Abstract: The study aimed at searching for the most sensitive bands of Quickbird to estimate soil pH values. Soil salinization or alkalization is an important problem of land degradation and environmental degeneration in arid regions. Laboratory determination and research on spectral data are the main methods to estimate the degree of soil salinization or alkalization. In this study, Qitai County, a typical region with soil salinization or alkalization along the southeastern marginal zone of the Junggar Basin in Xinjiang Uygur Autonomous Region, was selected as the study area to explore the feasibility of using the Quickbird image in studying soil salinization or alkalization. Through the correlation analysis between the values of reflectance from Quickbird and the soil pH values at all the sample sites, it was found that the “sensitive”bands could be used to predict soil salinization or alkalization and to build the different linear regression forecasting models. The results showed that all the bands of Quickbird could well reflect the degree of soil salinization or alkalization, and band3 of the Quickbird (630-690 nm) is the most “sensitive” band used to predict the pH values of saline or alkaline soil. The precision of the inversion model developed based on band1, band2 and band3 was the highest (82.41%). The quantitative model of Quickbird to predict soil pH values provides a new approach for monitoring soil salinization or alkalization.

Key words: Quickbird, soil alkalization, spectral signature, quantitative monitoring, prediction model, Qitai, Xinjiang