Some Factors Which Influence the Toxicity of UHF Energy to Weed Seeds

Abstract

UHF energy (2450 MHz) was applied to seeds and seed-soil mixtures with a waveguide under controlled conditions. After treatment, seeds were germinated at 27 C to determine viability. Seeds were either killed or seedlings grew normally with no intermediate levels of inhibition typical of that produced with sub-lethal dosages of herbicides. The energy required to kill several species of dry seeds ranged from 88 to 183 J/cm2and could be reduced 12 to 42% by a 24-hr imbibition period prior to treatment. When several seed-soil mixtures were treated, the greatest toxicity occurred in a moist muck and clay loam soil, with the least toxicity on a dry loamy sand soil. Although attenuation of activity occurred in dry soils of three types, less energy was required to kill seeds in moist soils than was required in the absence of soil. Increasing the power levels reduced the time of exposure necessary to kill barnyardgrass [Echinochloa crus-galli(L.) Beauv.] seeds. Less energy was required to kill seeds as the soil temperature was increased from −20 to +18 C.

Germination of Exhumed Weed Seed in Nebraska

“…There has been, however, only limited success in destroying weed seed in soil by such practices as soil fumigation (8,11,15,20), which has been economically feasible only on high -value crops (8,15). Other attempts such as ultrahigh -frequency electromagnetic fields, various chemicals, heat, and tillage have not materialized as commercially acceptable procedures (1,7,10,16,19,21). Since some of these proposed procedures for destroying weed seed have failed because they were uneconomical, the increasing costs of energy make such methods even less practical.…”

Non‐Chemical Weed Management

“…Germination of the wild oat was reduced while wheat and oat were almost unaffected. Moist seeds were more susceptible than dry seeds, hence seeds in wet soils were more easily killed than in dry (Rice & Putnam, 1977). The damage to seeds is likely to be thermal but this is not certain (Davis et al, 1973).…”

“…It makes a significant contribution to the process of plant succession (Numata, 1982). The broad ecological role of allelopathy is discussed at length by Rice (1984). Widdowson (1987) considers the allelopathic interactions that are important in progressing towards holistic agriculture.…”

Influence of Humidity and of the Electric and Magnetic Microwave Radiation Fields on the Remediation of TCE-contaminated Natural Sandy Soils

“…In this regard, theoretical calculations by Nelson 14 suggested that the use of microwaves for soil disinfestation is not practical because of the high amount of energy required to obtain sufficient results. Echoing this concern, Rice and Putham 15 and Lal and Reed 16 also considered that microwave treatments are too expensive, particularly when soil surface humidity is high. Along similar lines, Mavrogianopoulos and coworkers 17 examined the energy consumption in applying microwaves for soil disinfection and disinfestations, concluding that despite some advantages offered by the use of microwaves e.g.…”