MAPPING SOIL SALINITY, CROP AND INFILTRATION VARIABILITY USING SOIL CONDUCTANCE AND AERIAL PHOTOGRAPHY.

This paper reports preliminary results obtained from a study to determine if new methods to measure soil conductance coupled with computer techniques to characterize spectral transmittance of aerial photographs can be used to characterize infiltration variability of cropped fields. The hypotheses of this project are: 1) soil salinity variability results primarily from water infiltration variability, 2) soil salinity influences the spectral properties of the crop, and 3) new resistivity and electromagnetic methods facilitate rapid measurement of soil salinity variability and, if hypotheses 1 and 2 are valid, of infiltration variability also. Estimates of infiltration variability may be possible from either soil-conductance measurements or from spectral transmittance provided field-specific soil conductance and associated spectral transmittance data are correlated. The advantage of the spectral transmittance method is that each number represents an area from 1 to 10 m**2 and the data for a 30-ha field can be digitized by the computer/camera system in less than 1 minute.