长期施肥对旱地红壤微团聚体磷素有效性的影响

【目的】土壤微团聚体是磷素储存与周转的重要载体，明确长期施肥下旱地红壤微团聚体中赋存磷素的形态及其生物有效性，为磷肥的高效合理施用提供理论依据。【方法】以位于鹰潭农田生态系统国家野外科学观测研究站院内的长期肥料定位试验(1988～2014)为依托，分别以有机无机配施区的1/2 NPK(CK)、低量NPK+稻秆(RS)与低量NPK+猪厩肥(PM)处理及无机肥区的NK与NPK处理的旱地红壤为研究材料，采用水分散-吸管法逐级提取了土壤中0.25～0.05 mm、0.05～0.01 mm、0.01～0.005 mm与<0.005 mm粒级微团聚体，对比分析了各粒级微团聚体中全磷、有效磷及磷活化系数的变化差异。基于土壤磷素分级结果，分析了旱地红壤中大小粒级微团聚体中极有效磷、中等有效磷及非有效磷对长期施肥的响应。借助于结构方程模型探讨了微团聚体中各形态磷、磷活化系数、颗粒组成、有机质、铁铝氧化物等因子与有效磷的互应关系。【结果】长期配施猪粪可以显著增加旱地红壤各粒级微团聚体中全磷、有效磷、磷活化系数及极有效磷、中等有效磷及非有效磷的含量，且<0.005 mm粒级微团聚体中的各组分磷增...

Effects of Long-term Fertilization on Availability of Micro-aggregate Associated Phosphorus in Upland Red Soil

  Objective  Soil micro-aggregates are the important carriers of phosphorus(P) storage and turnover. To clarify the form and bioavailability of soil microaggregate associated P in upland red soil under long-term fertilization can provide the theoretical basis for the efficient and rational application of P fertilizers.  Method  Based on the long-term fertilization experiment (1988 - 2014) located at the Red Soil Ecological Station in Yingtan, Jiangxi Province, China, total 15 soil surface samples (0 - 15 cm) were collected from the combined application of organic-inorganic fertilizer plot (Treatment 1/2 NPK (CK), low quantity NPK + rice straw (RS) and low quantity NPK + pig manure (PM)) and the single application of chemical fertilizer plot (Treatment NPK and NK), respectively. Soil micro-aggregate size in 0.25 - 0.05 mm, 0.05 - 0.01 mm, 0.01 - 0.005 mm and < 0.005 mm were sequentially extracted by pipette method after the water disperses. The changes of soil total P (TP), Bray-P and the P activation coefficient (PAC) in various soil micro-aggregates were analyzed, and the extremely available P (EAP), medium available P (MAP) and non-available P (NAP) of micro-aggregates response to the long-term fertilization were also analyzed based on the results of soil P fractionation. And the relationships between the soil P fractionation, PAC, particle composition, soil organic matter, iron-aluminum oxides and Bray-P were discussed based on the structural equation model.   Result  Long-term combined application of pig manure can significantly increase the TP, Bray-P, PAC and EAP, MAP, NAP in various micro-aggregates, and the increase proportion of them in < 0.005 mm micro-aggregate was higher, but the combined application of rice straw only can significantly decrease the P content of 0.01 - 0.005 mm micro-aggregate. Compared with NPK treatment, NK treatment can significantly decrease the contents of all P fractions in various micro-aggregates, and also can significantly decrease the PAC of 0.25 - 0.05 mm and 0.05 - 0.01 mm micro-aggregates, but significantly increased the PAC of 0.01 - 0.005 mm and < 0.005 mm micro-aggregates. The fitting results of structural equation model show that the inorganic P component was the positive influence factor for Bray-P, but the organic P component was the negative influence factor for Bray-P. Based on the stepwise regression analysis, the inorganic P components extracted by the NaHCO₃ and HCl were the main influence factors for PAC of upland red soil.   Conclusion  The combined application of organic fertilizers, especially combined with pig manure, can significantly increase and promote the transformation of the high stable organic P components into low stable inorganic P in upland red soil.