秸秆还田对我国南方典型水稻土壤硅素释放过程影响的定量研究

Straw is an important source of soil silicon library. Release process of silicon (Si) in soil with straw returning is closely related to the quality of cultivated land and crop yield, which is an important part of the terrestrial biogeochemical cycle of silicon. However, previous studies of straw returning on silicon releasing in soil were mainly focused on the initial and final state of straw returning. Few studies focused on the decomposition process of different source of silicon, especially quantitative research on releasing process of silicon in soil has never been reported.In this project,two major types of paddy soils in south China are selected to study the characteristics of soil silicon releasing with straw returning. Based on the test results and the dynamic changes of tracing phytolith occluded C, the method of measuring phytolith C isotope will be established using Nano-SIMS. Experiments studying on decomposition of 13C labeled rice straw using Nano-SIMS method carried out in laboratory to research the release from straw Si and soil original Si comparing phytolith C dynamic changes with straw returning or without. The results will provide a theoretical basis and technical support for soil silicon nutrition regulation,the development of reasonable fertility measures and agricultural production management measures and understanding the biogeochemical cycling of silicon.

秸秆是土壤硅库的重要来源，秸秆还田下硅素的释放过程与耕地质量和作物高产紧密相关，是陆地硅循环的重要组成部分。然而，目前有关秸秆还田对土壤硅释放的相关研究多集中在秸秆还田的初态和终态，对不同来源硅分解过程的研究很少，特别是定量研究硅素在土壤中的释放过程目前还未见报道。本项目选择我国南方具有代表性的不同母质的两种水稻土壤为研究对象，在研究秸秆还田下土壤硅素释放特征的基础上，从示踪秸秆植硅体锢囚碳（C）的动态变化入手，建立利用Nano-SIMS测定植硅体C同位素的方法，通过13C标记秸秆室内培养降解试验，综合对比秸秆还田与不还田处理下秸秆植硅体C和土壤植硅体C的动态变化，定量研究水稻秸秆还田过程中秸秆硅和土壤原有硅的释放过程。研究结果将为土壤硅素营养调控，制定合理的培肥措施和农业生产管理措施，理解硅的生物地球化学循环提供理论依据和技术支撑。

水稻是典型的喜硅作物，特别是随着水稻产量及稻田复种指数的不断提高，土壤中的硅大量的被输出。秸秆是土壤硅库的重要来源，植物吸收的硅主要以植硅体的形式存在，植硅体除含有大量的硅外，还固囚了部分的有机碳。秸秆还田下硅素的释放过程与耕地质量和作物高产紧密相关，同时也与温室气体二氧化碳的扣押紧密相关。本项目以水稻为研究对象，从示踪秸秆植硅体 锢囚碳（C）的动态变化入手，分析植硅体碳的形态，通过室内培养试验，对比秸秆还田、植硅体还田过程中硅素释放和二氧化碳释放过程，结果表明，硅素释放量随着秸秆或植硅体添加量的增加而增加，二氧化碳释放量并不随添加植硅体量而变化；施用硅肥显著增加了水稻的产量，水稻地上部的植硅体含量也随之增加，植硅体固囚的碳含量也增加。这些研究成果为土壤硅素营养调控，制定合理的培肥措施和农业生产管理措施，也为提高作物产量，减少温室气体排放及硅肥的大面积施用提供理论依据和技术支撑。