The field soil surface spectral reflectance，total soil salt and other salt parameters in northern Yinchuan City

Ningxia Hui Autonomous Region were quantitatively analyzed.The field reflectance data were transformed to several spectral indices to extract sensitive wavelengths of salt parameters in surface soil.Quantitative inversion models of soil salt parameters were constructed by total regression and stepwise multiple linear regression analysis.Results showed that there were significantly positive correlations between the total salt content in surface soil and its original spectral reflectance(r)

transformation of smoothing reflex tance(R)and logarithmic reflectance[lg(R).There were significant negative correlations between the total salt content and the reciprocal of reflectance(1/R)and logarithmic reciprocal of reflectance[lg(1/R).The first derivate differential(R')and the first derivate differential of logarithmic reciprocal of reflectance[lg(1/R)]'had better effect in some specific single wavelengths. The correlation between the spectral reflectance of surface soil and CO32- was the strongest in all anions and The stepwise regression by using [lg(1/R)]'gave better effect in fitting Na+

K+ and Mg2+ contents

as compared with other transformations.Fitting degrees of prediction model on the soil total salt and Na+were higher in all models and the two models had higher accuracy and strong predictive ability.Moreover

the predictive ability of spectral reflectance for SO42+ and Mg2+ were stronger than other ions.There were poor performance on stability

forecast ability and the precision of the prediction models about Cl- and Ca2+.SO42-

next;spectral reflectance and Na-content had strongest relationship by the four kinds of transformation method;the next was Mg2+;and the correlation with Ca2+was weakest.The R based regression equation was the optimal model for prediction of the total salt content.The accuracy of CO32- content predicted was slightly better than HCO-.The determinative coefficient for SO2+ predicted based on the sensitive wavelengths was significantly higher than other anions.