Cover crop species can increase or decrease the fertilizer-nitrogen requirement in maize

Abstract

Cover crop species and termination date could affect fertilizer-nitrogen (N) management and N diagnostic methods traditionally used in bare fallow-maize (Zea mays L.) systems. Our objectives were to (a) assess the effect of cover crop termination date on maize yield and response to fertilizer-N, (b) determine maize yield at varying N rates following different cover crop species and mixtures, and (c) evaluate the chlorophyll meter reading (CMR), grain N concentration (Nc), and grain N nutrition index (NNI) as N diagnostic methods. Experiments were conducted at four sites in the southeastern Argentinean Pampas with maize planted after cover crops. Factors investigated were cover crops with vetch (Vicia villosa Roth), vetch–oat (Avena sativa L.) mixture, or bare fallow; early termination of cover crops or ∼3 wk later; and maize fertilizer-N at 0, 50, 100, and 200 kg N ha–1. The minimum N rate that maximized grain yield was higher in vetch–oat mixture (100 kg N ha–1) than in vetch (50 kg N ha–1). Maize yield was not affected by cover crops with 200 kg N ha–1. Late termination dates of vetch–oat mixture reduced maize yield by 15% compared with early termination dates, while there was no effect of vetch termination date. Cover crop termination date did not affect yield response to fertilizer-N. Relative CMR at silking, grain Nc, and especially grain NNI at maturity were useful tools to diagnose maize N status and cover crop effect. Cover crop management should be considered to adjust the fertilizer N rate and optimize maize productivity.