Abstract:The rapid, nondestructive and quantitative analysis of the composition and content of soil salt ions is an important basis for the treatment, improvement and utilization of salinized soil. Taking the saline soil of Xinjiang as the research object, the hyperspectral analysis technique was used to obtain the spectral characteristic of soil salt ions in different regions;compared the effect on the accuracy of the soil salt ions fitting model in different treatments which included fresh soil, air drying and ovendry sample and different particle sizes (2mm, 1mm and 0.15mm, respectively). After the transformation of spectral data, the spectral inversion models of main salt ions were established based on support vector machine (SVM), and the accuracy and universality of the model were tested. The results showed that there was no significant correlation between the original spectral characteristics and soil salt ions content, and the maximum correlation coefficient was Na+ (R=0.41). It was clear that the spectral data transformation can significantly enhance the correlation between the characteristic bands and the ions content, the optimal transformation forms of K+,Na+, Mg2+,Ca2+, SO2-4, Cl-and HCO-3 were (lgR)′, (lgR)′, R′, (lgR)′, CR, R′ and CR, respectively. The fitting models of T1 treatment cannot inverse the ions content very well, the accuracy of T3 model was better than that of T2, and the smaller the soil particle size was, the better the spectral inversion effect of soil ions content was. The prediction accuracy of the ions fitting model was the highest by T3 and over 0.15mm sieves, the relative prediction deviation of K+, Na+, Ca2+ and SO2-4 were 2.153, 2.6745, 2.051 and 2.7864, respectively，the universality test of four ion models was carried out by using samples from Shihezi area other than modeling and validation, the R2 of test models were 0.6214, 0.6897, 0.6144 and 0.6507, respectively. The models were suitable for estimating the content of soil K+, Na+, Ca2+ and SO2-4 in Xinjiang area.
