近30年山东省耕地土壤pH时空变化特征及影响因素

通过研究山东省第二次土壤普查省级汇总(1984年)和省级耕地地力评价(2015年)耕地土壤pH数据,分析了土壤酸化的总体情况和动态变化,探讨了土壤酸化的自然和人为驱动因素。结果表明,30年来,山东省耕地土壤pH平均值由7.6降至7.2,降低了约0.4个单位,整体表现为酸性耕地面积明显增加,弱碱性和中性耕地面积相对减少,局部耕地酸化。目前,山东省弱碱性、中性和弱酸性耕地土壤比较多,占92.74%,酸性耕地土壤占7.04%;酸性耕地土壤主要分布于胶东半岛和东南部沿海的威海、烟台、青岛、日照、临沂和枣庄等6个市。不同地市酸碱度变化差异较大,威海变化最大,降低了1.3个单位;其次是泰安、日照、烟台和青岛,分别降低了1.1、1.1、1.0和1.0个单位。全省耕地土壤pH变化由大到小依次为:水稻土(潮土型)、棕壤、粗骨土、砂姜黑土、褐土和潮土。全省耕地土壤酸化主要影响因素为土壤类型、植物收获以及化肥不适当施用。

Spatio-temporal Variation of Farmland Soil pH and Associated Affecting Factors in the Past 30 Years of Shandong Province, China

【Objective】Soil pH is a key index for quality evaluation of cultivated lands.So this paper explored temporal and spatial changes in soil pH of farmlands in Shandong Province in the past 30 years,analyzed overall situation of and dynamic changes in soil acidification,and discussed natural and human-driven factors affecting soil acidification,so as to provide certain scientific references for prevention and control of soil acidification in Shandong Province.【Method】Based on the soil pH data cited from the“Second Provincial Soil Survey in 1984”and the“Provincial Arable Land Fertility Evaluation(PALFE)in 2015”,the soils of the province were sorted into seven grades,i.e.I.Highly acidified soil(pH≤4.5),II.moderately acidified soil(4.58.5),in line with the criteria for soil grading in terms of soil pH(Cultivated Land of Shandong)and in light of the reality of the province.The Kriging method and some other statistical methods commonly used in geostatistics were adopted to analyze the data with the aid of ArcGIS,Excel and some other software.【Result】According to the second provincial soil survey,the soils of the province was averaged 7.6 in soil pH,and no soils were sorted into GradeⅠ,GradeⅡor GradeⅢ.The soils of GradeⅣ,GradeⅤ,GradeⅥand GradeⅦwere 94.49×10⁴,259.0×10⁴,498.8×10⁴and 1.03×10⁴hm2 in area or 11.07%,30.36%,58.45%and 0.12%,respectively,of the total cultivated land area.The soils of Grade IV were distributed mainly in 7 cities(Weihai,Yantai,Qingdao,Rizhao,Linyi,Weifang and Tai'an).According to the Provincial Arable Land Fertility Evaluation,the soils were averaged to be 7.2 in pH,and no soils were sorted into GradeⅠ.The soils of GradeⅡ,GradeⅢ,GradeⅣ,GradeⅤ,GradeⅥand GradeⅦwere 7.48×10⁴,46.09×10⁴,155.4×10⁴,202.8×10⁴,347.3×10⁴and 1.647×10⁴hm2,respectively,or 0.98%,6.06%,20.43%,26.66%,45.65%and 0.22%of the total cultivated land area of the province.Soils of GradeⅢwere found in 6 cities(Weihai,Yantai,Qingdao,Rizhao,Linyi and Zaozhuang)in the Jiaodong Peninsula and along the southeast coast,and soils of Grade IV in the 12 cities,except for Dezhou,Liaocheng,Binzhou,Heze and Dongying in the alluvial plain of the Yellow River.According to the Second Provincial Soil Survey,the main types of soils in the province were sorted,in terms of soil pH,as follows:Fluvo aquic soil>Paddy soil(Fluvo aquic type)>Cinnamon soil>Sandy black soil>Skeletal bone soil>Brown soil>Fluvo aquic soil,varying in the range from 8.0 the highest to 6.8 the lowest,and showing a difference of 1.2 units between the highest and the lowest.According to the PALFE,the soils exhibited a similar order,in terms of soil pH,i.e.Fluvo aquic soil>Cinnamon soil>Sandy black soil>Paddy soil(Fluvo aquic type)>Skeletal soil>Brown soil,ranging from 7.8 the highest to 6.0 the lowest,and showing a difference of 1.8 units.Comparison of the two datasets shows that the soils of Shandong as a whole dropped from 7.6 to 7.2 in soil pH in the past 30 years,and the area of alkaline arable land increased slightly,while that of the weakly alkaline and neutral arable lands decreased relatively,but the area of acidic arable land remained increasing significantly,and some of them even were acidified.【Conclusion】Since the Second Soil Survey of Shandong Province,the average soil pH of the cultivated lands had decreased by 0.4 units.The drop of soil pH was mostly found in regions of lands of Grade IV.Changes in soil pH of cultivated lands varied sharply from region to region and from type to type of the soil.Soil acidification occurred mainly in Weihai,Yantai,Rizhao,Qingdao,Linyi and Zaozhuang,especially,in skeletal soil and brown loam derived mainly acidic parent material.The Fluvo aquic soil and Cinnamon soil derived from Yellow River alluvial deposit and limestone were both alkaline,relatively high in pH.Natural acidification,crop harvest and improper use of chemical fertilizers are the main factors triggering decline of soil pH and even acidification in Shandong.