缓释功能材料增强土壤磷持留机理及相应新型磷肥评估

The difficulty of the control of phosphorus (P) loss from soils lies in not only fixing excessive P in the soil, but also in the hope that the fixed P could be slowly released and utilized by plants. However, current researches rarely combine both. It has been found that slow-released functional materials (SRFM), such as layered double hydroxides (LDH), biochar-LDH, and biochar-metal-metal oxides composites, are very effective for P adsorption in water, and P intercalation on SRFM can be used as slow-released fertilizer. However, little focus on the application of SRFM to the treatment of P loss in excessive fertilization soil. This project is the first to apply SRFM to the study of control of soil P loss. The adsorption of SRFM was used to control P loss from soils and slow release of P in the later stage thus improves the persistent and effective utilization of P in soil. Combining with migration experiment and numerical simulation, the migration and retention mechanism of P in SRFM added soil were studied under various environmental factors, and then the slow-released mechanism of P immobilized by SRFM in soil was studied, which could provide experimental and theoretical support for application of SRFM to prevent P loss in soil and increase soil nutrients. On this basis, SRFM with high P adsorption capacity was synthesized and screened as the base of slow-released P fertilizer. The fertility, cost and suitable soil types of SRFM based P fertilizers were evaluated through plant experiments of multiple tillage and fallow rotation, which could provide the evaluation basis and theoretical support for the commercialization of these slow-released P fertilizers.

土壤磷流失治理的难点在于既要将过量的磷固定在土壤中，又希望固定的磷后续可缓释被植物利用，目前国内外的研究很少将两者相结合。文献报道缓释功能材料（SRFM），如层状双氢氧化物（LDH）、生物炭-LDH、生物炭-金属-金属氧化物复合材料等，是非常有效的水体磷吸附材料；并且磷插层在SRFM上可作为缓释肥。然而还未有研究将SRFM应用到土壤磷流失治理中。本课题首次将SRFM应用到土壤磷流失控制中，利用其优良的吸附性能控制磷流失，结合后期缓释磷特点，提高磷在土壤中的持久利用性。研究拟结合迁移实验和数值模拟，探索各环境因素下磷在添加SRFM的土壤中的迁移、持留及缓释机理，可为SRFM应用到土壤中防治磷流失、增加土壤营养成分提供实验和理论依据。在此基础上，以高吸附磷性能的SRFM为基底合成缓释磷肥，通过多次耕休轮作的植物实验，评估其肥力、成本及适用土壤类型，可为此类缓释磷肥商业化提供评估基础及理论支持。

土壤磷流失治理难点在于既要将过量的磷固定在土壤中，又希望固定的磷后续可缓释被植物利用，目前国内外的研究很少将两者相结合。文献报道缓释功能材料（SRFM），包括层状双氢氧化物（LDH）、生物炭-LDH、生物炭-金属-金属氧化物复合材料等，是非常有效的水体磷吸附材料；并且磷插层在SRFM上可作为缓释肥。然而还未有研究将SRFM应用到土壤磷流失治理中。本课题首次将SRFM应用到土壤磷流失控制中，利用其优良的吸附性能控制磷流失，结合后期缓释磷特点，提高磷在土壤中的持久利用性。研究结合迁移实验和数值模拟，探索了不同环境因素下磷在添加SRFM土壤中的迁移、持留及缓释机理，主要的研究结果如下：SRFM添加量增加，流速降低，pH值增高，阳离子价态增加、离子强度（IS）增加等条件都增强了磷在SRFM-土壤中的截留，降低其迁移行为。模拟结果显示磷的不可逆截留起到主导作用。pH值及流速变化对磷的解吸在短期条件下影响较小。此外，钾IS降低、碳酸盐存在、有机磷植酸共存下会带来磷酸盐的解吸。土壤阳离子交换和离子强度降低可以减少土壤粘结力，促进磷伴随铁铝氧化物迁移。此外，植酸在添加LDHs土壤中的固持受到IS、阳离子类型和碳酸盐的强烈影响，而其释放只受磷酸盐共存的影响。植酸在高IS下的迁移还伴随有机质的共迁移。这些研究可为SRFM应用到土壤中防治有机、无机磷流失、增加土壤营养成分提供实验和理论依据。. 在此基础上，本项目对比了LDH、生物炭-LDH、载镁生物炭、钙基生物炭对磷的负载性能及相关机制，筛选出负载性能最好的钙基生物炭（~200 mg/g）合成缓释磷肥并评估了其肥效。研究发现，磷肥和钙基生物炭的联合施用在农业生产中显示出更大的潜力，大豆株高显著增加了13.8-26.7%。钙基生物炭可通过化学沉淀以及含氮官能团带来的氢键和静电吸引等机制固定大部分磷肥，控制土壤有效磷含量，防止磷肥流失，之后通过酸溶及增加酸性磷酸酶及微生物量磷的周转，增强磷的缓释利用潜力，这些研究可为此类缓释磷肥商业化提供评估基础及理论支持。