绿肥翻压下双季稻区稻田土壤磷素形态转化及机理研究

The green manure becomes more significant with the development of green agriculture. Phosphorus is a crucial nutrient element for crop growth. The application of green manure will influence the availability, forms and transformations of phosphorus in soils. In this study, the forms, distribution and transformation of phosphorus in different soil aggregates will be investigated to analyze the properties and the process of phosphorus transformation and the restricting factors for phosphorus availability. The restricting factors of phosphorus forms in soil will be quantified. Secondly, the effects of long term green manure rotation on the immobilization and release of phosphorus on soil different particles will be studied to assess the soil phosphorus loss risk. Finally, combined with the rice yield, soil properties, the forms of phosphorus in paddy soil, the utilization period and the sustainability of phosphorus will be estimated by long term green manure application. Research results will be to elucidate the phosphorus availability and the sustainable utilization of phosphorus stored in soil, and will provide the scientific basic for phosphorus management by long term green manure application in paddy soils.

随着绿色农业的发展，绿肥的作用更加凸显。磷素是作物生长发育所必需的营养元素。绿肥翻压还田会显著影响土壤中磷素的存在形态和转化过程。本项目首先研究绿肥翻压后磷素在稻田土壤不同团聚体组分中的形态和转化来分析不同团聚体组分中磷素的赋存特征和影响磷素转化和有效性的制约因子，对土壤中磷素转化影响因子进行量化分析；其次在提取稻田不同粒径土壤颗粒基础上研究磷素在土壤颗粒表面的吸持和释放，对土壤磷素潜在流失风险进行评估；最后借助于长期定位试验结合水稻产量和土壤磷素赋存特征估算长期绿肥翻压下土壤磷素可利用时间，对磷素利用可持续性能力进行评估。本研究将为阐明长期绿肥翻压还田磷素可持续性利用和磷素的科学管理提供理论依据。

本项目以安徽省早稻-晚稻-紫云英为依托，利用田间长期定位试验重点研究了紫云英翻压后磷素在水稻土中形态转化特征以及影响磷素形态变化的制约因子；结合室内土培试验研究紫云英翻压还田后土壤颗粒对磷素的吸附固持能力；对紫云英翻压还田下土壤磷素潜在流失风险进行评估，为阐明绿肥翻压土壤磷素可持续利用和磷素管理提供科学依据。结果表明：.（1）长期紫云英翻压还田显著提高早稻、晚稻的产量和肥料利用率和土壤肥力；证明了长期紫云英翻压还田对土壤的培肥效应，其中减施化肥30%配施紫云英翻压还田22500 kg/hm2时早晚稻的产量最高。.（2）紫云英翻压提高了土壤Al-P、Fe-P含量，降低O-P含量；同时提高中等活性磷和中稳性磷，特别是中等活性有机磷，降低高稳性有机磷的占比。31P-NMR图谱分析表明在减施化肥30%配合紫云英翻压30000 kg/hm2的土壤正磷酸盐与100F处理相当。.（3）随着紫云英翻压量的增加促进>2mm和2-0.25mm粒级团聚体中的磷素含量、富集与储存，降低<0.053mm团聚体中全磷含量、分布和储存；同时显著提高土壤团聚体中总磷储量；还提高了>2mm和2-0.25mm团聚体中的速效磷含量；降低了<0.053mm团聚体中的速效磷含量。.（4）紫云英添加提高了砂粒、粉粒、粘粒对磷的理论最大吸附量、本底吸磷量、吸附强度、初始吸附速率和吸附速率；在砂粒中添加紫云英有效提高对磷的吸附量；在粉粒中添加紫云英有效提高了对磷的吸附强度、磷临界浓度和本底吸磷量。等温吸附参数与土壤各养分含量分别呈显著或极显著相关关系。.（5）紫云英翻压还田提高了土壤Olsen-P，降低了CaCl2-P以及降低了PSI、PAC和DPS值。随机森林树分析表明土壤全磷、pH、Alox、FeDCB、AlDCB和交换性Mg2+均对Olsen-P和CaCl2-P达到显著性的影响。通过偏最小二乘法路径模型表明紫云英对Olsen-P的影响较小，而化肥的施用对Olsen-P具有显著的正效应；化肥的施用对于CaCl2-P具有显著正效应，而紫云英具有负效应，也即在一定程度上紫云英的施用降低了土壤磷素的流失风险。.紫云英翻压还田不仅有助于提高水稻产量和土壤肥力，提高土壤磷素的有效性，还能降低磷素的流失风险。