Selecting Cover Crop Species/Varieties

It is now well established that cover crops should be considered as an integral part of any cropping system that seeks to become more sustainable since they provide documented environmental and soil health benefits. These benefits arise from:

•    Providing soil cover to prevent erosion in the off-season;

•    Increasing water infiltration into the soil;

•    Reducing nutrient loss and leaching from the soil profile;

•    Lowering residual nitrogen (N) content in the soil;

•    Reducing herbicide runoff;

•    Suppressing or reducing early-season weeds and weed biomass;

•    Providing plant residues to increase soil organic matter; and

•    Increasing the soil N supply for a following summer grain crop.

Now is the time to plant cover crops for the 2021-2022 season that is to bridge the gap between 2021 and 2022 summer crops. When selecting a cover crop species or a particular variety within a species to plant, the following should be considered.

•    Major categories of cover crops are: 1) grasses such as wheat, rye, and oats; 2) legumes such as vetches, peas, and clovers; and 3) brassicas.

•    The reason for planting a cover crop should be determined–e.g. is it to: 1) provide winter cover to reduce or prevent erosion; 2) provide ground cover and biomass to suppress or prevent weed emergence and growth; 3) add nitrogen (N) to the soil; 4) remedy soil problems such as compaction; 5) scavenge soil N that is left over from a preceding summer grain crop; or 6) increase soil organic carbon (SOC).

•    Cover crops should be planted early enough to: 1) establish an adequate stand before the onset of low temperatures; 2) achieve the desired growth for biomass production and weed suppression; and 3) achieve adequate growth for significant N fixation (legumes).

•    A cover crop following corn can be used to allow a greater amount of corn residue to be harvested for sale as cellulosic ethanol feedstock.

•    Choose a cover crop that is the opposite type of the subsequent summer crop; i.e. soybeans should be preceded by a winter small grain such as wheat or rye, and corn should be preceded by a legume.

•    The desired benefit should be determined before selecting a cover crop species. If the intent is: 1) to add N to the soil, choose a legume; 2) to scavenge unused N from a preceding crop, choose a cereal such as rye; 3) to aid in weed control, choose a species that will produce the most biomass; 4) to break up soil compaction, choose a brassica such as tillage radish or canola; and 5) to add organic matter to the soil, choose a crop such as cereal rye that has a dense root system.

Scientists at both Miss. State Univ. and the Univ. of Tenn. have published results from cover crop variety trials that have been conducted in those states. Producers are encouraged to consult the results from these trials to find the species and varieties within species that have the greatest potential for providing the maximum desired benefit from inserting a cover crop into a cropping system.

Click here for a White Paper on this website that discusses use of cover crops in detail.

Composed by Larry G. Heatherly, Sept. 2021, larryh91746@gmail.com