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Identification of Saline Soils with Multiyear Remote Sensing of Crop Yields

^a Energy and Environment Directorate, Lawrence Livermore National Lab., Livermore, CA 94550
^b International Maize and Wheat Improvement Center (CIMMYT), Wheat Program, Apdo, Postal 6-641, 06600 Mexico DF, Mexico
^c Centro de Estudios Superiores, del Estado de Sonora, C.P. 83400, San Luis Rio Colorado, Mexico
^d Centro de Estudios Superiores, del Estado de Sonora, C.P. 83400, San Luis Rio Colorado, Mexico

View larger version (102K): [in this window] [in a new window]   Fig. 1. The San Luis Rio Colorado Valley study region, as seen in Band 3 of a Landsat Thematic Mapper image from 31 Mar. 2002. Pixels with wheat appear dark in this image. Locations of field samples in surveys are also shown.

View larger version (17K): [in this window] [in a new window]   Fig. 2. Simulated root mean square error for predicting field-average soil extract electrical conductivity using different sample sizes and sampling designs (random vs. stratified random). These calculations were made using maps of within-field salinity for 10 fields derived from EM-38 surveys. Error bars show standard error of RMSE for 100 separate simulations.

View larger version (18K): [in this window] [in a new window]   Fig. 3. Comparison of image-based yield estimates with farmer-reported yields for 43 fields.

View larger version (10K): [in this window] [in a new window]   Fig. 4. Histograms of field-average soil electrical conductivity (EC) at depths of 0 to 30 and 30 to 60 cm.

View larger version (12K): [in this window] [in a new window]   Fig. 5. Comparison of soil electrical conductivity (EC) measured in January 2005 at (a) 0 to 30 cm, (b) 30 to 60 cm, and (c) 0 to 60 cm with image-based yield estimates for 2005.

View larger version (14K): [in this window] [in a new window]   Fig. 6. Histograms of the number of years a pixel exceeded the (a) 50th and (b) 80th percentiles of yield in the San Luis Rio Colorado Valley (black lines). Only pixels with yields in all 6 yr were included in histogram. Dashed gray lines show null distribution expected for random yield variations. Significantly more fields than expected by chance were never above the given yield percentiles, suggesting the existence of factors that consistently suppress yields.

View larger version (28K): [in this window] [in a new window]   Fig. 7. Histograms of field-average soil electrical conductivity (EC) at depths of 0 to 30, 30 to 60, and 60 to 90 cm for 30 randomly chosen fields (left) and 30 "targeted" fields (right), which had remotely sensed yields always below the 80th percentile.