30年间河北省曲周县土壤速效钾的时空变异 特征及其影响因素

【目的】速效钾是土壤肥力的重要指标之一，与作物产量和品质密切相关。最近10年随着农业结构调整，机械化程度不断提高，秸秆还田等技术的不断推广，迫切需要研究这些因素对土壤速效钾含量时空变化的影响，从而为土壤肥力评价和管理提供指导。【方法】通过野外调查、采样分析和资料搜集得到了河北省曲周县1980年、2000年和2010年3个不同时期耕层土壤速效钾含量的数据，首先对不同时期土壤速效钾含量进行了常规统计和正态性检验；然后应用地质统计学方法分析了不同时期耕层土壤速效钾含量的空间结构特征，结合GIS空间插值、叠置分析和面积统计功能研究了该区耕层土壤速效钾含量的时空变异特征；最后对各种影响因素（土壤质地、土壤类型和土地利用类型）下的土壤速效钾含量进行了方差分析。【结果】3个时期土壤速效钾的平均含量分别为167.1、90.0和87.7 mg•kg-1，2000年的平均含量比1980年减少了46.1%，2010年比2000年减少了2.6%。具体变化为：1980年速效钾含量为I级地（＞200 mg•kg-1）和II级地（150-200 mg•kg-1）的面积比例分别为5.2%和82.9%，而到2000年和2010年时基本减少到无。1980年III级地（100-150 mg•kg-1）的面积比例为11.9%，到2000年增加到22.3%，2010年进一步增加到31.2%。1980年时没有IV级地（50-100 mg•kg-1），而2000年和2010年该等级面积比例最大，分别为78.7%和68%。1980年、2000年和2010年土壤速效钾的空间相关距离分别为8.1、2.8和9.8 km。前20年变程呈减小的趋势，而后10年变程呈增加的趋势，这是区域因素与随机因素共同作用的结果。不同质地土壤的速效钾含量顺序为：砂土＜砂壤＜轻壤＜中壤＜黏土。潮土的速效钾含量明显高于盐土。各种农用地中，林地的速效钾含量变化最大，1980年和2000年其含量最小，到2010年其含量最大。【结论】30年来曲周县土壤速效钾含量随时间的推移呈递减的趋势，前20年下降很快，后10年表现为总体略有下降，但局部有上升的趋势。土壤类型、土壤质地、土地利用类型和人为管理措施是其主要影响因素。秸秆还田和平衡施肥等措施对于保持和提升土壤速效钾含量起到了非常重要的作用，需进一步大力推广。

Spatio-temporal Variability and the Influencing Factors of Soil Available Potassium in 30 Years in Quzhou County,Hebei Province

【Objective】Soil available potassium (AK) is one of the main soil fertility indicators and has a close relationship with grain quality and yield. With the rapid adjustment of agricultural structure, improvement of mechanization level and recommendation of straw return technology in recent 10 years, it is urging to explore the effect of those factors on the change of soil AK. The objectives of this study were to analyze the spatio-temporal variability and its influencing factors of soil AK over the past 30 years in Quzhou county, Hebei Province, and to provide a guidance for soil fertility evaluation and soil management.【Method】By field investigation and soil sampling, the contents of AK in the plow layers in 1980, 2000 and 2010 were collected and measured. The traditional statistical method was used to analyze the datasets of soil AK in three periods. Normality of the datasets was assessed using the Kolmogorov-Smirnov test. Geostatistical analysis consisting of variogram calculation, cross-validation, kriging and mapping was performed using the geostatistical analyst extension of ArcGIS 10.0. Firstly, the unobserved value was estimated by the kriging method, then transferred the file format into raster format; finally the raster calculator was used to obtain the distribution map of the difference in AK between two time intervals. Overlap analysis was used to assess the effect of soil texture, soil type and land use type on soil AK content. Analysis of variance and t-test was also conducted using Least Significant Difference procedure.【Result】It showed that the average AK contents were 167.1, 90, and 87.7 mg•kg-1 in 1980, 2000 and 2010, respectively, showing a decreasing trend over the investigated period. The average AK content was decreased by 46.1% from 1980 to 2000, while it was only decreased by 2.6% from 2000 to 2010. AK levels were classified into five grades from high to low (＞200, 150-200, 100-150, 50-100 and ＜50 mg•kg-1), the percentages of land with the highest and second-grade AK were 5.2% and 82.9% in the study area in 1980, respectively, but the area of the highest and second-grade reduced to almost zero in 2000 and 2010. The third-grade land in 1980 accounted for 11.9%, while it was increased to 22.3% in 2000 and 31.2% in 2010. There were no fourth-grade land in 1980, but it was increased to 78.7% in 2000 and 68% in 2010. Semivariogram analysis results showed that the spatial correlation distances of AK were 8.1 km, 2.8 km and 9.8 km in 1980, 2000 and 2010, respectively, reflecting that the influence of human activities on AK content increased over time. The spatial correlation range decreased with time with a rapid decrease of 5.3 km in the first two decades (1980-2000), while it showed an increase trend in the recent decade (2000-2010), which due to the combined effect caused by anthropic activities and regional factors. The AK contents for different soil textures had the following order: clay＞medium loam＞light loam＞sandy loam＞sand. The AK content in fluvo-acquic soil was significantly higher than that in saline soil. It was found that the AK content in forest land was the lowest in 1980 and 2000, but it was the highest in 2010. 【Conclusion】The AK content showed a decreasing trend over the past 30 years. Soil type, soil texture, land use type and farming practices were the main influencing factors. Straw return and fertilizer application based on soil test technology should be recommended. Straw return practice and balanced fertilization technology played an important role in effectively increasing the AK content in this region and should be adopted as the long-term management practice.