Change of Soil Salinity in Mulched Gravel-sand Soil in the Arid Area of Northwestern China

ZHAO Wenju; TANG Xuefen; FAN Yanwei; YU Wen

doi:10.13522/j.cnki.ggps.2017.08.005

Abstract：This paper investigated soil salinization development in mulched gravel-sand field in northwestern arid area of China.The results showed that the average relative errors of salt distributions in bare soil,young,middleage and matured gravel-sand fields were-15.43％～28.14％ and the associated standard deviation were 4.44％～31.02％.The spearman coefficients were high and significantly correlated.The spatially mean soil salinity in bare soil,mulched young,middle-age and matured gravel-sand soils could be represented by measurements from 49,41,35 and 8 points respectively.The correlation coefficients of the mean soil salinity and that measured from these points varied from 0.762 to 0.952 and were significance at 0.05 level,with small standard error deviation.The relative errors of the soil salinity distribution measured in 20th July and 28th July ranged from 29.30％ to 35.91％.Spearman rank correlation coefficient of mean salinity and representative measuring points of bare land,new gravel-sand mulched field,middle gravel-sand mulched field and old gravel-sand mulched field were high,and they were significance at 0.01 and 0.05 level which showed that soil salinity in study area represented high time stability during measuring period.The results of time-space modelling for soil salinity of NGM of different period showed that the pattern of soil salinity cumulative oversize distribution curve were similar,and there were little difference in simulation value and measured value and the space distribution basic trend equated measured value and the trend of semi-variance was significant.Standard error of simulation value and measured value ranged from 0.012 9 to 0.164 7,and relative error of simulation value and measured value ranged from-35.99％ to 45.82％,and simulation effect was better simulation value had high precision.The change trend of semi-variance of soil salinity simulation value of different period was significant and the trend were similar.The curve was smoothly when the soil salinity was small and the relative frequency increased heavily with the increase of soil salinity and reach 100％ finally.The mean soil salinity of each period belonged to moderate lower variability,and the soil salinization was bare land (CK) ＞ old gravel-sand mulched field (OGM) ＞ new gravel-sand mulched field (NGM) ＞ middle gravel-sand mulched field (MGM).The reversal evolvement of gravel-sand mulched field soil salinization had always happened,soil salinity decreased gradually with the increase of planting years,and the soil salinity of MGM decreased and reached to minimum and the soil salinization degree was lowest,while soil salinity of OGM increased,soil salinity was aggravation and evolvement of soil salinization faded gradually with the increase of planting year and the increase of the ratio of soil and sand.The reversal evolvement characteristics of gravel-sand mulched field not only existed in time series but also in space.