Nitrogen and Sulfur Recycling and Diagnostic in Cover Crop-Maize Systems

Abstract

It remains uncertain how oat (Avena sativa L.) and hairy vetch (Vicia villosa Roth.) impact both nitrogen (N) and sulfur (S) recycling in cover crop-maize (Zea mays L.) systems as well as N and S diagnostic methods in maize. Field trials were conducted at three sites in the southeastern Argentinean Pampas to evaluate the effect of oat, hairy vetch, and bare fallow combined with four N and S fertilization treatments (unfertilized, N-, S-, and NS-fertilized) on maize. Soil N and S content at maize sowing, chlorophyll meter reading (CMR) at silking, and grain yield were determined. Overall, soil NO3−-N content (0–60 cm) at maize sowing was hairy vetch > bare fallow > oat, while SO4−2-S content was hairy vetch > bare fallow = oat. Maize yield response to N was predicted from soil NO3−-N content (R2 = 0.80). The CMR was negatively correlated with cover crop residue quality (carbon (C)/N and C/S ratios). Also, CMR accurately predicted variations in maize grain yield. In the unfertilized treatment, maize yield was hairy vetch > bare fallow > oat, in two of the three sites. There was no yield response to N or S with hairy vetch. Oat and hairy vetch differentially affected N and S recycling in cover crop-maize cropping systems. Soil NO3−-N and SO4−2-S content at maize sowing combined with CMR are reliable diagnostic tools to assess maize N and S, allowing for sustainable fertilization management.