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| Publication Type:
| Report |
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| Author(s): | Ehr, Robert J.;
Gerwick, B. Clifford |
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| Author Affiliation: | Ehr: Senior Research Biologist; Gerwick: Project Leader, The Dow Chemical Company, Agricultural Products Deptartment, Midland, MI. |
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| Title: | Properties influencing soil residual activity of the new postemergence grass herbicides |
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| Section: | Physiology, edaphic factors and control of specific weeds
Other records with the "Physiology, edaphic factors and control of specific weeds" Section
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| Meeting Info.: | Winnipeg, Manitoba, Canada: December 4-6, 1984 |
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| Source: | Proceedings: North CentralWeed Control Conference. Vol. 39, 1984, p. 82. |
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| Publishing Information: | [Urbana, Illinois: Department of Agronomy, University of Illinois] |
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| # of Pages: | 1 |
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| Keywords: | TIC Keywords: Residues; Postemergence herbicides; Weed control; Herbicide rates
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| Abstract/Contents: | "Soil residual activity of varying duration has been observed following foliar applications of the new postemergence grass herbicides. Field studies in Minnesota with postemergence applications at the labeled or proposed rates on a 5.6% O.M. loam soil demonstrated the following ranking of soil residual control: haloxyfop-methyl fluazifop-butyl DPX-Y-6202 sethoxydom. Soil residual activity is influenced by field parameters such as soil type and rainfall, by application parameters such as rate, and by chemical and physical properties inherent in each graminicide. In order to better understand field performance of these material, this study was conducted with the purpose of characterizing and comparing inherent properties that influence soil residual activity such as: activity level on roots of grass, soil degradation rate, and soil mobility pattern. In these studies, the parent acid of each aryloxyphenoxypropionate was used. Barnyardgrass [Echinochloa crus-galli (L.) Beauv.] was utilized in the bioassays because it is moderately susceptible to all compounds and was compatible with all bioassays used in these studies. Soil degradation and mobility studies were conducted with a 3.0% O.M. catlin silt loam. The inherent activity of these materials on roots was evaluated by the dose sensitivity of barnyardgrass root growth. Pre-germinated seeds were placed on filter paper discs moistened with solutions of each compound. Concentrations encompassed a broad dose range. The GR50 concentrations of DPX-Y-6202, haloxyfop, fluazifop, and sethoxydim were: 0.1, 0.24, 1.4 and 1.6 micromolar respectively. Soil degradation rate was characterized by incorporating rates of each chemical into soil. A portion of the soil was stored at -20°C and the remainder was incubated at 27°C. Samples from each temperature were bioassayed at 0, 14, 28, and 42 days. Differences between the frozen and 27°C treatments at the GR50 level were taken as estimates of compound degradation. From the slope of the degradation curve, soil half-lives of haloxyfop, fluazifop, DPX-Y-6202 and sethoxydim were estimated at 18.5, 16.0, 10.5 and 4.5 days, respectively. Soil mobility patterns were studied by preparing soil columns and adding a thin band of soil in which each material was incorporated. A sufficient amount of each herbicide was added so as to equal the herbicidal activity of 0.5 lb/acre of haloxyfop-methyl. These amounts were determined by comparing GR50 concentrations of these compounds in the root activity test described above. The columns were leached with four acre inches of water for 24 hours at which point the water front had moved 14.4 inches. The column was then laid horizontal, sliced open and seeded with barnyardgrass. The bioassay showed sethoxydim moved with the water front. A reduction in plant growth was observed from the top of the column to a depth of 14 inches. Haloxyfop produced a zone of inhibition extending from the top of the column to a depth of 11 inches. Fluazifop moved as a band and inhibited plant growth in a zone from 5 to 11 inches from the top of the columns. DPX-Y-6202 inhibited shoot growth only in the top one inch of the column. Root growth was not affected. The graminicides evaluated in this study were limited to varying degrees by one or more of the inherent properties. The low soil residual activity of sethoxydim is the composite effect of a short half-life of less than five days and the lowest level of activity on barnyardgrass roots. DPX-Y-6202 demonstrated very restricted soil mobility. The low water solubility of the parent acid additionally may restrict activity. Thus, although DPX-Y-6202 does have the highest activity level on barnyardgrass roots, compound availability and an intermediate half-life of 10.5 days strongly act to reduce soil residual activity. Fluazifop was not quickly degraded and seemed to possess sufficient soil mobility. The intermediate soil residual activity is apparently governed by the lower level of activity on barnyardgrass roots and by the fact that postemergence rates do not always furnish the level needed for activity on roots. Haloxyfop appears to have a favorable combination of soil mobility and activity level on grass roots. These factors, combined with a slower degradation rate relative to the other materials in the study, give rise to the 4 to 6 weeks of residual control observed with haloxyfop." |
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| Language: | English |
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| References: | 0 |
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| Note: | This item is an abstract only! |
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| ASA/CSSA/SSSA Citation (Crop Science-Like - may be incomplete):
Ehr, R. J., and B. C. Gerwick. 1984. Properties influencing soil residual activity of the new postemergence grass herbicides. Res. Rep. North Cent. Weed Control Conf. 39:p. 82. |
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