By Sara Bauder, Extension Agronomy Field Specialist
As we put most of July behind us, it always seems that summer winds down quickly. Producers across South Dakota are harvesting small grains. These crops provide an excellent window for adding a cover crop into your rotation. Whether you grow a small grain or would like to fit a cover crop into your row crop rotation, there are many considerations to make.
Herbicide History. Consider your crop rotation as well as haying/chopping and grazing restrictions of herbicides previously applied; this includes herbicides applied before planting cover crops this season as well as those applied in the previous season.
Insurance, FSA Guidelines. Be sure to check with your insurance agent and FSA representative on all details regarding the seeding of your cover crop. Frequently asked questions and answers regarding insurance can be found on the Risk Management Agency (RMA) website.
Purpose. Always begin with the end in mind. Soil health, weed suppression, nutrient capture, soil moisture management, additional harvested forage, and grazing may all be common reasons to plant a cover crop. Try focusing on relevant objectives when creating a planting plan. The SD cover crop poster lists most common cover crops grown in South Dakota and their purpose ratings, seeding rates, and seeding depths can be found at the NRCS South Dakota website.
Seed Availability, Price. This is important to take into consideration before choosing a mix. Although most producers want to keep costs low, do remember that forage crops and/or improved soil health does come at a price, and some investment will be necessary.
Crop Rotation. Keep your previous crop and intended crop for next season in mind; it is generally recommended to plant cover crops of diverse growth habit to the subsequent cash crops, i.e., primarily broadleaves prior to grass cash crops, and vice versa.
Termination. Many cover crops will winter kill for the most part. However, some species may over winter such as cereal rye, winter wheat, triticale, etc. and/or have seed that can stay dormant for a prolonged period (hard seed) such as some ryegrass and vetch. This does not eliminate these crops as an option; it simply requires prompt spring attention and management as these crops may be of great value to utilize excess moisture in a potentially wet spring.
Weed Control. Often times, if a diverse cover crop mix is planted, it is nearly impossible to chemically control weeds during the growth of the cover crop. If a mix is well-planned and grown under ideal growing conditions, this is not typically an issue. However, if a particular weed is of concern, this should be considered before selecting cover crops. Winter rye is known for its inherent allelopathic characteristics, i.e. its ability to suppress weeds by the production of a biological chemical substrate that is harmful to other surrounding species; yet, other grasses as well as sprawling or more ground covering broadleaf crops (such as vetches, or radish and turnip) can aid in weed suppression by keeping soils covered.
Soil Fertility. If a producer is intending to use the cover crop as forage, nitrogen application may be required. Consider previous crop credits if legumes were planted, and current soil test levels. In many situations, low nitrogen application rates (30-60lbs/a) will provide considerable growth for cover crops; it is important to apply the appropriate rate of nitrogen when planting for forage purposes to avoid nitrate buildup in the plant which may cause toxicity to animals. Check the “South Dakota Fertilizer Recommendations Guide” for suggested soil fertility guidelines for major South Dakota crops.
Planting Time. As most cover crops are grown in blends, it is difficult to establish an exact seeding date based on individual crop species. However, there are suggested planting timing windows for crop types based on the proportion of different cover crops species in the blend. Cool season cover crops such as small grains, peas, clovers, vetch, and brassicas should be planted near or around the third week of July as average daily temperatures tend to decrease due to lower night temperatures; this creates a better growing environment for cool season species.
On the other hand, warm season species (forage sorghums, sorghum-sudangrass, buckwheat, sunflower, teff grass, etc.) can be planted prior to the third week of July, but ideally no later than the first week of August. Typically, these crops are planted in June. When planted within these suggested guidelines, cover crops should have ample growth to be harvested for forage after September 1. Remember that due to growth habit, some species in the mix may mature faster than others, which should not inhibit forage harvest.
The Bottom Line. Although there are many factors to take into consideration, cover crops can be an excellent tool to not only reduce fallow acres but also enhance soil health and provide supplemental forage. For more information, please do not hesitate to contact your nearest SDSU Extension regional center or local NRCS office for cover crop recommendations and other assistance.