A study has been made of the determination of arsenic, bismuth, germanium, antimony, selenium, tin and tellurium by conversion into the hydrides by reaction with sodium borohydride in dilute hydrochloric acid followed by measurement with atomic-absorption spectrophotometry in an argonhydrogen flame. A general study, involving 48 elements, of interferences has been carried out and i t has been shown that significant interference occurs in many instances but that the procedure is simple to carry out and gives a considerable increase in sensitivity and detection limits for the elements listed, with the exception of tin, for which high blank values were obtained owing to the presence of tin in the sodium borohydride reagent.

Allelopathy, the direct or indirect effect of one plant on another through the production of chemical compounds that escape into the environment, occurs widely in natural plant communities and is postulated to be one mechanism by which weeds interfere with crop growth. The purpose of this research was to determine the potential allelopathic influence of selected cool‐season grass species on species interseeded into the pasture ecosystem. Aqueous extracts of tall fescue (Festuca arundinacea Schreb.), Italian ryegrass (Lolium multiflorum Lam.), and little barley [Critesion pusillum (Nutt.) A. Löve; syn. Hordeum pusillum Nutt.] leaf and stem tissue harvested at the mature stage of plant development reduced seed germination and seedling growth of alfalfa (Medicago sativa L.) and Italian ryegrass. It was estimated that 2.8 and 2.5 g L−1 aqueous extracts of mature tall fescue stem tissue, resulted in a 50% reduction in alfalfa seed germination and seedling growth, respectively. For the extracts from Italian ryegrass and little barley, it was estimated that tissue concentrations of near 5.0 g L−1 resulted in a 50% reduction in seed germination and seedling growth for the two bioassay species. Leaf and stem tissue concentrations of the three grasses >7.0 g L−1, resulted in complete inhibition of alfalfa seedling growth. The potential concentration for foliage tissue in soil solution of the pasture ecosystem for tall fescue, Italian ryegrass, and little barley would be 28, 23, and 9 g dry wt. L−1, respectively. Therefore, the allelopathic characteristics of these species could be of economic importance in the pasture ecosystem when overseeding the pasture with annual ryegrass or alfalfa.

Soybean {Glycine max (L.) Merr.) cultivars have been reported to range in tolerance to injury by 4-amino-6-tert-butyl-3-(methylthio)-a5-triazine-5(4H)one (metribuzin), from tolerant (e.g. 'Bragg') to susceptible (e.g. 'Coker 102' and 'Semmes'). 'Bragg', 'Coker 102', and 'Semmes' soybeans were grown in sand subirrigated with nutrient solution containing labelled (^^Ccarbonyl metribuzin) and nonlabelled metribuzin to determine cultivar variability in absorption, translocation, and metabolism of metribuzin. Plants were periodically harvested, autoradiographed, and radioactivity in tissue extracts quantified. Data indicated that all 3 cultivars readily absorbed and translocated metribuzin. However, 'Bragg' tissues accumulated greater quantities of metribuzin metabolites than the other two cultivars. The major ^*C-containing metabolite in 'Semmes' and 'Coker' roots and stems was 6-tert-butyl-a^-triazine-3-5-(2H,4H)-dione, whereas the major ^*C-metabolite isolated from 'Bragg' roots and stems was a glucose conjugate. Results indicated that differentialintraspecific responses to metribuzin may resuit from differential capacities for herbicide detoxification by conjugation.