Cover crops scavenge soil nutrients as they grow and
ultimately release them for following crops to use. This
reduces the potential for nutrient losses, especially N.
Cover crops help hold soil in place, reduce crusting
and protect against erosion due to wind and rain.
Cover crop biomass contributes to soil organic matter,
which helps to improve soil structure, water infiltration,
and water-holding and nutrient-supply capacity.
Cover crop roots can act as “living plows,” breaking up
compacted soil layers. Cover crop shoots can also
help protect the soil from the impact of heavy rains.
Leguminous cover crops fix N as they grow. This N
mineralizes after the cover crop is terminated and
becomes available for use by future crops.
Cover crop residues increase water infiltration and
limit soil evaporation. This helps to reduce moisture
stress during drought conditions.
Cover crops shade the soil, which can reduce weed
germination and growth. Some cover crops also have
an allelopathic effect on weeds.
In some areas, it may be possible to graze, hay or
chop cover crops before terminating in the spring.
In recent years, interest in adding cover crops to corn and soybean cropping systems has increased as their potential benefits have become more widely recognized. Most of these benefits are realized over time as their ongoing use improves soil quality and function (Table 1). Thus, cover crops are best viewed as a long-term investment in soil productivity.
Grasses, including winter cereals such as rye, wheat, barley and triticale, are the most widely used cover crops in corn and soybean cropping systems. Winter cereals are typically planted in late summer through late fall and produce a small to moderate amount of root and above-ground biomass before going dormant in the winter. Vigorous growth resumes in early spring, and large amounts of biomass are produced by mid to late spring. Some growers prefer non-winterhardy cereals like oats, which establish rapidly in the fall but winterkill and leave behind little residue to manage in the spring. Annual ryegrass is another option if spring residue levels are a concern.