The Dynamic Changes Of Carbon,Nitrogen And Phosphorus In Upland Soil Of The Northern Jiangsu Province Based On High-resolution Soil Database

Soil organic carbon?SOC?,total nitrogen?TN?and available phosphorus?AP?are the important index in the terrestrial ecosystem.It is necessary to study changes in C,N,and P content of the upland soil for estimating fertility and sustainable utilization of soil resource.Because the samples and spatial database were lacking,recent years most study focus on small scale,with the conclusions about just one period but not dynamic.This paper was oriented to analyze spatio-temporal variation of C,N,and P content in the farmland of Northern Jiangsu Province during the 29 years after the Second National Soil Survey in the 1980s and explore relationships between climate,agricultural management and changes in C,N,and P.1.The spatio-temporal change of SOC content during 1980 and 2008 was analyzed using the GIS spatial analysis technique.By using a 1:50000 soil database,the farmland soil organic carbon content in the 0-20 cm layer in Northern Jiangsu Province was estimated,which containing a total of 17024 polygons.Comparative study based on the soil samples collected during the second national soil survey and fertilizer recommendation in 2008 which include nitrogen fertilizer and organic fertilizer.The meteorology data include temperature and precipitation in the past 29 years of Northern Jiangsu Province.Results are shown as follows:?1?the mean of SOC content in the farmland increased by 4.30 g kg^-1 in the study region from 1980 to 2008.Spatially,the SOC content of the middle part increased more than other part of the area.?2?Among the main types of soils that northern Jiangsu province has during the past 29years,fluvo-aquic soil increased the most by 5.12 g kg^-1 in SOC content,and was followed closely by brown soil and purplish soil,which did by4.9 g kg^-1 and 4.79 g kg^-1,respectively.The SOC variation of Limestone soil was the lowest all the soil groups,which was 0.01 g kg^-1.?3?Among the different administration areas,Huaian City and Huaiyin County with the highest in SOC variation being 5.02 g kg^-1 and 7.11 g kg^-1 respectively,and the lowest were 3.31 g kg^-1 and 1.18 g kg^-1 did by Yancheng City and Jianhu County separately.Fertilizer application is the main factor significantly influencing variation of SOC content in the farmland.2.From the perspective of temporal and spatial changes of total nitrogen,the total nitrogen content in surface soil of farmland in Northern Jiangsu Province in 1980 and 2008 were 0.73 g kg^-1 and 1.09 g kg^-1respectively,with an increase of 49.3%in the past 30 years.?1?The total nitrogen content of brown soil and purple soil increased the most in all types of soil with 0.53 g kg^-1 and 0.49 g kg^-1 respectively.The most less variation of total nitrogen content was found in the lime concretion black soil,with the variation of 0.12 g kg^-1.?2?In the point of the changes of total nitrogen content in upland soil in diffierent administration areas,from 1980 to 2008,the changes of total nitrogen content in Suining County,Huaiyin County and Siyang County were higher than 0.58 g kg^-1.The counties that with small increases were Jinhu County,Xuzhou Suburb and Dafeng County.The changes were 0.10 g kg^-1,0.11 g kg^-1 and0.12 g kg^-1,respectively.3.From the perspective of spatial and temporal changes of available p phosphorus,the soils with high changes in content of upland soil in the study area from 1980 to 2008 were purple soil,lithosols soil and brown soil,which were 14.5 mg kg^-1,13.9 mg kg^-1 and 13.65 mg kg^-1,respectively.The lowest change of available phosphorus contnet was limestone soil with 5.70 mg kg^-1.According to the change of upland soil available phosphorus content in administration areas,from 1980 to 2008,all counties'available phosphorus in upland were increased except Jinhu County,among which Tongshan County,Shuyang County and Yancheng County's administration areas increased higher than another counties by18.01 mg kg^-1,18.55 mg kg^-1 and 17.87 mg kg^-1 respectively.In this study,according to the grey relational analysis?GRA?,it was found that variation of C,N,and P content were mainly related to the N-fertilizer and manure application,thus the government should establish appropriate agriculture management for the soil sustainable development in the future.