Soil Nutrient Status And Soil Fertility Evaluation Of Farmland In Yanqi Basin

Taken farmland in Yanqi Basin as the study material, and using ArcGIS, Access, county level farmlandresource management information system, and statistical methods such as GIS spatial analysis, fuzzymathematical method and analytic hierarchy process, this research studied the spatial distribution of soilnutrients, their abundance and shortage situation as well as the fertility of cultivated land. Factors that leadto different soil fertility in the area were also discussed, which might provide a basic theory and somemeasures for soil improvement in Yanqi Basin. Main conclusions are as followed:(1) Content of soil organic matter in the study area was17.7g/kg on average,ranging from10to20g/kg,which is on the medium level. Content of nitrogen was averagely69mg/kg, ranging from30to60mg/kg.Content of available phosphorus was17.5mg/kg, ranging from10to20mg/kg. Content of availablepotassium was128mg/kg, and ranged from100to150mg/kg. Moreover, trace element contents were:content of effective iron was16.07mg/kg, content of effective manganese was9.25mg/kg, content ofeffective copper was2.60mg/kg and the content of available zinc was1.18mg/kg on average. Soils ofYanqi Basin were short of nitrogen and zinc, better but not abundant for phosphorus, potassium, andmanganese, and were abundant of copper and iron.(2) Compared with results of the Second National Soil Survey, content of organic matter and availablepotassium in meadow soil and fluvo-aquic soil definitely decreased, and contents of nitrogen, phosphorus,effective iron, manganese, copper, and zinc increased obviously. Furthermore, for brown desert soil,contents of organic matter, available potassium, and available copper decreased obviously, while contentsof nitrogen, phosphorus, iron, manganese and zinc increased significantly.(3) The107476.69hm~2farmlands in Yanqi Basin could be divided into six grades, i.e., the first grade13807.82hm~2, the second grade19947.56hm~2, the third grade20868.13hm~2, the fourth grade19832.76hm~2,the fifth grade17669.27hm~2, and the sixth grade15351.15hm~2. The area percentages were12.85%,18.56%,19.42%,18.45%,16.44%, and14.28%for farmland from the first grade to the sixth grade.(4) Soil fertility in Yanqi Basin was generally in the middle level. The first and the second grade landmainly distributed in the former agricultural area, with high invest from local farmers. Reasons accountingfor lower grade farmland include both natural and human factors. Natural factors were mainly low soilnutrient content and high degree of salinization. Human factors mainly involved imperfect canal andwindbreaks supporting measures, and unreasonable irrigation.