The present invention relates to a method and a system for irrigation and fertilization control in a vast area, based on measuring the soil resistive electrical conductance values, during watering and fertilization cycles. A continuous electric field is created below the subsurface of the large soil area by a device that is spaced many feet apart in order to propagate an electric field through the soil. This alternating electric field averages soil conductance and therefore eliminates effects of non-uniformity in a monitored area. Furthermore, absolute conductance variations over long time periods offer the accurate point in time for soil fertilization.
