Nitrogen fertilizer effects on sugarcane growth, nutritional status, and productivity in tropical acid soils

Knowing the influence of long-term N fertilization is a key aspect in improving the yield of most crops, including sugarcane (Saccharum spp.). We aimed to assess the effect of N-fertilizer sources and rates on sugarcane yield, biomass partitioning, juice quality, nutrient accumulation, and N efficiency in acid soils. Two field experiments were carried out in southeastern Brazil for consecutive five years. Six N-fertilizer managements {[}ammonium nitrate and urea at a rate of 100 kg N ha(- 1) (AN100 and UR100, respectively), calcium ammonium nitrate at a rate of 50, 100, 150, and 200 kg N ha(- 1) (CAN50, CAN100, CAN150, and CAN200, respectively)] were applied to acidic soils. Nitrogen fertilization did not affect sugarcane and sugar yields at the site with previous rotation with peanut (Arachis hypogea) before crop replanting. Conversely, at the site under continuous monoculture, AN100, CAN100, and CAN150 showed increases of 7-25% in sugarcane and sugar yields, and 3-7% in Brix and recoverable total sugar content. We conclude that in responsive sites, fertilizer N additions improve crop yield and juice quality, although high N inputs in the long term (> 100 kg N ha(- 1)) can reduce sugarcane sustainability. Similarly, non-responsive sites can exhibit substantial economic losses and environmental pollution. Identifying responsive and non-responsive sites to fertilizer N is required for improving N use efficiency and reducing environmental risks and economic losses. (AU)