近35年红壤稻区土壤肥力时空演变特征——以进贤县为例

Spatiotemporal Variability Characteristics of Soil Fertility in Red Soil Paddy Region in the Past 35 Years——A Case Study of Jinxian County

【目的】明确红壤稻区典型县域农业生产中土壤养分的变化特征以及当前土壤肥力水平,为红壤稻田土壤培肥改良提供依据。【方法】通过数据收集和野外采样分析得到江西省进贤县1982年、2008年和2017年3个时期稻田耕层土壤属性的数据,统一选取土壤pH、有机质、碱解氮、有效磷和速效钾作为土壤综合肥力评价指标,首先对3个时期各项肥力指标进行常规统计和差异性分析,采用主成分分析找出不同时期肥力差异的关键因子并确定权重,通过隶属度函数得到各项肥力指标的隶属度值,将各项肥力指标的权重和隶属度值加乘得到土壤综合肥力指数,最后结合土壤各项肥力指标和综合肥力指数的GIS空间分布图探究该区域稻田土壤肥力时空演变特征。【结果】1982—2017年进贤县稻田土壤有机质、碱解氮、有效磷和速效钾均呈不同程度的上升趋势,土壤pH呈下降趋势。1982、2008和2017年3个时期进贤县土壤pH的平均值分别为5.9、5.1、4.8,年均下降0.03个单位;35年来土壤pH整体由西部向东南和西北下降速率逐渐减低,2017年99%的稻田土壤处于酸性水平(4.5—5.5)。35年间稻田土壤有机质含量的平均值由28.1 g·kg^-1上升至36.8 g·kg^-1,1982—2008年和2008—2017年土壤有机质年均增加速率分别为0.21和0.31 g·kg^-1,2017年土壤有机质含量在30—40 g·kg^-1之间的稻田占比达94%,1982—2017年土壤有机质整体由东北向西南上升速率逐渐降低。1982—2017年土壤有效磷含量的平均值由7.0 mg·kg^-1上升至32.1 mg·kg^-1,2017年进贤县以土壤有效磷含量在20—40mg·kg^-1的稻田为主,占比75%。1982—2017年稻田土壤速效钾累积缓慢,1982—2008年和2008—2017年土壤速效钾年均增加速率分别0.58和0.53 mg·kg^-1,2017年进贤县稻田土壤速效钾含量平均值为73.2 mg·kg^-1。稻田土壤碱解氮在1982—2008年和2008—2017年两个阶段增长均呈先快后慢的趋势,前后两个阶段的年增长速率分别为1.24和0.29 mg·kg^-1,1982—2017年进贤县土壤碱解氮含量东南地区上升速率高,西北地区上升速率低。1982、2008和2017年进贤县稻田土壤综合肥力指数的平均值分别为0.43、0.50和0.55。3个时期稻田土壤肥力指标综合得分分别为:碱解氮有效磷>pH>速效钾>有机质(1982年);pH>有效磷>速效钾>有机质>碱解氮(2008年);速效钾>有效磷>pH>碱解氮>有机质(2017年)。【结论】经过35年的长期耕作,进贤县稻田土壤肥力得到改善。当前进贤县稻田土壤仍存在碱解氮过量、速效钾亏缺、土壤酸化严重等问题。土壤碱解氮、pH和速效钾分别为1982年、2008年和2017年3个时期造成进贤县稻田土壤肥力空间分布差异性的关键因素。

【Objective】The aim of this study was to clarify the changes of soil nutrients and the current fertility level in the actual agricultural production in the typical county of red soil,which provided the basis for the improvement of red soil paddy soil.【Method】Data of paddy field soil properties in Jinxian County of Jiangxi Province in 1982,2008 and 2017 were obtained through data collection and field sampling analysis.Soil pH,organic matter,alkalide nitrogen,available phosphorus and available potassium were selected as soil comprehensive fertility evaluation factors.Firstly,the conventional statistics and differential analysis of various fertility factors in the three periods were carried out.Principal component analysis was used to find out the key factors of fertility differences in different periods and the weight was determined.The membership value of each fertility factor was obtained by membership function.The soil integrated fertility index was calculated by weight values and membership values.Finally,the spatial and temporal evolution characteristics of paddy field soil fertility in this region were explored based on GIS spatial distribution maps of soil fertility factors and integrated fertility index.【Result】From 1982 to 2017,soil organic matter,alkalide nitrogen,available phosphorus and available potassium of paddy soil in Jinxian County increased in varying degrees,while soil pH value decreased.The average pH values of Jinxian County in the three periods of 1982,2008 and 2017 were 5.9,5.1 and 4.8,respectively,with an average annual decrease of 0.03 units.In the past 35 years,the overall decline rate of soil pH from west to southeast and northwest gradually decreased.In 2017,99%of the paddy soil was at an acidic level(4.5-5.5).The average content of soil organic matter increased from 28.1 to 36.8 g·kg^-1 in 35 years.The average annual increase rates of soil organic matter from 1982 to 2008 and from 2008 to 2017 were 0.21 and 0.31 g·kg^-1,respectively.In 2017,the proportion of paddy fields with soil organic matter content between 30 and 40 g·kg^-1 reached 94%.From 1982 to 2017,the increasing rate of soil organic matter decreased gradually from northeast to southwest.From 1982 to 2017,the average content of available phosphorus in soil increased from 7.0 to 32.1 mg·kg^-1.In 2017,the paddy fields with soil available phosphorus content ranging from 20 to 40 mg·kg^-1 were dominant in Jinxian County,accounting for 75%.The accumulation of available potassium in paddy soils was slow from 1982 to 2017.The annual average increase rates of available potassium in paddy soils from 1982 to 2008 and from 2008 to 2017 were 0.58 and 0.53 mg·kg^-1,respectively.In 2017,the average content of available potassium in paddy soil in Jinxian County was 73.2 mg·kg^-1.The alkalide nitrogen in paddy soils increased first and then slowly in the two stages of 1982-2008 and 2008-2017.The growth rates of the two stages were 1.24 and 0.29 mg·kg^-1,respectively.From 1982 to 2017,the increase rate of soil alkalide nitrogen content in Jinxian County was higher in Southeast China and lower in Northwest China.The average values of the integrated fertility index of paddy soil in Jinxian County in 1982,2008 and 2017 were 0.43,0.50 and 0.55,respectively.The general scores of soil fertility factors in three periods were as follows:alkalide nitrogen>available phosphorus>pH>available potassium>organic matter(1982),pH>available phosphorus>available potassium>organic matter>alkalide nitrogen(2008),available potassium>available phosphorus>pH>alkalide nitrogen>organic matter(2017).【Conclusion】After 35 years of long-term cultivation,the soil fertility of rice fields in Jinxian County has been improved.At present,the paddy soil in Jinxian County still has problems such as excessive alkalide nitrogen,available potassium deficiency,and serious acidification of the soil.Soil alkalide nitrogen,pH and available potassium were the key factors for the spatial distribution of soil fertility in Jinxian County during the three periods of 1982,2008 and 2017,respectively.