Cover crops can be beneficial to the environment and also to a dairy producer's forage options.
By: Karla Hernandez, Forages Field Specialist, SDSU Extension
Grain producers are often looking for ways to increase revenues from their land. In the Upper Plains it might not be economical, or even practical, to plant another grain crop during the growing year; however, it may be in the producer’s interest to consider a cover crop. Cover crops provide multiple benefits to the producer and the environment. The primary benefit is additional forage production from the growth of the cover crop which can be used by the producer for on-farm uses or sold to other livestock producers. Environmentally cover crops offer benefits including improved soil quality by protecting soil from erosion, increased soil microbial activity and nutrient cycling, all while managing nitrogen and adding carbon to the soil. Some of the main concerns for producers adding cover crops into their production scheme are: (1) When will I plant? (2) When and how to harvest? and (3) Which cover crops provide the best forage?
When and What to Plant
Cover crops create new opportunities to enhance rotation diversity. A significant consideration in favor of cover crops is that they offer a break in the insect growth cycle which can in turn aid with following crop yields by reducing pest influence and insecticide usage. Cover crops are often described in four broad categories: cool season grasses (barley and oats), cool season broadleaves (field peas and turnips), warm season grasses (millet and sorghum), and warm season broadleaves (cowpea and sunflower). The decision of what to plant is highly variable, depending upon many factors including: 1) remaining growing season, 2) the soil-types in the producer’s field, 3) how adaptable the cover crop is to growth practices used by the producer including equipment available and herbicides used, and 4) what can be obtained from the local seed provider.
Many cover crops can work for forage supply, but the selection of which cover crop to use will depend on when you want to plant it and what is the purpose. Usually cover crops are planted from July through middle of September after small grain or corn silage is harvested. A useful guide to cover crop mixes after small grains can be found at the NRCS website.
Incorporation of Cover Crops for Forage Supply
One way to incorporate cover crops into a grain or livestock production system is to seed winter rye after corn silage has been completed. Another possibility is incorporation of winter rye into a corn-soybean rotation following the fall harvest. Either option can improve soil quality, reduce soil erosion, suppress winter annual weeds, and increase overall forage production for hay or silage. In a recent study conducted by SDSU, winter rye planted after corn was harvested for grain and to observe rye biomass used as a forage crop. The trials were conducted at the Beresford and South Shore SDSU Research Farms during the 2012 to 2013 winter/spring growing seasons. Rye biomass was determined in the spring before planting soybeans during both years. Overall, winter rye biomass at 15% moisture was 3580 lbs/acre at Beresford, whereas at South Shore, it was 1260 lbs/acre. The average crude protein (CP) was around 19%, whereas relative feed value (RFV) ranged from 118 (South Shore) to 144 (Beresford) between both locations. In these studies, differences among rye biomass grown after corn with differing maturity levels was minimal, which suggest that using rye cover crops after regular maturity corn would maximize profits. The impact of the rye forage crop on soybean yields depended on summer rainfall. At Beresford and under the extreme 2012 drought, soybean yields severely decreased when a rye forage crop was used. In 2013 however, when rainfall was adequate, no negative impact on soybean yield was observed.
Other cover crops options producers are using across the region include seeding into a harvested corn-field a 2 to 3 pounds per acre mix of turnips, crimson clover and annual ryegrass. Seed may be broadcasted or spread with a modified "Hi-boy" spreader. Shade-tolerant Crimson clover may be sown with oats when the oats are planted, creating a "layered" field. After the oats are harvested, the clover continues to grow and its growth is stopped by the fall frost. Oats and field peas may be sown together for silage, diversifying the crop rotation. This can be followed with a complex cover crop blend that includes millet, sorghum, sudangrass, sunflower, buckwheat, brassicas, cowpea, soybeans, and others.
Incorporation of Cover Crops for Dairy Production Systems
Several opportunities exist to incorporate cover crops into dairy forage production systems. According to the most recent reports, cows that are normally fed corn silage and are then put into a grazing routine of cover crops near the dairy see no substantial reduction in milk production. Cover crops mixes can be harvested and ensiled, but soil health benefits are not as strong as grazed cover crops. Producers should remember that the careful planning of planting and grazing or harvest times of cover crops is essential to maximize their utilization as feedstuffs in dairy cattle diets.
Cover crops planted after grain or silage harvest provide a quality grazing forage alternative in late fall or early winter. Major things to consider when planting cover crops are seed price and compatibility with the chemicals used in the preceding crops. Using a cover crop different in growth requirements than those of the crop to follow would help break pest cycles in the field. A producer with an integrated grain and cover crop plan stands to see some significant gains for their operation in both economic and environmental terms.