秸秆还田对稻田土壤磷素形态及磷循环微生物功能基因的影响

Effects of Straw-returning on Phosphorus Morphology and Microbial Phosphoruscycling Genes in Rice Paddy Soil

【目的】以南方酸性土壤连续8年秸秆还田定位试验田为研究对象,探究秸秆还田对水稻分蘖期与成熟期土壤磷循环微生物功能基因的影响。【方法】定位试验共设置5个处理:化肥+无秸秆还田(CK)、化肥+当季秸秆全量还田(CKS)、化肥+当季秸秆全量还田+秸秆替代10%钾肥(S10)、化肥+当季秸秆全量还田+秸秆替代20%钾肥(S20)和化肥+当季秸秆全量还田+秸秆替代30%钾肥(S30)。利用Guppy土壤磷素连续浸提法和宏基因组测序技术,分别测定土壤磷素组分和磷循环微生物功能基因数据。【结果】秸秆还田处理显著提高了Guppy土壤磷分级中可利用磷组分NaHCO_(3)-Pi的含量(P<0.05),其中S10、S20处理较CK处理提升了5.88%~8.73%;中等可利用磷组分中NaOH-Pi为南方酸性稻田土壤最主要的磷素形态,含量为154.03~202.11 mg·kg^(-1)。同时,秸秆还田还显著影响了土壤磷循环微生物功能基因的丰度,其中无机磷溶解基因pqqC对秸秆全量还田处理的响应更为明显。秸秆还田条件下磷循环功能基因(如phnW、phnO、pqqB、pqqC)促进了盐酸磷和残余磷向可利用磷库的活化,appA、phnX、ppx基因参与了稳定态磷的活化过程,NaOH-Pi为关键的过渡态磷素,参与长期的磷素转化过程。此外,土壤有机碳和pH是决定功能基因丰度的主要影响因子。【结论】秸秆还田通过影响土壤理化性质,改变了稻田土壤磷循环功能基因丰度,促进了南方酸性稻田土壤磷素转化过程。

【Objective】Effects of straw-returning on phosphorus morphology and microbial phosphorus-cycling genes in paddy soil at rice tillering and maturing stages were investigated.【Method】In consecutive 7 years on a rice field in southern China under a positioning experiment,spent straws were returned to the acidic soil.The implemented treatments included:(1)chemical fertilizer without straw-returning(CK),(2)chemical fertilizer+100%straw-returning in same season(CKS),(3)CKS+straws to replace 10%potassium fertilizer(S10),(4)CKS+straws to replace 20%potassium fertilizer(S20)or(5)CKS+straws to replace 30%potassium fertilizer(S30).At end of the treatments,Guppy soil phosphorus continuous extraction method and metagenomic technology were applied to determine the composition of phosphorus of different forms and microbial phosphorus-cycling genes.【Result】Straw-returning significantly increased the available NaHCO3-Pi in soil(P<0.05)—the S10 and S20 treatments resulted in an increase by 5.88%-8.73%over CK.NaOH-Pi was the main form of phosphorus in the acid paddy soil in southern China with a content ranging from 154.03 mg·kg^(−1)to 202.11 mg·kg^(−1).By turning the spent straws into the field,the abundance of phosphorus-cycling genes,especially the inorganic phosphorus dissolution gene pqqC under CKS,was significantly affected.The genes,such as phnW,phnO,pqqB,and pqqC,activated the conversion of hydrochloric acid phosphorus and residual phosphorus into available form;those like appA,phnX,and ppx,participated in the formation of stable phosphorus;and NaOH-Pi played a key role in the long-term transformation of the mineral.And the main factors that governed the abundance of the functional genes appeared to be the organic carbon and pH of the soil.【Conclusion】Through altering the soil physiochemical properties,returning spent straws to the ground significantly enriched the microbial phosphorus-cycling genes that promoted the mineral transformation of the acidic paddy soil in southern China.