Different rates of biochar application change 15N retention in soil and 15N utilization by maize.

Biochar application to soil may impact soil nitrogen (N) dynamics, but the effects on N uptake and utilization by crop remain largely unknown, especially the effects of the rate of biochar application. To investigate the effects of biochar on soil 15N retention rate and 15N utilization efficiency (15NUE) by maize, a six‐month 15N isotope tracer technique combined with in situ pot experiment was conducted in Mollisol. The experiment included four treatments: no biochar applied (CK) and biochar applied at the rates of 12 t ha−1 (P12), 24 t ha−1 (P24) and 48 t ha−1 soil (P48). Compared with CK, biochar application reduced soil bulk density and 15N loss rate, and significantly improved total N and 15N retention amount in the 0–30 cm soil depth. The P24 treatment had the largest increase in 15N retention rate throughout the 0–40 cm depth. After biochar application, the 15N uptake and 15NUE were significantly increased in the grain and leaf, which promoted grain yields. Contrary to this, the P48 treatment appeared to lower 15N uptake and 15NUE compared with P12 and P24. In conclusion, biochar application improves the potential of the soil to retain N and the improvement in 15N uptake and utilization are more pronounced in maize leaves and grain. Moreover, biochar application promotes 15N utilization in maize plant and improves maize yield. However, when biochar application rate is high (i.e. P48 treatment), the 15N retention by the soil and 15N utilization by the maize are reduced markedly compared with P12 and P24. [ABSTRACT FROM AUTHOR]