Cover Crop and No-Tillage Impacts on Soil Health and Soil Nitrogen in Indiana
Cover crops, plants grown during the fallow period between cash crop growing seasons, have gained increasing amounts of attention throughout the agriculture industry in recent years. Many producers use them to reduce soil erosion, scavenge nutrients, and improve soil structure, water infiltration, and soil health, but questions still remain on maximizing cover crop benefits while simultaneously maintaining or improving cash crop production. This study measured cover crop and no-tillage effects on soil nitrogen and cash crop yield across multiple sites in Indiana beginning in fall 2015 and ending in fall 2017, typically in a corn (Zea mays L.)/soybean ( Glycine max L. Merr.) rotation. Many of the sites had utilized cover crops for at least three to four years by fall 2015 as part of the Conservation Cropping Systems for Soil Health and Productivity (CCSSHP) Project, which was initiated in fall 2012. Cover crops generally reduced soil nitrate-N levels compared to no cover crops in the fall when good cover crop growth occurred. The same trend occurred in the spring, again when cover crops had good growth and did not winter kill. Cover crops did not negatively influence cash crop yields in fall 2016 or fall 2017. In addition, in 2017 a subset of three sites comparing cover crops versus no cover crops in no-tillage, and one with a tillage and no cover crop conventional neighbor, were selected for an in-depth look at soil health indicators across five sampling dates during the cash crop growing season. In previous years of the study, soil health indicators were measured once yearly at V3-V6 growth stages in corn. In order to determine if sampling at that time was ideal for detecting real differences in soil health indicators between cover crop and no cover crop treatments, four additional sample times were selected for comparison. The indicators discussed included active carbon and soil respiration, as measured by the Cornell Comprehensive Assessment of Soil Health (CASH), as well as arbuscular mycorrhizal fungi (AM-fungi), gram positive bacteria, gram negative bacteria, non AM-fungi, fungi:bacteria ratio, actinobacteria, protozoa, and total PLFA, which is used as an estimate of total microbial biomass, as measured by a PLFA analysis conducted by the University of Missouri Soil Health Assessment Center. Results indicated that sampling time selection should be chosen based on the goals of the sampler. To find differences between a cover crop and no cover crop comparison, when ample cover crop biomass growth occurs in the spring, sampling at V3-V6 growth stages in corn may be best. To detect the highest values throughout the whole season, particularly in indicators measured in the PLFA analysis, sampling at the end of the season after cash crop harvest may be best.
Kladivko, Purdue University.
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