水稻土结构动态及其对水稻根系生长的影响

Management of soil structure to benefit rice growth is an important agricultural activity. An overall understanding of the dynamics of soil structure, and its interaction with rice roots, is fundamental to optimize the management strategies. This study aims to address these questions and three-scaled work will be conducted. The first part will be based on field tillage experiment, including moldboard tillage, rotary tillage, and no-tillage. The dynamics of soil structure and root elongation will be monitored with a serious of cutting-edge techniques, including thermal-TDR technique, X-Ray computed tomography (CT), and rhizoscanner et al. The soil physiochemical properties will also be determined. These works will get an knowledge of the dynamics of soil structure and the underlying mechanisms, as well as its effects on root elongation at field conditions. The second part involves lab incubation experiments to explore different management practices on soil structural properties and root growth. The examined factors including plough layer depth, puddling intensity and compaction. The three-dimensional root architecture and pore structure will be dynamically scanned. Two rice genotypes, i.e. shallow root genotype and deep root genotype, will be considered in the incubation experiments. Based on previous part works, the last part will look into details of the growth of a single root using synchrotron based micro-CT, with the aim to understand root growth strategies when encountered different structural properties, including different porosities, pore sizes, and aggregate sizes. Integrating the three works, this project will help understand: (1) the dynamics of paddy soil structure and underlying mechanisms, (2) the effect of soil structure on soil thermal and hydrological properties and nitrogen mineralization processes, and (3) the effects of the dynamic soil structure on rice roots growth and the underlying mechanisms. The outcome of this project will provide new insight that helps the management of paddy soil and rice cultivation.

在水稻种植过程中，可以通过管理措施改变土壤结构，调控水稻生长。而准确认识土壤结构的变化规律，及其对根系生长的影响，是合理调控的理论基础。基于此目的，本研究从三个层面展开工作：首先，基于田间耕作试验，综合应用原位的、非破坏性的先进方法，监测土壤结构动态、根系生长规律和土壤养分动态，分析土壤结构变化影响根系生长的规律。其次，作为田间试验的补充，室内模拟不同管理措施，针对性的分析它们对根系生长的影响，研究的因素包括耕层厚度、容重、搅拌强度等。因为不同基因型水稻的响应可能不同，拟选择深根型和浅根型的两种水稻开展试验。第三部分则是上述工作的深入，利用同步辐射显微CT技术，研究水稻根系在不同结构条件下的微观生长策略和规律。综合上述工作，系统分析水稻土结构动态及其引起的物理性质和养分动态，进而探讨结构对根系生长的影响。希望本研究能够加深对水稻土结构和根系动态关系的理解，为水稻种植提供理论依据。

在水稻种植过程中，可以通过管理措施改变土壤结构，调控水稻生长。准确认识土壤结构的变化规律，及其对根系生长的影响，是合理调控的理论基础。基于此目的，本研究测定分析了研究区稻田耕层和犁底层土壤结构状况；基于田间耕作试验，综合应用原位的、非破坏性的先进热TDR方法，监测土壤结构动态，进而分析了土壤结构变化影响根系生长的规律。研究发现热TDR技术能够监测水稻土结构动态变化，并捕捉到不同处理间的差异。发现土壤大孔隙结构促进了水稻根系发育，深根型和浅根型的两种基因型水稻的响应不同。通过区域采样分析，发现研究区稻田存在耕层浅的结构障碍。开展了免耕直播试验，发现能够保持土壤大孔隙结构，减少温室气体排放，并提高综合收益。