Spatial And Temporal Variation Of Soil Nutrients And Its Influencing Factors

Cultivated land is the material basis for human survival and development.The quality of cultivated land is not only related to the sustainability of resources,environment and ecosystem,but also directly affects the national food security.With the continuous decrease of cultivated land resources and the increasing population,the protection of cultivated land quality is becoming more and more important.The factors that affect the quality of cultivated land include the natural processes and human activities.With the intervention of human activities on cultivated land,the influence of social factors such as social economy and policy systems on soil nutrients is increasing.Most of the previous studies on soil nutrients mainly focus on the explanation of natural factors.However,there are few studies for the influence of socioeconomic factors on soil nutrients.And the data are mostly in 2000 and 1980,and there are few studies using continuous time series of data.In this paper,we analyzed the continuous time series of data that include soil nutrients and socio-economic to understand the evolutionary trend of soil fertility after 2000,and then explored the influence of social and economic factors on soil nutrient changes.These work can provide us with a reference for the improvement of cultivated land quality,the implementation of precision agriculture strategy and the adjustment of agricultural structure.In this paper,we chose Wudi County of Shandong Province as the typical research area,and selected soil organic matter,available nitrogen,available phosphorus,available potassium and pH as the basic evaluation indexes for soil fertility.The sample data are the experimental observation value of soil nutrients from 2006 to 2015.By using classical statistical method and geostatistical method,we analyzed the spatial and temporal variation of soil nutrients and pH in the last ten years.Then we used the comprehensive index method to calculate the soil comprehensive fertility,and analyzed its temporal and spatial variation.Finally,we collected natural and socioeconomic data in the corresponding period to analyse the effects of natural factors and socio-economic factors on soil nutrients and fertility changes.The results of this study showed that the soil nutrients and fertility of the cultivated land had a descendent tendency in the last ten years,but the regional differences were gradually narrowing.Specifically,in addition to the soil organic matter,the amount of available nitrogen,available phosphorus and available potassium decreased at different degrees,especially the amount of available potassium having decreasd significantly.In addition,the soil pH showed an upward trend in the later period.From the spatial perspective,the spatial variability of soil fertility and soil nutrients decreased and the random variation increased,indicating that the soil nutrients were deeply influenced by human factors,and resulting in the reduction of regional differences.After analyzing the influencing factors of soil nutrients and fertility,we found that the influences of natural factors on soil nutrients changes become weaker,but the influences of human factors continue to strengthen.Among the natural factors,the soil pH has a great influence on soil nutrients and fertility.Among the social and economic factors,the increase of non-agricultural employment and the increase of farmers' per capita income have a significant negative impact on the change of soil fertility.The unbalance of fertilizer application and the concept of paying more attention to the nitrogen fertilizer are the important reasons for the reduction of available phosphorus and available potassium.The decrease of multi-cropping index has a significant negative impact on soil nutrients and comprehensive fertility.Because the standard of agricultural subsidies is too low,the incentive effect of subsidies to farmers' enthusiasm for grain and protecting the quality of cultivated land is insufficient.In addition,the amount of fertilizer applied in the study area is too high,which easily leads to the degradation of soil fertility.Based on the results of this study,we propose the following suggestions:First,promote the soil testing and fertilizer recommendations technology to guide the farmers to carry out scientific fertilization,and pay more attention to the market supply of organic fertilizer to increase the application of organic fertilizers.Second,guide the land circulation and cultivate the land transfer market.In addition,we also need to improve the rural social security system to provide greater activity space for land circulation.Third,increase the agricultural subsidies to improve the agricultural production efficiency.And in order to improve soil fertility,it is particularly important to establish and support the protective subsidy policy for cultivated land.Fourth,cultivate the professional service market for soil fertility protection to protect and improve the quality of cultivated land.