The potential nitrogen (N) losses from soils with fertilizer addition can be reduced when biochar is co‐applied, but this effect is influenced by the methods of biochar and fertilizer application. In a 60‐d laboratory incubation experiment, we investigated how two fertilizer application methods (surface placement and soil incorporation) affected N transformation in soils under the following treatments: control (soil with no biochar and urea [C]), biochar (150 mg N g⁻¹ soil [B]), urea (150 mg N g⁻¹ soil [U]), and the combination of B + U (75 mg N g⁻¹ soil each B and U). Our results showed that at Day 30, the concentrations of soil NH₄⁺–N and NO₃⁻–N remained significantly higher for U but were relatively similar to control for biochar‐included treatments, indicating that the presence of biochar slowed the mineralization of urea during that period. The concentration of soil NO₃⁻–N and cumulative N₂O production under B + U treatment at 60 d was around two times higher for incorporation treatment compared with the surface treatment, indicative of a longer‐term N regulatory effect of biochar with the surface application method. Additionally, we observed a higher number of amoA gene transcripts when B + U was incorporated in the soil compared with applied to the surface at the later stage of incubation, indicative of higher potential nitrification activity. These results suggest that the surface application of B + U can be used as a slow release N source that can provide long‐term N supply to the crops, while the soil incorporation method could be used for crops that need low N at the beginning of the growth but require a substantial amount of it later. Surface co‐application of B + U can also be a good strategy to reduce soil N losses by slowing down ammonification, nitrification, N₂O emission, and ammonia oxidizing bacteria activity.

中文翻译：

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施用方法影响生物炭与肥料相互作用对土壤氮动力学的影响

共同施用生物炭可以减少土壤中氮肥的潜在损失，但是这种影响受生物炭和肥料施用方法的影响。在一个60天的实验室孵化实验中，我们研究了两种肥料施用方法（表面放置和土壤掺入）如何在以下处理下影响土壤中的氮转化：对照（无生物炭和尿素[C]的土壤），生物炭（150 mg N g ^-1土壤[B]），尿素（150 mg N g ^-1土壤[U]）和B + U（B和U分别为75 mg N g ^-1土壤）的组合。我们的研究结果表明，在第30天，土壤的浓度NH ₄ ⁺ -N和NO ₃ ^-对于U，-N仍显着较高，但与含生物炭处理的对照相对相似，表明在此期间生物炭的存在减缓了尿素的矿化。与表面处理相比，B + U处理60 d时B + U处理的土壤NO ₃ ^-- N浓度和累积N ₂ O产量比表面处理高约2倍，表明生物炭对土壤氮素的长期调节作用表面施涂方法。此外，我们观察到更多的amo与在孵化后期将B + U掺入土壤相比，将B + U掺入土壤的基因转录本表明其潜在的硝化活性更高。这些结果表明，B + U的表面施肥可以用作缓释氮源，可以为作物提供长期的氮素供应，而土壤掺入法可以用于土壤氮素含量高的作物。增长，但以后需要大量增长。通过缓和氨化，硝化，N ₂ O排放和氨氧化细菌的活性，B + U的表面共施用也是减少土壤氮损失的好策略。