GIS Based Evaluation On Nutrients Spatial Variation And Soil Fertility In Shawan County

As the key reasons to evaluated the soil fertilities, we conducted our research on soil nutrient status of Shawan County in Xinjiang, China. Field sampling and laboratory experiment were involved in the assessment on spatial variation of soil alkali-hydrolysable nitrogen(AN), available phosphorus(AP),available potassium(AK), organic matter(OM) and p H value. Furthermore, the status and trends of soil fertility were analyzed, soil fertility were classified to help and support on the construction of high-standard farm land and the fertilizer recommendation.Based on the dataset of the Second National Soil Survey of China(SNSS) in 1982, Shawan County was selected as our research area. Resampling was conducted in the same area during the periods October to November in 2012 and 2013, respectively. Traditional statistics was used to assess the soil fertility status and tendency, geostatistics was used to evaluate the spatial variation of soil fertility, and the Delphi Method was chosen to grade the soil productivity and fertility.(1)Averaged contents of soil AN, AP, AK and OM were 86.7 mg kg-1, 16.2 mg kg-1, 195.3 mg kg-1 12.4g kg-1 in current based on the traditional statistic analysis, respectively. The significant decrease were found on OM and AK contents which compared to the contents from SNSS, while the AN, AP and p H value were significant increased, as well as the contents of soil Cu, Fe, Mn, B and Zn.(2)The coefficient of variation for all the nutrients belonged to the middle intensity, the CV value of phosphorus contributes the largest(83.33%) in all the soil nutrients. Dataset of soil nutrients were well fitted the normal distribution, and their values of Nuggets and sill were between 0.25 and 0.75, which indicated the middle spatial correlation patterns.(3)Contents for AN in soil between 60 mg kg-1 and 90 mg kg-1 accounts for 67.93% area of the county,for the AP between 10 mg kg-1 and 20 mg kg-1 accounts for 74.98%, and the OM between 10 g kg-1 and 20 g kg-1 accounts for 71.21%, as well as the AK greater than 150 mg kg-1 accounts for 94.85%. The spatial variance of soil nutrients content were largely affect by the topography, the nutrients concentration in regions with higher altitude and steep slope were usually lower than in regions with lower altitude and gentle slope. This reflects in Shawan County as the higher concentration in east and north part and lower concentration in west and south part.(4)Soil fertility was distinguished into six degrees across Shawan Country. Area of the first degree was4418 hm2, and 7728 hm2 for the second degree that less than 10% of the total arable land. While sum area o f the third and forth degrees were 36657 hm2, account for about half of the total farmland area. The rest was accounted by the fifth and sixth degrees together, whose area were 29257 hm2 and account 37.8% of the tot al farmland. In short, the averaged soil fertility in Shawan was in lower-middle class.In the recent 30 years, AN and AP were accumulated while OM, AK, micro elements were depleted due to the unreasonable fertilizer application. In spatial, soil fertility were higher in the north and east than in south and west of Shawan County, and the overall fertility was mainly low. This suggest the synthesis consideration of spatial variance, fertility status and nutrients concentration difference used in fertilizer recommendation for the high-productivity cropland construction.