Biochar application to rice with 15N-labelled fertilizers, enhanced leaf nitrogen concentration and assimilation by improving morpho-physiological traits and soil quality

Abstract Leaf nitrogen (N) concentration plays an important role in biochemical and physiological functions, and N availability directly influences rice yield. However, excessive N fertilization is considered to be a root cause of environmental issues and low nitrogen use efficiency. Therefore, the selection of appropriate nutrient management practices and organic amendments is key to maximizing nitrogen uptake and maintaining high and sustainable rice production. Here, we evaluated the effects of different 15N-labelled nitrogen sources (urea, ammonium nitrate, and ammonium sulfate at 315 kg ha−1) with or without biochar (30 t ha−1) on paddy soil properties, root growth, leaf gas exchange, N metabolism enzymes, and N uptake in the early and late seasons of 2019. We found significant differences among N fertilizer sources applied with or without biochar (P