Conservation Tillage Impacts and Adaptations in Irrigated Corn Production in a Humid Climate

We initiated a long-term experiment in 2008 on 1.25-ha farm-scale plots to assess the production impacts of no-till with full residue retention (NT) system over a conventional tillage (CT) system under irrigated corn (Zea mays L.) production on a Dundee silt loam soil in a humid climate. Data collected in the experiment from 2009 to 2015 were mainly confined to grain yield at harvest. In 2016 and 2017, additional data were collected including soil surface crop residue mass and soil surface residue cover; corn leaf area index (LAI) and biomass; soil water, temperature, N, C, and bulk density (Db); and the corn phenology. In 7 out of 9 yr (2009-17), harvested grain yields under NT were significantly lower than those harvested under CT. To investigate the possible reasons for the yield decreases under NT, we integrated the experiment with the Root Zone Water Quality Model to synthesize information on the various components in the system. The N loss to runoff and deep percolation, denitrification caused by higher soil water content, and a low N mineralization rate caused by lower soil temperatures under NT potentially contributed to the observed grain yield decrease under this treatment. Simulations showed that an additional N application at 40 kg ha(-1) at planting or a split application of 50 kg ha(-1) at planting and the remaining 174 kg ha(-1) in the second week of May could make the yield return under NT comparable to that under CT.