INHIBITION OF WEED SEED-GERMINATION BY MICROWAVES

Irradiation with radiofrequency energy (RF), which includes microwaves, brings about dielectric heating of moist materials. Some agricultural applications of dielectric heating by RF have included insects control in stored grains and improved germination of seed stocks. The objective of the present research was to evaluate microwave heating of soils as a technique for weed control. Approximately 800-g masses of soil of variable wetness (10-280 g H2O/kg soil) containing seeds of oat (Avena sativa L.) and indigenous weeds were heated in a microwave (2.45 GHz) oven for 15 to 240 s. Soil masses were 5 cm deep in flats. Oat seeds were placed 2 cm deep into the soil. Heating of soils to 80-degrees-C or higher inhibited emergence of oats and weed species. About 120 s of heating were needed to reach 80-degrees-C. Maintaining this temperature for 30 s was needed for strong inhibition. Moisture content in this experiment had little effect on dielectric heating. Time required to heat soil to killing temperatures appears to be a factor limiting application of this technique. The procedure may be applicable to soil sterilization in cases in which other physical processes or chemical means are inconvenient or undesirable.