γ-PGA微生物有机肥保水机理研究

The development of water-retaining technology to improve water use efficiency is one of the main ways for the development of modern water-saving agriculture. Application of water-retaining bioorganic fertilizer is an important means for soil water retainment. Researches of the water-retaining bioorganic fertilizer, at present, are more focused on the fermentation process and plant growth after the fertilizer application, and lacked the exploration of the soil water-retaining mechanism. Based on the soil column and lysimeter experiment, this project wishes to study the soil water-retaining mechanism of γ-poly glutamic acid (γ-PGA) bioorganic fertilizer which produced by solid fermentation with microbial. After the soil applied with γ-PGA bioorganic fertilizer, the project will study the dynamic of bacteria synthesizing γ-PGA or glutamic acid in the soil, γ-PGA stability, variation of microbial ecology, mechanisms of the formation of soil aggregates and the change of soil pore properties, the effect of soil surface crust, hydraulic conductivity, soil characteristic curve, water availability and water availability, as well as determination of surface runoff, deep percolation, soil water retention, soil evaporation, plant transpiration for the field water movement. The project will provide theoretical and practical basis for the application of γ-PGA bioorganic fertilizer in increasing use efficiency of rainfall and water-saving agricultural irrigation.

开发高效蓄水保墒技术提高水资源利用效率，是发展现代化节水农业的主要途径之一。微生物保水肥料应用是实现土壤蓄水保墒一个重要手段。目前微生物保水肥料的研究侧重于发酵工艺开发和施用后生物学生长指标测定，缺乏土壤保水机理的探索。本项目基于土柱和蒸渗仪模拟实验，研究土壤施用微生物固体发酵生产的γ-多聚谷氨酸(γ-PGA)微生物有机肥后，对土壤γ-PGA合成菌株和谷氨酸合成菌株行为动态、γ-PGA的稳定性、微生物生态学的影响及变化规律；分析土壤团聚体的形成和孔隙属性变化原因；监测土壤表层结皮、导水率、水分特征曲线、水分有效性等物理学属性变化；测定田间地表径流、深层渗漏、土壤保蓄、土壤蒸发、植物蒸腾等指标变化，阐述基于γ-PGA土壤行为动态、土壤微生物生态学、土壤物理学以及田间水分运移规律的γ-PGA微生物有机肥土壤保水机理，为微生物保水有机肥在提高降水利用率和农业灌溉节水中的应用提供理论和实践基础。

生产γ-多聚谷氨酸（γ-PGA）微生物有机肥（PGAB）的、具有合成谷氨酸和γ-PGA功能的微生物菌株，分离自江苏海涂重盐土壤，鉴定为解淀粉芽孢杆菌（Bacillus amyloliquefaciens）和黄色短杆菌（Brevibacterium flavum）。采用响应曲面法以农业固体废弃物为主要原料、以γ-PGA为有效物质进一步优化发酵工艺，获得发酵工艺参数为：B. flavum 接种量5.73%，B. amyloliquefaciens接种量5.90%，向1000g猪粪堆肥中添加尿素80.82 g、玉米粉65 g、糖蜜渣150 g、K2HPO4 7.5 g、MgSO4 3.5 g、MnSO4 3.62 g，获得PGAB中γ-PGA含量12.25 g kg-1，而且γ-PGA降解周期最长，有利于农业应用。.PGAB对土壤理化性质的影响表明，施用PGAB处理土壤总氨基酸的量比对照高18.50倍(P < 0.05)，游离谷氨酸是对照的19.72倍，对照处理没有检测到γ-PGA，而PGAB处理的γ-PGA量为265.67 mg kg-1。相较于对照处理，PGAB处理土壤总孔隙度、田间持水量和大团聚体比例增加了53.05%、45.7%和193%，细菌、真菌和放线菌数量分别高59.25、7.33和6.80倍（P<0.05）。.PGAB在生理干旱的沿海盐碱土壤中的保水效果研究表明，其对土壤的保水改良效果显著。相较于对照处理，PGAB处理碱蓬鲜重增加了95.5%，干重增加了1.3倍；组织MDA含量降低了61.2%，根系活力增加了2.8 倍；组织可溶性糖、氨基酸、有机酸和脯氨酸的量分别增加了69.3%、87.1%、75.1%和1.1倍，Na+、Cl-、K+和Ca2+离子浓度增加量分别为18.1%、1.5倍、1.2倍和36.3%；根际土壤细菌、真菌和放线菌的数量分别增加了31.7 倍、56.8倍和8.1倍，氨化细菌、硝化细菌、解磷菌和解钾菌数量分别增加了27.3倍、7.8倍、25.8倍和9.8倍；土壤容重和含盐量分别降低了20.6%和41.1%，土壤总孔隙度和田间持水量分别增加了23.8%和11.1%。.在控制灌溉（节水）条件下，PGAB处理水稻没有显著地减产，但是水分利用效率由对照处理的0.93 kg m-3提升为0.98 kg m-3，PGAB显著提高水稻灌溉水水分利用效率。