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Availability of dissolved organic carbon drives differences in microbial nitrogen-cycling processes between two sites with cover crops interseeded into corn
  • Andrew Curtright,
  • Karen Renner ,
  • Lisa Tiemann
Andrew Curtright
Michigan State University College of Natural Science

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Karen Renner
Michigan State University College of Agriculture and Natural Resources
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Lisa Tiemann
Michigan State University College of Agriculture and Natural Resources
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Interseeding cover crops into corn has been proposed as a technique to extend the cover crop growing window, but interseeded cover crops may reduce N availability and compete with corn for available nutrients. To assess N-cycling dynamics in soils where cover crops have been interseeded into corn for one or two years, plots were established in duplicate at two sites in Michigan with differing edaphic properties. Annual ryegrass (Lolium multiflorum Lam.), crimson clover (Trifolium incarnatum L.), oilseed radish (Raphanus sativus L.), or a mixture of ryegrass and clover were interseeded into corn at the V3 or V6 stages of corn growth and compared to control plots that did not receive cover crops. We measured active C and N pools during the growing season and after harvest as well as potential activities of microbially mediated nutrient-cycling processes via extracellular enzymes, nitrification, and denitrification. We found that after two years, interseeded cover crops had little to no effect on active pools of C and N or on microbial nutrient-cycling activities. However, we observed major differences in these parameters between sites, with finer-textured soils exhibiting increased dissolved organic C availability and greater peptidase activity compared to coarser-textured soils. Our results reveal important spatial and temporal trends that suggest greater C availability can lower the potential for N loss while maintaining a rapid flux of N through the N cycle.