Cover crops after small grains

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Farm Forum

BROOKINGS, S.D. – Due to consistent moisture and humid conditions this growing season, small grain harvests have slowed down a bit across South Dakota.

“Because things have slowed down, some growers may already be thinking about the next crop,” said David Karki, Ph.D., SDSU Extension Agronomy Field Specialist.

As of Aug. 24 2014, the USDA National Agricultural Statistics Service showed total oat harvest yield averages to be about the same as it has been the last five years whereas winter wheat and spring wheat are behind 4 percent and 20 percent respectively.

Karki said interest in using cover crops after small grain is increasing in South Dakota. “Cover crops provide diversity into the cropping system, reduce soil erosion, increase soil biological activity, and also help recycle moisture and nutrients in the soil,” he said.

In addition, Karki said due to diverse growing habits between the major crop and selected cover crop species, it helps to break disease and weed pressure in the field.

“Growers, especially in the eastern part of the state, may be thinking of putting fall cover crops on grounds harvested to small grains to be followed by either corn or soybean in the following spring,” he said. “Also, depending upon the need of the farm, cover crops can be used as supplemental fall grazing.”

Single species or mixes

Cover crops are grown as single species or in a mixture of variety of crops. Selecting fall cover crop mix is very critical, Karki said because it should benefit your cropping system and not harm your next cash crop.

For example, he said if your ground is going into corn next season, the majority of the mix should contain cool season broadleaf species.

Two major categories of broadleaf cover crop species are non-legumes (i.e. turnip, radish, canola or rape, etc.) and legumes (i.e. chickling vetch, clovers, pea, lentil, etc.). These species Karki said have rapid fall growth and will provide high residue biomass in the spring.

“Species like radish and turnip have enhanced tap roots which will aid in breaking compaction in the ground. In addition, legumes will help fix atmospheric nitrogen which will add to the soil nitrate content and would be readily available for the corn next spring,” he said.

These species are generally winter killed.

However, if your rotation is soybeans, Karki said it is suggested to put a mixture high in cool season grasses such as rye, oat, barley, triticale, annual ryegrass and broadleaf. “These will produce significant amount of biomass the next spring,” he said.

He added that cold tolerant species like rye can be used as forage (hayed) or spray killed early spring or before seeding soybean depending upon the moisture availability in the ground. Principle belief is that the cover crops planted should possess contrasting characteristics or growth habit than the major cash crop to be planted in the coming season.