Beehler, J. 2016. The effect of cover crop on soil carbon and soil water retention in topographically diverse terrain. Thesis, Michigan State University, East Lansing, Michigan.
Farmers must consider real-world landscape variability to maximize yields and minimize environmental impacts when using cover crops in corn-based cropping systems. In the Midwest corn belt much of the variability farmers encounter is due to the topographical diversity of the undulating landscape. The objectives of this study are to explore the interactive effects of the presence or absence of cover crops and topography (summit, slope, and depression positions) on total soil organic carbon, on its labile form, particulate organic carbon, carbon dioxide emissions, cover crop decomposition, soil water retention, and crop growth. A cereal rye cover crop was established each fall after the main crop (corn and soybean) harvest from 2011-2015 at two experimental sites, Kellogg Biological Station (Kellogg) and Mason, which have loam and fine sandy loam soils, respectively. Main crop and cover crop growth were both higher in the depression, but did not differ in topographical position and main crop growth did not differ in the presence/absence of the cover crop. In the absence of the cover crop, topography affected particulate organic carbon but not in the presence of the cover crop (p<0.1). Decomposition and carbon dioxide emission followed the trend depression>summit>slope, but no one variable accounted for the distribution of particulate organic carbon. Total organic carbon and water retention were not affected by the cover crop in this study. A long-term study may reveal additional significant changes in the presence of a cover crop not detectable in a five-year study.
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