DETERMINATION OF THE SALINITY OF AN IRRIG ATED SOIL BY ELECTROMAGNETIC CONDUCTVITY

A prerequisite for the control of salinity in soils is the determinati on of the salinity of the upper first metre of the soil with the great est accuracy. This is commonly done from saturated paste extracts but on too small a volume and too restricted a number of samples. This mus t be done without modification of the soil structure and on a sufficie ntly narrow grid. Electromagnetic conductivity meters of Slingram type are convenient to indirectly determine the salinity by measurement of electrical conductivity. However the depth of investigation commonly exceeds the first metre and the saturated salted zone beneath signific antly influences the results. A theoretical study together with a comp lete calibration test on the border of Chott El Guettar (Tunisia) conf irms that short coil separation (60 cm) increases the sensitivity of t he apparatus to conductivity variations in the first metre of soil.