Crops assemble and rely on rhizosphere-associated microbiomes for plant nutrition, which is crucial to their productivity. Historically, excessive nitrogen fertilization did not result in continuously increasing yields but rather caused environmental issues. A comprehensive understanding should be developed regarding the ways in which crops shape rhizosphere-associated microbiomes under conditions of increased nitrogen fertilization. In this study, we applied 16S and 18S ribosomal RNA gene profiling to characterize bacterial and fungal communities in bulk and rhizosphere soil of rice subjected to three levels of nitrogen fertilization for 5 years. Soil biochemical properties were characterized, and carbon-, nitrogen-, and phosphorus-related soil enzyme activities were investigated, by assays. Increasing nitrogen fertilization led to a decreasing trend in the variation of microbial community structures and demonstrated a more definite influence on fungal rather than bacterial community compositions and functions. Changes in the level of nitrogen fertilization significantly affected chemical properties such as soil pH, nutrient content, and microbial biomass levels in both rhizosphere and bulk soil. Soil enzyme activity levels varied substantially across nitrogen fertilization intensities and correlated more with the fungal than with the bacterial community. Our results indicated that increased nitrogen input drives alterations in the structures and functions of microbial communities, properties of soil carbon, nitrogen, and phosphorus, as well as enzyme activities. These results provide novel insights into the associations among increased nitrogen input, changes in biochemical properties, and shifts in microbial communities in the rhizosphere of agriculturally intensive ecosystems.

作物聚集并依赖与根际相关的微生物组来获取植物营养，这对其生产力至关重要。从历史上看，过度施氮并没有导致产量不断增加，反而会导致环境问题。应全面了解作物在氮肥增加的条件下塑造根际相关微生物群落的方式。在这项研究中，我们应用 16S 和 18S 核糖体 RNA 基因分析来表征经过 5 年三种水平施氮的水稻的大块土壤和根际土壤中的细菌和真菌群落。对土壤生化特性进行了表征，并通过测定研究了与碳、氮和磷相关的土壤酶活性。增加施氮导致微生物群落结构变化的减少趋势，并证明对真菌而不是细菌群落组成和功能的影响更明确。氮肥水平的变化显着影响了根际和大块土壤的化学性质，如土壤 pH 值、养分含量和微生物生物量水平。土壤酶活性水平在施氮强度之间存在很大差异，并且与真菌群落的相关性比与细菌群落的相关性更大。我们的研究结果表明，氮输入的增加驱动了微生物群落结构和功能、土壤碳、氮和磷的特性以及酶活性的改变。