长期施肥下典型稻田土壤镉的（微）空间分异及其环境效应

Long-term fertilization, especially phosphorus fertilizer and manure, resulting in accumulation of Cd in farmland has been attracted wide attention. It's important to study the distribution, extractability and phytoavailability of Cd in long-term fertilized farmland in investigation the environmental risks of Cd in soils. Long-term fertilization experiments of three typical paddy soils in Hunan province conducted since 1986 were used in this proposal. A combination of technical route will be used as field experiments and control experiments. Firstly, the distribution of Cd in different sizes aggregates and profile layers soils (micro-spatial variations of Cd in paddy soils) will be investigated. Whilst, the relationships between the sorption-desorption of Cd, physical and chemical properties in soil aggregates and profiles soils samples, soil Cd in-out balance and (micro-) spatial variations of Cd in soils will be analyzed. These results will be used in illumination of the mechanisms of Cd (micro-) spatial variations of Cd in long-term fertilized paddy soils. The extractability of Cd in different size aggregates and profile soils will be tested using single extraction (water and TCLP) and sequential extraction methods. The relations between the (micro-) spatial variations and uptake of Cd by rice were analyzed. Finally, the environmetal effects of Cd (micro-) spatial variations in paddy soils were revealed. These results of this proposal will be usefull in exploitation rational fertilization ways in paddy soils, and provide a scientific basis for the sustainable of rice farming and assurance of rice quality.

长期施肥，尤其是磷肥和有机肥，导致的农田土壤镉累积问题已受到广泛关注。研究农田土壤中镉的去向、释放特点和植物有效性及其对长期施肥的响应，对于明确和规避其环境风险具有重要意义。申请项目拟依托3种典型稻田土壤的长期（26年）施肥定位试验，采用田间定位试验与室内控制试验相结合的技术路线，研究并阐明长期不同施肥方式下稻田土壤的镉(微)空间分异(团聚体和剖面中镉的分布)特征，同时建立其与土壤的镉吸附解吸特点、理化性质以及土壤镉表观平衡的关系，揭示土壤中镉（微）空间分异的驱动机制；探明不同粒级团聚体和剖面层次土壤中镉的释放规律及其对水稻吸收镉的供应关系，综合阐释长期不同施肥方式下典型稻田土壤镉（微）空间分异的环境效应；探讨防控稻田镉污染风险的优化施肥措施，为稻作农业的可持续发展和保障稻米质量安全提供科学依据。

本项目的目标是探明长期不同施肥方式下，镉在稻田土壤剖面和团聚体中的分布特征，并探讨镉（微）空间分异与镉植物有效性关联机制及其对植物吸收镉的影响，最终为指导稻田的合理施肥、防控稻田镉污染风险及保障稻米质量安全提供重要理论支撑。项目以宁乡（河砂泥）和南县（紫潮泥）两个长期30年定位施肥点为基础，以其不同施肥条件下的土壤和晚稻为对象开展研究，主要检测指标包括土壤理化性质、土壤镉全量、镉的有效性、镉的形态分级、植物镉含量、土壤对镉的吸持能力等。研究发现长期施用有机肥显著提高了耕层土壤有机质和全氮含量，提高了大团聚体的比例。长期施用低量（LM）和高量有机肥（HM）后，河砂泥耕层土壤全镉含量提高了36%和81%、有效态镉含量提高28%和74%，紫潮泥耕层土壤全镉含量和有效态镉含量略有增加。长期施用有机肥对土壤全量和有效态重金属含量的影响可以达到0~30 cm土层。长期施用有机肥显著改变了河沙泥团聚体中镉的分布规律，提高了团聚体中镉的有效性，但对紫潮泥影响相对较小。河沙泥长期施用低量和高量有机肥后，水稻对镉的吸收和累积量显著提高，与对照相比，其植株各部位镉含量显著提高59.84-120.75%和95.12-152.64%。进一步分析发现，河沙泥长期不同施肥处理，水稻的镉吸收累积量主要取决于1-2 mm团聚体和0-30 cm层剖面中镉的有效性，且土壤有机碳含量是影响土体空间中镉的有效性和水稻镉吸收能力的主要因素。在以镉为主要研究对象的同时，还研究了铅、铜和锌在土壤耕层、团聚体和剖面以及水稻中的分布特征，为镉的空间分异特征提供辅助数据支撑。. 项目执行过程中已发表论文7篇，其中包括SCI论文5篇，申请国家发明专利1项，培养研究生4名。