A Novel Microwave Applicator for Sandy Soil Disinfection

This paper presents a novel microwave applicator for disinfection of agricultural sandy soil. The proposed microwave system consists of a modified commercial microwave oven that includes a 700-watts magnetron source operating at 2.45 GHz, a designed waveguide, and a microwave applicator. An ordinary horn antenna was used first to apply the microwave power for one and two minutes through a sandy soil with soil moisture content of 3.4% which contains organic tissues with high water content buried at different depths. The temperature of the buried organic tissue was measured using a pulp thermometer. S11, and the electric field distribution through the soil was simulated for the microwave applicator using CST Studio Suite. A structure formed by metal strips was mounted on the circumference of the horn antenna aperture to form a new microwave applicator. The same procedures were followed for the new microwave applicator to measure the organic tissues temperature rise. By comparing the S11 simulation for the two microwave applicators, a matching improvement was observed in favour of the new microwave applicator. By comparing the simulation of the electric field distribution for the two microwave applicators, a reduction of the leaked microwave radiation out of the soil, a confinement of the wave within the soil volume that intended to be treated, and intensive electric field through the soil volume that intended to be treated were observed in favour of the new microwave applicator. By comparing the temperature measurements for the two microwave applicators, an increment of 20°C in the temperature on average for depths more than 5 cm was observed in favour of the new microwave applicator.