近30年南方丘陵山区耕地土壤养分时空演变特征--以江西省为例

Characteristics of Spatiotemporal Variability of Cultivated Soil Nutrients in the Southern Hilly Area of China in the Past 30 Years——A Case Study of Jiangxi Province

为了掌握南方丘陵山区耕作土壤养分的时空演变规律,以江西省为例,利用1985年江西省第二次土壤普查数据和2012年测土配方施肥项目采集的大量耕层(0—25cm)土壤样点数据,借助SPSS经典统计方法、ArcGIS地统计学和半方差分析技术,运用全局空间自相关(Global Moran′s I)和普通克里金(Ordinary Kriging)插值分析相结合的方法,对比分析了近30年耕地土壤全氮(TN)、全磷(TP)、全钾(TK)、有机质(SOM)和酸碱度(pH值)5种养分要素的时空变异特征。结果表明:1985—2012年,江西省耕地土壤养分存在较大的时空差异,2012年土壤养分Moran′s I指数和块金系数较1985年表现为具有较强的空间正相关集聚特性。1985年除土壤pH值符合球状模型外,其余4种养分要素属于指数模型,2012年土壤TN,TP和SOM符合球状模型,TK和pH值符合指数模型,两个时期交叉验证结果均达到显著水平。30年来,研究区耕作土壤养分有升有降,以升为主。土壤TN和SOM处于丰富级水平,其含量显著上升,平均级别分别提升了0.41,0.44个单位;TP处于中等水平,全磷水平上升较为显著,平均级别提升了0.39个单位;TK处于低量级水平,全钾含量急剧下降,平均级别降低了0.89个单位;土壤pH值处于酸性水平,pH值下降较为明显,平均级别降低了0.66个单位。近年来,由于受到人为耕作方式、施肥结构、秸秆还田、工业污染及酸性沉降物等的影响,江西省耕地土壤TN,SOM和TP含量有所提升,TK含量急剧降低,土壤严重酸化。研究结果为江西省土壤养分分区管理、精准高效施肥、土壤养分可持续利用和提升耕地质量提供基础理论和科学依据。

This study aimed to understand the spatialtemporal evolution patterns of cultivated soil nutrients of Jiangxi Province from 1985 to 2012.The data were obtained from the second national soil survey(SNSS)in 1985 and the soil test and fertilizer recommendation in 2012 in Jiangxi Province.Classical statistics of SPSS,geo-statistics and semi-variance function of ArcGIS were used to process data,the global Moran′s I and ordinary Kriging method were applied to analyze the characteristics of spatiotemporal variability of TN,TP,TK,SOM and pH value of the cultivated soils during the past 30 years.The results showed that there were major differences in cultivated soil nutrients of Jiangxi Province from 1985 to 2012,global Moran′s I value and Nugget/Sill of soil nutrients presented as the strong positive spatial autocorrelation in 2012 compared with that in 1985.In 1985,the variograms of cultivated soil nutrients belonged to exponential model except that soil pH value fitted the spherical model.TN,TP,and SOM fitted the spherical model in 2012,while TK and pH value fitted the exponential model.All the results of cross-validation reached significant level during the two periods.During 30 years,cultivated soil nutrient contents of study area dropped or rose,showing the dominant rise as a whole.TN and SOM were at the high levels and the increases were particularly obvious,average grades increased 0.41 and 0.44 units,respectively.TP was at the middle level and the rise was more significant,average grade increased 0.39 units.TK was at the lowest level and the increase sharply dropped,average grade decreased 0.89 units.Soil pH value was at the acid level and dropped obviously,average grade decreased 0.66 units.In recent years,the increases of TN,SOM and TP contents,the decreases of TK content and pH value should be attributed to the effects of different tillage methods and fertilization,straw returning,industrial pollution,together with acid precipitation.The results of the study can provide theoretical supports and the scientific basis for soil regionalized soil nutrient management,high efficiency fertilization,soil nutrient sustainable utilization and cultivated land quality improvement in Jiangxi Province.