Effect of biochar on nitrogen use efficiency, grain yield and amino acid content of wheat cultivated on saline soil

Biochar can potentially increase crop production in saline soils. However, the appropriate amount of biochar that should be applied to benefit from resource preservation and increase both grain yield (GY) and quality is not clear. A pot experiment was conducted to evaluate the effects of biochar applied at various rates (i.e., 0, 5, 10, 20, 30, 40 and 50 t/ha) on the nitrogen use efficiency (NUE), GY and amino acid (AA) contents of wheat plants in saline soils. The results showed that the application of 5-20 t/ha biochar increased wheat NUE by 5.2-37.9% and thus increased wheat GY by 2.9-19.4%. However, excessive biochar applications (more than 30 t/ha) had negative effects on both the NUE and GY of wheat. Biochar had little influence on leaf soil and plant analyzer development (SPAD) values, the harvest index or yield components. The AAs were significantly affected by biochar, depending on the application rate. Among the application rates, 5-30 t/ha biochar resulted in relatively higher (by 5.2-19.1%) total AA contents. Similar trends were observed for each of the 17 essential AAs. In conclusion, the positive effects of biochar occurred when it was applied at appropriate rates, but the effects were negative when biochar was overused.