Study on spatio-temporal variability of soil available nutrients in typical vegetable field of South China：A case study at Guangxingzhou, Junshan, Yueyang

The available nutrients (N, P and K) in the soil, collected in the cultivate layer using grid sampling method in summer and winter, was tested and the data were analyzed with classical and geography statistical methods. The result showed: 1) The available N, P and K in two seasons conformed to normal distribution, and almost remained constantly in different seasons, but coefficients of variation of all indexes was larger in August than in December. 2) The available nutrients were significantly correlative in same season, and the coefficient of determination between available N and P was larger than the others. There was steady proportion among available nutrients, being little influenced by the rotation of crops. The change of available nutrients between different seasons were significantly correlative, among which the coefficients of determination between　ΔP and ΔK was largest. The available N in different seasons were also significantly correlative, the coefficients of correlation of available N was smallest, which means the change trend of available N in different seasons was not as significant as the other two available nutrients. 3) Available nutrients in deferent seasons had strongly spatial structure, the semivariance function of available N in December could be defined as spherical model while the other function could be defined as potential model. The spatial dependence of available nutrients was moderate except those of available P in August, which was weak. The spatial variability of available N was correspondingly steady in different seasons, the maximum correlative ranges stabilized at 450 meters, the spatial variability of available P and K in December was larger than that in August. The maximum correlative ranges for avail. P and available K were 497 and 413 meters in August, and 141 and 157 meters in December respectively.