长江三角洲典型地区农田土壤速效钾时空演变特征及其驱动力

研究农田土壤速效钾的时空演变规律对改善土壤管理和提高土壤质量具有重要的指导作用．以长江三角洲地区的江苏省如皋市为例，对不同时期农田土壤速效钾的时空分异进行了研究．结果表明，自1982—1997—2002的20多年来，虽然速效钾在空间分布模式上变化不大，但近年来，空间分布趋于复杂化．土壤速效钾具有明显的时间分异特征，总体上经历了先下降后又有所回升的动态演变过程，在90年代中期土壤速效钾普遍亏缺，但近年来有显著回升．不同土壤类型速效钾的时空分异特征有明显差别．由江淮冲积物或长江现代冲积物发育而成的，质地较粗的雏形土（磨头系、郭园系和张黄港系）20年来持续下降，但下降幅度较小．由浅湖相冲积物发育而成的，质地较细的水耕人为土（白蒲系）和长江现代冲积物发育而成的，质地较细的潮湿雏形土（长青沙系）早期下降幅度较大，但近年来回升幅度也较大．其余土系则遵循先下降后上升的总体规律．影响土壤速效钾变化的驱动力分析表明，造成这些时空演变规律的主要因素包括：秸秆还田、施肥管理、种植结构和土地利用方式的改变等．且随着时间的推移，这些因素的影响趋于多元，导致农田土壤速效钾的空间变异性逐渐增强．

Spatio-temporal Variability of Exchangeable Potassium in Agricultural Soils and Its Driving Factors in a Typical Area of Yangtze River Delta Region

Understanding spatio-temporal variability of exchangeable potassium(K) in agricultural soils plays a key role in improving the quality of agricultural soil and products.On the basis of geo-statistics combined with GIS technique,this paper analyzed the spatio-temporal variability and the spatial distribution pattern for exchangeable K in agricultural soils at three periods in Rugao county,Jiangsu province.The results showed that since 1982,spatial distributions of exchangeable K had tended to be complex,although the spatial distribution pattern changes little during the past two decades.Temporally,the soil exchangeable K experienced a dynamic process from a decrease to an increase in the past two decades.Compared to the soil exchangeable K at the beginning of 1980s,it was significantly lower at the middle of 1990s and showed K-deficient at large,but increased back at present.The temporal variability was of different tendency among soil series.For the sandy Cambosols(Motou,Guoyuan and Zhanghuanggang) derived from river alluvium,the exchangeable K continually and smoothly decreased during the past two decades.But for the loamy Anthrosols(Baipu) developed from lacustrine sediment and the clayey Cambosols(Changqingsha) derived from river alluvium,the exchangeable K significantly increased in recent years after experienced a decrease at the middle of 1990s.The temporal variability of the rest of soils followed general tendency.It was showed that the driving factors affected spatio-temporal variability of soil exchangeable K included returning of plant residues,fertilization,plant rotation,and land utilization.These factors increasingly affected and developed towards diversification over time.