稻麦两熟农田土壤速效钾时空变异及原因分析--以江苏省仪征市为例

Spatio-temporal variation of soil available potassium under wheat-rice double cropping system——A case study in Yizheng City,Jiangsu Province

以江苏省仪征市稻麦两熟农田为分析样区，利用1984年、1994年、2000年、2005年4期土壤普查数据，应用地统计学方法和GIS技术进行了土壤速效钾时空变异特征及肥力水平分析。结果发现：1984～1994年土壤速效钾平均含量由91．20mg·kg^-1减少为73．63mg·kg^-1，2005年又恢复到91．62mg·kg^-1。速效钾空间分布也存在明显的变化趋势，变程从1984至1994年由20．28km减少到8．32km，2000年增加到24．18km，2005年又减少到8．18km，呈先减后增再减趋势。块金值与基台值之比范围为48．48％～74．33％，说明土壤速效钾空间分布表现为中等程度自相关，且1994年和2005年空间分布自相关程度明显高于1984年和2000年。对1980～2005年间的耕作制度、肥情、粮食产量和农户生产情况等历史资料分析表明，历年土壤速效钾时空变异原因主要受农户的栽培管理措施、政府政策、社会经济发展情况等人为因素的影响。2005年74．76％面积的土壤速效钾含量达到农业部测土施肥确定的土壤速效钾Ⅱ级标准，但其平均值均在90mg·kg^-1左右，为Ⅱ级标准偏下。故不能盲目的因速效钾含量等级高而忽视钾肥的施用，而应更重视钾肥的施用和管理。

General soil data for 1984 - 2005 were used to analyze for spatio-temporal variation of available potassium of field of wheat-rice double cropping system in Yizheng City through Geo-statistical method and GIS technique. The results show average concentration of available potassium to be 91.20 mg·kg^-1 in 1984; the value decreases down to 73.63 mg·kg^-1 in 1994, but then increases up to 91.62 mg·kg^-1 in 2005. There is also an obvious trend of spatial distribution over a given distance for available potassium, which decreases from 20.28 km in 1984 to 8.32 km in 1994, but again increases to 24.18 km in 2000 before finally decreasing to 8.18 km in 2005. Nugget to sill ratio of available potassium changes from 48.48% to 74.33% , showing medium spatial heterogeneity in different years. However, the degree of spatial heterogeneity in 1994 and 2005 is higher than that in 1984 and 2000. Investigation of agricultural management practices, soil fertility, grain yield, fertilizer application method and history, etc. , from 1980 to 2005 in Yizheng City, indicates that soil available potassium variation is dependent mainly on mass fertilizer application, changes in tillage method, government policy, cropping system and soil management. Soil available potassium analysis for 2005 shows that 74.76% of the study area meets soil available potassium grade 11 standard, with a mean available potassium of 90 mg·kg^-1. Therefore, instead of neglecting potassium fertilization and management, we rather emphasize its strengthening.