稻田土壤结构变化及其主控因素研究

The soil structure in paddy fields is strongly dynamic due to the influences of soil management practices, which accordingly affects soil fertility and soil ecological environment. Long-term organic and inorganic fertilizaiton or crop residue incorporaiton may increse soil organic matter through an increase of the amount of organic materials into soil, which will not only promote formation of soil structure, but also control the initial soil structure after puddling and then affect the dyanmics of soil structure induced by wetting and drying cycles during the rice growth period. By applying field monitoring in the long-term experiments in combination with conducting simulated experiements using soils from those experiments, and focusing on the influences of soil organic fractions on soil structural stability and shrinkage and swelling behaviour, the objectives of this study are: 1）to detminer the dynamic characterization of soil structure in paddy fields and the controlling factors; 2) to elucidate the effect of soil organic matter on the soil strural properties against the destruction of puddling and shrinkage and swelling and their interaction; 3) to determine the dynamics of soil structure after incorproaiton of crop residues under wetting and drying cycles and the microbial mechanisms invovled. This will further improve our understanding how soil structure change in paddy soil and provide fundamental knowledge for fostering paddy soil fertiltiy.

稻田土壤结构受土壤管理影响而具有强烈变化特征，影响土壤肥力和生态环境。长期施肥（有机/无机肥）或秸秆还田不仅可通过提高还田有机物数量提高土壤有机质，促进土壤结构形成，而且控制土壤水耕后的初始土壤结构，进而造成水稻生长期灌排引起的土壤结构变化差异。本项目拟利用长期施肥和秸秆还田定位实验，结合田间监测和模拟实验，从土壤有机质组分影响土壤结构稳定性和收缩膨胀性入手开展综合研究，研究目标有： 1）探明稻田土壤结构的季节性变化和主控因素；2）揭示土壤有机质对稻田土壤结构水耕破碎、收缩膨胀的控制作用；3）阐明有机物分解过程对稻田土壤团聚结构形成的微生物驱动作用。研究结果对深入理解稻田土壤结构变化过程和调控机制、优化稻田土壤肥力的定向培育措施具有重要意义。

稻田土壤结构受土壤管理影响而具有强烈变化特征，影响土壤肥力和生态环境。长期施肥或秸秆还田不仅可通过提高还田有机物数量、增加土壤有机质，促进土壤稳定结构的形成，进而造成水稻土生长期动态土壤结构变化差异。本项目利用进贤及余江两地的长期施肥（有机/无机肥）和秸秆还田定位实验，田间监测结合化学分散及模拟水耕的室内实验分析发现：长期不同有机物料投入量的差异，导致土壤团聚体组成、各级团聚体颗粒内有机碳及氧化铁含量和紧实团块量的改变，从而影响土壤结构的稳定性；稻田土壤抗破碎能力、涨缩性能、伸展系数、下陷阻力、抗张强度和贯穿阻力均与有机碳投入量呈显著正相关。此外本项目利用水耕前后的动态监测结合干湿交替培养实验发现：长期不同施肥和秸秆还田制度下各处理土壤的季节性变化也存在很大的差异，调控季节性变化的主要因素是与有机物投入量有关的可溶性碳含量、氧化还原状态比值（pH/Eh）、无定形铁氧化物含量（FeO）及土壤的团聚体稳定性参数（NMWD）和各处理土壤的孔隙状态等。稻田土壤内新添加有机物料的分解过程改变土壤呼吸速率、土壤容重和体积以及微生物群落结构，但微生物与其土壤结构变化相关关系还需进一步研究。