Preliminary investigation into microwave soil pasteurization using wheat as a test species
Graham BrodieA, Catherine BottaA and Jon WoodworthB
A The University of Melbourne, Dookie College, Victoria 3647, Australia.
B Environmental Consultant, PO Box 63, Mackay, Queensland 4740, Australia.
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 microwave 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 air-dry 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.
Plant Protection Quarterly (2007) 22 (2) 72-75.