Spatial Distribution Of Soil Salinity For Water-Saving Irrigation Conditions In Manas River Basin Irrigated Areas

Object: With a view of comprehensively promptly keeping abreast of cotton field soil salinity’s spatial variability and variation characteristics, judging from soil salinity accumulate situation in cotton field with long-term mulched drip irrigated on river basin scale, the results provide a basis for sustainable development of mulched drip irrigation technology.Methods: The study is based on a great deal of collected data and field sampling points data before sowing and after harvesting, which comprehensive application of classical statistical methods, geostatistical methods, GIS technique and grey correlation analysis.Results: This article studied the spatial variability of soil salinity in Manas River basin irrigated areas before sowing and after harvesting; and drew the spatial distribution maps of soil salinity using Empirical Bayesian Kriging; explored the spatial distribution characteristics and influencing factors of soil salinity.Conclusion:(1) Spatial variability analyses showed soil salinity before sowing and after harvesting with moderate variability, and soil salinity in 0, 30 and 60 cm soil layer had a strong spatial correlation and mainly affected by structural factors, and soil salinity in 100 cm soil layer had a middle spatial correlation pattern which affected by structural factors and random factors. Soil salinity before sowing is highly affected by structural factors than after harvesting. Soil salinity before sowing and after harvesting showed the anisotropy along to the contour line and showed the isotropy perpendicular to the contour line.(2) The study selected 5 interpolation methods interpolating soil salinity, including Inverse Distance Weighting(IDW), Radial Basis Functions(RBF), Ordinary Kriging(OK), Universal Kriging(UK) and Empirical Bayesian Kriging(EBK). As a result, EBK was better accurate than others by Cross-validation and ROC curve analysis.(3) The spatial distribution maps of soil salinity were drawn using the degree of soil salinization as classification threshold. The results showed that the threat of soil salt-alkalinization to cotton field in the Manas River basin irrigated areas were not serious. Each layer’s soil before sowing and after harvesting didn’t exist heavy salinized soil and saline soil area. Individual layer’s soil existed moderate salinized soil area, but moderate salinized soil area was less than whole irrigated areas. The high soil salinity areas mainly distributed around the plain reservoir and in river basin’s downstream, and the low soil salinity areas mainly distributed around the southern mountains region and northeast of the research region. After a growth period of water leaching, moderate salinized soil area was loss 21%, and plowing layer’s soil salinity moved toward deeper layer obviously. The spatial distribution maps of soil salinity were drawn using early warning value of mulched-drip-irrigation’s salinity tolerance as classification threshold. The results showed that soil salinity in the interval of hazard’s land was loss 42%, and plowing layer’s soil salinity tended to be safer because growth period used mulched drip irrigation. Soil salinity didn’t in the interval of serious damage’s land, soil salinity of 0 cm layer before sowing in the interval of warning’s land was one-third of whole irrigated areas.(4) Soil salinity changed during growth period positively correlated with evaportranspiration from cotton. It’s mainly reflected in 0 cm soil layer; and deeper soil layer’s effect was not obvious. Soil salinity changed during growth period negatively correlated with the monthly average groundwater table; it’s mainly reflected in 0 and 100 cm soil layers. Soil salinity changed during growth period positively correlated with mineralization of groundwater; it’s mainly reflected in 0 and 100 cm soil layers. Grey correlation degree analysis showed that groundwater had a powerful impact on the spatial distribution of soil salinity after harvesting and soil salinity changed during growth period, surface elevation had a little influence. The evaportranspiration from cotton had a powerful impact on soil salinity changed during growth period...