Estimation of Soil Salinity at IARI Farm by Inductive Electro-Magnetic Technique

The basic principle of IEM (Inductive Electro-Magnetic) Technique is that a transmitting source induces circular eddy current loops in the soil whose magnitude is directly proportional to the conductivity of the soil. Each current loop generates a secondary electr-omagnetic field which induces a current in the receiver and the output voltage of the receiver is linearly related to the depth weighted bulk soil electrical conductivity. The main advantages of. this technique are: rapidity and non-requirement of sample and sample preparation. IEM investigations, were carried out at the farm of IARI, New Delhi. Results indicated that the bulk soil electrical conductivity (EC_a) values, computed from IEM survey data, were compared with those measured by the conventional method [BC (1:2 soil:water ratio)] to understand the feasibility of IEM-meter for estimating bulk soil EC_a values. No effects of soil moisture content, clay content and soil temperature on EC_a were observed. Predictive equations for estimation of bulk soil EC (termed as EC_pr) values were subsequently developed and verified from independent observations. The predictive equations were found to be quite different from those reported by Rhoades and others. Finally, the spatial and temporal variations of EC_pr were studied to have the present status of soil salinity at the IARI farm.