The effects of land use and fertilization regimes on soil denitrification potential (SDP) are often investigated, but less is known about the responses of SDP to different types of land use with different fertilization regimes in soils derived from the same parent material. We conducted a study using soil samples from 2 long-term (over 30 years) fertilization experiments to determine the difference in SDP between paddy soil and upland soil derived from the same quaternary red clay parent material. The results showed that the SDP in paddy soil was 6.82 times higher than the upland soil, which was due to the higher abundances of narG, nirS, and nirK genes and nirS-denitrifying bacteria (Bradyrhizobium, Cupriavidus, and Herbaspirillum) in paddy soil. Inorganic fertilization regimes did not significantly affect the SDP of upland soil over the control group, whereas SDP in the NPK and 2NPK treatments in paddy soil were reduced relative the control group by 26.48% and 75.65%, respectively. Compared with the control, the NPKOM treatment consistently yielded the highest SDP in both soils, with 2.47 times and 2.86 times higher for paddy soil and upland soil, respectively. The SDP of paddy soil was significantly correlated with narG and nirS genes mainly regulated by amorphous aluminum oxide, whereas the treatment effect on SDP for upland soil largely depended on differences in nirS-denitrifying bacteria at the genus level (Herbaspirillum, Sulfuritalea, and Cupriavidus) and species level, which were mainly controlled by soil pH. Partial least squares path models further demonstrated that the direct effects of functional genes on SDP were greatest for paddy soil, whereas nirS-denitrifying bacterial communities played a larger role in upland soil. The results presented herein represent a key step toward understanding the mechanisms that govern SDP under land use and long-term fertilization.

中文翻译：

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源自相同母材的水稻和旱地土壤的反硝化潜力对长期施肥的反应不同

人们经常研究土地利用和施肥制度对土壤反硝化潜力 (SDP) 的影响，但人们对 SDP 对不同类型土地利用的反应知之甚少，在源自相同母体材料的土壤中使用不同的施肥制度。我们使用来自 2 个长期（超过 30 年）施肥实验的土壤样本进行了一项研究，以确定源自相同第四纪红粘土母质的水稻土和旱地土壤之间的 SDP 差异。结果表明，稻田土壤的SDP比旱田土壤高6.82倍，这是由于稻田土壤中narG、nirS和nirK基因以及nirS反硝化细菌（Bradyrhizobium、Cupriavidus和Herbaspirillum）的丰度较高。与对照组相比，无机施肥方案对旱地土壤的 SDP 没有显着影响，而水稻土中 NPK 和 2NPK 处理的 SDP 相对于对照组分别降低了 26.48% 和 75.65%。与对照相比，NPKOM 处理在两种土壤中始终产生最高的 SDP，分别是水稻土和旱地土壤的 2.47 倍和 2.86 倍。水稻土的SDP与主要受无定形氧化铝调控的narG和nirS基因显着相关，而旱地土壤对SDP的处理效果很大程度上取决于属水平的nirS反硝化细菌（Herbaspirillum、Sulfuritalea和Cupriavidus）的差异和物种水平，主要受土壤 pH 值控制。偏最小二乘路径模型进一步表明，功能基因对 SDP 的直接影响在稻田土壤中最大，而 nirS 反硝化细菌群落在旱地土壤中发挥更大的作用。本文中呈现的结果代表了了解在土地利用和长期施肥下控制 SDP 机制的关键一步。