Spatial Distribution Characteristics Of Soil Nutrients And Fertility Evaluation And Fertilization Management In Xiliaohe Fertilization Management District Of Inner Mongolia

There is a vast territory and a large span from east to west in Inner Mongolia.The climatic conditions,soil conditions,planting systems,and fertilization systems are different among different regions.Adopting high precision and specific quantitative methods are important technical means for scientifically and rationally dividing soil nutrients and fertilization management subdivisions.They are also important technical supports for evaluating soil nutrient fertility and formulating fertilization recommendations for different management areas.The research was based on a large number of soil test and field test data.Research methods mainly included geostatistics,GIS methods,mathematical statistics and recommended fertilization methods.In the research,the scope of the Xiliaohe fertilization management district in Inner Mongolia was delineated.The spatial distribution characteristics of soil nutrients,evaluation of soil nutrient fertility,soil nutrient management and regional fertilization of Xiliaohe fertilization management district were researched systematically.It aims to reveal the spatial variability and distribution characteristics of soil nutrients and explore the methods of fertilization division and Soil fertility evaluation.At the same time,it aims to explore advance nutrient management technology to provide theoretical basis for agricultural production and scientific fertilization.The main findings are as follows:1.The scope of the Xiliaohe fertilization management district in Inner Mongolia was determined with the quantitative and qualitative method.（1）In the research of fertilization management division in Inner Mongolia,among15 indicators,the coefficient variation of p H was 9.30%.It belonged to the weak variation.The coefficient variation of the other indicators were in the range of 11.77%to73.64%belonged to above medium variation.These indicators were suitable to be used as the evaluation indexes for fertilization management division.（2）There were different correlations among the indexes,especially among soil nutrient indexes and meteorological indexes which had significant correlations.It was suitable for using factor analysis to reduce the impact of index information overlap on evaluation results.（3）Inner Mongolia was divided into five first-level fertilization management zones with the methods of factor analysis and K-means cluster analysis and combined with qualitative judgment.The Xiliaohe fertilization management district included Keerqin,Kailu,Kezuozhong,Kezuohou and Naiman.2.The spatial variability,distribution characteristics and patterns of soil nutrients in Xiliaohe fertilization management district were researched with the methods of geostatistics and GIS.（1）The regional characteristics changed little after removing the abnormal values of soil nutrients and p H by domain method.The mean of p H increased by 0.1.The mean,standard deviation and coefficient variation of other soil nutrients decreased slightly.（2）The normality of indicators were checked and the indicators which did not conform to the rule of normal distribution were treated with logarithmic transformations.After logarithmic transformations,the indicators were close to normal distribution.（3）The results showed that there were significant spatial autocorrelations in the ten soil indicators.By fitting the semi-variance function of soil indexes,the optimal spatial distribution theoretical models of soil indexes were determined.p H,TN,AN,AK selected the gaussian models.AP choose spherical model.OM,AFe,AMn,ACu,AZn selected exponential models.（4）With the method of ordinary Kriging,the spatial interpolation were carried out for soil p H and soil nutrients of xiliaohe fertilization management district.According to the classification of the second soil census,the nutrients levels were classified and the spatial distribution maps of soil nutrient contents were made.3.The spatial distribution characteristics of soil nutrient contents and p H of xiliaohe fertilization management district are as follows:（1）Spatial distribution characteristics of soil p H:The p H were generally high,mainly concentrated in the range of 8.0～8.5,accounting for 63.2%of the total area.The area that p H less than 7.5 only accounted for 0.1%,so that most of the soil were alkaline.（2）Spatial distribution characteristics of mass nutrients:The OM content was medium,and the soil area with medium level of 10～20mg/kg accounted for 76%.The area of low level accounted for 22.1%.The content of soil TN was generally lower.The soil area accounted for 51.1%which were less than 0.75g/kg and the soil area accounted for 36.4%which was between 0.75mg/kg and 1.0mg/kg.The content of AN was medium,and the soil area with medium level of 60～90mg/kg accounted for 58.1%.The area of low level accounts for 33.8%.The AP content was at medium levels in most soil.The soil area accounted for 57.0%which was between 5 and 10mg/kg.The area of low level accounted for 33.3%.The AK content was medium.The soil area accounted for 53.3%which was between 100 and 150mg/kg.The area of low level which was less than100g/kg accounted for 29.1%.（3）Spatial distribution of micronutrients:The content of AFe was higher.The content mainly concentrated in the range of more than 10mg/kg.The soil area of this grade accounted for 52.31%and 4.5～10mg/kg soil accounted for 45.6%.The AMn content was medium.The soil area accounted for 88.9%which was between 5 and15mg/kg.The soil ACu content was lower.The area accounted for 54.7%of low level which was less than 1.0mg/kg.The soil area accounted for 44.5%which was between 1.0and 1.8mg/kg.The AZn content was medium.The soil area accounted for 76.9%which was between 0.5 and 1.0mg/kg.Low level and high level distributions were less.The area of low level and high level soil accounted for 16.3%and 6.9%respectively.4.Based on the application of GIS technology,four different methods were used to evaluate the soil fertility of cultivated land in the Xiliaohe fertilization management district.The first method was a classification method only based on the comprehensive score of the factors.The second method was a classification method based on comprehensive score in factor analysis by cluster analysis.The third method was a fuzzy comprehensive clustering method based on correlation coefficient weight.The fourth method was a fuzzy comprehensive clustering method based on common factor variance weight.There were some differences in the evaluation results of the four evaluation methods.In the clustering grading method based on the comprehensive score of factor analysis,the comprehensive score had the highest correlation with the linear yield of corn.The fitting effect of the linear relation in this method was optimal.The evaluation results of this method can reflect the actual level of soil fertility more accurately.5.Based on the spatial interpolation of soil nutrients,the management zones of NPK were divided in the Xiliaohe fertilization management district,and the fertilizer dosage in different zones were determined.（1）Based on the results of spatial interpolation of AN and AP and AK in cultivated soil in Xiliaohe fertilization management district,the nutrient management zones were divided with the method of soil nutrient abundance and deficiency index.（2）The fertilizer dosage of the most economic yield and maximum yield were calculated with the method of fertilizer effect function.（3）There was a better logarithmic relationship between the contents of AN,AP,AK and optimal dosage of N,P₂O₅,K₂O for maize in Xiliaohe fertilization management district.In the research,the fertilization model of NPK for maize were obtained and the optimal fertilizer dosage were determined under different indexes of nutrient abundance and deficiency.（4）The optimal dosage of nitrogen fertilizer were≥182.5kg/hm²at low level,137.4～182.5kg/hm²at medium level,and<137.4kg/hm²at high level.The optimal dosage of phosphate fertilizer was≥122.4kg/hm²at low level,89.5～122.4kg/hm²at medium level,and<89.5kg/hm²at high level.The optimal dosage of potassic fertilizer were≥64.4kg/hm²at low level,50.8～64.4kg/hm²at medium level,and<50.8kg/hm²at high level.The regional nutrient management map were made about soil AN,AP and AK in Xiliaohe fertilization management district and county territory.The combined distribution map of N,P₂O₅and K₂O fertilizer dosage for corn were made,so as to realize the regional management of soil nutrients and the regional variable fertilization.