The agricultural practice of straw incorporation is often employed to enhance soil fertility, improve soil properties and reduce nitrate leaching via deep burying. Nevertheless, the tradeoff between nitrate leaching and NO emissions caused by deep straw incorporation in various soil types remains uncertain. To address this knowledge gap, a mesocosm column experiment was established to evaluate the impact of straw amendment (NS) and of straw plus application of denitrifying bacterial agents (NSS) at column depths of 20–60 cm on NO-N leaching and NO emission across four soil types (brown, cinnamon, fluvo-aquic and mortar black soil) in the North China plain. The results showed that the NS and NSS treatments significantly reduced NO-N leaching by 47%–73% and 37%–81%, respectively, across four soil types, in comparison to the control without straw and bacterial agents (N), with the greatest reduction recorded in the mortar black soil (by 73% for NS and 81% for NSS). Meanwhile, the NS and NSS treatments resulted in a significant increase in cumulative NO emissions (by 289% for NS and 598% for NSS) in the acidic brown soil with a soil pH ranging between 4.8 and 6.5, but showed no significant effect in the remaining three soil types in which soil pH is above 7.5. When compared to the NS treatment, NSS treatment reduced the cumulative NO emissions in the fluvo-aquic soil by 42%. We further showed that soil type is the primary driver of bacterial community composition ( = 62.3%; < 0.001), followed by soil depth ( = 5.2%; < 0.001). The incorporation of straw and denitrifying bacterial agents induced significant change in the bacterial community in the middle depth layers, and increases in gene abundance and the relative abundance of inoculant-similar OTUs significantly by 0.5–37 folds and 2.8–6900 folds, respectively, in all soil types, suggesting the colonization of denitrifying bacterial agents. Our results further suggested that the Streptomycetales were the most important predictors for NO emissions, and the relative abundance of Streptomycetales was highly positively correlated with NO emissions across the four soil types. Overall, the study suggests that deep straw incorporation as soil amendment is effective in mitigating nitrate leaching in all four soil types, especially in the fluvo-aquic soil, due to its dual effects on controlling nitrate leaching and NO emissions. However, it is not recommended for the acidic brown soils as it may cause increased NO emissions.

中文翻译：

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秸秆深埋和反硝化菌剂减少华北平原四种土壤类型硝态氮淋溶和N2O排放的效果及机制

秸秆还田的农业实践通常用于提高土壤肥力、改善土壤性质并通过深埋减少硝酸盐淋失。然而，不同土壤类型中秸秆深层掺入所引起的硝酸盐淋滤与氮氧化物排放之间的权衡仍不确定。为了解决这一知识差距，建立了中生态柱实验，以评估秸秆改良剂（NS）和秸秆加反硝化细菌剂（NSS）在20-60 cm柱深的应用对NO-N浸出和NO排放的影响华北平原的四种土壤类型（棕壤、褐土、潮土和砂浆黑土）。结果表明，与没有秸秆和细菌剂（N）的对照相比，NS和NSS处理在四种土壤类型中分别显着减少了NO-N淋溶47%–73%和37%–81%，砂浆黑土中记录的最大减少量（NS 减少了 73%，NSS 减少了 81%）。同时，NS和NSS处理导致土壤pH值在4.8至6.5之间的酸性棕壤中NO累积排放量显着增加（NS增加了289％，NSS增加了598％），但在土壤pH值范围为4.8和6.5之间没有表现出显着影响。其余三种土壤类型的土壤 pH 值高于 7.5。与NS处理相比，NSS处理使潮土中NO累积排放量减少了42%。我们进一步表明，土壤类型是细菌群落组成的主要驱动因素（= 62.3%；< 0.001），其次是土壤深度（= 5.2%；< 0.001）。秸秆和反硝化细菌剂的掺入引起了中深层细菌群落的显着变化，基因丰度和类似接种剂OTU的相对丰度分别显着增加了0.5-37倍和2.8-6900倍。所有土壤类型，表明反硝化细菌剂的定殖。我们的结果进一步表明，链霉菌是 NO 排放最重要的预测因子，并且链霉菌的相对丰度与四种土壤类型的 NO 排放呈高度正相关。总体而言，该研究表明，深层秸秆掺入作为土壤改良剂可有效减轻所有四种土壤类型的硝酸盐淋溶，特别是在潮土中，因为它具有控制硝酸盐淋溶和二氧化氮排放的双重作用。但不建议用于酸性棕壤，因为它可能会导致 NO 排放增加。