 and June 13, 2010), the soil CO2

fluxes from CT were 1.40–4.60 times higher than those from NT (P<0.05).

http://www.ncbi.nlm.nih.gov/core/lw/2.0/html/tileshop_pmc/tileshop_pmc_inline.html?title=Click%20on%20image%20to%20zoom&p=PMC3&id=3344821_pone.0034642.g002.jpg



Cao Cou-Gui.

CH4 Emission

Application of N fertilizer in the present study increased CH4 emissions from paddy fields because of the promotion of rice growth, providing additional C sources and

emission pathways [32]. Lindau and Bollich [33], in a study on a Louisiana rice field, which also had a humid subtropical climate, reported similar results from silt loam soil.

However, Wassmann et al. [34] and Lu et al. [35] indicated no significant effect of N fertilizer application on CH4 emissions from paddy fields in Zhejiang Province, China.

Schütz et al. [36] found that the application of urea significantly decreased CH4 emissions from paddy fields in Italy. Results varied among studies because of the

differences in soil texture or climate. These findings show that further study is needed to understand the functioning of these complex and dynamic systems.

The decrease in CH4 emissions under NT may be attributed to the differences regarding the size and activity of the methanotrophic community between tillage treatments [37]. Tillage also affects gaseous diffusivity and the rate of supply of atmospheric CH4 [38].

By contrast, NT improves macroporosity and maintains its continuity [39]. The improvement probably allows greater air diffusion, increasing CH4 uptake and

decreasing CH4 emissions.

1. [32]. Neue HU, Roger PA. Rice agriculture: factors controlling emissions. In: Khalil MAK (ed.), Atmospheric Methane. Its Role in the Global Environment, 2000;134–169

2. [33]. Lindau CW, Bollich PK. Methane emissions from Louisiana first and Ratoon crop rice. Soil Sci. 1993;156:42–48.

3. [34]. Wassmann R, Schüetz H, Papen H, Rennenberg H, Seiler W, et al. Quantification of methane emissions from Chinese rice fields (Zhejiang Province) influenced by fertilizer treatment. Biogeochemistry. 1993;20:83–101.

4. [35]. Lu WF, Chen W, Duan WM, Lu Y, Lantin RS, et al. Methane emission and mitigation options in irrigated rice fields in southeast China. Nutr Cy Agroecosyst. 2000;58:65–73.

5. [36]. Schütz H, Holzapfel-Pschorn A, Conrad R, Rennenberg H, Seiler W. A 3–year continuous record on the influence of daytime, season and fertilizer treatment on methane emission rate from an Italian rice paddy. J Geophys Res. 1989;94:16406–16416.

6. [37]. Ussiri DAN, Lal R, Jarecki MK. Nitrous oxide and methane emissions from long–term tillage under a continuous corn cropping system in Ohio. Soil Till Res. 2009;104:247–255.

7. [38]. Hütsch BW. Tillage and land use effects on methane oxidation rates and their vertical profiles in soil. Biol Fertil Soils. 1998;27:284–292.

8. [39]. Ball BC, Scott A, Parker JP. Field N2O, CO2 and CH4 fluxes in relation to tillage, compaction and soil

quality in Scotland. Soil Till Res. 1999;53:29–39.Diunduh dari sumber: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3344821/…….. 31/10/2012









PLoS One. 2012; 7(5): e34642. Published online 2012 May 4. EFFECTS OF TILLAGE AND NITROGEN FERTILIZERS ON CH4 AND CO2

EMISSIONS AND SOIL ORGANIC CARBON IN PADDY FIELDS OF CENTRAL CHINA

Li Cheng-Fang, Zhou Dan-Na, Kou Zhi-Kui, Zhang Zhi-Sheng, Wang Jin-Ping, Cai Ming-Li, and Cao Cou-Gui.

CO2 EmissionsApplication of N fertilizer increases plant biomass production, stimulating

soil biological activity, and consequently, CO2 emission [40]. Wilson and Al-Kaisi [41], as well as Iqbal et al. [13], observed increased CO2 emissions

caused by N fertilizer application. By contrast, Burton et al. [15] and DeForest et al. [16] indicated that reduced extracellular enzyme activities and

fungal populations resulting from N fertilizer application resulted in decreased soil CO2 emissions. We observed no significant effect of N

fertilizer application on cumulative CO2 emissions , consistent with the results reported by Almaraz et al. [42]. This finding may be due to the fact

that CO2 is reduced to CH4 under anaerobic conditions, thus leading to significant differences in CH4 emissions rather than in CO2 emissions

between fertilized and unfertilized treatment areas.

1. [13]. Iqbal J, Hu RG, Lin S, Hatano R, Feng ML, et al. CO2 emission in a subtropical red paddy soil (Ultisol) as affected by straw and N fertilizer applications: a case study in Southern China. Agric Ecosyst Environ. 2009;131:292–302.

2. [14]. Xiao Y, Xie G, Lu G, Ding X, Lu Y. The value of gas exchange as a service by rice paddies in suburban Shanghai, PR China. Agric Ecosyst Environ. 2005;109:273–283.

3. [15]. Burton AJ, Pregitzer KS, Crawford JN, Zogg GP, Zak DR. Simulated chronic NO3-deposition reduces soil respiration in Northern hardwood forests. Global Change Biol. 2004;10:1080–1091.

4. [16]. DeForest JL, Zak DR, Pregitzer KS, Burton AJ. Atmospheric nitrate deposition, microbial community composition, and enzyme activity in Northern hardwood forests. Soil Sci Soc Am J. 2004;68:132–138.

5. [40]. Dick RP. A review: long term effects of agricultural systems on soil biochemical and microbial parameters. Agric Ecosyst Environ. 1992;40:25–36.

6. [41]. Wilson HM, Al-Kaisi MM. Crop rotation and nitrogen fertilization effect on soil CO2 emissions in central Iowa. Appl Soil Ecol. 2008;39:264–270.

7. [42]. Almaraz JJ, Zhou XM, Mabood F, Madramootoo C, Rochette P, et al. Greenhouse gas fluxes associated with soybean production under two tillage systems in southwestern Quebec. Soil Till Res. 2009;104:134–139.Diunduh dari sumber: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3344821/…….. 31/10/2012







ARSENIC AS A FOOD CHAIN CONTAMINANT: MECHANISMS OF PLANT UPTAKE AND METABOLISM AND MITIGATION

STRATEGIESAnnual Review of Plant Biology. Vol. 61: 535-559 (Volume publication date June 2010)

Fang-Jie Zhao, Steve P. McGrath, and Andrew A. Meharg

Rice is efficient at As accumulation owing to flooded paddy cultivation that leads to arsenite mobilization, and the inadvertent yet efficient uptake of

arsenite through the silicon transport pathway.

Diunduh dari sumber: http://www.annualreviews.org/doi/abs/10.1146/annurev-arplant-042809-112152?journalCode=arplant …….. 31/10/2012

EKOSISTEM SAWAH

Reducing the unnecessary insecticide uses, promoting natural biological control ecosystem services through enhancing organic

matter and enriching bunds and other surrounding areas with nectar rich plants can significantly prevent planthopper outbreaks.

Such practices that focus on biodiversity conservation, enhancing ecosystem services and avoiding pollution will build resilience in

production systems.

Diunduh dari sumber: http://allplantprotection.blogspot.com/2012/05/cultivating-flowers-on-rice-field-edges.html …….. 13/1/2013

ECOLOGY OF FLOODED RICE FIELDS I. WATANABE and P. A. ROGER

Proc. of Wopkshop Wetland Soils: Characterization, Classification, and Utilization, 26 March to 5 April 1984, IRRI, USAID, and Bureau of Soils,

Philippines. Pages 229-243. IRRI, Los Baños, Philippines..

The flooded soil-rice ecosystem consists of the following five major subsystems:

1. floodwater, 2. surface oxidized (or oxic) layer, 3. reduced (or anoxic) puddled layer, 4. subsoil (oxidized in well-drained condition,

reduced when water table is high), and 5. the rice plant and its phyllosphere (dipped in

water) and rhizosphere .

Transformation of nutrients in flooded rice soils has been a major topic of edaphological studies of these

soils. Attention has been paid largely to the transfomations in soil. Transformations of N have

been studied in floodwater considered as the site of loss of the surface-applied N Fertilizer. But

transformation and recycling of N within soil or floodwater and between the two have been relatively

neglected.

Diunduh dari sumber: pierre-armand-roger.fr/.../89_ecology_ricefiel...…….. 10/1/2013




FLOODWATER AND SOIL-WATER INTERFACE

In irrigated rice fields, the floodwater is an oxic-photic environment. The transition between the

flood-water and the anoxic-aphotic reduced soil is made by the oxidized soil-water layer. The

floodwater and the oxidized layer constitute a continuous ecosystem in

which four major mechanisms related to soil fertility take place:

1. Biological N-f ixation, 2. N losses by volatilization of NH3, in relation to

the photosynthetic activity of the biomass! and by the nitrification-denitrification process ,

3. Trapping and recycling by the photosynthetic biomass of C and mineral salts released fro m the soil and fertilizers, and

4. Transport of nutrients from the soil to the water by the phyto-plankton and the primary consumers.





Chemistry of the floodwater

The chemical status of standing water depend primarily on that of the irrigation water and the soil . However, its composition varies much during the crop cycle and within a field plot in relation to

1. Fertilizer application; 2. Mechanical disturbances of the soil, causin dispersion of soil

particles in the water; 3. Nature and biomass of the aquatic communities; 4. Dilution by rainfall and irrigation water; 5. Adsorption to surface soils; and 6. Rice growth.





Standing biomass and productivity of the floodwater The major components OE the total biomass in the standing water are: bacteria,

phytoplankton, aquatic macrophytes (mainly submerged and floating weeds) zooplankton, and aquatic invertebrates.

The only available quantitative evaluation of the bacterial biomass in the floodwater of a rice field (2).

Seems to indicate a low contribution of bacteria (0.01 mg/litre), However, bacterial blooms were observed by the authors in a Nistosol

in the Philippines.

Total algal biomass evaluations range from a few kilograms per hectare to 23 t fresh weight (FW) or to 500 kg dry weight (IN) (21). The N-

fixing algal biomass evaluations have the Same range (20). However the significance of these evaluations is of litt1e value without the record of either water or ash Content, or both, which vary within very large

limit (9).

1. (2) Baldensperyer , J. 1981. Short- term variation of microbiological and physiological parameters in submersion water over a rice field. Ann. Microbiol. ( Ins t. Pasteur) 132B: 101-122.

2. (9) IRR1 (International Rice Research Institute). 1984. Annual report for 1983. Los BaWos, Philippines. 494 p.

3. (20) Roger, P. A., and S. A. Kulasooriya. 1980. Blue-green algae and rice. International Rice Research Institute, Jas BaYlos, Philippines. 112 p.

4. (21) Roger, P. A., and I. Watanabe. 1984. Algae and aquatic weeds as a so'urce of organic matter and plant nutrients for wetland rice, Pages 147-1.68 - in Organic matter and" rice. International Rice Research Institute , Los BaEos , Philippines





Floral changes during the crop cycle.

The available information on the quantitative and qualitative variations of the algal flora has been summarized by Roger and Kulasooriya (20). Total algal biomass can reach a peak anytime

during the crop cycle. Its occurrence is related mainly to fertilizer application and climatic

conditions, especially light availability, aS affected by the season and the rice canopy, Algal successions are governed by a large set of factors, including climatic, trophic, biotic, and soil factors, as

well as agronomic practices. Factors that Lead to the development of a N-fixing algal, bloom

are still poorly understood and may include N depletion of the floodwater , P availability, low CO2 concentration due to alkaline reaction, low grazer populations or presence of algal populations

resistant to grazing , and optimal temperature and light intensities.

1. (20) Roger, P. A., and S. A. Kulasooriya. 1980. Blue-green algae and rice. International Rice Research Institute, Jas BaYlos, Philippines. 112 p.





Faunal changes during the crop cycle.

Little is known about faunal changes during the crop cycle. In a study of plankton successions’ in a rice field in Japan, Kurasawa (13)

observed a peak of phytoplankton 1 week after transplanting , followed 2 weeks later by a peak of zooplankton. Decline of the zooplankton

started 6 weeks later, before that of the phytoplankton , indicating that some algae were resistant to grazing.

Population changes of aquatic invertebrates were studied by Lim (15) in pesticide (carbof uran, carbaryl , endosulfan)- treated and -nontreated fields in Malaysia. Nematodes, hemipterans, and dipterans dominated in

nontreated plots whereas ostracods, dipterans, and conchostracans dominated in treated plots. Temporal changes , community structures , and populations were affected not only by pesticides but by cultural practices, fertilization, and the development of aquatic macrophytes. The overall invertebrate population was higher in pesticide- treated plots, mainly because of the rapid recovery of ostracods. But the

effects of pesticides may differ with their selectivity.

(13) Kurasawa, H. 1956. The weekly succession in the standing crop of plankton and zoobentos in the paddy field. Bull. Resourc. Sci.. Jpn. 41-42(4): 86-98.

(15) Gim, R. P. 1980. Population changes of some aquatic invertebrates in rice fields. Pages 971-980 in Tropical ecology and development. Part 2. The International Society of Tropical Ecology, Kuala Lumpur.





Recycling of nutrients : Carbon and nitrogen.

The photosynthetic biomass assimilates CO2 (and CH4 after it is oxidized to C02) evolved from the soil and returns it as algal cells and aquatic weeds, therefore preventing organic matter losses in the

form of CO2 (7). A similar role in preventing, to a certain extent, losses of NH3

dissolved in the floodwater is also possible. In lysimeter or pot experiments, Shioiri and MitSui (26) and Vlek And Craswell (28) recovered 10-30% of N added as urea or (NH4)2SO4 in

the algal biomass.

(7) Harrison, W. H., and P. A. S. Aiyer. 1916. The gases of swamp rice soils. III. A hydrogen oxidizing bacterium from these soils. Mem. Dep. Agric. India, Chem. Ser. 4( 4) :135-148.

(26) Shioiri, N. , and S. Mitsui. 1935. On the chemical composition of some algae and weeds developing in the paddy fields and their decomposition in the soil [in Japanese], J. Sci. Soil Manure. Jpn. 9 : 261- 268.

(28) Vlek, P. L. G., and E. 'F. Craswell. 1979. Effect of nitrogen source and management on ammonia volatilization losses from flooded rice-soil systens. Soil Sci. Soc. Am. J. 352-358.





Recycling of nutrients : Phosphorus.

Most of the soluble phosphate applied to flooded soils is fixed on the solid phase of the soil. Very little remains in the floodwater. Transfer of P from soil to standing water involves three major mechanisms : (i)

mechanical disturbances of the soil , (ii) diffusion from the soil, and (iii) activity of the plankton and the fauna.

When the soil is disturbed, the solid phase and soil solution are mixed with standing water, and P transfers from soil. This happens because of land preparation, cultural practices (weeding , pesticide and fertilizer

applications, etc.), and heavy rains. Short-term algal blooms were observed following disturbance of sediments in experimental ponds (1). In the IRRI farm we have occasionally observed the development of

blooms after a mechanical disturbance of the soil.


SAWAH: SIKLUS KARBON

1. Better understand the paddy ecosystem response to climate change

2. Quantify the impacts of climate change on methane emission (feedback effect)

3. Explore/test options to enhance adaptation/mitigation under future climate conditions

Diunduh dari sumber: http://www.niaes.affrc.go.jp/outline/face/english/target_e.html ...…….. 13/1/2013

.SAWAH: SIKLUS NITROGENFACE-N: Free-Air CO2 Enrichment study for paddy rice with a

focus on its effect on nitrogen cycle

1. Further understand the paddy ecosystem response to climate change through the interdependency of the carbon and nitrogen cycles

2. Quantify the N flow and the impacts of climate change on N2O and NH3 emissions

3. Develop a combined numerical models to describe the N cycle in the paddy ecosystem

Diunduh dari sumber: http://www.niaes.affrc.go.jp/outline/face/english/target_e.html ...…….. 13/1/2013

MICROBIAL ECOLOGY OF METHANE EMISSION IN RICE AGROECOSYSTEM: A REVIEW

S. K. DUBEY APPLIED ECOLOGY AND ENVIRONMENTAL RESEARCH 3(2): 1-27.

Methane has profound impact on the physico-chemical properties in atmosphere leading to global climate change. Out of the various sources of

CH4, rice fields are the most significant contributors. The processes involved in the emission of CH4 from rice fields to the atmosphere include

CH4 production (methanogenesis) in the soil by methanogens, methane oxidation (methanotrophy) by methanotrophs and vertical transfer of CH4

via plant transport and diffusion or ebullition.

In the overall methane dynamics rice plants act as : a) source of methanogenic substrate, b) conduit for CH4 through well developed system of inter cellular air space (aerenchyma), and c) potential methane oxidizing

micro-habitat in the rhizosphere by diffusing oxygen which favour the growth and multiplication of methanotrophs. Apart from mechanistic

uncertainties, there are several other uncertainties in the estimation of CH4 flux.

Methane dynamics in the paddy field is controlled by a complex set of parameters linking the biological and physical characteristics of soil

environment like temperature, carbon source, Eh, pH, soil microbes and properties of rice plants, etc. It has now become possible to isolate, detect and characterize the methanogens and methanotrophs by using molecular

biological tools like PCR, FISH, etc. techniques.

The apparent half saturation constant (Km) and maximum oxidation rate (Vmax) are distinctive parameters which determine the ability of bacteria to

survive on atmospheric methane.

Diunduh dari sumber: www.ecology.kee.hu/pdf/0302_001027.pdf ...…….. 12/1/2013



Atmospheric methane (CH4) is a potent greenhouse gas with high absorption potential for infrared radiation. Methane is present at about 1.8 ppmV in the atmosphere [135]. During the last 20 years, its concentration has been increasing, on an average at the rate of 0.8% y-1 [125]. Due to this, CH4 is of great concern as a greenhouse gas.

Although the tropospheric CH4 concentration is very low as compared to CO2 (357 ppmV), methane accounts for 15 to 20% of global warming [71].

The total annual source strength of all methane emissions from anthropogenic origin is estimated to be 550 Tg [133]. Major sources of this input include natural wetlands, rice fields, enteric fermentation in animals, termites and land fills. The contribution

from rice cultivation is estimated to range from 20-100 Tg CH4 y-1 with an average of 60 Tg CH4 y-1 [71].

The biogenic methane is mostly produced by methanogenic archaea (methanogens) in anaerobic environments i.e. sediments and flooded rice fields [59]. Each year

methanogens produce about 400 million metric tons of CH4 [49].

Recent studies have shown that methane is not only produced in anoxic rice fields soil but also directly from the roots of rice plants which are inhabited by a methanogenic

community different from that in the rice field soil [92].

1. [71] IPCC, (1996): XII summary for policy makers. In: (Houghton, IT., Meira, F., Callander, LG., Harris, B.A., Kattenberg, A., Maskell, K., (Eds.), Climate Change 1995: The Scientific Basis of Climate Change. − Cambridge University Press, Cambridge, UK. p. 572.

2. [92] Lehmann-Richter, S., Grosskopf, R., Liesack, W., Frenzel, P., Conrad, R., (1999): Methanogenic archaea and CO2 dependent methanogenesis on washed rice roots. − Environmental Microbiology 1, 159-166.

3. [125] Prinn, R.G., (1995): Global change: Problems and uncertainties. In: Peng. S., Ingram, K.T, Neue, H.D., Ziska, LH. (eds.), Climate Change and Rice, Springer, Berlin. pp. 3-7.

4. [133] Sass, R.L, Fisher Jr, F.M., (1994): CH4 emission from paddy fields in the United States gulf coast area. In: Minami, C.K., Mosier, A., Sass, R.L, (eds.) CH4 and N2O: Global Emissions and Controls from Rice Fields and other Agricultural and Industrial Sources. NIAES Series 2, Tsukuba, Japan. pp. 65- 77.

5. [135] Schimel, J., (2000): Rice, microbes and methane. − Nature 403, 375-377.




Chemical and biological processes consume methane in the global methane cycle. The only known biological sink for atmospheric methane is its oxidation in aerobic

soils by methanotrophic bacteria, this may contribute up to 10-20% to the total methane destruction [128], or between 15 and 45 Tg CH4 y-1 [71].

Methanotrophs oxidize CH4 with the help of methane monooxygenase (MMO) enzyme. These bacteria are classified into three groups (Type-I, Type-II and Type –X) based on the pathways used for assimilation of formaldehyde and other physiological

and morphological features [58].

An enormous effort is being made worldwide by microbial ecologists to isolate, detect and characterize methanotrophs and methanogens in different rice ecosystems by using

molecular biological tools and techniques [18, 46, 57]. Methanotrophy is an aerobic process [52], but in marine sediments and in some saline inland waters it could be

anaerobic [36]. The apparent half saturation constant (Km), and maximum rate (Vmax) of CH4

oxidation are characteristic parameters, which determine the ability of methanotrophs to grow on atmospheric CH4 [31].

1. [18] Bodelier, P.LE., Ros1ev, P., Henckel, T., Frenzel, P., (2000): Stimulation by ammonium based fertilizers of methane oxidation in soil around rice roots. − Nature 403, 421-424.

2. [31] Conrad, R., Schink, B., Phelps, T.J., (1986): Thermodynamics of H2 - consuming and H2 producting metabolic reactions in diverse methanogenic environments under in situ conditions. − FEMS Microbiology Ecology 38, 353-360.

3. [36] De Long, E.F., (2000): Resolving a methane mystery. − Nature 407, 577-579.4. [46] Dubey, S.K., P. Padamnabhan, H.J. Purohit and S.N. Upadhyay (2003): Tracking of methanotrophs and their

diversity in paddy soil: A molecular approach. − Current Science 85, 92-95.5. [52] Frenzel, P., (2000): Plant-associated methane oxidation in rice fields and wetlands. − Advances in Microbial

Ecology 16, 85-114.6. [57] Grobcopf, R., Stubner, S., Liesack, W., (1998): Novel euryachaeotal lineages detected on rice roots and in the anoxic

bulk soil of flooded rice microcosms. − Applied and Environmental Microbiology 64, 4983-4989.7. [58] Hanson, R.S., Hanson, T.E., (1996): Methanotrophic bacteria. − Microbiology Review 62, 439-471.8. [71] IPCC, (1996): XII summary for policy makers. In: (Houghton, IT., Meira, F., Callander, LG., Harris, B.A.,

Kattenberg, A., Maskell, K., (Eds.), Climate Change 1995: The Scientific Basis of Climate Change. − Cambridge University Press, Cambridge, UK. p. 572.

9. [128] Reeburgh, W.S., Whjalen, S.C., Alperin, M.J., (1993): The role of methylotrophy in the global methane budget In: Murrell, J.C., Kelly, D.P., (eds.), Microbial growth on CI compound. Intercept Ltd., Andover, D.K. pp. 1-14.




Several workers have reported that methane oxidation occurs in rice microcosm [56], wetland rice [40, 158] and dryland rice fields [44, 45].

Methane oxidation in rhizospheric soil is considered as an important sink for CH4 [44, 45, 56].

Therefore, the knowledge of several environmental factors (e.g. temperature, fertilizer inputs, crop phenology and soil moisture) that can provide

feedback on the capacity of soil to oxidize atmospheric CH4, may have significant consequences on the global atmospheric CH4 budget.

1. [40] Dubey, S.K., (2003): Spatio-kinetic variation of methane oxidizing bacteria in paddy soil at mid tillering: Effect of N fertilizer. − Nutrient Cycling in Agroecosystems 65, 53-59.

2. [44] Dubey, S.K., Sinha, A.S.K., Singh, J.S., (2000): Spatial variation in the capacity of soil for CH4 uptake and population size of methane oxidizing bacteria in dryland rice agriculture. − Current Science 78,617-620.

3. [45] Dubey, S.K., Sinha, A.S.K., Singh, J.S., (2002): Differential inhibition of CH4 oxidation in bare, bulk and rhizosphere soils of dryland rice field by nitrogen fertilizers. − Basic and Applied Ecology 3, 347-355.

4. [56] Gilbert, B., Frenzel, P., (1998): Rice roots and CH4 oxidation: the activity of bacteria, their distribution and the microenvironment. − Soil Biology and Biochemistry 30, 1903-1916.

5. [158] Watanabe, D., Hashmoto, T., Shimoyama, A., (1997): Methane oxidizing activities and methanotrophic population associated with wetland rice plants. − Biology and Fertility of Soils 24, 261-265.




Production of methane : Methanogens

Methanogens are strictly anaerobic unicellular organisms originally thought to be bacteria but now recognized as belonging to a separate phylogenetic domain, the archae [53]. 16S rRNA analysis suggested that methanogens can be categorized under three groups. Group I comprises Methanobacterium and Methanobrevibacter, Group II

contains Methanococcus, and Group III comprises the genera including Methanospirillum and Methanosarcina [53]. They proliferate in anaerobic fresh water

environments, such as sediments and the digestive tract of animals [147].

In these habitats, methanogens play an important role in the degradation of complex organic compounds. Most methanogens are mesophilic, able to function in temperature

ranging from 20 to 400 C [147]. They are also found in extreme environments like hydrothermal vents where they thrive at temperatures above 1000 C. Methanogens

mainly use acetate (contributes about 80% to CH4 production) as a carbon substrate but other substrate like H2/CO2 and formats also contribute 10-30% to CH4 production [27]. All methanogens use NH4 + as a nitrogen source, although the ability to fix

molecular nitrogen and the nif gene is present in all the three orders (Methanobacteriales, Methanococcales and Methanomicrobiales) of methanogens

[120].

1. [27] Chin, K. J., Conrad, R., (1995): Intermediary metabolism in methanogenic paddy soils and the influence of temperature. − FEMS Microbiology and Ecology 18, 85-102.

2. [53] Garcia, I.L., (1990): Taxonomy and ecology of methanogens. − FEMS Microbiological 3. Review 87, 297-308.4. [120] Palmer, R.R., Reeve, I.N., (1993): Methanogene genes and the molecular biology of

met ham biosynthesis. − In: Sebald, M.,(ed.), Genetics and Molecular Biology of Anaerobic Bacteria. Springer-Verlag, Berlin. pp. 13-35.

5. [147] Topp, E., Pattey, E., (1997): Soil as a source and sinks for atmospheric methane. − Canadian Journal of Soil Science 77, 167-178.




Methanogenesis

Methane is produced in the anaerobic layers of paddy soil by bacterial decomposition of organic matter [39]. The organic matter converted to CH4 is derived mainly from

plant-borne material, and organic manure [35], if applied. The anaerobic degradation of organic matter involves four main steps:

a) hydrolysis of polymers by hydrolytic organisms, b) acid formation from simple organic compound by fermentative bacteria, c) acetate formation from metabolites of fermentations by homoacetogenic or

syntrophic bacteria, and d) CH4 formation from H2/CO2, acetate, simple methylated compounds or alcohols

and CO2 [163].

CH4 is produced in rice fields after the sequential reduction of O2, nitrate, manganese, iron and sulphate, which serve as electron acceptors for oxidation of organic matter to

CO2 [164]. Methanogenesis from all substrates requires a number of unique coenzymes, some of which are exclusively found in methanogens [98]. At least nine methanogen-specific enzymes are involved in the pathway of methane formation from H2 and CO2 [140].

In paddy soil, acetate and H2 are the two main intermediate precursors for CH4 formation [162].

1. [35] Dannenberg, S. Conrad, R., (1999): Effect of rice plant on methane production and rhizospheric metabolism in paddy soil. − Biogeochemistry 45, 53-71.

2. [39] Dubey, S.K., (2001): Methane emission and rice agriculture. − Current Science 81, 345-346.3. [140] Shima, S.L., (1998): Mechanism of biological methane formation: Structure and function of methyl-

coenzyme M. reductase. Protein, Nucleic Acid and Enzyme 43, 1461-1467.4. [162] Yao, H., Conrad, R., (1999): Thermodynamics of methane production in different rice paddy soils from

China, the Philippines and Italy. − Soil Biology and Biochemistry 31, 463-473. 5. [163] Yao, H., Conrad, R., (2001): Thermodynamics of propionate degradation in anoxic paddy soil from

different rice-growing regions. − Soil Biology and Biochemistry. 33, 359-364. 6. [164] Yao, H., Conrad, R., Wassmann, R., Neue, H.D., (1999): Effect of soil characteristic on sequential

reduction and methane production in sixteen rice paddy soils from China, the Phillipines, Italy. − Biogeochemistry 47, 269-295.




Methanogenesis from acetate

Methanogenesis from acetate starts with its activation to acetyl-CoA. Methanosarcina and Methanothrix use different ways of acetate activation.

The former organism takes advantage of acetate kinase and phosphotans acetylase whereas the later makes use of acetyl-CoA synthatase. All three

enzymes are soluble and oxygen insensitive.

Further breakdown of acetyl- CoA catalyzes the cleavage of acetyl-CoA, giving rise to a methyl group, a carbonyl group and CoA, all of which are

transiently bound to the enzyme.

In a further step, the Co-dehydrogenase complex catalyzes the oxidation of the carbonyl group. The CO2 is thereby formed and CoA is released from the enzyme, where the methyl group is transferred to a corrinoid-Fe-S protein.

This complex catalyzes not only the cleavage of acetyl-CoA and oxidation of the carbonyl group but in addition, the transfer of the methyl moiety to

H4MPT. Further pathway from methyl H4MPT to CH4 takes advantage of the pattern

similar to that discussed for the utilization of the CO2/H2 [16, 98].

1. [16] Blaut, M., (1994): Metabolism of Methanogenes. − Antonie Van Leeuwenhoek 66, 187-208. 2. [98] Ludmila, C., Julia A., Rudoyk R., Toms M., Lidstrom E., (1998): G Transfer enzymes and coenzymes

linking methylotrophic bacteria and methanogenic archea. − Science 281, 99-101.




Thermodynamics of CH4 production

The process of methane production in paddy fields is thermodynamically exergonic [163]. The Gibbs free energy (∆G) for the process is mainly a function of the acetate concentration and H2-partial pressure. A pre-requisite for early methane production

seems to be a sufficiently high H2-partial pressure that corresponds to ∆G of H2 dependent methanogenesis (hydrogenotrophic) of less than about -23 kJ mol-1 CH4

[162]. The time until the onset of CH4 production and the magnitude of production is a function of the quantity of easily degradable organic matter, reducible Fe(III) and

sulfate [162]. Methanogens are energetically limited by availability of their substrates H2 and acetate as long as iron or sulfate reducers are able to compete for them [1]. The methanogens

have to compete for available substrates with other anaerobic bacteria, namely the nitrate, manganese, ferric iron and sulfate reducers. The competition for carbon

substrates in general follows thermodynamic rules: nitrate reducers outcompete the other anaerobic bacteria for the substrates [149].

Several studies have reported different ∆G values for methanogenesis in various paddy fields. For Italian paddy fields the values of ∆G for methane production were found to be -31.6 to 34.8 kJ mol-1 CH4 [1] and -24 to -38 kJ mol-1 CH4 [27]. Peters and Conrad [123] found that ∆G ranged

from -25 to -50 kJ mol-1 CH4 for German rice fields. Cultures of Methanobacterium bryantii required ∆G values of less than -30 kJ mol-1 CH4 for CH4 production [31].

1. [1] Achtnich, C., Bak, F., Conrad, R., (1995): Competition for electron donors among nitrate reducers, ferric iron reducers, sulfate reducers, and methanogens in anoxic paddy soil. − Biology and Fertility of Soils 19, 65-72.

2. [31] Conrad, R., Schink, B., Phelps, T.J., (1986): Thermodynamics of H2 - consuming and H2 producting metabolic reactions in diverse methanogenic environments under in situ conditions. − FEMS Microbiology Ecology 38, 353-360.

3. [123] Peters, V., Conrad, R., (1996): Sequential reduction processes and initiation of CH4 production upon flooding of oxic upland soils. − Soil Biology and Biochemistry 28, 371-382.

4. [149] Van Bodegom, P.M., Stams, A.J.M., (1999): Effect of alternative electron acceptors and temperature on methanogenesis in rice paddy soils. − Chemosphere 39, 167-182.

5. [162] Yao, H., Conrad, R., (1999): Thermodynamics of methane production in different rice paddy soils from China, the Philippines and Italy. − Soil Biology and Biochemistry 31, 463-473.

6. [163] Yao, H., Conrad, R., (2001): Thermodynamics of propionate degradation in anoxic paddy soil from different rice-growing regions. − Soil Biology and Biochemistry. 33, 359-364.




Pathways of methane emission

The net amount of CH4 emitted from soil to the atmosphere is the balance of two opposite processes - production and oxidation. Methane, the product of

methanogenesis, escapes to the atmosphere from soil via aerobic interfaces where CH4 oxidation takes place. There are three pathways of CH4-transport into the atmosphere

– molecular diffusion, ebullition and plant transport.

In the temperate rice fields more than 90% of the CH4 is emitted through plant transport [136] while in the tropical rice fields, significant amounts of CH4 may evolve by ebullition (gas transport via gas bubbles) in particular during the early period of the

season and in the case of high organic input [38].

Ebullition is also the common and significant mechanism of CH4 flux in natural wetlands [155]. According to Sass et al. [131], ebullition can play significant role in

CH4 transport under high organic fertilization. If soil is unvegetated or plant aerenchyma is not yet well-developed, ebullition plays a major role in CH4 emission [22] but it occurs only at surface layer and its rate is regulated by CH4 concentration,

temperature, soil porosity and plant aerenchyma [94].

1. [22] Byrenes, B.H., Austin, E.R., Tays, B.K., (1995): Methane emission from flooded rice soils and plants under controlled conditions. − Soil Biology and Biochemistry 27, 331- 339.

2. [38] Denier Van Der Gon, H.A.C., Neue, H.U., (1995): Influence of organic matter incorporation on the methane emission from a wetland rice field. − Global Biogeochemical Cycles 11, 11-22.

3. [94] Li, C.S., (2000): Modelling trace gas emission from agricultural ecosystem. − Nutrient Cycling in Agroecosystems 58, 259-267.

4. [131] Sass, R.L., Fischer Jr., F.M., Huang, Y., (2000): A process-based model for methane emission from irrigated rice fields: experimental basis and assumption. − Nutrient Cycling in Agroecosystems 58, 249-258.

5. [136] Schutz, H., Holzaptel-Pschorn, A., Conrad, R., Rennenberg, H., Seiler, W., (1989): A three-year continuous record on the influence of day time season and fertilizer treatment on methane emission rates from an Italian rice paddy. − Journal of Geophysics Research 94, 16405-16416.

6. [155] Wassmann, R, Martius, C.S., (1997): Methane emission from the Amazon flood plain. In: Junk,W.J., (Ed.), The Central Amazon floodplain: Ecological Studies 126.. Springer-Verlag, Berlin. pp. 137-143.




Conceptual schematic diagram of methane production, oxidation and emission from paddy field.




Factors affecting methane emission :

Soil pH. Eh and texture Methane production in flooded rice soils is very sensitive to pH with an optimum range between

6.7 and 7.1 [152]. Effect of soil pH on CH4 production varied by about two orders of magnitude in four different Indian soils but was found to be maximum at pH around 8.2 [121].

Yagi and Minami [161] reported that values of redox potential (Eh) varied from -100 to -200 mV for the initiation of CH4 production in paddy soils. Masscheleyn et al. [104] incubated rice soil under controlled redox levels ranging between -250 and +500 mV. They found the threshold for

methane production to be -150 mV. Some suggested that soils containing greater amounts of readily decomposable organic substrates (acetate, formate, methanol, methylated amines, etc.) and low amounts of electron acceptors (Fe3+, Mn4+, NO3-, SO42-) are likely to show high production of CH4. According to sequential oxidation -reduction order, molecular O2 is the first to be reduced at an Eh of about +30 mV followed by NO3- and Mn4+ at 250 mV, Fe3+ at + 125 mV and SO4=

at -150 mV (Patrick, 1981). Subsequent to SO4= reduction, methanogens will start producing methane [8].

As texture determines various physico-chemical properties of soil, it could influence CH4 production indirectly. Jackel et al. [72] found that rates of CH4 production increased when the aggregate size of the soil increased. A negative co-relationship between CH4 emission and clay

content was reported by Sass and Fisher [133]. Seasonal CH4 emissions indicated a negative relationship to clay content for Texan paddy soils [133].

1. [8] Aulakh, M.S., Wassmann, R., Reenberg, H., (2001): Methane emissions from rice fields quantification, mechanisms, role of management and mitigation options. − Advances in Agronomy 70, 193-260.

2. [72] Jackel, U., Schnell, S., Conrad, R., (2001): Effects of moisture, texture and aggregate size of paddy soil on production and consumption of CH4. − Soil Biology and Biochemistry 33, 965-971.

3. [104] Masscheleyn P.H., Delaune, R.D., Patrick, W.H., (1993): Methane and nitrous oxide emission from laboratory measurements of rice soil suspension. Effect of soil oxidation - reduction status. − Chemosphere 26, 251-260.

4. [121] Parashar, D.C., Rai, J, Gupta, P.K., Singh, N., (1991): Parameter affecting methane emission from paddy fields. − Indian Journal of Radio and Space Physics 20, 12-17.

5. [133] Sass, R.L, Fisher Jr, F.M., (1994): CH4 emission from paddy fields in the United States gulf coast area. In: Minami, C.K., Mosier, A., Sass, R.L, (eds.) CH4 and N2O: Global Emissions and Controls from Rice Fields and other Agricultural and Industrial Sources. NIAES Series 2, Tsukuba, Japan. pp. 65- 77.

6. [152] Wang, Z.P., Delaune, R.D., Masscheleyn, P.B., Patrick Jr., W.H., (1993): Soil redox and pH effects on methane production in a flooded rice soils. − Soil Science Society of American Journal 57, 382-385.

7. [161] Yagi, K., Minami, K., (1990): Effects of organic matter application on methane emission from some Japanese paddy fields. − Soil Science and Plant Nutrition 36, 599-610.




Factors affecting methane emission : Temperature

Methane emission is much more responsive to temperature. Temperature not only has an effect on methane production itself but also has an effect on the decomposition of

organic materials from which the methanogenic substrates are produced [27]. The influence of temperature on CH4 production rates has been reported for several

rice ecosystems [121, 145]. Wassman et al. [156] observed a faster development of CH4 production rate and

higher maximum value with increasing temperatures between 25 and 35°C. Hattori et al. [59] recorded optimum temperature of 40°C for CH4 production in

Japanies paddy fields due to dominance of methanogenic population at this temperature.

1. [27] Chin, K. J., Conrad, R., (1995): Intermediary metabolism in methanogenic paddy soils and the influence of temperature. − FEMS Microbiology and Ecology 18, 85-102.

2. [59] Hattori, C., Ueki, A., Seto, T., Ueki, K., (2001): Seasonal variations in temperature dependence of methane production in paddy soil. − Microbes and Environments 16, 227-233.

3. [121] Parashar, D.C., Rai, J, Gupta, P.K., Singh, N., (1991): Parameter affecting methane emission from paddy fields. − Indian Journal of Radio and Space Physics 20, 12-17.

4. [145] Thurlow, M., Karda, K.I., Tsurula, H., Minami, K, (1995): Methane uptake by unflooded paddy soils: The influence of soil temperature and atmospheric methane concentration. − Soil Science and Plant Nutrition 41, 371-375.

5. [156] Wassmann, R., Neue, H.D., Bueno, C., Latin, R.S., Alberto, MCR, Buendia, L.V., Bronson, K., Papen, H., Rennenberg, H., (1998): Methane production capacities of different rice soils derived from inherent and exogenous substrates. − Plant and Soil 203, 227-237.





Growth period and crop phenology Wassmann et al. [154] recorded lower CH4 fluxes in the early growth period of rice plant, which increased gradually during mid to late season and dropped to very low

level before or after harvest. Jermsawatdipong et al. [73] found that more than 50% of CH4 was emitted in the first half of the growth period in Thailand rice fields, while CH4

emissions in Japanese rice fields occurred mainly in the second-half of the growth period [81]. Jermsawatdipong et al. [73] argued that the high temperatures from the beginning of rice growth in

the tropics caused the main decomposition stage of soil and applied organic materials to shift to early growth stage which resulted in active CH4 production from the very beginning of rice

growth. Seiler [138] observed maximum CH4 emission at the end of heading and flowering stage off rice plants in Spain.

Flowering period is generally considered as the peak period for methane emission. The peak emission value remains for a period of 10-15 days in the crop duration of 90- 100 days. According to Holzapfel-Pschorn et al. [62] this period emits 90% of the total, methane during the whole crop season, because the biomass of rice crop increases gradually, reaching the maximum

weight by flowering. Up to 50 % of the total methane emission from rice fields can be due to root exudation [35]. Methane emission decreases after flowering because the rate of photosynthesis

declines after the commencement of grain development and hence the supply of available assimilates for methane production decreases [142].

1. [35] Dannenberg, S. Conrad, R., (1999): Effect of rice plant on methane production and rhizospheric metabolism in paddy soil. − Biogeochemistry 45, 53-71.

2. [62] Holzapfel-Pschorn, A., Conrad, R., Seiler, W., (1986): Production, oxidation and emission of methane in rice paddies. − FEMS Microbiology Ecology 31, 149-158.

3. [73] Jermasawatdipong, P., Murase, I, Prabuddham, P., Hasathon, Y., Khomthong, N., Naklang, K., Watanabe, A., Haaraguchi, H., Kimura, K., (1994): Methane emission from plots with dillerenes in fertilizer application in Thai paddy fields. − Soil Science and Plant Nutrition 40, 63-71.

4. [81] Kimura, M., Miura, Y., Watanabe, A, Katoh, T., Haraguehi, H., (1991): Methane emission from paddy field. (I) effect of fertilization, growth stage and midsummer drainage: pot experiment. − Environmental Science 14, 265-271.

5. [138] Seiler, W., Holzapfel-Pschorn, A, Conrad, R., Scharffe, D., (1984): Methane emission from rice paddies. − Journal of Atmospheric Chemistry 1, 241-268.

6. [142] Sinha, S.K, (1995): Global methane emission from rice paddies: Excellent methodology but poor extrapolation. − Current Science 68, 643-646.

7. [154] Wassmann, R., Lantin, R.S., Neu, H.D., Buendia, LV., Corton, T.M., Lu, Y., (2000): Characterization of methane emissions from rice fields in Asia. III Mitigation options and future research needs. − Nutrient Cycling in Agroecosystems 58, 23-36.





Rice cultivars, organic manures and crop residues

Rice cultivars have received high research priority because high yielding rice cultivars with low CH4 emission rates can be easily extended to farmer's fields without any

additional input and management practices [151].

Wang et. al. [153] argued that, cultivars influence the CH4 emission by providing the soil with root exudates, decaying root tissues and leaf littre while Aulakh et al. [7]

found significant variations in methane transport capacity of different rice cultivars.

In Korean rice cultivars, the CH4 flux among the rice varieties ranged from 36.9 g CH4 m-2 to 76.0 g CH4 m-2 [141].

The amendment of organic matter (cattle manure, pig manure, chicken manure, etc.) to a flooded rice field, increases CH4, production. It reduces the soil Eh and provides

carbon to methanogens. Organic materials influence the CH4 formation through change in qualitative and quantitative properties of soil.

1. [7] Aulakh, M.S., Bodenbender, J., Wassmann, R., Reenberg, H., (2000): Methane transport capacity of rice plants. II. Variations among different rice cultivars and relationship with morphological characteristics. − Nutrient Cycling in Agroecosystems. 58, 367-375.

2. [141] Shin, Y.K, Yun, S.H., (2000): Varietal differences in methane emission from Korean rice cultivars. − Nutrient Cycling in Agroecosystems. 58, 315-319.

3. [151] Wang, B., Adachi, K., (2000): Differences among rice cultivars in root exudation, methane oxidation and population of methanogenic and methanotrophic bacteria in relation to methane emission. − Nutrient Cycling in Agroecosystems 58, 349-356.

4. [153] Wang, Z.P., Zeng, D. Patrick Jr. W.H., (1997): Characteristics of CH4 oxidation in a flooded rice profile. − Nutrient Cycling in Agroecosystems, 49, 97-103.




Factors affecting methane emission : Fertilizers

Numerous studies have revealed the impact of chemical fertilizers on CH4 emissions [3, 136, 139]. The effect of fertilizers on CH4 emission depends on rate, type and mode of applications. Urea application enhances CH4 fluxes over the growth season possibly by increasing soil pH following urea hydrolysis and the drop in redox potential, which

stimulates methanogenic activities [152]. Lindau [95] reported decrease in CH4 emission rate with ammonium nitrate application

due to competitive inhibition of nitrate reduction in favour of methane production. Under field conditions, the application of sulphate based fertilizers such as (NH4)2

SO4 and CaSO4 have reduced CH4 emission [24] and application of K2HPO4 enhances the CH4 emission [4].

1. [3] Adhya, T.K., Bharati, K., Mohanty, S.R., Ramakrishnan, B., Rao, V.R., Sethunathan, N., Wassmann, R., (2000): Methane emission from rice fields at Cuttack, India. − Nutrient Cycling in Agroecosystems 58, 95-105.

2. [4] Adhya, T.K., Pattnaik, P., Satpathy, S.N., Kumaraswamy S., Sethunathan, N, (1997): Influence of phosphorus application on methane emission and production in flooded paddy soils. − Soil Biology and Biochemistry 30, 177-181.

3. [24] Cai, Z.C., Xing, H., Yan, X., Xu, H., Tsuruta, H., K. Yagi, K., Minami, K., (1997): Methane and nitrous oxide emissions from rice paddy fields as affected by nitrogen fertilizers and water management. − Plant and Soil. 196, 7-14.

4. [136] Schutz, H., Holzaptel-Pschorn, A., Conrad, R., Rennenberg, H., Seiler, W., (1989): A three-year continuous record on the influence of day time season and fertilizer treatment on methane emission rates from an Italian rice paddy. − Journal of Geophysics Research 94, 16405-16416.

5. [139] Sethunathan, N, Kumaraswamy, S., Rath, AK, Ramakrishnan, B., Satpathy, S.N., Adhya T.K, Rao, V.R, (2000): Methane production, oxidation and emission from Indian rice soils. − Nutrient Cycle in Agroecosystems 58, 377-388.

6. [152] Wang, Z.P., Delaune, R.D., Masscheleyn, P.B., Patrick Jr., W.H., (1993): Soil redox and pH effects on methane production in a flooded rice soils. − Soil Science Society of American Journal 57, 382-385.




Methane oxidation : Methanotrophs

Methanotrophs (gram negative, aerobic bacteria belonging to the subset of a physiological group of bacteria known as methylotrophs) oxidize CH4 via methanemonooxygenase (MMO) enzyme. These bacteria are classified into three groups: Type-I, Type-II and Type-X. According to Conrad

[29], all the methanotrophs that have so far been isolated and described belong to the Proteobacteria, of the γ sub-class (Type I) or sub-class (Type II). The Type I group is represented ∝by the Methylomonas, Methylocaldum, Methylosphaera, Methylomicrobium and Methylobacter.

The Type-II comprises Methylosystis and Methylosinus. The members of the genus Methylococcus occupy an intermediate position and have been kept in to a separate group Type-X [58]. By using molecular ecology techniques, it has become clear that methanotrophs are ubiquitous in nature

and well adopted to high or low temperature, pH and salanity [148]. Henckel et al. [61] found that both Type-I and Type-II methanotrophs were stimulated in rice fields with unsaturated water

content. Bodelier et al. [18] reported that Type II methanotrophs dominated in unplanted, unfertilized soils

and the presence of rice plant was an essential factor for Type-I methanotrophs to proliferate. Methanotrophic bacteria are present in the aerobic soil layer, rhizosphere [42, 56, 75] and on the roots and stem bases of flooded rice plants [158]. The physiology, biochemistry and ecology of

methanotrophic bacteria have been recently reviewed [29, 41].

1. [29] Conrad, R., (1999): Soil microorganisms oxidizing atmospheric trace gases (CH4, CO, H2, NO). − Indian Journal of Microbiology 39, 193-203. [41] Dubey, S.K., Kashyap, A.K., Singh, J.S., (1996): Methanotrophie bacteria, methanotrophy and methane oxidation in soil and rhizosphere. − Tropical Ecology 37, 167-182.

2. [42] Dubey, S.K., Singh, J.S., (2000): Spatio–temporal variation and effect of urea fertilization on methanotrophs in a tropical dryland rice field. − Soil Biology and Biochemistry 32, 521-525.

3. [56] Gilbert, B., Frenzel, P., (1998): Rice roots and CH4 oxidation: the activity of bacteria, their distribution and the microenvironment. − Soil Biology and Biochemistry 30, 1903-1916.

4. [58] Hanson, R.S., Hanson, T.E., (1996): Methanotrophic bacteria. − Microbiology Review 62, 439-471. 5. [61] Henckel, T., Friedrich, M., Conrad, R., (1999): Molecular analysis of the methane-oxidizing microbial

community in rice field soil by targeting the genes of the 16S rRNA, particulate methane monooxygenase, and methanol dehydrogenase. − Applied and Environmental Microbiology 65, 1980-1990.

6. [75] Joulian C., Escoffier, S., Lemer, J, Neue, H.U., Roger, P.A. (1997): Population and potential activities of methanogens and methanotrophs in rice fields: Relation with soil properties. − European Journal of Soil Biology 33, 105-166.

7. [148] Trotsenko, Y.A., Khmelenina, V.N., (2002): Biology of extremophilic and extremotolerant methanotrophs. − Archives of Microbiology 177, 123-131.

8. [158] Watanabe, D., Hashmoto, T., Shimoyama, A., (1997): Methane oxidizing activities and methanotrophic population associated with wetland rice plants. − Biology and Fertility of Soils 24, 261-265.




Kinetics of methane oxidation The apparent half saturation constant (Km), and maximum oxidation rate (Vmax) of

CH4 oxidation are characteristic parameters which determine the ability of methanotrophs to grow on atmospheric methane. The CH4 concentration is a key determinant of Km(app) but this could be mediated through the MMO enzyme, the methanotrophs or the bacterial community as a whole

[47]. Recent studies revealed that there are two types of CH4 oxidizers present in the soil. One population, having a high affinity for CH4, typically has Km in the range 1000 nM CH4, and the other population, having a high affinity for CH4, has Km in the range of 30 to 60 nM CH4 [13].

These methanotrophs typically occur in upland soils that consume atmospheric methane [11], but can also be activated in the paddy soils [10]. However, the atmospheric CH4 oxidation has hardly

been studied in irrigated rice fields soil. Henckel and Conrad [61] found that moisturised air dried paddy soil does not oxidize

CH4 at atmospheric concentration unless it has been pre-incubated under elevated CH4 concentration. A decreasing trend of Km and Vmax with decreasing CH4 uptake rate along the soil

depth was reported by Wang et al. [153]. Dubey et al. [44, 45] have found that Km and Vmax values for CH4 oxidation in dryland/flooded rice fields decreased from rhizosphere to bulk to bare soil in confirmity with the decreasing CH4 oxidation activity. Variations in kinetic parameters (Km and Vmax) for different rice fields are

shown in Table 5. Bender and Conrad [11] have stated that different Km values may indicate the existence of different types of methanotrophs in soils. According to Conrad [29] type II

methanotrophs, which are frequently found in soils, are able to adopt to CH4 concentration by changing their Km. This difference could be due to differences in species composition and/or due

to conditioning of methanotrophs under different soil microhabitats. According to King [82] all the methanotrophs that have been isolated from soil thus far do not possess the required kinetic

properties. These methanotrophs have an ecological niche that is characterized not by atmospheric CH4 oxidation but by oxidation of relatively high CH4 concentration that emerge in the proximity

of CH4 production sites i.e. wetlands [128].

1. [10] Bender, M., Conrad, R., (1992): Kinetics of CH4 oxidation in oxic soils exposed to ambient air or high CH4 mixing ratios. − FEMS Microbiology Ecology 101, 261-270.

2. [29] Conrad, R., (1999): Soil microorganisms oxidizing atmospheric trace gases (CH4, CO, H2, NO). − Indian Journal of Microbiology 39, 193-203.

3. [61] Henckel, T., Friedrich, M., Conrad, R., (1999): Molecular analysis of the methane-oxidizing microbial community in rice field soil by targeting the genes of the 16S rRNA, particulate methane monooxygenase, and methanol dehydrogenase. − Applied and Environmental Microbiology 65, 1980-1990.

4. [128] Reeburgh, W.S., Whjalen, S.C., Alperin, M.J., (1993): The role of methylotrophy in the global methane budget In: Murrell, J.C., Kelly, D.P., (eds.), Microbial growth on CI compound. Intercept Ltd., Andover, D.K. pp. 1-14.

5. [153] Wang, Z.P., Zeng, D. Patrick Jr. W.H., (1997): Characteristics of CH4 oxidation in a flooded rice profile. − Nutrient Cycling in Agroecosystems, 49, 97-103.




Factors affecting methane oxidation Oxygen availability

Oxygen availability depends upon soil porosity. As the porosity increases, a decreased volume of water is distributed in pore volume, decreasing the water film thickness. This increases the rate of

substrate (CH4) delivery to the methanotrophs for oxidation [102]. Methanotrophs in the rice rhizosphere do not have to compete for methane with microbial or chemical compounds, although

there is a strong sink of methane by methane transport. However, intensive competition for oxygen occurs. The available values for K(app) for O2 and CH4 indicated that uptake of both

substrates is saturated at concentrations of ≥ 10 µM [82].

Nitrogenous compounds and soil pH Inorganic N influences CH4 oxidation due to shifts in the population structure and the kinetics of methanotrophs [45]. This may affect the threshold value for CH4 oxidation [82]. NO3- -N fertilization did not affect the CH4 consumption but NH4+N fertilization

completely ceased CH4 oxidation [66]. Nitrite was found to inhibit CH4 oxidation in the cultures of Methylomonas albus BG8 and M. trichosperium OB3b [83]. Recently it was shown that

methane oxidation is stimulated by increased nitrogen availability due to unquantified nitrogen limitation of methanotrophs [18]. However, the most solidly substantiated explanation for

ammonium inhibition of methane oxidation is competitive inhibition at the enzyme level. This occurs because, at the molecular scale, methane and ammonium are similar in size and structure [135]. As a result, the enzyme MMO can bind to ammonium ion and react with it. Because the

possibility of competitive inhibition is fundamental to the biochemistry of methane oxidation, it was generally thought that inhibition should occur in paddy fields as well as in upland systems

[135].

1. [18] Bodelier, P.LE., Ros1ev, P., Henckel, T., Frenzel, P., (2000): Stimulation by ammonium based fertilizers of methane oxidation in soil around rice roots. − Nature 403, 421-424.

2. [45] Dubey, S.K., Sinha, A.S.K., Singh, J.S., (2002): Differential inhibition of CH4 oxidation in bare, bulk and rhizosphere soils of dryland rice field by nitrogen fertilizers. − Basic and Applied Ecology 3, 347-355.

3. [82] King, G.M., (1992): Ecological aspect of methane oxidation, a key determinant of global methane dynamics In: (Mashall, K.c., ed.), Advances in Microbial Ecology. Plenum, New York. pp. 431-468.

4. [83] King, G.M., Schnell S., (1994): Effect of increasing atmospheric methane concentration on ammonium inhibition of soil methane consumption. − Nature 370, 282-284.

5. [102] Mancinelli, R.L., (1995): The regulation of methane oxidation in soil. − Annual Review of Microbiology 49, 581-605.

6. [135] Schimel, J., (2000): Rice, microbes and methane. − Nature 403, 375-377.


Development of a dynamic transfer model of 14C from the atmosphere to rice plants

Takashi Tani , Ryuji Arai , Susumu Nozoe, Yasuhiro Tako , Tomoyuki Takahashi , Yuji Nakamura

Journal of Environmental Radioactivity. Volume 102, Issue 4, April 2011, Pages 340–347

A dynamic compartment model was investigated to describe 14C accumulation in rice plants exposed to atmospheric 14C with temporally changing concentrations. In the model, rice plants were regarded to consist of three compartments: the ear and the

mobile and immobile carbon pools of the shoot. Photosynthetically fixed carbon moves into the ear and the mobile carbon pool, and

these two compartments release a part of this carbon into the atmosphere by respiration. Carbon accumulated in the mobile carbon pool is redistributed to the ear, while carbon

transferred into the immobile carbon pool from the mobile one is accumulated there until harvest.

The model was examined by cultivation experiments using the stable isotope, 13C, in which the ratios of carbon photosynthetically fixed at nine times during plant growth to

the total carbon at the time of harvest were determined. The model estimates of the ratios were in relatively good agreement with the

experimental observations, which implies that the newly developed compartment model is applicable to estimate properly the radiation dose to the neighboring

population due to an accidental release of 14C from nuclear facilities.

Diunduh dari sumber: http://www.sciencedirect.com/science/article/pii/S0265931X11000191 ...…….. 12/1/2013

http://www.sciencedirect.com/science/journal/0265931X/102/4




Conceptual diagram of the developed dynamic compartment model. The dotted rectangle encloses the compartments for the shoot part of rice plant for a unified single compartment model. Photosynthesis here means the allocation of carbon fixed through

shoot photosynthesis to each of the rice plant parts within a day of photosynthetic carbon fixation. The root compartment is not included in the model (see text for

details).






Temporal changes in carbon mass of ear and shoot. Each point indicates the mean value and SD of four pots. The values of the mean and SD were obtained after dividing carbon masses of these parts per pot by the number of plants per pot (two plants).






Comparison of the observed RE(t) (ear) and RS(t) (shoot) with the ratio of daily net carbon gain in ear (a) and shoot (b) to the total carbon mass of each plant part at the time of harvest (NE(t)/ME(tH)

or NS(t)/MS(tH)). Each point indicates the observed value (mean ± SD, n = 4). The arrow in both graphs indicates the time of heading (74th DAS).






. The observed and model estimates of RE(t) (ear) and RS(t) (shoot). Each point indicates the observed value (mean ± SD, n = 4). The solid and broken lines indicate the model estimates

calculated by the three-compartment and two-compartment models, respectively. Values of model parameters kEA, kMA, kMI(t), and r are listed in Table 4. The arrow in both graphs indicates the time

of heading (74th DAS).



http://www.sciencedirect.com/science/article/pii/S0265931X11000191

Ecosystem services by paddy fields as substitutes of natural wetlands in Japan

Yosihiro NatuharaEcological Engineering. Available online 22 May 2012

This paper reviews research on the ecosystem services or multifunctionality of paddy rice cultivation in Japan, focusing on biodiversity as a basis for ecosystem services, with the aim of describing the current status and impact of the subject and exploring

options for sustainable practices. Ecosystem services provided by paddy fields include; groundwater recharge, production of non-rice foods, flood control, soil erosion and

landslide prevention, climate-change mitigation, water purification, culture and landscape, and support of ecosystems and biodiversity. Among these services, the value

of services that regulate ecosystem functions was estimated to be US$ 72.8 billion in Japan. More than 5000 species have been recorded in paddy fields and the surrounding

environment. Because paddy fields are artificially disturbed by water level management, plowing, and harvest, most species move between paddy fields and the

surrounding environment. The linkage between paddy fields and the associated environment plays an important role in biodiversity. Two changes that have affected the ecosystem of paddy fields are modernization and abandonment of farming. Satoyama, a traditional socio-ecological production landscape, which provided a functional linkage

between paddy fields and the associated environment has lost its functions. Biodiversity-conscious rice farming has been promoted by collaborations among

farmers, consumers and governments. Biodiversity certification programs are successful examples of biodiversity-conscious framing. In these programs incentives include direct payments and/or premium prices paid by consumers, as well as farmers

willingness to improve the safety of food and environment.

Diunduh dari sumber: http://www.sciencedirect.com/science/article/pii/S092585741200153X ...…….. 12/1/2013

http://www.sciencedirect.com/science/article/pii/S092585741200153X





Landscape of paddy fields and movement of species.







Water management of paddy field and life cycle of species. Timing of flooding and drainage affects survival of aquatic species. O. albistylum is a multivoltine.







Land consolidation and drainage improvement. Conversion to fields equipped with deeper ditches for rapid draining has almost eliminated wet winter paddy fields. The gap between paddy and drainage ditch prevents fish from

migrating to the paddy.







Impacts of changes in paddy field on fish. (Modified from Katano, 2000).






Provision of ecosystem services by paddy fields as surrogates of natural wetlands

Yosihiro Natuhara Graduate School of Environmental Studies, Nagoya University, Nagoya, Japan

Ecosystem services provided by paddy fields include the following; groundwater recharge, production of non-rice foods, flood control, soil

erosion and landslide prevention, climate-change mitigation, water purification, culture and landscape, and support of ecosystems and

biodiversity.

Rice-fish farming is practiced in many countries in the world, particularly in Asia (Halwart and Gupta 2004).

Although it is not a major system in Japan, carp and crucian carp are produced in paddy fields. Nigorobuna carp, an endemic species from Lake Biwa is important resource to

make local fermented sushi, “Funazushi”.

A large female fish is sold fo 5,000 yen. The yield of the Nigorobuna fishery has been decreased through degradation of spawning sites along the lakeshore.

This fish also spawns in paddy fields during the flooding period. However modernization of irrigation system now prevents the fish from running into the paddy

from river. Shiga Prefecture implemented a project for direct environmental payments of 3,500 yen per 1,000 square meters to groups that engage in water management and maintenance

of the fishways required for fish to run up the river to spawn.

1. Halwart, M. and Gupta, M.V. (2004) Culture of Fish in Rice Fields. FAO and The WorldFish Center, Rome.2008

Diunduh dari sumber: http://on-cue.co.nz/dipcon/Wetland%20ecosystem%20services%20symposium/Natuhara.pdf...…….. 12/1/2013



Paddy is an important part of water recycling system in the basin. The recharge in the paddy field in the middle Shira River Basin was estimated to be about half of the intake water from the Shira River in

Kumamoto area (Tanaka et al. 2010). The reduction of the cropping area led to a reduction in groundwater recharge from 3.0 x 108 m3 (267 km2) in 1970's to 1.5 x 108 m3 in 2008. This is about 25% of the annual recharge of this area in 2007

(6.00 x 108 m3/year). Ground water levels were 0.5-1 m higher and the ground water

storage 20% larger during the irrigation period in an alluvial plain (Anan et al. 2006).

1. Anan, M., Yuge, K., Nakano, Y., Saptomo, S. and Haraguchi, T. (2007) Quantification of the effect of rice paddy area changes on recharging groundwater. Paddy Water Environ. 5, 41-47

2. Tanaka, K., Funakoshi, Y., Hokamura, T. and Yamada, F. (2010) The role of paddy rice in recharging urban groundwater in the Shira River Basin. Paddy Water Environ. 8, 217-226




Paddy fields can act as flood control basins. For example, maintaining levees at 25 cm height can restore this function in the abandoned paddy

(3,800 km2), providing a reservoir of 4,900 m3 (http://www.jiid.or.jp/works/jishu/pdf/ 01.pdf).

Ichikawa City pays the owners of lowland paddy fields to conserve the fields for flood control. The Paddy Field Dam project is tested in Niigata Prefecture

(Yoshikawa et al. 2010). Runoff from paddy is regulated by runoff control devices when the water inflow from the paddy field to the drainage device exceeds the outflow

capacity. The result of simulation studies shows the discharge in the main channel could be decreased by 26% using these practices. Prevention of soil

erosion from paddy fields is estimated to be 0.83 t/ha/y in steep land with slopes greater than 1:20 in Okayama Prefecture. Several authors have

reported that paddy fields remove nitrogen from water (Maruyama et al. 2008).

Nitrogen removal depends on the concentration in the inflow water, with Tabuchi (1998) reporting net losses when the inflow rose to 2–3 mg N/L or

greater.

1. Maruyama, T. Hashimoto, I., Murashima, K. and Takimoto H. (2008) Evaluation of N and P mass balance in paddy rice culture along Kahokugata Lake, Japan, to assess potential lake pollution. Paddy Water Environ. 6, 355-362

2. Tabuchi, T. (1998) Science for clean water. Chapter V: Water cycle in watershed (Ed. Water quality environment committee). Jpn. Soc. Irrigat. Drain. Reclamat. Eng. 100–107, 115–118 (in Japanese)

3. Yoshikawa, N., Nagao, N. and Misawa, S. (2010) Evaluation of the flood mitigation effect of a Paddy Field Dam project. Agricultural Water Management 97, 259-270




Paddy fields have provided a subject for Japanese culture. Asahi Shimbun Newspaper Company selected the Top 100 Japanese Rural

Landscapes among 3,024 nominated sites by the public survey in 2008.

Keywords that appeared frequently in the nominations showed that Furusato (Home) was associated with paddy field (Iwata et al. 2011).

Terrace paddy, in particular, attracts people. For example an art festival held in the terrace paddy of Echigo-

tsumari drew 37,000 visitors in 2010.

1. Iwata, Y., Fukamachi, K. and Morimoto, Y. (2011) Public perception of the cultural value of Satoyama landscape types in Japan. Landscape Ecol. Eng. (DOI 10.1007/s11355-010-0128-x)




More than 5,000 species are found in paddy fields and associated environments such as irrigation ditch. Many of the species, such as red dragonfly and killifish are familiar in daily life. However the number of

species and abundance has decreased due to three causes: land consolidation and modernization of irrigation system, abandonment of cultivation, and use of agri-chemicals. Several species have become endangered. Some measures are used for conservation of biodiversity in paddy fields. Symbolic species are used as a target for biodiversity-conscious agriculture. Oriental white stork and crested ibis were extinct in the wild. Both species were breed in

captivity in Toyooka City and Sado City. These cities launched release programs and promoted agriculture-oriented projects to restore their habitats.

Agri-environment schemes and agriculture and biodiversity certification accompany these programs

(http://www.biodic.go.jp/biodiversity/shiraberu/policy/pes/en/index.html). Toyooka City encouraged farmers to apply “white stork-friendly farming

methods” in which farmers are required to reduce pesticide use by 75 percent, if not entirely, and to flood their paddies deeper and for a longer

period of time than for conventional farming methods. This allows tadpoles time to develop into frogs, etc. Toyooka City pays farmers who adopt this

method and certifies the flying-stork brand. Rice with this brand can be sold at higher price than ordinary rice. These efforts encourage eco-tourism, with

about 400,000 visitors each year visiting the Eco-Museum Center for Oriental White Stork in Toyooka City.


On-farm strategies for reducing water input in irrigated rice; case studies in the Philippines

D.F. Tabbal , B.A.M. Bouman , S.I. Bhuiyan , E.B. Sibayan , M.A. SattarAgricultural Water Management. Volume 56, Issue 2, 30 July 2002, Pages 93–112

Traditional transplanted rice with continuous standing water in Asia has relatively high water inputs. Because of increasing water scarcity, there is a need to develop alternative

systems that require less water. This paper reports results of on-farm experiments in the Philippines to reduce water

input by water-saving irrigation techniques and alternative crop establishment methods, such as wet and dry seeding. With continuous standing water, direct wet-seeded rice yielded higher than traditional transplanted rice by 3–17%, required 19% less water

during the crop growth period and increased water productivity by 25–48%.

Direct dry-seeded rice yielded the same as transplanted and wet-seeded rice, but can make more effective use of early season rainfall in the wet season and save irrigation

water for the subsequent dry season.

Direct seeding can further reduce water input by shortening the land preparation period. In transplanted and wet-seeded rice, keeping the soil continuously around saturation

reduced yields on average by 5% and water inputs by 35% and increased water productivity by 45% compared with flooded conditions. Intermittent irrigation further

reduced water inputs but at the expense of increased yield loss. Under water-saving irrigation, wet-seeded rice out-yielded transplanted rice by 6–36%

and was a suitable establishment method to save water and retain high yields.

Groundwater depth greatly affected water use and the possibilities of saving water. With shallow groundwater tables of 10–20 cm depth, irrigation water requirements and

potential water savings were low but yield reductions were relatively small.

The introduction of water-saving technologies at the field level can have implications for the hydrology and water use at larger spatial scale levels.


http://www.sciencedirect.com/science/journal/03783774/56/2






Schematic presentation of rice growth under four establishment systems: transplanting with seedbed in main field (A), transplanting with separate seedbed (B), direct wet

seeding (C) and direct dry seeding (D).








Components of the water balance of a flooded, puddled rice field.








Graphical presentation of the water-saving irrigation treatments of experiment 1 (see text and Table 1 for explanation of the eight water treatments).







. A coupled soil water and nitrogen balance model for flooded rice fields in India

V.M. Chowdary , N.H. Rao , P.B.S. SarmaAgriculture, Ecosystems & Environment. Volume 103, Issue 3, August 2004, Pages 425–441

Quantification of nitrate losses is important for devising measures to ensure sustainability of soil fertility and groundwater resources and for the development of crop nutrient management protocols. Hence, in the present study a simple model for assessing concentration of nitrate in water percolating out of the flooded rice (Oryza

Sativa) fields is presented. The model considers all the important nitrogen (N) transformation processes that take

place in flooded rice fields such as urea hydrolysis, volatilization, nitrification, mineralization, immobilization, denitrification, crop uptake and leaching. It is based on

coupling of soil water and N-balance models. The coupled model also accounts for weather, and timings and amounts of water and fertilizer applications. All the N-

transformations except plant uptake and leaching are considered to follow first-order kinetics. A heuristic procedure is developed for selection of the rate constants of the

transformation processes for different soil and environmental conditions.

The model is evaluated by comparing simulation results with published data of three field experiments conducted at two locations namely G.B. Pant University Farm,

Pantnagar, UP and IARI Research Farm, New Delhi of India, respectively.

The simulation results show that urea hydrolysis is completed within 7 days of fertilizer application. It was also observed that the volatilization loss of N varies from 25 to 33% of the applied fertilizer and 75% of the total volatilization loss occurs within 7 days of urea application. The modeled leaching losses from the field experiments varied from

20 to 30% of the applied N.

The N-uptake by the crop increased immediately after the application of fertilizer and decreased at 60 days after transplanting. The model is sufficiently general to be used in

a wide range of conditions for quantification of nutrient losses by leaching and developing water and fertilizer management strategies for rice in irrigated areas.

Diunduh dari sumber:.. http://www.sciencedirect.com/science/article/pii/S016788090300433X.…….. 13/1/2013





Schematic representation of the N-transformations in flooded rice field.






Zoning of ideal paddy field for N-balance studies.






Schematic representation of nitrogen balance model.






. Schematic representation of simulated nitrogen transformation processes in rice field (split application 60+30+30 kg N ha−1), Pantnagar, Uttar Pradesh,

India. (a) Urea hydrolysis, (b) volatilization, (c) nitrogen uptake and (d) nitrate leaching.






Nitrogen uptake in rice at Pantnagar, Uttar Pradesh, India. (a) Basal application (80 kg N ha−1) and (b) split application (40+20+20 kg N ha−1).




Nutrient Management for Improving Lowland Rice Productivity and Sustainability

N.K Fageria , N.A Slaton , V.C BaligarAdvances in Agronomy. Volume 80, 2003, Pages 63–152

Rice (Oryza sativa L.) is an important food crop for a large proportion of the world's population. Total rice production will need to increase to feed an

increasing world population. Rice is produced under both upland and lowland ecosystems with about 76% of the global rice produced from

irrigated-lowland rice systems. The anaerobic soil environment created by flood-irrigation of lowland rice creates a unique and challenging environment for the efficient management

of soil and fertilizer nutrients. Supplying essential nutrients in adequate rates, sources, application methods,

and application times are important factors that influence the productivity and sustainability of rice. This review emphasizes our current, research-based knowledge of N, P, K, Ca, Mg, S, B, Fe, Mn, and Zn management in regards to the efficiency and sustainability of lowland rice production and identifies

where additional research is needed to bridge information gaps.

Our goal is to provide a comprehensive review describing the nutritional problems, nutrient use efficiencies, and the production strategies used for

efficient nutrient use and production of lowland rice.

While the soils, climatic environments, cultivars, and degree of mechanization may vary considerably among the rice producing regions of

the world, the basic principles governing efficient nutrient use by flood-irrigated rice are relatively constant.

A summation of best management practices should help scientists develop practical, integrated recommendations that improve nutrient use efficiency in

lowland rice production systems.

Diunduh dari sumber:.. http://www.sciencedirect.com/science/article/pii/S0065211303800032.…….. 13/1/2013

http://www.sciencedirect.com/science/bookseries/00652113/80/supp/C




An illustration of the various N chemical forms, transformations and behavior in the flooded soil environment in which rice is grown. Nitrogen sources are in blocks, N chemical forms are in circles and the mechanisms

responsible for the various N transformations or behavior are located on the arrowed lines. (Reprinted with permission of R. J. Norman, C. E. Wilson, Jr.

and N. A. Slaton).






. Influence of N fertilizer rate on panicle length, panicle number per square meter, spikelet sterility, and 1000-grain weight of lowand rice. Values are the

average of 3 years of field experimentation. (Reproduced with permission from Fageria, N. K. and Baligar, V. C. 2001. Lowland rice response to nitrogen fertilization. Commun. Soil Sci. Plant Anal. 32: 1405–1429.

(Copyright Marcel Dekker, New York).).






. Response of flooded lowland rice to N fertilizer rate on a Brazilian Inceptisol. (Reproduced with permission from Fageria, N. K. and Baligar, V. C. 2001. Lowland rice response to nitrogen fertilization. Commun. Soil Sci.

Plant Anal. 32: 1405–1429. (Copyright Marcel Dekker, New York).).






Phosphorus concentration in rice plant shoots at different growth stages in Brazil and Arkansas, USA.




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