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

Abstract

Core Ideas Cereal rye reduced the NO 3 –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 (NO 3 –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 NO 3 –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 NO 3 –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 NO 3 –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.