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

Abstract

Core Ideas Cereal rye reduced the NO3–N leaching loads during the cover crop season. Nitrate‐N leaching in corn may increase following legume cover crops. Conventional tillage may result in greater N loss compared with no‐tillage. Poor synchronization of N supply‐demand by cash crop can result in higher N losses. 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.