Optimizing Nitrogen Use Efficiency for No-Till Corn Production by Improving Root Growth and Capturing NO3-N in Subsoil

Subsoil acidity restricts root growth and reduces crop yields in many parts of the world. More than half of the fertilizer nitrogen (N) applied in crop production is currently lost to the environment. This study aimed to investigate the effect of gypsum application on the efficiency of N fertilizer in no-till corn (Zea mays L.) production in southern Brazil. A field experiment examined the effects of surface-applied gypsum (0, 5, 10, and 15 Mg ha−1) and top-dressed ammonium nitrate (NH4NO3) (60, 120, and 180 kg N ha−1) on corn root length, N uptake, and grain yield. A greenhouse experiment was conducted using undisturbed soil columns collected from the field experiment site to evaluate NO3-N leaching, N uptake, and root length with surface-applied gypsum (0 and 10 Mg ha−1) and top-dressed NH4NO3 (0 and 180 kg N ha−1). Amelioration of subsoil acidity due to gypsum application increased corn root growth, N uptake, grain yield, and N use efficiency. Applying gypsum to the soil surface increased corn grain yield by 19%–38% and partial factor productivity of N (PFPN) by 27%–38%, depending on the N application rate. Results of the undisturbed soil column greenhouse experiment showed that improvement of N use efficiency by gypsum application was due to the higher N uptake from NO3-N in the subsoil as a result of increased corn root length. Our results suggest that ameliorating subsoil acidity with gypsum in a no-till corn system could increase N use efficiency, improve grain yield, and reduce environmental risks due to NO3-N leaching.