近40年陕西省农田土壤有机质时空变化及其影响因素

Temporal and spatial variation of soil organic matter in Shaanxi Province in the past 40 years and its influencing factors

了解农田土壤有机质的时空动态变化对促进农田生态系统绿色发展具有重大意义。本研究对陕西省耕地土壤有机质含量进行测定,以期探讨长期耕种下陕西省农田土壤有机质时空变化特征及其影响因素。于2017年采集耕层土样705份,采用重铬酸钾氧化—外加热法测定其有机质含量,并运用ArcGIS 10.5和GS+9.0软件进行了数据分析。结果表明:陕西省耕地土壤有机质平均含量为15.90 g·kg^(−1),4级水平占比最大;不同行政区有机质含量排序为:汉中>西安>安康>咸阳>宝鸡>商洛>渭南>铜川>延安>榆林;陕西省各市有机质含量较20世纪80年代均有不同程度的提升,其中汉中市提升幅度最大;陕西省农田土壤有机质具有强烈的空间自相关性,最优拟合模型为高斯模型,呈现南高北低的空间分布特征;结构性因素(坡度、海拔、经度、纬度)和随机性因素(施肥、耕作、秸秆还田等)共同作用导致了陕西省农田土壤有机质的空间分布差异,不同类型土壤有机质含量差异显著(P<0.05)。本研究为指导陕西省低碳农业的发展及实现碳达峰与碳中和提供了一定的科学依据。

Background,aim,and scope Spatial and temporal variation of soil organic matter has gradually become a global concern in order to seek a balance between climate change mitigation,food security and ecological safety in recent years.As a large agricultural province,Shaanxi Province has been paying much attention to its agricultural economic benefits.Although the overall food crop production in the province has maintained an upward trend in recent years,its position in the national food production ranking still needs to be improved,and the arable land resources are on a decreasing trend.This paper aims to provide some scientific basis for improving soil fertility and ensuring food security by studying the spatial and temporal variation of soil organic matter in cultivated land in Shaanxi Province.Materials and methods In 2017,705 soil samples were collected in Shaanxi Province to determine the content of soil organic matter.One-way ANOVA,correlation analysis and regression analysis were completed in SPSS 20.0,and the optimal semi-variance function fitting model was established using GS+9.0 software.ArcGIS 10.5 software was used for spatial autocorrelation and kriging spatial interpolation.Results The results showed that:(1)the average content of soil organic matter in cultivated land in Shaanxi Province was 15.90 g·kg^(−1),which was at the level 4 overall.The SOM content in different natural regions is:Southern Shaanxi>Guanzhong>Northern Shaanxi,and the order of SOM content in different administrative regions is:Hanzhong>Xi’an>Ankang>Xianyang>Baoji>Shangluo>Weinan>Tongchuan>Yan’an>Yulin.(2)In terms of time,the average soil organic matter content of each city in Shaanxi Province in 2017 has increased to varying degrees compared with the 1980s,and Hanzhong has the largest increase.(3)The spatial distribution of SOM content in Shaanxi Province is high in the south and low in the north,especially in the southwest region.The variation coefficient of soil organic matter content in cities in Shaanxi Province is between 10%—100%,which is a moderate variation.Among them,Hanzhong City has the largest variation in soil organic matter content and Shangluo City has the smallest variation.(4)The combined effect of structural factors(slope,altitude,longitude and latitude)and random factors(fertilization,tillage,straw returning,etc.)led to the spatial distribution pattern of soil organic matter in farmland in Shaanxi Province,and the content of different types of soil organic matter was significantly different(P<0.05).The organic matter content of yellow-brown earth and yellow-cinnamon soils is significantly higher than that of other soil types.Discussion(1)Straw return and long-term fertilization are the main reasons for the overall increase of soil organic matter content in the cultivated layer of agricultural land in Shaanxi Province in the past 40 years.However,due to the differences in fertilizer application,farming methods and crop types in different regions,the organic matter of cultivated land in Shaanxi Province has been enhanced differently under the combined effect of these factors.(2)The spatial distribution of soil organic matter in agricultural land in Shaanxi Province shows characteristics of high in the south and low in the north,and there is obvious spatial heterogeneity,which is closely related to structural factors such as topography,climatic conditions and soil-forming parent material and stochastic factors such as tillage and fertilization in Shaanxi Province.The organic matter content of different types of soils varies greatly,and climate directly affects plant growth,microbial activity in soil and soil respiration rate,which in turn affects soil organic matter content.Topographic factors can affect the spatial distribution of soil nutrients migration and vegetation types not only through,but also through soil erosion and soil erosion effects on the spatial distribution of organic matter.Conclusions Shaanxi Province should develop organic agriculture in light of local conditions,adopt reasonable agricultural management measures(including returning straw,organic fertilizer and biochar,and planting grass in orchards,etc.),extensively promote conservation tillage methods,and combine no-tillage with increasing multiple cropping index to improve soil fertility in Shaanxi Province.Recommendations and perspectives The temporal and spatial changes of soil organic matter in Shaanxi Province will guide the development of low-carbon agriculture in Shaanxi Province and provide a scientific basis for achieving carbon peaks and carbon neutrality goals.