Different rates of biochar application change15N retention in soil and15N 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(15)N retention rate and(15)N utilization efficiency ((NUE)-N-15) by maize, a six-month(15)N 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(15)N loss rate, and significantly improved total N and(15)N retention amount in the 0-30 cm soil depth. The P24 treatment had the largest increase in(15)N retention rate throughout the 0-40 cm depth. After biochar application, the(15)N uptake and(15)NUE were significantly increased in the grain and leaf, which promoted grain yields. Contrary to this, the P48 treatment appeared to lower(15)N uptake and(15)NUE compared with P12 and P24. In conclusion, biochar application improves the potential of the soil to retain N and the improvement in(15)N uptake and utilization are more pronounced in maize leaves and grain. Moreover, biochar application promotes(15)N utilization in maize plant and improves maize yield. However, when biochar application rate is high (i.e. P48 treatment), the(15)N retention by the soil and(15)N utilization by the maize are reduced markedly compared with P12 and P24.