基于时间序列的长江下游冲积平原区农田土壤质量演变特征

Evolution characteristics of farmland soil quality in alluvial plain area of lower Yangtze River based on time series

为揭示人类活动影响下土壤质量的演变趋势及其影响因素,在长江下游沿江平原典型区建立了0、60、160、280、2000和3000 a的土壤围垦时间序列,分析不同围垦时间与土地利用下土壤理化性质的差异。调查结果表明,围垦后表层土壤中的碳酸盐快速丧失,土壤逐渐由弱碱性转为弱酸性,围垦3000 a后旱地土壤pH值约降低了2。长期水旱轮作的利用方式下,由于稻季土壤复盐基作用和氧化还原交替的状态,酸化程度略低。围垦之后相当长的一段时间内有机碳(SOC)、全氮(TN)和凯氏氮(AN)含量均呈逐渐积累的趋势,在表层土壤无机碳逐渐降低的同时,SOC含量比围垦前总体有所提高,表明耕作培肥措施在一定程度上有利于SOC和养分的积累。但围垦历史最久的圩区其SOC、TN和AN含量又有不同程度的降低,全磷(TP)和有效磷(AP)含量除在围垦初期有所升高,后期则不断降低。水旱轮作的利用方式下,土壤磷素的耗竭问题尤其突出,显示区内农田养分的投入处于不同程度的亏缺状态。目前的管理方式下,土壤肥力质量退化的现象应当引起足够的重视。

In order to reveal the evolution trend and influencing factors of soil quality under the influence of human activities,soil chronosequence of 0,60,160,280,2000 and 3000 years were established in typical areas along the Yangtze River Plain in the lower reaches and the differences of soil physicochemical properties under different reclamation time and land use were analyzed.The survey results indicated that the carbonate in the surface soil was rapidly lost after reclamation,and the soil gradually changed from weakly alkaline to weakly acidic.After 3000 years of reclamation,the pH value of the dryland soil decreases by about 2.Under the long-term rotation of water and drought,the degree of acidification is slightly lower due to the alternation of soil salinization and redox during the rice season.After a considerable period of time after reclamation,soil organic carbon(SOC),total nitrogen(TN),and available nitrogen(AN)contents showed a gradual accumulation trend.While the inorganic carbon in the surface soil gradually decreased,SOC overall increased compared with before reclamation,indicating that tillage and fertilization measures are beneficial to the accumulation of SOC and nutrients to a certain extent.However,the polder areas with the longest history of reclamation have varying degrees of decrease in SOC,TN,and AN contents.Total phosphorus(TP)and available phosphorus(AP)contents increase in the early stages of reclamation,but continue to decrease in the later stages.Under the use of water drought rotation,the problem of soil phosphorus depletion is particularly prominent,indicating that the input of nutrients in the farmland in the area is in a state of varying degrees of deficiency.Under the current management mode,the degradation of soil fertility quality should be paid enough attention.