Impacts of Nitrogen Management on No‐Till Maize Production Following Forage Cover Crops

Abstract

Core Ideas Urochloa brizantha as cover crop produced more biomass and nutrient cycling than U. ruziziensis. Nitrogen fertilizer on Urochloa cover crops increased biomass production but limited maize yield. The highest maize yields were obtained when N was applied on day before seeding or under conventional method (N applied at seeding plus sidedressing). All N applied on Urochloa residue prior to maize can be an option, but is risky in regions of high rainfall. Crop residue decomposition is slower in no‐till (NT) systems, especially in high‐biomass systems. Adopting optimum nN management can provide increased soil coverage and synchronize the supply of nutrients with the period of highest crop demand in agroecosystems. A three‐year experiment was conducted to assess the feasibility of applying N on forage grass cover crops before termination {Urochloa brizantha (Hochst. Ex A. Rich.) R.D. Webster [syn. Brachiaria brizantha (Hochst. Ex A. Rich) Stapf] and Urochloa ruziziensis (R. Germ. and C.M. Evrard) Crins [syn. B. ruziziensis (R. Germ. and C.M. Evrard)]}, or on forage grass cover crop residues immediately before maize (Zea mays L.) seeding, aiming to supply N to the following maize crop. Urochloa brizantha had 25% higher biomass production and a higher amount of nutrient content than U. ruziziensis. The N application before termination increased biomass production and nutrient content in cover crop residues compared with the conventional fertilization method (30 kg N ha−1 in the maize seeeding plus 170 kg N ha−1 sidedressed in V6 growth stage). Nitrogen applied one day before seeding (DBS) of maize or using conventional method resulted in a higher number of ears per plant and more kernels per ear as well as a higher grain yields of maize (13.8 and 14.1 Mg ha−1, respectively) compared to N applied on cover crops. Our results suggest that, while both forage grass cover crops produced greater amounts of dry matter (DM) and released similar amounts of nutrients, applying all N to cover crops before maize is not a feasible alternative. Nitrogen application 1 DBS could be an alternative management option to supply N to maize because this method resulted in similar nitrogen use efficiency (NUE) as conventional fertilization method.