长期施肥对稻田不同土层反硝化细菌丰度的影响

为了探讨长期施肥对稻田不同土层关键反硝化功能种群丰度的影响及核心驱动因子，以湖南宁乡长期施肥定位试验田为平台，选取不施肥（CK）、全量化肥（NPK）和秸秆还田（ST）3个处理，结合实时荧光定量PCR（qPCR）技术，系统分析了稻田不同土层（0~10，10~20，20~30，30~40cm）关键反硝化功能基因（narG、nirK和nirS）的丰度及其与土壤理化性质的内在联系.结果表明，相比于不施肥处理（CK），施肥处理（NPK和ST）在0~40cm土层土壤SOC、TN、NO₃^--N、NH₄⁺-N和Olsen-P分别显著增加了2.2%~83.6%，3.5%~58.3%，70.8%~222.1%，0.9%~83.7%和16.5%~94.5%，pH值下降了0.31~0.67个单位；长期施用化肥和秸秆使narG、nirK和nirS基因丰度分别增加0.75~7.18倍，1.57~3.02倍和0.53~3.81倍，其中秸秆还田对反硝化细菌数量的影响比单施化肥更显著；稻田narG、nirK和nirS反硝化型细菌的丰度随土层深度增加而逐渐降低，具有明显的垂直分布特征；RDA分析结果显示，土壤养分如SOC和TN是影响水稻土narG、nirK和nirS反硝化型细菌垂直分布的关键因子，而pH值是调控反硝化细菌在稻田底土分布的核心驱动因子.研究结果可为提升稻田土壤肥力和减少稻田氮素损失和温室气体排放提供理论依据.

Effects of long-term fertilization on the abundance of the key denitrifiers in profile of paddy soil profiles

The aims of this study were to explore the effect of long-term fertilization on the abundance of the key denitrifiers in paddy soil profiles (0~40cm), and the core factors driving denitrifiers. Soils with non-fertilization (CK), inorganic fertilizer (NPK) and organic fertilizer (ST) were collected in Ning xiang County, Hunan Province, and real-time fluorescent quantitative PCR technology was used to analyze the abundance of narG-, nirK-and nirS-containing communities in paddy soil profile (0~10cm, 10~20cm, 20~30cm, 30~40cm) and their relationship with soil properties. The results showed that compared with CK, SOC、TN、NO₃^--N、NH₄⁺-N and Olsen-P in soil profile under NPK and ST increased by 2.2%~83.6%、3.5%~58.3%、70.8%~222.1%、0.9%~83.7% and 16.5%~94.5% respectively, and pH decreased by 0.31~0.67 units. Long-term application of inorganic fertilizer and organic fertilizer increased narG, nirK, and nirS gene abundance by 0.75~7.18 times, 1.57~3.02 times, and 0.53~3.81 times, respectively. And the effect of organic fertilizer on the abundance of denitrifiers was more significant than that of inorganic fertilizer application; The abundance of narG-, nirK-and nirS-containing communities decreased gradually with soil depth increasing, which presented an obvious vertical distribution; RDA analysis showed that soil nutrients such as SOC and TN were the core factors affecting the vertical distribution of narG-, nirK-and nirS-containing populations in paddy soil, especially in the cultivated horizon, while pH was the core driving factor regulating the distribution of denitrifying bacteria in paddy field subsoil. The results can provide theoretical basis for improving soil fertility and reducing nitrogen loss and greenhouse gas emission in paddy soils.