Rye cover crop retains nitrogen and doesn’t reduce corn yields
2018
Snapp, Sieglinde | Surapur, Sowmya
Intensive nitrogen (N) fertilization is often associated with corn (Zea mays L.) production, and winter cover in the form of rye (Secale cereale L.) is proposed as a means to conserve inorganic N and soil carbon (C). Yet the seasonal niche for cover crop in field crop rotation in North Central USA is highly variable, leading to uncertainty regarding cover crop benefits. An 8-year study in SW Michigan examined winter rye cover vs fallow in a corn-corn-soybean (Glycine max) sequence, and interaction with a 7-rate N fertilizer gradient. Soil C, water retention, pH and nutrient status were negatively affected by high N fertilizer. Rye cover had almost no detectable soil amelioration, but did maintain mid-season N availability relative to fallow plots, as indicated by soil inorganic N (90 kg ha−1 vs 57 kg ha−1) and consistently high corn SPAD readings by 1.5 units. Soil aggregation, porosity and soil C pools were not influenced by the presence of a rye cover crop, with the exception of large particulate organic matter C. Over 8 years corn yields were not reduced in plots with a winter rye cover, under widely variable weather conditions. Overall, a rye cover crop had minimal impact on soil C but was an effective N management tool with no corn yield penalty.
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