Preliminary investigation into microwave soil pasteurization using wheat as a test species

Microwave heating has been applied to various agricultural problems and products since the 1960s. Previous literature has demonstrated that microwave heating will kill seeds in the soil; however key issues such as the influence of soil moisture on microwave heating and determining whether the microwave energy directly interacts with the seeds have not been addressed. Experiments demonstrate that micro-wave treatment of soil reduces wheat seed germination if the temperature of the soil is raised above 65°C. The microwaves interact with soil rather than directly with seeds and heat is transferred from the soil to the seeds. Microwave heating is quicker in dry soil conditions due to less reflection of the microwave energy from the surface and greater penetration of the microwave fields through the soil. The energy requirements needed to suppress seed germination in the airdry soil samples was approximately 0.63 kW.h m-2. Assuming a typical electrical energy tariff of between $A0.20-0.30 per kW.h, the treatment costs were between $A0.13 m-2 and $A0.20 m-2. If off-peak tariffs of between $A0.03-0.05 per kW.h could be used, the treatment costs would be between $A0.02 m-2 and $A0.03 m-2.