Submitted to: National Congress Mexican Society for Soil Science
Publication Type: Proceedings
Publication Acceptance Date: September 20, 1996
Publication Date: N/A
Interpretive Summary: On a global scale 20 percent of irrigated land is estimated to be salt-affected, and in Mexico between 1.8 and 4.0 million of the 12 million hectares of irrigated land has high enough salt concentrations to reduce crop yields. New or improved methods of assessing the distribution of saline soils within irrigation districts are needed. In this study, methodology developed by ARS at Weslaco which utilizes satellite images wa applied and tested. It was found that of the 19,400 hectares of irrigated wheat in the El Carrizo Irrigation District near Los Mochis, Sinaboa, Mexico, 6930 hectares were salt-affected. It was concluded that soil salinity patterns could be determined using satellite imagery and that the salinity maps obtained are very useful for making decisions about reclamation. The work also resulted in the decision by personnel of the National Institute of Water Technology (Cuernavaca) and National Water Commission (Mexico City) to apply the procedures to other irrigation districts.
With the objective of obtaining a soil salinity map of Irrigation District No. 076, Carrizo Valley, Sinaboa, a study was undertaken in 1994 that used satellite images. The methodology of the USDA-ARS, Weslaco, TX was adopted that uses plants to indicate the occurrence and severity of soil salinity. Wheat was the dominant crop (19,400 hectares) and it was selected for study. At the flowering stage of the crop a Landsat Thematic Mapper (TM) and a SPOT panchromatic image were obtained. The salinity of the soil was measured at specific sampling points and the digital counts for TM bands, 2, 3, 4 and 5 were extracted for those same ground sites. Regression equations were developed between the salinity and spectral data. The spectral data for each pixel in the wheat mask were entered into the regression equations to produce a salinity map of all wheat fields in the irrigation district. It was concluded that satellite data permit the identification of saline areas and that the salinity maps are useful for making decisions about reclamation of saline soils and about conservation programs within the irrigation districts.