桂西北喀斯特桑园土壤氮转化过程对施肥策略的响应机制

土壤蛋白质解聚和初级氮矿化速率是土壤供氮能力的重要指标，对土壤生产力提升和农田可持续管理具有重要意义。微生物是土壤氮循环过程的重要驱动者，但微生物代谢作为微生物功能的核心对农田土壤氮素释放的调控机制尚不明确。本项目拟针对桂西北喀斯特区开展桑园土壤氮转化过程对不同施肥策略响应研究，通过连续监测喀斯特桑园土壤不同施肥策略土壤有效氮含量与桑叶含氮量，阐明喀斯特桑园土壤活性氮库的动态变化及与作物吸氮之间的关系；运用15N稳定同位素标记方法和分子生物学技术，明确不同施肥策略下土壤蛋白质解聚和初级氮矿化速率的变化特征及主控因素；进一步采用18O同位素标记方法研究并阐明微生物氮代谢对不同施肥策略响应的特征，最终揭示不同施肥策略下喀斯特桑园土壤氮素供应特征、关键控制因子及其驱动机制。结果将有助于更深入理解喀斯特农田土壤氮转化特征，为桑园氮素管理和合理施肥提供科技支撑。

Improvement of productivity and sustainable management of cropland have an inestimable significance and can be reached through a better understanding of gross nitrogen (N) transformation, which is an important aspect of soil fertility. Microbiota play a pivotal roles in belowground biogeochemical processes. However, the mechanisms of microbial metabolism in N release from cropland are still remaining unclear. Therefore, the proposed project aims at carrying out long-term monitoring of soil available N and mulberry leaves N contents to identify responses of the relationship of soil N supply and crop N uptake in karst mulberry field under different fertilization. Trying to elucidate the relationship between N transformation and soil N supply by using 15N stable isotope tracing method and molecular biology technique to measure gross N transformation rates. Meanwhile, to uncover mechanisms of microbial impact to soil N supply with help of 18O stable isotope tracing method to measure microbial metabolism. These results can provide scientific basis for N management and rational fertilization in mulberry field, and are helpful for understanding the characteristic of N transformation and their responses to different fertilization in karst cropland.