在2011年土壤采样的基础上,参照1981年沭阳县二次土壤普查资料,对该县土壤有机质和全氮30年来的时空演变进行了分析,并进一步讨论了时空演变的自然和人为因素.结果表明:30年来,沭阳县农田耕层(0～20cm)土壤有机质和全氮均明显增加,2011年土壤有机质和全氮的平均含量分别为23.12 g/kg和1.36 g/kg,分别比1981年增加了12.15 g/kg和0.61 g/kg,平均增加速率达0.41 g/(kg·a)和0.02 g/(kg.a).2011年土壤有机质和全氮的整体空间分布格局与1981年相似,均呈现北部黏性土壤高而南部砂性土壤低、东部水田高西部旱地低的空间分布格局.土壤质地是造成这种时空变异最主要的结构性因素,而秸秆还田量的增加、土地利用方式的转化是30年来影响土壤有机质和全氮时空演变的主要人为随机性因素.%Based on collected samples in 2011,by referring the data in the 2nd national soil survey in 1981,this paper evaluated the temporal and spatial variability of soil organic matter (SOM) and total nitrogen (STN) in farmlands during the past 30 years in Shuyang County,Jiangsu Province and further discussed natural and anthropic factors leading to the variability.The results showed that,in the past 30 years,SOM and STN in topsoil (0-20 cm) significantly increased.The contents of SOM and STN in 2011 were 23.12 g/kg and 1.36 g/kg,respectively,12.15 g/kg and 0.61 g/kg higher than those in 1981,the increasing rates were 0.41 g/(kg·a) and 0.02 g/(kg.a) for SOM and STN.In spatial,the SOM and STN in 2011 had the similar spatial distributions to those in 1981,showing that clayey soil in the north area had higher contents than sandy soil in the south area,and paddy fields in the east area had higher contents than dry fields in the west area.Soil texture was main natural structural factor affecting this temporal and spatial variability,while the increase of crop-residue incorporation and the transformation of land-use patterns were major anthropic random factors affecting them in the past 30 years.
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