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.

中文翻译：

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不同生物炭施用量改变了土壤中15 N的保留量和玉米15 N的利用率

生物炭在土壤中的施用可能会影响土壤氮素的动态，但是对农作物氮吸收和利用的影响仍然未知，尤其是生物炭施用量的影响。为了研究玉米生物炭对土壤中¹⁵ N保留率和¹⁵ N利用率（¹⁵ NUE）的影响，在Mollisol中进行了为期六个月的¹⁵ N同位素示踪技术与原位锅试验相结合。该实验包括四种处理：不施用生物炭（CK）和以12 t ha ^-1（P12），24 t ha ^-1（P24）和48 t ha ^-1土壤（P48）的速率施用生物炭。与CK相比，施用生物炭减少了土壤容重，降低了¹⁵氮素流失率，在0–30 cm的土壤深度中显着提高了总氮素和¹⁵ N的保留量。在整个0-40 cm深度，P24处理的¹⁵ N保留率增加最大。施用生物炭后，谷物和叶片中的¹⁵ N吸收和¹⁵ NUE显着增加，从而提高了谷物产量。与此相反，与P12和P24相比，P48处理似乎降低了¹⁵ N吸收和¹⁵ NUE。总之，生物炭的施用提高了土壤中固氮的潜力，玉米叶片和谷物中¹⁵ N吸收和利用的改善更为明显。此外，生物炭的应用促进了¹⁵玉米中氮素的利用并提高玉米产量。但是，当生物炭施用量较高时（即P48处理），与P12和P24相比，土壤¹⁵ N保留量和玉米¹⁵ N利用率显着降低。