[Monitoring and simulation of soil electrical conductivity based on the hyperspectral parameters of cotton (Gossypium hirsutum) functional leaves].

Taking the salt-tolerant cotton variety CCRI-44 and salt-sensitive cotton variety Sumian 12 as test materials, a two-year pot experiment was conducted at the Pailou experimental station of Nanjing Agricultural University in 2008 and 2009 to study the relationships of soil electrical conductivity (EC) with the spectral reflectance and hyperspectral indices of cotton functional leaves at different growth stages under five simulated salinity levels (0, 0.35%, 0.60%, 0.85%, and 1.00%) of coastal saline soils, and the quantitative monitoring models on the cotton soil EC were established. With increasing salinity level, the cotton functional leaves had an increased spectral reflectance in near-infrared and middle-infrared regions, and the spectral parameter normalized difference spectrum index (NDSI) based on 1350 nm and 2307 nm, i. e., NDSI (R1350, R2307), correlated well to the soil EC. With the NDSI (R1350, R2307) as independent variable, the soil EC monitoring model was constructed as EC = -42.899 NDSI (R1350, R2307) +27.338. Among the derivative spectral parameters, TM5-SWIR was most correlated to soil EC, and thus, the soil EC monitoring model was constructed as EC = 0.0574TM5-SWIR2-2.5928TM5 -SWIR+30.021. The two models with NDSI (R1350, R2307) and TM5-SWIR as the independent variables respectively all had higher prediction precision, with the determination coefficient being 0. 887 and 0. 814 and the root mean square error being 1.09 and 1.29 dS x m(-1), respectively, suggesting that using the hyperspectral parameters NDSI (R1350, R2307) and TM5-SWIR of cotton functional leaves could effectively monitor the soil EC of saline cotton fields.