长三角地区农田土壤养分空间变异及养分综合评价

以浙江宁波三七市镇的一块面积为 2562 hm2 的农田为研究区域，运用地统计学与GIS相结合的手段和方法对其土壤养分的空间变异特征展开研究。结果表明，5种养分要素的空间变异函数曲线的理论模型符合指数模型；速效钾、有机质和pH值的C0/(C0+C)<25%,表现出强烈的空间相关性，碱解氮和有效磷的C0/(C0+C)为25%~75%，具有中等的空间相关性。通过Kriging插值并依据养分的分级标准，所得的空间变异图能很好地反映农田土壤养分的空间变异特征和丰缺状况，几种养分要素中，碱解氮、有效磷和有机质含量总体丰富，而速效钾的含量处于中低水平，pH值较低，土壤呈现酸性。利用主成分分析结合空间插值的方法，还可以对研究区的土壤养分的综合状况进行评价。研究结果可为当地以及长江三角洲同类型地区在科学施肥、实行养分的分区管理以及农业面源污染的控制方面提供一定的科学依据和借鉴参考。

RESEARCH ON THE CHARACTERISTICS OF SPATIAL VARIABILITY OF SOIL NUTRIENTS AND GENERAL ASSESSMENT IN FARMLAND IN THE YANGTZE RIVER DELTA

By the method of geostatistics combined with GIS,spatial variability of soil nutrients and pH value were studied in a farmland covering an area of 256.2 hm2,located at Sanqishi Town in Ningbo City,Zhejiang Province.The result showed that semivariograms of soil nutrients were best described by exponential model;the ratios of nugget and sill of available kalium,OM and pH value were lower than twenty-five percent,which showed their strong spatial correlation;while that of available phosphorus and available nitrogen were in the range between 25% and 75%,which showed medium spatial correlation.By using Kriging interpolation and according to the nutrients' criterion of classification,we could master the levels and characteristics of spatial variability of nutrients of soil.In general,the contents of available nitrogen,available phosphorus and OM were rich in the studied area,while that of available kalium were between moderate and low.The value of pH was low and the soil showed acidic.By the principle components analysis combined with Kriging,the general status of the soil nutrients could be appraised.The investigation results could supply scientific foundation and reference for appropriate fertilization,site-specific management and effectively controlling agricultural nonpoint source pollution for local area and similar areas in the Yangtze River Delta.