Cover Crops For Nutrient Management

Carlene A. Chase; HOS 3430C; March 12, 2015

What are cover crops?

Provide ground cover Prevent soil erosion

Examples of species used as cover crops

Grasses Legumes Brassicas Other BL

Sorghum-sudangrass

Sunn hemp Oilseed radish

Buckwheat

Pearl millet Velvet bean Turnips Sunflower Rye Cowpea Mustards Marigold Wheat Sesbania Chicory Oats Vetches Phacelia Black oats Clovers Annual ryegrass

Medics

• Erosion control

• Increase organic matter

• Improve soil physical & biological properties

• Nutrient cycling

• Nitrogen fixation

• Disease and pest management

• Nematode suppression

• Weed suppression

Cover crops can provide valuable agroecosystem services

Top 10 cover crop benefits desired by users

0 20 40 60 80

Percentage of Respondents

Cover crops can protect topsoil from being eroded

Foliage intercepts raindrops and decreases soil particle dislodgment

Slow runoff

Promote infiltration and retention of water

Stabilize soil particles in the root zone

Cover crop residues add organic matter to soils providing many benefits

1. Improved soil structure:

Improved soil aggregation Polysaccharides produced by microorganisms that feed

on CC residues Glomalin: water-insoluble protein produced by

mycorrhizal fungi Root exudates

Benefits of organic matter from cover crops

2. Increased soil porosity

3. Increased infiltration and water-holding capacity

4. Increased cation exchange capacity

Nutrient cycling

Catch crops Reduce nitrate leaching

Nitrate is used by the catch crop

Crop also uses water so less is available for leaching

Non-legumes that quickly form deep, extensive root systems Eg cereal rye

Cover crops can decrease nitrate leaching

Treatment NO3-N

(mg)

Leachate reduction (%)

Total biomass (t/ha)

Fallow 14.3 a 43.7 d 2.6 c Sorghum-sudangrass 0.4 b 71.3 b 11.2 ab Velvetbean 2.5 b 55.0 c 7.8 b Cowpea 2.8 b 66.8 b 3.9 c Sunn hemp 2.3 b 90.8 a 12.1 a

Wang, Li, and Klassen. 2005. J. Soil & Water Conservation

Leguminous cover crops can add nitrogen

Vigna unguiculata cowpea

Mucuna deeringiana Velvetbean

Green manures are cover crops grown to provide nutrients for a subsequent crop

Legume cover crops Clovers, medics, hairy vetch,

cowpeas, soybeans, velvetbean

Rhizobium: soilborne bacteria symbiosis with legumes Nitrogen-fixation

Crotalaria juncea

http://drsohm.tumblr.com/post/57254986626/ nitrogen-fixation-may-change-the-world-all-over

Inoculant

Product to deliver the bacteria to the seed

Seed-applied or soil-applied

Several strains of Rhizobium available

Select appropriate strain for legume to be planted

Coated seed

Disease & pest management

Rotation with nonsusceptible cover crops

Disease suppressive soils

Adverse effects on pathogen populations

through competition, parasitism, predation or antagonism

Biofumigation

Food and habitat for beneficial arthropods

Verticillium Wilt Rating Based onStem Sap

Becker Field Trial 2002

Fallow Buckwheat Canola0

1

2

3 A

B

B

Green Manure

Wilt

Rat

ing

(Linda Kinkel)

Biofumigation

Plants from the Brassicaceae family for soil disinfestation Mustards, turnips

Isothiocyanate compounds

similar to that found in metam-Na, a soil fumigant

http://youtu.be/st3I2cct2Io

Nematode suppression

Rotation with nematode-suppressive crops

Effect of cover crops varies with nematode spp.

If several spp. present - focus on the most serious usually Meloidogyne spp.

Effective use of cover crops requires knowledge of

the nematodes present

the susceptibility of the cover crop

Egg mass indices of plants inoculated with Meloidogyne spp.

Crop M. incognita M. javanica M. arenaria Castor 0 b 0 b 0 b

Cowpea 0 b 0 b -

Crotalaria 0 b 0 b 0 b

Sunn hemp 0 b 0 b 0 b

Tomato 5 a 4 a 5 a

McSorley. R. 1999. Suppl. J. Nematol. 31(4S):619-623

0 – 5 scale: 0 = 0 egg masses, 1 = 1-2, 2 = 3-10; 3 = 11-30, 4 = 31-100, 5 = > 100

Differing sunn hemp susceptibility to sting nematodes

Accession Origin Nematodes/100 cm3 soil PI 207657 Sri Lanka 4.0 bc PI 219717 Myanmar 0.0 c PI 250485 India 3.4 bc PI 250486 India 3.8 bc PI 250487 India 0.0 c PI 314239 Fmr USSR 0.0 c PI 322377 Brazil 12.8 b PI 337080 Brazil 7.8 bc PI 391567 South Africa 0.0 c PI 426626 Pakistan 0.0 c PI 468956 US 0.0 c Corn US 60.0 a

Weed suppression with off-season cover crops

Sunn hemp Crotalaria juncea

Hairy indigo Indigofera hirsuta

Jointvetch Aeschynomene americana

Short-flower rattlebox Crotalaria breviflora

Effect of cover crops on total and broadleaf weed biomass

Effect of cover crops on grass and sedge weed biomass

R.B. Armecin, M.H.P. Seco, P.S. Caintic, E.J.M. Milleza

Industrial Crops and Products 21:317-323 (2005)

Effect of leguminous cover crops on the growth and yield of abaca (Musa textilis Nee)

What is a living mulch?

Photo Credit: Charles W. Miller/Shostal Associates

Abacá - Musa textilis - is a species of banana native to the Philippines that is grown as a fiber crop

Photo credits: Rainier Schultze-Kraft

Desmodium ovalifolium

Photo credits – Deryck Cooksley, Chris Gardiner, and CIAT

Centrosema pubescens

Photo credits – CIAT and http://oextensionista.blogspot.com/2010/10/serie-f-o-r-r-g-e-i-r-s-leguminosas.html

Calopogonium mucunoides

Effect of cover crops on growth parameters of abaca

Treatment

Stalk length (cm) Middle

circumference (cm) Leaf length (cm)

2000 2001 2002 2000 2001 2002 2000 2001 2002

No cover crop 162 192 b 130 b 23 24 c 21 144 158 b 119 b

D. ovalifolium 217 248 a 171 a 32 28 ab 25 200 193 a 156 a

C. pubescens 180 197 b 131 b 27 25 bc 21 165 158 b 117 b

C. muconoides 270 243 a 165 a 37 31 a 25 225 196 a 147 a

Prob. NS 0.01 0.01 – 0.001 NS NS 0.03 0.01

Means within columns followed by the same letter are not significantly different at P = 0.05 using Duncan’s Multiple Range Test (DMRT).

Fiber yield was enhanced by Calopogonium muconoides

Biomass production of the cover crops

Cover crops resulted in increased soil aggregation

Organic matter content of the soil was enhanced by the cover crops

Total soil nitrogen content increased with cover crop use from 2000 to 2002

Cover crops protected the soil from erosion by reducing runoff

Limitations of cover crops

High carbon:nitrogen ratio of grass/cereal cover crops can limit N availability during the subsequent cash crop.

Difficult to match nutrient availability with cash crop needs.

Nutrient credits from cover crops are a rough estimate. In arid regions, they can deplete soil moisture that is

needed for non-irrigated cash crop production. Can enhance some pests.

Limitations of cover crops

Additional cost and labor needed for establishment and termination.

Living mulches can compete for resources with the main crop.

Allelochemicals can inhibit the growth of subsequent cash crops.

Cover crop biomass management without appropriate equipment can be challenging.

Cost and availability of cover crop seeds.