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Cover crops grown in micro-plots
(note castor bean at left, and sorghum sudangrass at right,
in the foreground). |
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Cover Crops and Nematode Management
Use of cover crops is increasing in the mid-Atlantic region because
they have been proven to reduce soil erosion and nutrient loss and
improve soil health. Additionally, reductions in soil-borne and
foliar disease may result from cover crop use. Nematode-suppressive
cover crops provide the additional benefit of nematode disease suppression.
Two non-host cover crops that can be grown in the mid-Atlantic
and may provide root-knot nematode population reduction are sorghum
sudangrass and castor bean. In cropping system experiments in Maryland,
sorghum sudangrass grown annually as a green manure crop following
a nematode–susceptible potato or cucumber crop reduced the
RKN population as effectively as a nematicide application prior
to production of a susceptible soybean cultivar. An annual green
manure crop of castor bean also significantly reduced RKN, but annual
inclusion of these crops is necessary to maintain reduced populations.
In addition, results may be variable (i.e. the nematode suppressive
effect is not observed every year) due to other environmental influences
upon the nematodes.
Field procedures
Sorghum sudangrass cv. ‘Green Grazer’ (AgriBiotech Brand,
Inc.) can be planted following an early season vegetable crop such
as potato, processing cucumber, pea or snap bean. Planting seed
at 20 lb/acre in mid to late July produced adequate biomass to suppress
RKN. For best suppression, the sorghum sudangrass crop should be
chopped and incorporated into the soil in mid October. (Note: Although
we used cv. ‘Green Grazer’, research throughout the
U.S. has shown that other varieties also should work well.)
Castor bean cv. ‘Mall’ grown for green manure is seeded
at a relatively low density-11,500 seeds/acre in mid to late July
following spring vegetable crop production. Again, approximately
three months of growth should produce adequate biomass to suppress
nematodes. Castor bean should be mowed or chopped and the biomass
tilled into soil in mid October. Table 2 provides planting dates
and seeding rates for these cover crops in Maryland.
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