The influence of several environmental and edaphic factors on alachlor [2-chloro-2′,6′-diethyl-N-(methoxymethyl)acetanilide] selectivity in snap bean (Phaseolus vulgarisL.) was examined. Crop safety was consistently improved when alachlor was applied preplant incorporated as compared to surface preemergence treatment. Under field conditions, maximum injury occurred either when temperatures during germination were cool and rainfall was minimal, or when temperatures approached or exceeded 27 C and the soil was saturated. In the growth chamber, more damage occurred under low temperature regimes, although volatilization of alachlor from moist soil also produced injury under higher temperatures. Injury was less severe in soils high in organic matter content. Alachlor injury decreased after 5 cm of simulated rainfall were applied on a loamy sand.

The uptake, translocation, and metabolism of14C-alachlor [2-chloro-2′,6′-diethyl-N-(methoxymethyl)acetanilide] by germinating and emerged snap bean (Phaseolus vulgarisL.) seedlings were monitored under 16-h daylength (21 klux) comparing 16 C night/21 C Day and 27 C night/32 C day temperature regimes. Total uptake of14C-alachlor by germinating snap beans was greater under the higher temperature, however, the compound was localized primarily in the roots where it was rapidly metabolized. At the lower temperature, the label was located in approximately equal amounts in all plant parts except cotyledons and significantly less of the alachlor was metabolized. Root uptake of14C-alachlor and translocation of labeled compounds to the shoots were significantly greater under the higher temperatures. Approximately 60% of14C-alachlor was shown to volatilize from a watchglass after 48 h at 27 C. After volatilization, uptake of14C-alachlor occurred in adjacent snap bean plants in a closed system.

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.

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