| The cumulic epipedon of Lou soil is formed by dung stacking therein and tilled to slaking.The thickness of cumulic epipedon can reflect the fertility level of Lou soil and the effect of human activities on the soil forming process.In this paper,we designed grid sampling sites（5 km×5 km）in the Guanzhong region and investigated the thickness and spatial distribution characteristics of cumulic epipedon in 273 Lou soil profiles.The spatial differentiation characteristics of cumulic epipedon thickness and soil nutrients were analyzed by geostatistical Kriging interpolation method.Random forest and geodetector were used to further explore the dominant factors affecting cumulic epipedon thickness and spatial variation of Lou soil nutrients.At the same time,principal component analysis was used to evaluate the comprehensive fertility of the Lou soil and zoning,which could provide the basis for soil nutrient storage and agricultural sustainable development.The main results of this study are as follows:（1）The thickness of the cumulic epipedon in Guanzhong region ranged from 14 to 130cm,with an average thickness of 55 cm,and its coefficient of variation was 34.28%,which belongs to medium degree of variation.The thickness of the cumulic epipedon was relatively higher in the Hancheng,Heyang,and Chengcheng counties in the eastern of the Guanzhong region,while the thickness was concentrated in the range of 25～70 cm in the Weihe River Basin of the Guanzhong region.The thickness of cumulic epipedon had a significant positive correlation with the change of latitude and longitude,and a significant negative correlation with the slope,temperature and humidity.The influence of human factors was directly proportional to the increase of population and inversely proportional to the decrease of per capita cultivated land area.The spatial distribution of Lou soil increased first and then decreased slowly with the increase of distance from the river.The comprehensive interpretation of the 13 influencing factors in this study was 64.36%for the thickness of the cumulic epipedon.The results of importance ranking showed that the change of per capita cultivated land area had the most significant effect on the thickness of the cumulic epipedon,followed by the change of population.The formation and distribution of the cumulic epipedon is more deeply affected by human factors than the"five soil forming factors",especially with the development of productivity in the past hundred years,and its influence on the spatial distribution and thickness of the cumulic epipedon is also more significant.（2）The spatial distribution of Lou soil nutrients showed a trend of high in the central and western parts of Guanzhong and low in the eastern part,and gradually decreased in the south bank of Weihe River to the north.The total Lou soil nutrients were at the medium and low level of soil nutrient classification standard in Shaanxi Province,and the spatial variation of Lou soil nutrients was greatly affected by random factors.In the vertical direction,the nutrient content was the highest in the cultivated horizon Aup1,and gradually decreased with the increase of soil depth.In this study,the results of correlation analysis and geodetector analysis showed that the dominant factors affecting the spatial differentiation of soil nutrients were still natural factors,among which the correlation of meteorological factors was better.Factor detection showed that relative humidity was the dominant factor affecting soil nutrients,and sunshine duration and temperature had a greater effect on soil p H.Precipitation and relative humidity had great influence on Ca CO3.Except for alkali-hydrolyzed nitrogen,all kinds of soil nutrients were greatly affected by relative humidity in cultivated horizon Aup1 and cultivated horizon Aup2.Due to the long history of soil formation and the influence of parent material of soil formation,the dominant influence factors of buried cultivated horizon Aupb are different greatly.The interaction between relative humidity and other meteorological factors is still the main interaction,which indicates that better hydrothermal conditions are beneficial to the soil genesis.（3）Based on the study of spatial distribution characteristics and influencing factors of soil nutrients,an assessment that can directly affect soil fertility was selected,including:organic matter,total nitrogen,available potassium,available phosphorus,alkali-hydrolyzable nitrogen and soil bulk density.In addition,the impact of the cumulic epipedon thickness on the soil fertility is also considered in this study.The weight of evaluation factors was determined by principal component analysis.By using the method of fuzzy mathematics,the level of Lou soil comprehensive fertility in this study ranged from 0.13 to 0.66.The soil fertility in Baoji-Fengxiang-Meixian-Wugong area in the upper reaches of Weihe River in Guanzhong area is relatively high.The soil fertility gradually decreases along the Weihe River Basin eastward,the eastern Pucheng,Chengcheng and Hancheng areas have the characteristics of relatively high soil fertility in some areas.According to the average comprehensive Lou soil fertility of each county,the soil distribution area was divided into the eastern thick cumulic epipedon low fertility area,the middle wide flat medium fertility area and the west narrow flat high soil fertility area.Guanzhong region is the main grain producing area of Shaanxi Province.In the future agricultural development process,it is suggested to rationally utilize land resources,attach importance to green fertilizer cultivation,improve field management facilities and attach importance to green ecological agriculture. |
PDF Full Text Request