Nitrogen Non-Cycling from Cover Crops Grown Before Corn and Spring Wheat-Unexpected Early Project Results
Nitrogen credits in North Dakota State University fertilization recommendations include those anticipated from the previous year annual legume crops (field pea, lentil, soybean, chickpea) and from terminated alfalfa. In addition, it was established in the region that sugarbeet tops returned to the soil may have an N credit potential of up to 80 pounds of N per acre (Crohain and Rixhon, 1967; Moraghan and Smith, 1994a; Moraghan and Smith, 1995a; Moraghan and Smith, 1995b; Franzen et al., 2002). Given the success of sugarbeet top N release to the subsequent crop, in theory it would be likely that any cover crop with a low C/N ratio would also provide N to the subsequent crop. Several Extension circulars and journal articles indicate that release of N to the next crop is possible if the percent N in the cover crop is greater than 1.5% (Sullivan and Andrews, 2012), a cover crop grass is sufficiently rich in N (Magdoff and van Es, 2010) or is terminated several weeks prior to planting season (Ketterings et al., 2015), or the cover crop is a legume (Gentry et al., 2013). The purpose of this on-going study is to determine the N credit from cover crops to corn and spring wheat in North Dakota.