Alachlor [2-chloro-2′,6′-diethyl-N-(methoxymethyl)-acetanilide] mixed with plaster-of-paris in concentrations of 0.5, 1, 2, and 4% (w/w) was cast into tablets of three sizes. The controlled release of the herbicide was tested by the following methods: (a) in the laboratory with eduction by soaking tablets in water, (b) in the greenhouse with azalea (Rhododendron obtuseumPlanch. ‘Richardii’) stock in container, and (c) in the lathe house with azalea stock in containers. In the laboratory experiment, the quantity of herbicide educed from tablets of equivalent volumes, weights, and concentrations were similar regardless of surface area of the three tablet sizes. Successively decreasing quantitites of alachlor were educed with each of the first 10 soakings. Following these soakings, the quantity of alachlor educed per soaking stabilized for the next 30 soakings. In both greenhouse and lathe house experiments, azalea plants treated with as much as 45 kg/ha alachlor formulated in tablet(s) were not damaged. In the best greenhouse treatments, two small tablets per container, effective weed control was obtained for up to 7.5 months from a single application of alachlor at rates of 11, 22, and 45 kg/ha.
Magnetic Resonance Imaging (MRI) provides intriguing opportunities for studying soil organisms and plant roots. However, the usefulness of MRI is sometimes limited by iron fractions which interfere with image quality. Data were collected which quantified hydrogen MR image intensity versus concentration of total iron in selected soils. It is suggested that one compare MRI signal intensity of water in a standard material such as purified quartz and in the natural soil of interest when doing quantitative hydrogen MRI studies involving soil plants or other organisms.
INTRODUCTIONMagnetic Resonance Imaging (MRI) provides excellent quality in situ images of plant roots and soil insects under certain conditions. Rogers and Bottomley (1987) obtained images of Vicia Faba seedlings in Wynnville fine sandy loam, Lucy loamy sand, Dothan sandy loam, Lakeland sand, Kingston loamy sand, Blanton loamy sand and Houston clay. Tollner et al. (1986) successfully imaged insects in Lakeland sand, purified quartz sand, but not in Tifton sandy loam and Cecil clay loam. The Rogers and Bottomley (1987) images were of varying quality even though the soils were selected as a result of screening
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