Tillage Effects on Nitrogen Recovery by Corn from a Nitrogen‐15 Labeled Legume Cover Crop

Abstract

Abstract The purpose of this study was to determine the effects of tillage on corn ( Zea mays L.) total N uptake and recovery of N from 15 N‐depleted legume residue. A conventional tillage (CT) variable was introduced into a 7‐yr‐old no‐tillage (NT) corn study in 1984 by moldboard plowing and disking half of each no N plot having either corn residue (winter fallow) or hairy vetch ( Vicia villosa Roth.) cover. Prior to plowing each year, in situ hairy vetch vegetation was removed and replaced with fresh 15 N‐depleted hairy vetch vegetation at a comparable rate. In 1984, final total N uptake by corn with vetch cover was 31 kg ha −1 greater with CT than with NT; however, no difference in grain yield occurred. This was a year characterized by limited precipitation during grain fill. In 1985, early season N uptake was greater with CT but there was no difference in final total N accumulated between tillage systems. Averaged across cover treatments, CT resulted in more grain yield than with NT. With vetch, corn N uptake in excess of that with corn residue averaged 60 kg ha −1 yr −1 across tillage systems. Recovery of vetch ( 15 N (N v ) averaged over years was 32% with CT and 20% with NT. In both years this difference was established by 42 d after planting and the pattern of N v recovery after this day was similar for both tillage systems. Residual recovery of N v by corn the second year after application was greater with NT (7%) than with CT (3%). With vetch cover, extractable soil N levels were most elevated early in the growing season, particularly with CT in the 0.1‐ to 0.2‐m soil depth.