Water and Soil Quality Respond to No-Tillage and Cover Crops Differently Through 10 Years of Implementation

Abstract

Addressing the global problem of eutrophication will require better management of inorganic nitrogen (N) on the agricultural landscape. This study investigates the impacts of no-tillage (NT), no tillage with winter cereal rye (NTr), and conventional tillage with rye (CTr), and a perennial (P) in comparison to a control system of conventional tillage without a cover crop (CT). All plots are individually drained and, except for P, in a corn/soybean rotation which dominates much of the Midwestern U.S. Drainage quantity and nitrate-N concentration were measured from individually drained plots 2011 to 2020. Treatments P, CT, and CTr began in 2004 and we report on years 7 to 11 (phase 1) and years 12 to 16 (phase 2). Treatments NT and NTr began in 2010 and we report on years 2 to 6 (phase 1) and 7 to 11 (phase 2). CTr and P functioned similarly throughout with consistent reductions in NO3-N concentration in leachate and loading. In contrast to initial expectations, when comparing NT to CT, there were consistent reductions in NO3-N concentration in leachate and loading in phase 1, but not in phase 2. Similarly, NTr did not reduce NO3-N concentration compared to NT in phase 1, but it did in phase 2. These results both indicate that there were possible changes to soil properties in the NT and NTr systems that influenced N cycling that could be unique to high carbon artificially drained environments. Soil quality improvements were detected in these mollisols after 15 years of cover crops in the conventional system, and after 10 years of NT and NTr. In this study, CTr was more consistent at improving water quality and maintaining cash crop yields than NTr. Both NTr and CTr had greater cover crop growth when the cover crop seeding method changed from drill-seeding after harvest in phase 1 to broadcast seeding in a standing crop in phase 2 due to a longer growth period. That water and soil quality responses changed over the years emphasizes the need for long-term studies.

Keywords: Nitrate-nitrogen, Cover crops, No tillage, Subsurface drainage, soil organic matter