Soil mineral nitrogen content and grain yield with enhanced efficiency fertilizers in maize

Abstract

Urea is the most common N fertilizer worldwide, but N from urea breakdown can be easily lost through ammonia (NH3) volatilization, ammonium (NH4+) nitrification, nitrate (NO3−) denitrification or NO3−–leaching processes. Enhanced efficiency fertilizers (EEFs) are formulated to minimize N losses and maximize plant N uptake and crop yields. The capacity of urea EEFs (urea with urease inhibitor, nitrification inhibitor, both urease and nitrification inhibitors, and polymer-coated) to maintain N in the soil profile throughout the growing season was determined by the analysis of [NH4+–N] and [NO3−–N] in three top-soil depth increments at three dates in three seasons of no-till maize (Zea mays L.). Surface-applied EEFs, untreated urea, and injected urea ammonium nitrate (UAN) were compared at an application rate of 168 kg N ha−1. Within and across years, soil [NO3−–N] and [NH4+–N] typically decreased with depth and time since urea application. Among the EEFs, only a polymer-coated urea produced greater [NO3−–N] and [NH4+–N] at several sampling dates and depths, and greater grain yields than untreated urea across the 3 yr. Nonetheless, the polymer-coated urea resulted in significantly greater fertilizer use efficiency (FUE) than untreated urea in only 1 of 3 yr. Several EEFs increased grain yields compared to untreated urea each year, but FUE generally was similar to that with untreated urea. Environmental conditions influenced the effectiveness of EEFs in improving soil mineral N availability and increasing grain yield.