Cover Crop Bicultures and Their Effects On Phosphorus Cycling and Soil Conservation.

Cover crops have received a great deal of attention throughout the U.S. Corn Belt as a result of recent focuses on long-term soil quality. Oilseed radish (Raphanas sativas L.) (OSR) has become a popular cover crop among producers because of its many benefits in soil. With its large tuber, OSR can take up large amounts of phosphorus (P) and can biologically till the soil before winter-killing. Because OSR consists of a low C:N ratio, it decomposes and releases nutrients rapidly in the spring. This rapid decomposition could lead to losses of bio-tilled soil and released P via runoff and erosion. Species of cover crops such as oats (Avena sativa L.) and cereal rye (Secale cereal L.) have higher C:N ratios and decompose more slowly in the spring. Mixing OSR with oats or cereal rye (bicultures) could provide the benefits of an OSR cover crop while also maintaining released-P and bio-tilled soil at the surface. A field study was conducted at three sites in Indiana to observe the effects of cover crops on soil P, runoff and erosion, and subsequent crop yield. The four treatments were OSR (alone), OSR/Oats, OSR/Rye, and no cover crop. Three fields were established in fall 2011, and one was established in fall 2012. Soil samples were obtained at four times: before cover crops, fall, spring, and at V6 of corn following cover crops at multiple depths and row positions. Corn was planted in the same plots following the 2011 cover crops. Soil P increased over time at the soil surface and near the roots, but levels were no different following cover crops than they were before cover crops. The OSR/Rye treatment significantly decreased soil and P losses through runoff and erosion. The treatments did not have a significant effect on subsequent corn yield.