An assessment of microwave soil pasteurization for killing seeds and weeds

Graham BrodieA, Steve HamiltonB and Jon WoodworthC

A University of Melbourne, Dookie College, Victoria 3647, Australia.

B Hamilton Environmental Services, 2345 Benalla-Tatong Road, Tatong, Victoria 3673, Australia.

C Environmental Consultant, 22 Edmonds Street, Bucasia, Queensland 4750, Australia.


Microwave heating has been applied to various agricultural problems and products since the 1960s. Interest in soil pasteurization as an alternative method of weed control has been proposed for some time. Soil pasteurization requires the projection of microwave energy into the soil using an antenna. The pyramidal horn is probably the easiest microwave antenna to fabricate. This paper explores the use of a pyramidal horn antenna as a microwave applicator for soil pasteurization, with a particular focus on suppression of seed germination and control of already established weed infestations.

A laboratory system, energized from the magnetron of a modified microwave oven operating at 2.45 GHz, with a wave-guide and pyramidal horn was developed for these experiments. Calibration of the microwave oven revealed that 205 ± 10 Watts of microwave power was delivered from the horn antenna. The H-plane temperature distribution within the soil has the maximum temperature about 3 cm below the surface along the centre line of the horn antenna, which proved to be effective at killing Malva parviflora seedlings and wheat seeds to a depth of about 6 cm.


Plant Protection Quarterly (2007) 22 (4) 143-149.