Surapur, S. 2014. Effects of long-term cereal rye winter cover crop on soil quality, soil N availability and yields across a nitrogen gradient in a rainfed Michigan corn system under conventional tillage. Thesis, Michigan State University, East Lansing, Michigan.
The objectives of this study were to (1) evaluate the 9-year cumulative effects of a winter rye cover crop on soil quality in a corn-corn-soy rotation, (2) measure N supply and soil N pools after cereal rye WCC incorporation and its impacts on corn N availability across an N fertilizer gradient (0, 34, 67, 101, 134, 168, or 202 kg ha-1) during the 2013 growing season, and (3) assess N response to corn yield under WCC and no cover crop (fallow) treatments from 2006 to 2013. This experiment was conducted at Michigan State University’s W.K. Kellogg Biological Station using a split-split plot RCBD with a main plot effect of winter rye cover crop versus winter fallow, split into seven subplots, which were randomly assigned to a gradient of N fertilizer. Between 2006 and 2013, the annual aboveground cereal rye WCC accumulation ranged between 0.53 to 1.46 Mg ha-1. Cereal rye WCC did not affect soil structure (bulk density, water stable aggregates), soil-water relationships (total porosity, soil water retention), or soil biological activity (POXC, soil enzyme activity, litterbag decomposition rates). Our most interesting finding was the effect of WCC on enhanced POM-C content of the large POM fraction (p=0.05), but no other measure of soil organic matter pools. Our results find evidence of synchrony of N mineralization to crop N demand after cereal rye WCC compared to fallow plots during the 2013 corn growing season. Over the 9-yr period of this study, WCC posed no negative impacts on corn yields compared to fallow treatment plots.
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