Black paddy soil (BP) and gleyed paddy soil (GP) are typical rice-planting soils distributed in two different climatic zones in China. The nitrogen utilization efficiency (NUE) of rice growing on the BP was higher than that in GP even when the soils were transplanted to the same location and subjected to the same agricultural management. In this study, we aimed to explore the microbial mechanisms underlying the difference in nitrogen transformation between the two types of soils. The microcosm experiments using BP and GP were performed under different aeration and temperature conditions with controlled ammonium or nitrate. The results indicated that the nitrification of GP was stronger than that of BP, which was associated with the higher relative abundance of ammonium-oxidizing genes in GP than in BP and a group of specialized ammonium-oxidizing species in GP. It indicated that GP had more vigorous nitrifiers, which is not conducive to the nitrogen utilization of ammonium-preferring rice due to faster ammonium consumption. Moreover, more nitrate was consumed in BP than in GP owing to the higher relative abundance of narG and carbon fixation gene accA in BP. Simultaneously, the overall N₂O accumulation in BP was obviously higher than that in GP, which was associated with higher relative abundance of narG, nirK, and norB and the lower relative abundance of nosZ, as well as some specific norB species enriched in BP. These findings advance our understanding of the microbial mechanism of distinct nitrogen metabolism driving the different NUEs in two types of paddy soils.

黑水稻土(BP)和油水稻土(GP)是分布在我国两个不同气候带的典型水稻种植土。即使移栽到同一地点并进行相同的农业管理，BP上种植的水稻的氮利用效率（NUE）也高于GP上的水稻。在这项研究中，我们旨在探索两种土壤之间氮转化差异背后的微生物机制。使用 BP 和 GP 的微观实验是在不同的通气和温度条件下使用受控的铵或硝酸盐进行的。结果表明，GP的硝化作用强于BP，这与GP中铵氧化基因的相对丰度高于BP以及GP中一组专门的铵氧化物种有关。这表明GP具有较强的硝化菌，由于铵消耗较快，不利于喜铵水稻的氮素利用。此外，由于BP中narG和固碳基因accA的相对丰度较高，BP中消耗的硝酸盐比GP中更多。同时，BP中N ₂ O积累量明显高于GP，这与narG、nirK和norB相对丰度较高， nosZ相对丰度较低以及BP中富集的一些特定norB物种有关。 。这些发现增进了我们对驱动两种水稻土不同氮利用效率的不同氮代谢的微生物机制的理解。