Effect of combined application of biochar and N-fertilizer on yield and C:N:P ratio of spring wheat

Carbon (C), nitrogen (N) and phosphorus (P) are the 3 main elements existing in living organisms. It has long been known that C:N:P stoichiometry of consumers and their resources affect both the structure and function of the food web that eventually influence broad-scale processes such as global carbon cycles. The balance of these nutrients can influence plant growth and its stoichiometry in ecosystems. Wheat is one of the most important food crops and wheat production affects global food security. The combined application of biochar and N fertilizer has been reported to be a beneficial agronomic measure, and noted to affect grain yield and C:N:P allocation patterns in wheat. In addition, the study of different N fertilizer and biochar on wheat yield, C, N and P contents and their ratio have been closely linked with nutrient limitation and rational fertilization. In this study, we explored the yield and C, N and P contents and their ratios of wheat under different N-fertilizer and biochar treatments (50 kg·hm^-2 N-fertilizer, 100 kg·hm^-2 N-fertilizer, biochar, biochar combined with 50 kg·hm^-2 N-fertilizer, biochar combined with 100 kg·hm^-2 N-fertilizer and no N-fertilizer or biochar as control). The results showed that different treatments significantly increased wheat straw and grain yield, compared with that of control treatment. Except for the single biochar application, other treatments increased N contents of wheat organs. Biochar combined with different doses of N-fertilizer significantly increased C and P contents of both wheat stem and grain. Biochar combined with 50 kg·hm^-2 N-fertilizer significantly decreased leaf C:N and C:P ratios. Then biochar combined with 100 kg·hm^-2 N-fertilizer significantly reduced stem C:N, C:P and N:P ratios and grain C:N and C:P ratios. In terms of nutrient limitation, N:P ratio in wheat leaf in the study area was 18-23, wheat may be limited by P element. Biochar combined with N-fertilizer significantly increased wheat yield and CNP nutrient contents. At the same time, it decreased wheat C:N, C:P and N:P ratios. From the above, the comprehensive performance of biochar plus 100 kg·hm^-2 N-fertilizer was the best pattern to enhance wheat productivity.