Cover Crop Nutrient Cycling on Western South Dakota Croplands

Cover crops (CC) are widely gaining attention and implementation by producers. Much of this is due to the positive influence that CCs can have. Increases in crop yield, biological diversity, water infiltration, and nutrient cycling have been observed as well as reductions in wind and water erosion. The semiarid climate of western South Dakota presents a challenge in the use of CCs with the limited rainfall received. Little research has been done in this area on the effects of CCs on cropland. Three studies were performed to evaluate CCs on nutrient cycling, forage production and crop yield. First, is an examination on the replacement of summer fallow with cover crops. Minimal differences were observed, though greater phosphorus cycling and availability occurred through use of cover crops. The second study involved the use of a winter cover crop planted after wheat harvest. Three CC mixes were planted along with an unplanted control. A grass, broadleaf, and 50/50 mix were used, where each mix contained the same eight CC species, however, varying in percentage of CC composition. Levels of zinc (Zn) were found to be affected by the use of CCs, where greater amounts of Zn were seen after CC growth, particularly in the broadleaf CCs. The third experiment immediately followed the second, where grain sorghum was planted in the spring following the winter CCs. After emergence of the grain sorghum, six nitrogen (N) rates were applied at 0, 40, 80, 120, 160, and 200 lbs N/A. Yield of the grain sorghum was then evaluated on CC effect, N response curve, and economic optimums. Grain sorghum yield consistently trended greater following the broadleaf CC, until very large N rates were applied, where the grass CC then had a trend of resulting in slightly greater grain sorghum yield. Broadleaf CC then again trended with the lowest optimum N rate for the greatest sorghum yield, but also the greatest revenue with the least applied N, when evaluating N response and economic optimum curves. Benefits of CC use can be seen in western SD in nutrient cycling, forage production and crop yield, though more research is still needed