Evolution And Driving Factors Of Soil Fertility In Cultivated Land In Yangzhou City

Based on soil fertility of cultivated land in Yangzhou City of Jiangsu Province, the main soil fertility indexes (pH, organic matter, available phosphorus, available potassium) in the years of 1984,1994,2005,2014 and their spatial and temporal evolution were researched in detail by using GIS technology combined with statistical methods, and analyzing the effect of the landform type, soil parent material, fertilization, straw returning, planting system on soil fertility. The results showed:(1) 4107 soil samples were collected in 1984. The average value of pH, organic matter, available P and available K were 7.51,21.62g/kg,6.42mg/kg and 108mg/kg. 2862 soil samples were collected in 1994, The average value of pH, organic matter, available P and available K were7.07、16.15 g/kg、6.60 mg/kg、63mg/kg.4018 soil samples were collected in 2005, The average value of pH, organic matter, available P and available K were6.83、28.39 g/kg、14.39mg/kg、116mg/kg.6005 soil samples were collected in 2014, The average value of pH, organic matter, available P and available K were 6.74、27.63 g/kg、13.88mg/kg、99mg/kg。(2) The spatial distribution patterns of soil pH, organic matter, available phosphorus and available potassium from 1984 to 2014 were basically unchanged. The pH pattern is LIXIAHE region> Along the Yangtze River Region> High Sandy areas> Hill region. The OM pattern is LIXIAHE region> Along the Yangtze River Region> Hill region> High Sandy areas. The available P pattern is LIXIAHE region> Along the Yangtze River Region> High Sandy areas> Hill region. The available K pattern is LIXIAHE region> Along the Yangtze River Region>Hill region> High Sandy areas.(3) There was a declining trend with soil pH in the 30 years in Yangzhou, with a great decrease in the first twenty years, and a stable state in the latter 10 years. The area suffering a decline of 0-1 unit covered 47.15% of the total area and the area suffering a decline of>1 unit was 39.33%. Soil organic matter had a downward trend in the first 10 years, and gained steady recovery in the latter 20 years. The area with an increase of 0～20g/kg covered 79.2% of the total area. Soil available phosphorus had a stable trend in the first 10 years, relatively increased fast in the middle 10 years, and had a high state stability in the last 10 years. The area with an increase of 0-20mg/kg covered 89.67% of the total area. Soil available potassium decreased rapidly in the first 10 years, picked up in the middle 10 years, and had a decline trend in the last 10 years.(4) Effects factors of soil fertility spatial variation of cultivated land are the landform type, soil parent materials; Effects factors of soil fertility time variation of cultivated land are mainly fertilization, straw returning, planting system.