Spatial variability of nutrients in irrigation-silted soil in north Yinchuan,Ningxia

Spatial distribution and variability of organic matter,available Ca,Mg,N,K,P,S in irrigation-silted soil in Huinong,Ningxia Hui Autonomous Region were characterized using classic statistics and geostatistics with grid sampling and systematic approach for soil nutrients status evaluation.The results showed that the content of the organic matter,N,K and P in topsoil were deficient and the percentage of soil available N,K,P below critical values were 100%,1.8% and 22.7%,respectively.On the other hand,the content of Ca,Mg and S was abundant,even excessive.The variation coefficient of available Ca was the highest(131.13%) and that of the other available nutrition elements was between 32.97% and 77.45%.The spherical model was used to model the experimental semivariogram.Spatial autocorrelation of organic matter,Ca,Mg and K was strong and the ratios of nugget to sill+nugget of them were between 1.6 and 20%.Whereas spatial autocorrelation of N showed pure nugget,which indicates the spatial variability was mainly influenced by random factors such as irrigation,fertilization and management.Ordinary kriging interpolation was used to map the available content of Ca,Mg,K,S.