بررسي تغييرات مكاني شوري خاك در مناطق شيب آب و پشت آب پايين دشت سيستان

The soil salinity is important parameter affecting the design of subsurface drainage and the land reclamation projects. The main aim of this research is the study of spatial variability and estimation of soil salinity data. The data set consisted of 638 sampling points with an average distance of 600 m, three depths of 0-50, 50-100 and 100- 150 cm, in Shib-Ab and Posht-Ab Payeen regions of Sistan plain. In this research, the ordinary kriging, logkriging and cokriging have been used and precision of each method was evaluated by the cross - validation technique. The results showed that precision of all experimental semivariograms were low with a —7- of 89%, 83% and 75% for ordinary kriging, logkriging and cokriging, respectively. The logkriging method had the highest precision (MAE equal to 12. 375 dS/m) for estimation of soil salinity. In each depth, the MAE of all methods has been compared with is average amounts, The results showed that the relative error of all methods reduced from surface layer to subsurface layers. Consequently, the results indicated low spatial correlation for soil salinity in Sistan plain.