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Sorption of Bentazon and Degradation Products in Two Mississippi Soils
- Lewis A. Gaston, Martin A. Locke, Steven C. Wagner, Robert M. Zablotowicz, Krishna N. Reddy
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- Journal:
- Weed Science / Volume 44 / Issue 3 / September 1996
- Published online by Cambridge University Press:
- 12 June 2017, pp. 678-682
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Bentazon degradation in soil typically proceeds with development of bound residue. Low sorption of bentazon suggests that this residue consists of degradation products; however, there is little data on the sorption behavior of these products. This study was undertaken to determine the sorption of bentazon and the degradation products 2-amino-N-isopropyl benzamide, 2-aminobenzoic acid, and N-methyl bentazon in Dundee silt loam and Sharkey clay, two common agricultural soils of the Mississippi Delta. Greater sorption of bentazon and degradation products in the Sharkey soil was related to finer texture and higher organic C content. Isotherms were nonlinear, with sorption increasing in the order bentazon ≪ 2-amino-N-isopropyl benzamide < N- methyl bentazon. In general, methanol extraction indicated reversible sorption of these compounds. Therefore, it is unlikely that sorption of either 2-amino-N-isopropyl benzamide or N-methyl bentazon contributes to bound residue. In contrast, essentially all of the 14C sorbed from radiolabeled 2-aminobenzoic acid solution remained bound after methanol extraction. However, due to degradation of 2-aminobenzoic acid, it was not possible to conclude the extent to which this compound contributed to bound 14C. Sorption of 14C from 2-aminobenzoic acid exceeded that of N-methyl bentazon, and at low initial concentrations (≤ 20 μM) was nearly 1000-fold greater than bentazon sorption.
Conservation cotton production in the southern United States: herbicide dissipation in soil and cover crops
- Martin A. Locke, Robert M. Zablotowicz, Philip J. Bauer, R. Wade Steinriede, Lewis A. Gaston
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- Journal:
- Weed Science / Volume 53 / Issue 5 / October 2005
- Published online by Cambridge University Press:
- 20 January 2017, pp. 717-727
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Soil and surface residues from cotton field studies in Stoneville, MS (1994 through 1996) and Florence, SC (1995 through 1996) were sampled to evaluate effects of cover crop and tillage on herbicide dissipation. Mississippi treatments included tillage (conventional [CT]; none [NT]) and cover crop (ryegrass; none [NC]). South Carolina treatments included tillage (CT; reduced tillage [RT]) and cover crop (rye; NC). Fluometuron was applied preemergence (PRE) in both Mississippi and South Carolina, and norflurazon was applied PRE in Mississippi. Soils were sampled various times during the growing season (depths: 0 to 2 cm, 2 to 10 cm). Cover crop residues were sampled from RT or NT cover crop areas. Soil and cover crop sample extracts were analyzed for herbicides. Soil organic carbon tended to increase with tillage reduction and presence of cover crop and was positively correlated with herbicide sorption, especially in the surface. Across locations, herbicide half-lives ranged from 7 to 15 d in the soil surface. Tillage had mixed effects on herbicide persistence in surface soil, with higher herbicide concentrations in CT at early samplings, but differences were insignificant later on. The most consistent effects were observed in RT/NT with cover crops, where cover crop residues intercepted applied herbicide, impeding subsequent movement into soil. Herbicide dissipation in cover crop residues was often more rapid than in soil, with half-lives from 3 to 11 d. Herbicide retention in cover crop residues and rapid dissipation were attributed to strong herbicide affinity to cover crop residues (e.g., fluometuron Kd = 7.1 [in rye]; Kd = 1.65 [in Mississippi Dundee soil CT, NC]) and herbicide co-metabolism as cover crop residues decomposed. A fluometuron metabolite, desmethyl-fluometuron, was observed in most soil and cover crop samples after 1 wk. Only minimal herbicide or metabolite moved into the subsurface, and little treatment effect could be ascribed to herbicide or metabolite movement below 2 cm.
Contributors
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- By Graeme J.M. Alexander, Heung Bae Kim, Michael Burch, Andrew J. Butler, Tanveer Butt, Roy Calne, Edward Cantu, Robert B. Colvin, Paul Corris, Charles Crawley, Hiroshi Date, Francis L. Delmonico, Bimalangshu R. Dey, Kate Drummond, John Dunning, John D. Firth, John Forsythe, Simon M. Gabe, Robert S. Gaston, William Gelson, Paul Gibbs, Alex Gimson, Leo C. Ginns, Samuel Goldfarb, Ryoichi Goto, Walter K. Graham, Simon J.F. Harper, Koji Hashimoto, David G. Healy, Hassan N. Ibrahim, David Ip, Fadi G. Issa, Neville V. Jamieson, David P. Jenkins, Dixon B. Kaufman, Kiran K. Khush, Heung Bae Kim, Andrew A. Klein, John Klinck, Camille Nelson Kotton, Vineeta Kumar, Yael B. Kushner, D. Frank. P. Larkin, Clive J. Lewis, Yvonne H. Luo, Richard S. Luskin, Ernest I. Mandel, James F. Markmann, Lorna Marson, Arthur J. Matas, Mandeep R. Mehra, Stephen J. Middleton, Giorgina Mieli-Vergani, Charles Miller, Sharon Mulroy, Faruk Özalp, Can Ozturk, Jayan Parameshwar, J.S. Parmar, Hari K. Parthasarathy, Nick Pritchard, Cristiano Quintini, Axel O. Rahmel, Chris J. Rudge, Stephan V.B. Schueler, Maria Siemionow, Jacob Simmonds, Peter Slinger, Thomas R. Spitzer, Stuart C. Sweet, Nina E. Tolkoff-Rubin, Steven S.L. Tsui, Khashayar Vakili, R.V. Venkateswaran, Hector Vilca-Melendez, Vladimir Vinarsky, Kathryn J. Wood, Heidi Yeh, David W. Zaas, Jonathan G. Zaroff
- Edited by Andrew A. Klein, Clive J. Lewis, Joren C. Madsen
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- Book:
- Organ Transplantation
- Published online:
- 07 September 2011
- Print publication:
- 11 August 2011, pp vii-x
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