| This study is based on the projects about soil formula fertilization on country,the soil sampling data was obtained through the cultivated land fertility on the districts and counties of Yan'an City,Shanxi Province,including 31428 organic matter samples,31201 effective phosphorus,31248 available potassium,23816 total nitrogen,30252 available nitrogen and 30907 pH samples.The spatial variability analysis and influencing factors of soil nutrients were analyzed by combining methods of geostatistics and GIS,hierarchy process and multiple regression analysis method to evaluate the fertility of cultivated land in Yan'an City.Here are the results:(1)The average soil organic matter content in the study area was 9.24 g / kg,which was located at 7th grade of soil nutrient content standard in Shaanxi Province.The average contents of soil total nitrogen,available phosphorus and available nitrogen were 0.59 g / kg,9.94 mg / kg,and 40.46 mg / kg,respectively,all at level 6 of the standard,the average content of available potassium was 121.57 mg / kg,and the p H value of soil pH was between 6.8 and 9.4,with an average value of 8.09,which meets the 4th grade.Soil nutrients except quick-acting potassium in Yan'an City were at a low level,and the soil was weak alkaline.(2)The optimal semi – variance fitting function model used for soil organic matter,total nitrogen and available nitrogen in this paper is the spherical model,while model chosen for available phosphorus and available potassium is the exponential model,and Gaussian model was adopted for p H value fitting.Nugget variance of 6 soil samples were between 34% and 53%,which indicates moderate correlation.The soil nutrient fractal dimension was high,ranging from 1.832 to 1.939.The semi-variance function,fractal dimension were used to analyze the spatial correlation of soil nutrients in the study.(3)The soil organic matter in the study area was lower in north and east than south and west.The soil pH and the nitrogen content was lower in north and west than south and east.The total nitrogen content in the soil decreased progressively from southwest to northeast.Soil in south area maintained higher available potassium and effective phosphorus content than the north.(4)The soil components in the studied area shows significant correlated with factors like annual precipitation,?10 ? accumulated temperature and sunshine hours on 0.01 level.The correlation extent about the effect of annual precipitation on soil nutrient was significantly higher than that of ?10 ? and its influence on potassium and organic component is much stronger than other nutrients.Besides the fact that available phosphorus and slope were less correlated,other nutrient contents are correlated with the terraces including elevation,slope and fluctuation degree on 0.01 level.The terrace condition affected nutrition content in the soil.Also,the soil type own a significant effect on nutrient content.(5)The total area of cultivated land studied in this work is 4266.64km2,of which Grade1 takes up 16.82%,18.52% for Grade2,10.65% for Grade3,21.78% for Grade4,4.55% for Grade 5,and 7.70% for Grade 6.The land form the Grade 1 to Grade 3 are mainly from the Loess Plateau like the eastern Yanchuan-extension-Yichuan area and the southern Yanchuan-Huangling-Fuxian area,while Grade 4 to Grade 6 are distributed In the northern counties of Yan'an. |
PDF Full Text Request