Cover Crops and Tillage Influence on Nitrogen Dynamics in Plant-Soil-Water Pools

Cover crops (CCs) planted after cash crop harvest have the potential to improve vadose zone water quality through scavenging residual soil N. Limited research is available on N release from the biomass after CC termination and its subsequent leaching. This study examined the influence of rotations corn (Zea mays L.)-no cover crop (noCC)-soybean [Glycine max (L.) Merr.]-noCC (CncSnc), corn-cereal rye (Secale cereale L.)-soybean-hairy vetch (Vicia villosa Roth) (CcrShv), corn-cereal rye-soybean-oat+radish (Avena sativa L.+Raphanus sativus L.) (CcrSor) and tillage (conventional-tillage [CT] and no-tillage [NT]) on available N in soil, N accumulation in plant biomass, and N leaching to pan lysimeters. The rotations CcrShv and CcrSor with hairy vetch and oat+radish resulted in 89% (37.7 vs. 20.0 kg ha-1) and 68% (33.5 vs. 20.0 kg ha(-1)) more nitrate N (NO3-N) leaching than CncSnc during cash crop season in fall 2015. Under CT in fall 2017, the rotation CcrShv (19.4 kg ha(-1)) had higher NO3-N leaching than CncSnc (3.2 kg ha(-1)) and CcrSor (1.4 kg ha(-1)). During CC season in spring 2016, cereal rye in CcrShv and CcrSor reduced NO3-N leaching by 84 and 78% compared with the CncSnc, respectively, under CT. Our results indicated that CT had greater N leaching losses than NT. The higher NO3-N leaching during cash crop season with rotations having CCs was due to the mismatched timing of N availability and demand by the cash crop.