Evaluation of Ammonium Sulfate Effect

on Rice Production in Madagascar

(2012-2013)

October 27, 2013

Project for Rice Productivity Improvement in the Central Highland of Madagascar

(PAPRiz: Projet d'Amélioration de la Productivité Rizicole sur les Hautes Terres

Centrales) in collaboration with FOFIFA, FIFAMANOR and CFAMA

Content

Abstract 1

Introduction 1

Materials and Methods 1

Results 9

Discussion 15

Acknowledgments 20

Notes 20

References 20

Abbreviations

AS Ammonium sulfate

CALA Complexe Agricoles du Lac Alaotra, FOFIFA

CFAMA Centre de Formation et d'Application du Machinisme Agricole

DAT days after transplanting

FIFAMANOR Fiompiana Fambolena Malagasy Norveziana (Centre de Recherche

Malgacho-Norvegien pour le développement de l'elevage et de

l'agricullture)

FOFIFA Foibem-pirenena momba ny Fikarohana ampiharina amin ny

Fampandrosoana ny Ambanivohitra (Centre National de la Recherche

Appliquée au Développement Rural)

GY grain yield in each unit area

NUE nitrogen use (absorption) efficiency

OM organic matter

PAPRiz Projet d'Amélioration de la Productivité Rizicole sur les Hautes Terres

Centrales

PC Périmètre de Colonisation

YC yield component

1

Draft 2 (2013/10/27)

Evaluation of Ammonium Sulfate Effect on Rice Production in Madagascar

(2012-2013)

Project for Rice Productivity Improvement in the Central Highland of Madagascar (PAPRiz)

Abstract

Rice plants were grown with urea or ammonium sulfate (AS) combined with NPK compound

fertilizer in various agro-climatic zones of Madagascar. AS was effective in rice production as

urea was both in lowlands and uplands. Organic matter or dolomite incorporation hardly

influenced the AS effect on grain production. In a typical upland soil likely lacking in sulfur, AS

took advantage over urea of containing sulfur. Nitrogen use efficiency was frequently low,

probably owing to poor water control and prevailing deficiency of nutrients other than nitrogen

like phosphorus. To find a strict effect of AS, an experiment with a single source of phosphorus

and potassium fertilizers is essential.

Introduction

Cultural improvement certainly promotes crop production, but the improvement would not be

beyond a certain yield level. Crops hardly display their full potential nor attain abundant

production in infertile soils without nutrient input. Highly weathered soils widely spread in

Malagasy agricultural lands because of their geological background. The country has been

importing all chemical fertilizers as many developing countries have. Fortunately, she is now

favored with producing ammonium sulfate (AS) by herself.

AS is an effective nitrogenous source to crop production, and its effectiveness has been proved

in history of worldwide use. Besides, AS greatly contributes to better crop production in sulfur

deficient soils. In contract, it may cause acidity and sulfur excess problems in some specific

circumstances. General advantage and disadvantage of AS are described elsewhere (PAPRiz,

2012).

PAPRiz initiated a set of AS trials to evaluate AS effect on rice production in Madagascar in

2011 (PAPRiz, 2012). The present study in 2012-2013 was a follow-up trial of the experiment in

the last year with the similar fertilizer treatment. Three organizations as the same as in the

previous year collaborated with the experiment: FOFIFA, FIFAMANOR and CFAMA.

Materials and Methods

1. Experiment sites

Five experiment sites, Kianjasoa, Mahitsy, Ambohitsilaozana, Anosiboribory and Mimosa, were

the same as in the last trials and one site at Antsoantany was added as a typical upland field at

the central highland (Table 1 and Fig. 1). Agro-climatic zones of these sites covered middle-

west, central highland and Alaotra area.

2

Altitude of respective site is ca.750 m in Alaotra area, 910 m at Kianjasoa, 1,200 m at Mahitsy,

ca. 1,600 m at Mimosa and Antsoantany. In all those areas, rice is grown both in lowlands and

uplands during the main (rainy) season. During the off (dry to early rainy) season, lowland rice

and winter crops are grown respectively below and above ca. 1,000 m, when irrigation water is

available.

Table 1. Locations of the ammonium sulfate trials in three agro-climatic zones, two agro-ecologies (lowland and

upland) and two cropping (main and off) seasons (2012-2013)

Agro-climatic Location Altitude Agro-ecology Direction

zone (site) Lowland Upland Organization Person

(m) Main Off

Region season season

Middle west

Bongolava Kianjasoa (a) 910 * * * FOFIFA Kianjasoa Pierre Rasolofo

Central highland

Analamanga Mahitsy 1,200 * FOFIFA Antananarivo Joseph Randrianampy

Vakinankaratra Mimosa (b) 1,610 * FIFAMANOR Noroseheno Ralisoa

Antsoantany (c) 1,650 * ditto ditto

Lac Alaotra

Alaotra-Mangoro Ambohitsilaozana 780 * FOFIFA CALA Arsène Randrianantenaina

Anosiboribory (d) 750 * CFAMA Nénée Lalanekenarisoa T.

* Practiced.

a) Lowland at Ambalavao. Hydromorphic soil, being relatively poor in organic matter. Experiment plots and the field design

(sub-plots allocation) were the same both in main and off seasons. b) 5 km east of Andranomanelatra, Antsirabe II district.

Relatively flat plain on Oxisols (Ferralsols), yearly well applied with farmyard manure and dolomite, and planted with maize in

the previous off-season. c) Undulating fields (ca. ±50 m) on Oxisols, being one of representative farmers' fields in the central

highland. Applied with a certain quantity of organic matter. Planted with sweet potato in the previous off-season. d) Peaty

flood plain, located in PC23.

Fig.1 Locations of the

AS trials

3

2. Cropping season and agro-ecology

Planting seasons and agro-ecologies at each site were selected in accordance with natural

environment (topography, temperature, etc.) and irrigation facility availability. The experiment

was carried out both in the main and off seasons in 2012-2013. Note that the former is

appropriated for the cultural year of 2013 and the latter for that of 2012 in agricultural statistics,

although the off season rice in 2012 was frequently harvested in the early 2013.

Two agro-ecologies of rice culture were practices: lowlands and uplands. In this text, 'lowland' ,

or occasionally called as ‘wetland’, signifies a field where rice is grown under submerged

condition during most growth stages, and 'upland', or sometimes called as ‘dryland’, does a

free-drained field where rice is grown without submergence: the plant growth totally depends on

rainfall.

3. Fertilizer treatment

To verify an AS effect on rice production in the Malagasy condition, three types of fertilizer

treatments were set up: the standard design for comparing AS with urea in combination of

organic matter and dolomite treatments, a simple comparison of urea and AS in a large-scale

cultivation, and the treatment to find an effect of AS with timing and split-application. The

standard nutrient treatment was the same as in 2011-2012.

3-1. Standard treatment for comparing AS with urea

For lowland rice, NPK high-analysis compound fertilizer (N-P2O5-K2O = 11-22-16%) was

applied as a basal application and the effect of AS (21% N and 24% S) was compared with urea

(46% N) by applying as a top-dressing (Table 2). The treatment was combined with and without

organic matter (OM) application. The lowland treatment was adopted at Kianjasoa, Mahitsy and

Ambohitsilaozana in the main season and at Kianjasoa in the off season.

For upland rice, the standard set of nutrient treatments for lowland rice was combined with

dolomite (36% CaO and 16% MgO) treatment (Table 3). The standard treatment for upland rice

was adopted at Kianjasoa, Mimosa and Antsoantany.

Table 2. Standard fertilizer treatment in lowlands

Treat- OM Chemical fertilizer (kg/ha) Nutrient applied with chemical fertilizers

ment Basal Top dressing (N-P2O5-K2O-S kg/ha)

no. (ton application Basal Top-dressing Total

/ha) (NPK) Urea AS application (a)

T1 0 0 0 0 0 - 0 - 0 - 0 0 - 0 - 0 - 0 0 - 0 - 0 - 0

T2 0 200 83 0 22 - 44 - 32 - 0 38 - 0 - 0 - 43 60 - 44 - 32 - 0

T3 0 200 0 181 22 - 44 - 32 - 0 38 - 0 - 0 - 0 60 - 44 - 32 - 43

T4 5 0 0 0 0 - 0 - 0 - 0 0 - 0 - 0 - 0 0 - 0 - 0 - 0

T5 5 200 83 0 22 - 44 - 32 - 0 38 - 0 - 0 - 43 60 - 44 - 32 - 0

T6 5 200 0 181 22 - 44 - 32 - 0 38 - 0 - 0 - 0 60 - 44 - 32 - 43

OM: organic matter. Ingredient (N-P2O5-K2O-S %): 11-22-16-0 in NPK compound fertilizer

(NPK), 46-0-0-0 in urea, and 21-0-0-24 in ammonium sulfate (AS).

a) At Kianjasoa and Ambohitsilaozana (CALA), top-dressing was evenly split in two. At

Mahitsy, top-dressing was applied together with basal application to avoid runoff by expected

4

Top-dressing was generally split into two (Table 4). Exception was in upland rice at Kianjasoa,

where top-dressing was not split. At Mahitsy, all fertilizer doses were given as the basal

application due to expected flooding.

All trials of the standard treatment were categorized as a fertilizer experiment at research centers

in a small scale (240-2,160 m2). Note that OM comprehended farmyard manure, compost

(mostly composed from plant materials) and their mixture.

Table 3. Standard fertilizer treatment in uplands

Treat- Dolo- OM Chemical fertilizer (kg/ha) Nutrient applied with chemical fertilizers

ment mite Basal Top dressing (N-P2O5-K2O-S kg/ha)

no. (kg (ton application (a) Basal Top-dressing Total

/ha) /ha) (NPK) Urea AS application (a)

T1 0 0 0 0 0 0- 0- 0- 0 0- 0- 0- 0 0- 0- 0- 0

T2 0 0 200 83 0 22-44-32- 0 38- 0- 0- 0 60-44-32- 0

T3 0 0 200 0 181 22-44-32- 0 38- 0- 0-43 60-44-32-43

T4 0 5 0 0 0 0- 0- 0- 0 0- 0- 0- 0 0- 0- 0- 0

T5 0 5 200 83 0 22-44-32- 0 38- 0- 0- 0 60-44-32- 0

T6 0 5 200 0 181 22-44-32- 0 38- 0- 0-43 60-44-32-43

T7 300 0 0 0 0 0- 0- 0- 0 0- 0- 0- 0 0- 0- 0- 0

T8 300 0 200 83 0 22-44-32- 0 38- 0- 0- 0 60-44-32- 0

T9 300 0 200 0 181 22-44-32- 0 38- 0- 0-43 60-44-32-43

T10 300 5 0 0 0 0- 0- 0- 0 0- 0- 0- 0 0- 0- 0- 0

T11 300 5 200 83 0 22-44-32- 0 38- 0- 0- 0 60-44-32- 0

T12 300 5 200 0 181 22-44-32- 0 38- 0- 0-43 60-44-32-43

Dolomite contains 36% CaO and 16% MgO. See footnotes in Table 2 for other chemical

fertilizers.

a) At Mimosa and Antsoantany, top-dressing was evenly split in two.

Table 4. Dates of chemical fertilizer application (2012-2013)

Location Cultivar Basal application Top-dressing

1st 2nd

Main season Lowland

Kianjasoa Mailaka Feb.13, 2013 Mar. 1, 2013 Mar. 21, 2013

Mahitsy FOFIFA 160 Jan. 9, 2013 n/p n/p

Ahi

Tsilaozana Madikatra Jan. 7, 2013 Jan. 30, 2013 Mar. 7, 2013 (a)

Anosiboribory Makalioka 34 Dec.12-22, 2012 Feb. 11-13, 2013 Mar. 19-21, 2013

Tsemaka Jan.24-28, 2013 Feb.14-16, 2013 Mar. 22-24, 2013

Upland

Kianjasoa Fotsiambo Dec. 29, 2012 Jan. 22, 2013 n/p

Mimosa FOFIFA 161 Dec. 10, 2012 Dec. 10, 2012 Jan. 15, 2013

Antsoantany ditto Dec. 4, 2012 Dec. 4, 2012 Jan. 11, 2013

Off season Lowland

Kianjasoa Mailaka Sep. 24, 2012 Oct. 10, 2012 Oct. 30, 2012

TS ditto Sep. 24, 2012 Oct. 10, 2012 Nov. 4, 2012

Abbr.: n/p: not practiced. TS: Timing and split-application experiment of AS.

5

3-2. Fertilizer treatment in large-scale cultivation

Large-scale (ca. 22 ha), mechanized rice cultivation is practiced at Anosiboribory. Diammonium

phosphate (DAP: 18% N and 46% P2O5) was used as a basal fertilizer, and urea or AS was

applied as top-dressing (Table 5). No OM was applied.

3-3. Timing and split-application treatments of AS

NPK compound fertilizer (N-P2O5-K2O = 12-24-12%) was basally applied. Total quantity of AS

(172 kg/ha or 36 kg N/ha) was applied either at 0 or 15 days after transplanting (DAT) and a

half of it was at 15 and 50 DAT respectively (Table 6). These nutrient treatments were

combined with and without dolomite application. The experiment was carried out at Kianjasoa

during the off season.

4. Cultivar, planting density and plot size

Cultivar used was a leading one in the respective site (Table 7). Cultural practices like planting

density (22-33 hills/m2), the number of plants in each hill, plot size (e.g., sub-plot size for the

Table 5. Fertilizer treatment in a large-scale trial at Anosiboribory (PC23),

Lac Alaotra area (a)

Treat- Chemical fertilizer (kg/ha) Nutrient applied (N-P2O5-K2O-S kg/ha)

ment Basal Top dressing (b) Basal Top-dressing Total

(DAP) Urea AS application

T1 100 80 0 18-46-0- 0 37- 0- 0- 0 55-46- 0- 0

T2 100 0 175 18-46-0- 0 37- 0- 0-42 55-46- 0-42

a) No farmyard manure was applied. Ingredient (N-P2O5-K2O-S %) of DAP

(diammonium phosphate): 18-46-0-0. See footnotes in Table 2 for other chemical

fertilizers. b) Top dressing was split in two: 50 and 30 kg/ha for urea and 104 and

71 kg/ha for AS as the first and second top-dressing, respectively.

Table 6. Timing and split-application treatments of ammonium sulfate (AS)

in the lowland at Kianjasoa during off season (a)

Treat- Basal application AS application Total nutrients

ment (kg/ha) (kg/ha) applied

no. Dolo- NPK 0 15 50 (N-P2O5-K2O-S

mite comp. (DAT) kg/ha)

T1 0 0 0 0 0 0 - 0 - 0 - 0

T2 0 200 172 0 0 60 - 48 - 24 - 41

T3 0 200 0 172 0 60 - 48 - 24 - 41

T4 0 200 0 86 86 60 - 48 - 24 - 41

T5 200 0 0 0 0 0 - 0 - 0 - 0

T6 200 200 172 0 0 60 - 48 - 24 - 41

T7 200 200 0 172 0 60 - 48 - 24 - 41

T8 200 200 0 86 86 60 - 48 - 24 - 41

Abbr.: DAT: days after transplanting.

Ingredient (N-P2O5-K2O-S %): 12-24-12-0 in NPK compound fertilizer.

See footnotes in Tables 2 and 3 for other chemical fertilizers.

a) Compost was applied at 5 ton/ha in all plots.

6

standard design: 13-60 m2), etc., were according to the routine method in respective

organization. Plot arrangement of the main season crop succeeded that of the off season crop in

lowland rice at Kianjasoa.

5. Dates of sowing and transplanting

Lowland rice was transplanted and upland rice was directly sown. In lowland rice, transplanting

was from December to January for the main season and September for the off season planting,

and in upland rice, sowing was from November to December (Table 8).

6. Field management

General land preparation in the central highland and surrounding areas starts with plowing

(together with incorporation of OM) about one month (sometimes a few months) before sowing

or transplanting. For lowland rice, fields are puddled a few days before transplanting and

leveling and fertilizer application are one day before transplanting. When the main season

cultivation followed the off season crop (either of rice or winter crops) in the same site, fields

were forced to plow shortly before transplanting. For upland rice, OM is applied, soils are

crushed and fields are leveled about one week before sowing, and chemical fertilizers are

applied on the day of sowing. Dolomite was preferred to incorporate at the time of plowing.

Most of the present trials adopted the general procedure of land preparation and field

management (Tables 9 and 10). Dolomite incorporation resulted in the sowing date at Mimosa,

because the experiment site was located in a part of the large field of FIFAMANOR. As the

need arose, herbicides, insecticide and raticides were applied (Table 11).

Table 7. Cultivars used, plant densities and plot sizes at respective sites (2012-2013)

Hill Hill Seedlings Sub-plot Total

Location Cultivar spacing density or seeds Size (m2) Replica- area

(cm x cm) (hill/m2) per hill Planted Harvested tion (m

2)

Main season Lowland

Kianjasoa Mailaka (a) 25 x 20 20 2 13.2 7.2 3 238

Mahitsy FOFIFA 160 (b) 20 x 20 25 2 40.0 21.9 4 960

Ahi

Tsilaozana Madikatra (c) 25 x 20 20 2-3 25.0 25.0 3 450

Anosiboribory Makalioka 34 20 x 15 33 2-3 (f) 17,500 17,500 3-4 (i) 122,500

Tsemaka (d) 20 x 15 33 2-3 (f) 16,370 (h) 16,370 (h) 3 98,200

Upland

Kianjasoa Fotsiambo (e) 20 x 20 25 3-5 60.0 45.0 3 2,160

Mimosa FOFIFA 161 (b) 20 x 20 25 4-5 (g) 20.0 20.0 2 ca. 600

Antsoantany ditto 20 x 20 25 4-5 (g) 20.0 20.0 2 ca. 600

Off season Lowland

Kianjasoa Mailaka (a) 25 x 20 20 2 13.2 7.2 3 ca. 240

TS ditto 25 x 20 20 2 9.0 4.4 3 ca. 220

Abbr.: Ahi Tsilaozana: Ambohitsilaozana. TS: Timing and split-application experiment of AS.

a) Pedigree: X265 = 3914 = IR 15579-24-2. b) Line in the FOFIFA breeding program. c) Pedigree: X1648 = IR15569

-22-2-3-2-3-1-1-3. d) Pedigree: 4012. e) Pedigree: B22. f) Seeds were used at 45 kg/ha. g) Seed rate at 60 kg/ha.

h) Sub-plot size varied 15,500-17,000 m2 (= 15.5-17 ha). i) Number of replications is 3 for urea and 4 for AS

treatment.

7

Table 8. Growth stage of rice plants in the ammonium sulfate trials (2012-2013)

Location Cultivar Growth stage

Sowing Transplanting Flowering Harvest

Main season Lowland

Kianjasoa Mailaka Jan. 24, 2013 Feb. 14, 2013 Apr. 20-25, 2013 (a, b) Jun. 3, 2013 (e)

Mahitsy FOFIFA 160 Dec. 14, 2012 Jan. 11, 2013 n/r May 28-Jun. 4, 2013

Ahi

Tsilaozana Madikatra Dec. 14, 2012 Dec. 29, 2012 Mar. 22, 2013 (c) May 23, 2013

Anosiboribory Makalioka 34 Nov.26-28, 2012 Dec.12-22, 2012 Mar.25-Apr.15, 2013 (d) May 20-Jun.10, 2013

TsemakaDec.29, 2012-

Jan.2, 2013Jan.24-28, 2013 Apr.1-22, 2013 (d) May 20-Jun.10, 2013

Upland

Kianjasoa Fotsiambo Dec. 31, 2012 n/a Mar. 19-26, 2013 (a, b) Apr. 25-29, 2013 (b)

Mimosa FOFIFA 161 Nov. 17, 2012 n/a n/r Apr. 24, 2013

Antsoantany ditto Nov. 11, 2012 n/a n/r Apr. 26, 2013

Off season Lowland

Kianjasoa Mailaka Sep. 3, 2012 Sep. 25, 2012 Dec. 6-13, 2012 (a, b) Jan. 10-16, 2013 (a)

TS ditto Sep. 3, 2012 Sep. 25, 2012 Dec. 16-19, 2012 (a, b) Jan. 16-21, 2013

Abbr.; n/a: not applicable. n/r: not recorded. TS: Timing and split-application experiment of AS.

a) 75% flowering. b) Growth stage was delayed about one week in none treatment (without N either of urea or AS

application). c) Based on one-day observation, varied from 50% heading (block 3) to nearly the end of heading (block 1).

d) Ranges were from initiation to the end of flowering. e) All plots were harvested at the same date to avoid crop damages

from locust (Locusta migratoria ) invasion at May 29, 2013.

Table 9. Dates of land preparation, organic matter and dolomite application (2012-2013)

Land preparation Organic matter Dolomite

Location Cultivar application application

1st (a) 2nd

Main season Lowland

Kianjasoa Mailaka Jan. 22, 2013 Feb. 13, 2013 (b) Jan. 22, 2013 n/a

Mahitsy FOFIFA 160 Dec. 12, 2011 Jan. 9, 2013b (b) Nov. 19, 2012 n/a

Ahi

Tsilaozana Madikatra Nov. 19, 2012 Dec. 9, 2012 Dec. 9, 2012 n/a

Anosiboribory Makalioka 34 Oct. 13, 2012 n/p n/p n/a

Tsemaka Oct. 13, 2012 n/p n/p n/a

Upland

Kianjasoa Fotsiambo Nov.?, 2012 Dec. 28-29, 2012 (c) Nov.?, 2012 Dec. 28-29, 2012

Mimosa FOFIFA 161 n/r Nov. 16, 2012 Nov. 16, 2012 Nov. 16, 2012

Antsoantany ditto n/r Oct.12, 2012 Oct.12, 2012 Oct.12, 2012

Off season Lowland

Kianjasoa Mailaka Aug. 18, 2012 Sep. 24, 2012 (b) Aug. 18, 2012 n/a

TS ditto ditto ditto ditto Sep. 24, 2012

Abbr.: n/a: not applicable. n/p: not practiced. TS: Timing and split-application experiment of AS.

a) Mostly plowing. b) Puddling and leveling. c) Plowing and and leveling.

8

7. Measurements

Grain yield (GY) was measured at full maturity. All rice plants in a sub-plot were harvest at

Anosiboribory, Mimosa and Antsoantany, whereas harvested area excluded the border in

another sites (Table 7).

Yield components (YCc) were measured at many sites (Table 12). At several sites, the number

of tillers, plant height and leaf color at successive growth stages and straw weight at harvest

were measured. At Kianjasoa, rainfall was recorded, and soil samples were taken before and

after the experiment for chemical analyses.

Table 10. Dates of weeding (2012-2013)

Weeding by rotary weeder Manual weeding

Location Cultivar 1st 2nd 1st 2nd

Main season

Lowland

Kianjasoa Mailaka Mar. 1, 2013 Mar. 21, 2013 Mar. 2, 2013 Mar. 22, 2013

Mahitsy FOFIFA 160 Jan. 25, 2013 Feb. 11, 2013 Jan. 25, 2013 Feb. 11, 2013

Ahi

Tsilaozana Madikatra Jan. 29, 2013 Feb. 19, 2013 (b) Jan. 30, 2013 Feb. 13, 2013 (b)

Anosiboribory Makalioka 34 Feb. 9-15, 2013 n/p Mar.?, 2013 n/p

Tsemaka Feb. 15-21, 2013 n/p Mar.?, 2014 n/p

Upland

Kianjasoa Fotsiambo n/a n/a Jan. 22, 2013 Feb. 14, 2013 (c)

Mimosa FOFIFA 161 n/a n/a Dec. 3, 2012 Dec. 26, 2012

Antsoantany ditto n/a n/a Dec. 4, 2013 n/p (e)

Off season Lowland

Kianjasoa (a) Mailaka Oct. 10, 2012 Oct. 30, 2012 Oct. 10, 2012 Oct. 30, 2012

Abbr.; n/a: not applicable. n/p: not practiced.

a) The same practices on the timing and split-application experiment of AS. Additional weeding (3rd):

(b) Mar. 5, 2013, (c) Feb. 20, 2013, and (d) Feb. 26, 2013. e) Unnecessary because of few weeds.

Table 11. Dates of chemical control for weeds, insects and rats (2012-2013)

Cropping Location Chemical control

season Herbicide Insecticide Raticide

Main Lowland

season Kianjasoa n/p n/p n/p

Mahitsy n/p Feb. 05, Feb.13 & Mar.27, 2013 n/p

Ahi

Tsilaozana n/p n/p Mar. 1 & Apr. 2, 2013 (e)

Anosiboribory D1 (a, b) D2 (d) n/p

Upland

Kianjasoa Feb. 4, 2013 (a) n/p n/p

Mimosa n/p Sep. 25, 2012 (c) Dec. 3, 2012 (d) n/p

Antsoantany n/p n/p n/p

Off Lowland

season Kianjasoa (f) n/p n/p n/p

n/p: not practiced.

a) 2,4-D. b) 'Rifit', effective to Mahabanky spp. c) 'Insecto'l (seed treatment). d) 'Cigogne' (active ingredient:

cyperméhrine 240 g/L). e) 'PH3' (5% zinc phosphorus with 95% rice bran). f) No chemical control in the split

application experiment of ammonium sulfate.

D1: 2,4-D was applied at the rate of 1 L/ha before the second application of nitrogen. Rifit was applied before

transplanting or 1-3 days after transplanting. D2: Cigogne was applied whenever insects were detected in plots.

9

Note 1: YC measurement procedure, for example at Mimosa, was: (1) randomly sampled 4

(representative) hills in a sub-plot, (2) counted the number of panicles per hill, (3) threshed all

spikelets, (4) separated and dried filled and unfilled grains, (5) Weighed total filled and unfilled

grains, and (6) counted the total number of 20-g filled grains and 5-g unfilled grains.

Note 2: No soil analytical result is shown in the text because chemical analyses are under

execution.

Results

1. Problems encountered during plant growth

Rice plants faced various problems during the plant growth: insect infestation at Kianjasoa and

Mahitsy, and overgrown weeds in upland field at Kianjasoa, rats at Ambohitsilaozana, flooding

brought with cyclones at Mahitsy, and drought at Ambohitsilaozana (Table 13). Necessary

counter-measures by spraying chemicals were taken against problems (Table 11), but no

effective control was made against flooding, drought and locust attack.

Rainfall at Kianjasoa was larger in 2012-2013 than in other years (Fig. 2), which stimulated

weed growth in upland fields at early growth stages and later lowered grain yield and grain

quality.

2. Growth stage development

Lowland rice flowered from March to April in the main season and in December for the off

season planting, and upland rice did in March (Table 8).

Growth duration was shortened with fertilizer application: i.e., rice plants flowered earlier with

fertilizer application than without it in lowland rice at Mahitsy and in upland rice at Kianjasoa

(Table 14). Similar trend was found in lowland rice at Kianjasoa too. No difference in flowering

date was observed irrespective of N sources and OM application. Dolomite application slightly

shortened the growth duration from sowing to flowering in upland rice at Kianjasoa.

Table 12. Plant growth monitoring and various measurements (2012-2013)

Cropping Agro- Location Plant height Tiller Leaf Straw Yield Soil Rainfall

season ecology number color weight comp. analysis

(Gr. St.) (Harv.) (Gr. St.) (Gr. St.) (Harv.) (Harv.) (a)

Main Lowland Kianjasoa * * * * - * * *

season Mahitsy - * * - * * - -

Ahi

Tsilaozana - * - - - * - -

Anosiboribory - - - - - - - -

Upland Kianjasoa * * * * - * * *

Mimosa - - - - - * - -

Antsoantany - - - - - * - -

Off Lowland Kianjasoa * * * * - * * -

season TS * * * * - * - -

Abbr.: * measured, - not measured. (Gr. St.): at successive growth stages. (Harv.): at harvest. Yield comp.: yield

components. TS: Timing and split-application experiment of AS.

a) Under the execution of chemical analyses.

10

Harvesting dates for main season rice were from the end of May to the early June in lowlands

and at the end of April in uplands and those of off season rice were in the middle of January

(Table 8).

Table 13. Problems encountered during the experiment and observation on rice plants (2012-2013)

Cropping Agro- Location Problems and observation

season ecology

Main Lowland Kianjasoa Locust (Locusta migratoria ) infestation on May 29, 2013.

season

Mahitsy

Insect attack by 'Pou de riz' (Trichispa sericea Guerin and Hispa gestroï

/Dicladispa gestroïchap ) at tillering stage. Submergence of 50 cm for 2-3

days by 2 cyclones (Jan. 22-23 and Jan. 28-29, 2013) at tillering stage.

Low temperature at flowering and ripening stages. Insect attack of cutting

leaves by Nymphula spp. and Borbo spp. at vegetative growth stage.

Ahi

TsilaozanaDrought due to canal water shortage derived from less rainfall at tillering

stage (January 2013).

Anosiboribory Nothing in particular: good vegetative growth and uniform ripening.

Upland

Kianjasoa

Hill missing caused with an insect (Heteronychus spp.) in several plots

shortly after sowing (a). Weed, 'borreria' (Eleusine indica ) was overgrown

at the vegetative growth stage owing to high rainfall. Heavy rainfall (832

mm) in January and February lowed grain yield (considered to be nutrient

leaching) and grain quality.

Mimosa

Slight infection of leaf blast (Pyricularia oryzae ). Leaves turned to reddish

and then plants were dried up along one side (a few hills) of the border: a

cause was unknown.

Antsoantany Slight erosion in lower slope (Replication 2).

Off

season

Lowland

Kianjasoa

Locust (L. migratoria ) infestation in several plots on Oct. 4, 2012, causing

missing hills in all treatments at replication (rep.) 3, T4 at rep. 1 and 3, and

T6 at rep.2, but plant growth was recovered soon after.

TS

Locust infestation at T1, T2 and T7 in replication 2 and T3, T4, T6 and

T7 in replication 2 on Oct. 4, 2012. Majority of plots were temporally

suffered from water shortage on Nov. 1, 2012.

TS: Timing and split-application experiment of AS.

a) The proportion of missing hills was 3-7% at T3, T5, T10 andT11 and 14% at T12 in replication 1, 6% at T5

in replication 2, and 16-20% at T3 and T6 in replication 3. b) The similar problem in the timing and split-

application experiment of AS.

0

500

1,000

1,500

2,000

2,500

200

5-2

006

200

6-2

007

200

7-2

008

200

8-2

009

200

9-2

010

201

0-2

011

201

1-2

012

201

2-2

013

Tota

l R

ain

fall

(m

m)

Fig. 2 Total rainfall at

Kianjasoa in the past 8 years

11

3. Grain yield (GY)

GY of lowland rice with the standard fertilizer treatment varied 1.5-4.3 ton/ha (Table 15 and Fig.

3). It was larger with fertilizers than without them and there was no apparent difference between

fertilizer types (i.e., urea and AS). GY at Kianjasoa was larger in the main season than in the off

season.

GY of upland rice was 0.6-4.1 ton/ha (Table 15 and Fig. 4). GY without fertilizers at Kianjasoa

was larger with dolomite than without it, whereas GY with fertilizers was similar irrespective of

fertilizer types and dolomite application. GY without fertilizers at Mimosa (3.7 ton/ha) was

much larger than that at Antsoantany (0.6 ton/ha) and it was larger than GY with fertilizers.

Table 14. Duration from sowing or transplanting (T/P) to flowing in lowland rice

during main season

Treatment Days after T/P Days after sowing

Organic Chemical in lowland (main season) in upland

matter fertilizer at Mahitsy (a) at Kianjasoa

application Panicle Flowering Flowering

(ton (N-P2O5-K2O-S emergence (75%)

/ha) kg/ha) Begin- End Begin- End Dolomite

ning ning - +

0 0- 0- 0- 0 94 102 103 106 88 84

0 60-44-32- 0 83 96 97 99 84 82

0 60-44-32-43 89 95 97 101 84 82

5 0- 0- 0- 0 94 102 103 106 85 83

5 60-44-32- 0 87 95 97 101 83 81

5 60-44-32-43 88 96 97 101 83 81

Abbr.: + and -: With and without dolomite application respectively.

a) 28 days from sowing to transplanting.

Table 15. Grain yield of rice plants grown with urea and ammonium sulfate (AS) at various locations

(2012-2013)

Cropping Agro- Dolo- Grain yield (ton/ha)

season ecology Location Cultivar mite Without OM With OM

(kg/ha) 0 Urea AS 0 Urea AS

Main Lowland Kianjasoa Mailaka - 2.4 3.2 3.2 2.6 3.0 3.4 a

season Mahitsy FOFIFA 160 - 1.5 3.4 3.4 1.6 3.4 3.6 a

Ahi

Tsilaozana Madikatra - 3.5 4.0 4.1 3.4 4.1 4.3 a

Anosiboribory Makalioka 34 - - 3.0 2.8 - - - b

Tsemaka - - 2.9 2.6 - - - b

Upland Kianjasoa Fotsiambo 0 1.4 2.0 2.3 1.6 2.7 2.8 a

300 1.9 2.2 2.5 2.0 2.8 2.5 a

Mimosa FOFIFA 161 0 3.7 3.2 3.1 3.5 3.0 2.6 b

300 4.1 3.8 3.7 3.6 3.1 2.9 b

Antsoantany FOFIFA 161 0 0.6 2.1 2.0 1.4 2.1 2.5 b

300 1.2 1.9 2.2 1.4 2.0 2.6 b

Off season Lowland Kianjasoa Mailaka 2.6 3.8 3.7 2.8 4.1 3.6 a

TS Mailaka 0 - - - 2.5 - 3.1 a

300 - - - 2.8 - 3.1 a

OM: organic matter. a and b: Grain yield with (a) and without (b) moisture adjustment to 14%.

TS: Timing and split-application experiment of AS.

12

Fig. 4. Grin yield at various sites in uplands

In the large-scale rice cultivation at Anosiboribory, there was no apparent difference in GY

between fertilizer types, when GY was averaged over sub-plots (Table 15). GY was higher at

upper side, especially at sub-plot 1 and 2, than at the middle and lower sides (Fig. 5). GY at the

sub-plots 3 and 13 with AS application was lower than that at the other sub-plots.

Fig. 3. Grain yield at various

sites in lowlands. Main and

Off signify main and off

season crops respectively.

13

Although GY difference between the application timing and between split application methods

of AS was not apparent at Kianjasoa, GY tended to be larger with two split application of top

dressing (Table 16).

3. Yield component (YC)

All yield components (YCs) except 1,000-grain weight of lowland rice at Kianjasoa was

decreased without chemical fertilizers in the off season (Table 17). The total number of spikelets

per panicle was slightly largely decreased in comparison with the other YCs, and it was fewer in

panicles with AS than those with urea. In upland rice at Kianjasoa, the number of panicles per

hill and percentage of filled grains tended to be small without chemical fertilizers (Table 18).

For reference, the percentage of filled grains was larger without fertilizers (91%) than with them

(86-89%) in lowland rice at Ambohitsilaozana (Table 19). It was very small (29-30%) without

chemical fertilizers and OM in upland rice at Antsoantany.

0

1

2

3

4

5

1 2 3 4 5 6 7 8 9 10 11 12 13

Upper Lower

Makalioka 34

Tsemaka

A

A

A

A

A

A

Sub-plot number

Gra

in y

ield

(to

n/h

a)

A

U

U

U

UU

U

Table 16. Timing and split-application experiment of ammonium sulfate (AS) in

lowlands at Kianjasoa (off season in 2012)

Treat- Basal application Split-appl. of AS Total nutrients GY

ment (kg/ha) 0 15 50 applied

no. Dolo- NPK (DAT) (N-P2O5-K2O-S (ton/ha)

mite comp. [basal] kg/ha)

T1 0 0 0 0 0 0 - 0 - 0 - 0 2.5

T2 0 200 172 0 0 60 - 48 - 24 - 41 3.0

T3 0 200 0 172 0 60 - 48 - 24 - 41 2.6

T4 0 200 0 86 86 60 - 48 - 24 - 41 3.6

T5 200 0 0 0 0 0 - 0 - 0 - 0 2.8

T6 200 200 172 0 0 60 - 48 - 24 - 41 2.9

T7 200 200 0 172 0 60 - 48 - 24 - 41 3.2

T8 200 200 0 86 86 60 - 48 - 24 - 41 3.3

DAT: days after transplanting. Compost was applied at 5 ton/ha in all plots.

See Tables 2 and 3 for chemical fertilizer ingredients.

Fig. 5 Grain yield of 2 varieties

affected with sub-plot location at

Anosiboribory, PC23, Lac Alaotra area.

U and A signify urea and ammonium

sulfate respectively. Sub-plot size:

1.55-1.75 ha.

14

Table 17. Yield components of lowland rice grown in dry season at Kianjasoa (2012-2013) (a)

Treatment No. of Total Percent 1,000- Grain yield

OM Chemical fetilizer panicle no. of of grain (ton/ha) Check

no. (ton (N-P2O5-K2O-S /hill spikelets filled weight Cal'd Actual

/ha) kg/ha) /panicle grains (g) A B (A/B)

T1 0 0 - 0 - 0 - 0 12 72 61 26 2.7 2.6 1.03

T2 0 60 - 44 - 32 - 0 13 89 66 25 3.9 3.8 1.01

T3 0 60 - 44 - 32 - 43 13 79 70 26 3.8 3.7 1.01

T4 5 0 - 0 - 0 - 0 12 79 65 25 3.1 2.8 1.10

T5 5 60 - 44 - 32 - 0 15 87 67 25 4.3 4.1 1.04

T6 5 60 - 44 - 32 - 43 14 80 66 25 3.8 3.6 1.06

OM: organic matter. Hill density = 20/m2. Grain weight was adjusted to 14% moisture.

a) Cal'd: calculated grain yield (GY) based on YCs was 1-10% larger than the actual GY.

Table 18. Yield components of upland rice at Kianjasoa (2012-2013) (a)

Treatment No. of Total Percent 1,000- Grain yield

Dol. OM Fetilizer panicle no. of of grain (ton/ha) Check

no. (kg (ton (N-P2O5-K2O-S /hill spikelets filled weight Cal'd Actual

/ha) /ha) kg/ha) /panicle grains (g) A B (A/B)

T1 0 0 0 - 0 - 0 - 0 6.0 62 68 24 1.5 1.4 1.09

T2 0 0 60 - 44 - 32 - 0 7.0 79 76 22 2.3 2.0 1.12

T3 0 0 60 - 44 - 32 - 43 8.0 78 70 23 2.5 2.3 1.11

T4 0 5 0 - 0 - 0 - 0 7.1 71 68 25 2.1 1.9 1.10

T5 0 5 60 - 44 - 32 - 0 9.0 60 76 25 2.5 2.2 1.11

T6 0 5 60 - 44 - 32 - 43 7.0 71 76 28 2.7 2.5 1.05

T7 300 0 0 - 0 - 0 - 0 7.0 75 67 21 1.8 1.6 1.11

T8 300 0 60 - 44 - 32 - 0 9.1 68 75 26 3.0 2.7 1.12

T9 300 0 60 - 44 - 32 - 43 7.9 79 78 26 3.1 2.8 1.12

T10 300 5 0 - 0 - 0 - 0 7.0 66 74 26 2.2 2.0 1.12

T11 300 5 60 - 44 - 32 - 0 8.0 68 82 28 3.2 2.8 1.12

T12 300 5 60 - 44 - 32 - 43 8.9 61 83 24 2.7 2.5 1.11

Dol.: dolomite. OM: organic matter. Hill density = 25/m2. Grain weight was adjusted to 14% moisture.

a) Cal'd: calculated grain yield (GY) based on YCs was 5-12% larger than the actual GY.

Table 19. Percentage of fillled grains and 1,000-grain weight of lowland rice at

Abohitsilaozana and of upland rice at Antsoantany in the main season

Treatment Lowland rice Upland rice

OM Chemical at Ahi

Tsilaozana at Antsoantany

fetilizer Percentage 1,000- Percentage 1,000-grain

(ton (N-P2O5-K2O-S of filled grain of weight

/ha) kg/ha) grains weight filled grains (g)

(g) -Dol +Dol -Dol +Dol

0 0 - 0 - 0 - 0 91 23 29 30 27 26

0 60 - 44 - 32 - 0 86 23 59 38 27 27

0 60 - 44 - 32 - 43 89 23 52 43 27 26

5 0 - 0 - 0 - 0 91 23 54 47 28 28

5 60 - 44 - 32 - 0 89 24 44 37 27 27

5 60 - 44 - 32 - 43 88 23 55 45 27 27

OM: organic matter. +Dol and -Dol.: with and without dolomite application

respectively. Grain weight was adjuted to 14% moisture.

15

Note that YCs were measured in almost all trials (Table 12), but only the YC data were

presented in the report, when the calculated GY based on YCs was within 12% error of the

actual GY. Grain filling percentage and 1,000-grain weight were supplemented because they

might be less erroneous.

5. Harvest index

Harvest index was 0.48-0.49 and 0.37 respectively with and without chemical fertilizer

application in lowland rice at Mahitsy (Table 20).

Discussion

1. Relative grain yield (GY)

GY itself varied among sites and agro-ecologies. To verify the effect of AS based on urea,

relative increment of GY with AS over that with urea application was calculated;

Relative increment by AS = (B - A) * 100 / A,

where A and B were GY with urea and AS respectively.

In many cases, the relative increment by AS was within the range of ±15% (Table 21). Such a

range is assumed to be an error that frequently experienced in field trials. Hence, AS is effective

in grain production as urea was whether rice plants are grown in lowlands or in uplands.

The relative increment by AS in upland rice at Antsoantany was 19-27% irrespective of

dolomite application when rice was grown with OM. The fact shows that the soil lacks not only

nitrogen but also sulfur. The field is located in an upland cropping area with Oxisols, which was

widely-distributed in the central highland of Madagascar. Farmers have grown upland rice,

maize, potatoes, leguminous crops, etc. with a certain quantity of OM for a long time. Sulfur

deficiency would widely spread over the area. In such an area, AS functions as double sources

of plant nutrients, nitrogen and sulfur.

Velly, et al. (1966) reported sulfur deficiency in Madagascar already 50 years ago. Nevertheless

its importance has been ignored for the time being. PAPRiz is now undertaking a series of pot

experiments to evaluate soil fertility. The result shows that sulfur deficiency is necessarily

seldom in a wide range of soils.

Table 20. Harvest index of lowland rice at Mahitsy

Treat- Organic Nutrients Air-dry weight Harvest

ment matter applied (ton/ha) index

no. (ton (N-P2O5-K2O-S

/ha) kg/ha) Grain Straw

T1 0 0- 0- 0- 0 1.5 2.5 0.37

T2 0 60-44-32- 0 3.4 3.6 0.49

T3 0 60-44-32-43 3.4 3.7 0.48

T4 5 0- 0- 0- 0 1.6 2.8 0.37

T5 5 60-44-32- 0 3.4 3.6 0.49

T6 5 60-44-32-43 3.6 3.8 0.49

16

GY at Mimosa was slightly decreased with fertilizer application regardless of fertilizer types

(Table 15). FIFAMANOR is raising a large number of cattle, so that the soil fertility has been

enriched with abundant farmyard manure in addition to dolomite application. GY of 4 ton/ha by

upland rice is worthy of remark, but at the same time, we should bear in mind that such a yield

would be an upper limit of GY in upland conditions.

2. Effect of organic matter (OM) on AS application

Contribution of OM to GY increment was less than 0.2 ton/ha in many cases of lowland and

upland rice irrespective of chemical fertilizers and dolomite application (Table 21). An

exception was found only in upland rice at Antsoantany without dolomite.

OMs found in the area are various: nearly pure farmyard manure, compost made from weeds,

twigs, home waste, etc., and their mixture, being frequently mixed with soils. Decomposition

degree also varies: some are well decomposed and the others not. Therefore, the chemical

property of OMs collected in several places varied greatly. Total concentration of inorganic

elements on the basis of dry matter was: 50-400 C g/kg, 4-15 N g/kg, 2-5 P g/kg and 3-13 K

g/kg, for instance (unpublished data). Moisture amount was 20-80%. Total ash concentration

varied 150-850 g/kg depending upon the proportion of soils, which farmers mixed into OM as a

source of nutrients: so they believed, but we must verify the fact.

Table 21. Relative increment of grain yield by ammonium sulfate application and the effects of

organic matter and chemical fertilizer application on grain yield (GY), and N efficiency

Dolo- Relative Effect on GY (ton/ha)

Cropping Agro- Location mite increment OM Chemical NUE

season ecology by AS (%) fertilizer

(kg/ha) -OM +OM -OM +OM mean (%)

Main Lowland Kianjasoa - 1 12 0.3 0.9 0.6 0.7 26

season Mahitsy - -2 6 0.2 1.9 1.9 1.9 70

Ahi

Tsilaozana - 0 5 -0.1 0.6 0.9 0.7 27

Anosiboribory - -7 - - - - - -

- -11 - - - - - -

Upland Kianjasoa 0 12 6 0.2 0.7 1.1 0.9 34

300 13 -12 0.0 0.4 0.7 0.5 20

Mimosa 0 -2 -15 -0.2 -0.6 -0.7 -0.7 -24

300 -3 -7 -0.5 -0.3 -0.6 -0.4 -16

Antsoantany 0 -4 19 0.8 1.5 0.9 1.2 43

300 13 27 0.2 0.9 0.9 0.9 33

Off season Lowland Kianjasoa - -3 -14 0.2 1.2 1.0 1.1 40

+OM and -OM: with and without organic matter (OM).

Calculations:

1) Increment of GY by AS (%): GY increment by AS application over fairly negative

GY by urea application fairly positive

= (B - A) * 100 / A, where A is GY with urea and B is GY with AS largely positive

2) Effect of OM application on GY = GY with OM - GY without OM

3) Effect of chemical fertilizer application on GY: the balance of GY with and without chemical

fertilizers (average of urea and AS)

4) NUE: Nitrogen use (or absorption) efficiency of applied fertilizers by rice plants, assuming that

22 N kg/ha was required to produce 1 ton/ha of grain production: i.e., N concentration of grain and

straw was 10 N g/kg and harvest index was 0.45. NUE = (Yn - Yo) x 22 x 100 / Nr, where Yn and

Yo are GY (ton/ha) with and without nitrogen application respectively and Nr is nitrogen application

rate (N kg/ha). Averaged over urea and AS application.

17

Collaborators simply described in their reports that they applied farmyard manure or compost at

the rate of 5 ton/ha. Yet, their properties were unknown at all: what the material was, how far it

was decomposed, what the moisture content was, etc. Whenever the OM is used, one should

clarify all such information, together with chemical and physical properties.

GY increment by AS was little affected with or without OM application (Table 21). Several

researchers emphasize the necessity of OM for AS application to mitigate a soil acidity problem,

although there is no scientific evidence to support it. The present study showed that GY was

unaffected by AS application irrespective of OM.

OM contribution to GY was the largest (0.8 ton/ha) at Antsoantany without dolomite application,

where GY was very low (0.6 ton/ha) without chemical fertilizer (Table 15). Low GY on the

original soil denotes poor fertility, so that OM would play an important role as a nutrient

supplier. Whatever the OM properties were its application rate at 5 ton/ha as in the present

experiments might be much larger than the rate by farmers' practice.

3. Effect of dolomite on AS application

The effect of dolomite on GY is marginal in many cases (Tables 15 and 21). Dolomite

application increased GY of upland rice at Kianjasoa and Mimosa, but the increase is minor:

2.2-2.5 vs. 2.0-2.3 and 3.7-3.8 vs. 3.1-3.2 ton/ha with and without dolomite application. The

dolomite effect was little affected with fertilizer types. Besides, dolomite application hardly

affected GY when rice plants were grown with OM. GY in lowland rice was little influenced

with dolomite treatment too.

It is well known that pH of lowland soils, whether it is originally high or low, is neutralized to

about 6.5 with submergence (Ponnamperuma. 1965). The fact that there was little effect of

dolomite application on GY shows that peculiar soils (i.e., harmful soils affecting GY by AS

use) would scarcely exist at the experiment sites. On the whole, the result indicates that AS

application would hardly induce an acidity problem in the central highland, Alaotra area and

middle-west zones.

Note that the fertilizer application rate in the present experiment was modest: the rate was

principally based on the recommended rates by FOFIFA and partly on the current socio-

economic condition in Madagascar. Few farmers use chemical fertilizers in rice cultivation

todays. We must re-examine an AS side-effect when a large quantity of AS, being similar to any

other chemical fertilizers, is used.

4. Nitrogen use efficiency and split application effect

Nitrogen use (absorption) efficiency (NUE) is about 50% with basal dressing, and it attain 80%

or higher with top-dressing. Top-dressing will help avoid eventual losses by volatilization,

runoff and leaching.

The number of trials of which NUE was higher than 40% was three, and NUE in seven other

trials was lower than 40%. NUE is generally higher when fertilizer rate was smaller (Table 21).

As described previously, fertilizer rate was modest in the present experiment, so that one has to

find the reason why the NUE was low.

18

The first possibility would be ill-water management, which was reflected in the relatively low

maximum GY. Rainfall in 2012-2013 was larger than the past average at Kianjasoa (Fig. 2),

where NUE was as low as 20-34%, possibly induced with nutrient leaching.

The second possibility would be a deficiency of nutrients other than nitrogen. Phosphorus and

potassium rates were small in comparison with nitrogen rate in the present treatment (Tables 2,

3, 5 and 6), so that NUE would be lowered if phosphorus, for example, might have been a

principal limiting factor.

Split application instead of basal application likely enhanced GY at Kianjasoa (Table 16). In

contrast, NUE was the highest at Mahitsy among all trials (Table 21), where all fertilizers were

given as basal application (Table 4). Split application of fertilizers generally promotes NUE,

which will result in higher GY. In practically, however, NUE will be influenced with soil

condition, water management (rainfall for upland rice), climatic condition, etc. Therefore, the

general tendency would not be applicable to specific cases.

Note that the reason why the NUE at Mahitsy was high was unknown although the rice field was

flooded. A feasible possibility would be derived from the wrong calculation of NUE: e.g.,

nitrogen concentration was lower and harvest index was higher in the actual plants than the

assumption. The other would be an error on yield measurement.

5. GY comparison with 2011-2012

Relative difference of GY between 2011-2012 and 2012-2013 plantings based on the former

was -20% or smaller in all treatments of lowland rice at Ambohitsilaozana and of upland rice at

Kianjasoa (Table 22). As for the former, water shortage during vegetative growth stage and as

for the latter insect damage and high rainfall would be the dominant factors for low GY in 2012-

2013 (Table 13).

Although GY tended to be lower with AS than with urea at Mahitsy and Ambohitsilaozana in

2011-2012, when AS was applied without OM (PAPRiz, 2012), such tendency was not observed

in 2012-2013 (Table 15). The result suggests that AS application will not be necessarily

accompanied with OM as an acidification remedy, especially in lowland rice.

Table 22. Relative difference of grain yield (GY) between 2012-2013 and 2011-2012 (a)

Agro- Dolo- Relative GY difference (%)

ecology Location Cultivar mite Without OM With OM

(kg/ha) 0 Urea AS 0 Urea AS

Lowland Kianjasoa Mailaka - -14 2 2 -7 -9 4

Mahitsy FOFIFA 160 - 7 12 34 -25 2 6

Ahi

Tsilaozana Madikatra - -29 -32 -16 -37 -29 -27

Anosiboribory Makalioka 34 - - -11 -14 - - -

Tsemaka - - 27 20 - - -

Upland Kianjasoa Fotsiambo 0 -23 -48 -36 -32 -36 -31

300 -19 -37 -30 -16 -18 -32

Mimosa FOFIFA 161 0 115 - - 66 47 5

300 - - - - - 17 -23

OM: organic matter.

a) Relative difference of GY (%) = (B-A) x 100/A, where A and B were GY in 2011-2012 and

that in 2012-2013 respectively.

19

GY was larger with AS than with urea in upland rice at Mimosa in 2011-2012, but there was no

difference between the two fertilizer sources in 202-2013. Although the field has been yearly

received abundant farmyard manure and dolomite, the entire FIFAMANOR farm was so large

and slightly undulating that the depth of surface and sub-layers would differ, farmyard manure

incorporation would not be uniform, and soil fertility would be affected with preceding crops.

GY of Tsemaka in 2012-2013 was larger than that in 2011-2012 at Anosiboribory. Nitrogen and

phosphorus application rates in 2011-2012 were respectively 1.6 and 2.1 times larger than those

in 2011-2012 but potassium was not applied. Larger doses of the two nutrients might have

contributed to the GY increase in Tsemaka. Instead, GY of Makalioka 34 was smaller in 2012-

2013 than in 2011-2012. One might carefully assess the mutual relationship between varietal

characteristics and fertilizer response.

6. Growth development affected with fertilizer application

Rice plants flowered earlier with fertilizer application than without it regardless of nitrogen

sources (Table 14). Because it is evident that nitrogen application delays flowering, the above-

mentioned phenomenon is not caused with nitrogen. Other nutrient like phosphorus, for example,

might concern it, but a real cause was remained unknown.

7. Yield components (YCs) and harvest index

To obtain reliable yield components (YCs) data, a systematic approach, especially of plant (hill)

sampling, is inevitable: random sampling will easily cause an arbitrary choice of hills. Such hills

are obvious to be far from representatives. The majority of YC data reported was invalid, being

beyond an allowable error, so that any valuable GY analysis was impossible. Besides, 1,000-

grain (filled) weight of a cultivar seldom varied 21-28 g with fertilizer treatments (Table 19), for

instance. YC measurement is a long-winded work and falls into a waste of time and money if it

is not rewarded with scientifically valid information.

Harvest index is an important indicator, which shows how efficiently plants convert total

biomass into grain. Modern, high-yielding rice varieties have been developed with harvest index

improvement based on the concept of ideal plant type. Because it is well known that fertilizer

application decreases harvest index, the result obtained in Table 20 contradicted the universal

fact. Harvest index is surely worthy in GY analysis if sampling and drying methods were

improved.

8. Strict evaluation of AS effect

In the present study, NPK compound fertilizer was forced to use for supplying phosphorus and

potassium, because the two elements were possibly deficient in the study area and single

fertilizers of phosphorus and potassium were unavailable in the market. Because of a nitrogen

ingredient in the NPK compound fertilizer, the present study fell into inadequate comparison of

the two nitrogenous fertilizers, urea and AS. Two single fertilizers like triple superphosphate

and potassium chloride are essential for fair evaluation of the AS effect.

Note that potassium sulfate is sometimes available in the market, but it is not acceptable in the

present experiment owing to its S ingredient.

20

Nevertheless, the present study would be worthy of comparing the two fertilizer sources, AS and

urea, although the effect would have been somewhat diluted. Nitrogen quantity in NPK

compound fertilizer and AS or urea in the standard treatment was respectively 22 and 38 kg/ha

(Tables 2 and 3), being the ratio of about 1:2. Besides, the sulfur rate was maintained in excess

condition. The N/S ratio was still as low as 1.4 in the standard treatment: it was 10-15 in plants

and 3-5 for the estimation of sulfur fertilizer to crop fields.

At the same time, one must consider whether the nutrient composition (i.e., the proportion of

nitrogen, phosphorus and potassium) in the present treatment well matches the soil fertility

condition or not. The nutrient rate in the present experiment was principally based on the

fertilizer rate recommended by FOFIFA. Appropriate fertilizer composition surely varies with

locations and the total quantity of fertilizers depends on yield levels. In the present study, the

rate of phosphorus and potassium was smaller than that of nitrogen. Because phosphorus

deficiency prevails in the area, the result might not properly evaluate a real nitrogenous effect.

At Anosiboribory, DAP and urea or AS were applied, where potassium is absent. If the soil were

deficient in potassium, fair comparison of urea and AS would not be satisfied. Such an issue will

be the subject in future.

Acknowledgments

PAPRiz is deeply grateful to the Ambatovy project for the provision of 3-ton AS, which was

fully used in the present field trials. We thank all of the researchers, officials and staff at

FOFIFAs, FIFAMANOR and CFAMA for conducting the AS trials.

Notes

Dr. J. Yamaguchi, a JICA short-term expert (ex-professor of Hokkaido University, Japan)

established the experiment framework and compiled the results. Dr. N. Kabaki, a chief advisor,

and Mr. R. Habara, a JICA expert, of PAPRiz, coordinated the trials.

Reports from each station are not attached to the present report. Some detailed data might

provide additional information. They are available upon request to the PAPRiz office:

pap.riz@moov.mg.

References

PAPRiz, 2012: Evaluation of ammonium sulfate effect on rice production in Madagascar (Main

season, 2011-2012), PAPRiz, Antananarivo, Madagascar

Velly, J., Celton, J. and Roche, P., 1966: Fertilisation de Fond en Rizière à Madagascar -

Redressement de la Fertilité Résultats 1964-1966. Institut de Recherches Agronomiques à

Madagascar. pp.87. IRAT, Documnent no. 103.