A comprehensive analysis of the nitrogen synchrony between cover crops release and maize uptake

Abstract

Background and aims: Quantitative analyses of the synchrony between nitrogen (N) release from cover crops (CCs) and maize (Zea mays L.) uptake remain limited. This study aimed to i) develop a method to assess N synchrony, ii) analyze how CC species and termination dates affect N synchrony, and iii) relate N synchrony to CC characteristics, maize yield, and associated N traits. Methods: We quantified N synchrony as the percentage match between daily N release from CCs and the portion of maize N uptake not met by soil supply. This approach was used to calculate N synchrony and excess-asynchrony for three CCs [oat (Avena sativa L.), hairy vetch (HV, Vicia villosa Roth.), and an oat–HV mixture (Mix)] with two termination dates (early and late) over two seasons. Results: Nitrogen synchrony was higher in HV and Mix than in oat (81%, 70%, and 23%, respectively), and higher in late terminations (~ 1 week before maize sowing) than early terminations (~ 4 weeks before sowing) (65% vs. 51%). An N accumulation of ~ 140 kg N ha−1 in CC aboveground biomass optimized the balance between N synchrony and excess-asynchrony. N accumulation, C:N ratio, and the days between CC termination and maize sowing explained N synchrony variability (R2 ≥ 0.77). N synchrony was negatively related to maize yield response to N and positively related to N use and recovery efficiencies. Conclusion: This analysis provides insights to guide CC management for improving maize yield, optimizing N fertilization, and reducing environmental N losses.