Fate of molinate in water used in rice production /
Rice (Oryza sative L.) is a water-use intensive crop. Texas' flooded rice culture requires relatively large water volumes which eventually discharge into tributaries and rivers draining into the Gulf of Mexico. Nutrients and pesticides that move off-site from their target areas have the potent...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
2001.
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| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=728908631&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | Rice (Oryza sative L.) is a water-use intensive crop. Texas' flooded rice culture requires relatively large water volumes which eventually discharge into tributaries and rivers draining into the Gulf of Mexico. Nutrients and pesticides that move off-site from their target areas have the potential to adversely affect receiving waters. After the rice plant develops its second tiller, the general practice is to permanently flood the field supplying the plant with needed moisture and serving as a cultural weed control system. Weed infestation problems occurring after flood establishment are chemically controlled. One herbicide used for weed control in a rice paddy is molinate or Ordram ® 15-G. This farm-scale size study was conducted with minimum interference of the producer's cultural management methods. The intent was to collect as much information as possible in a real-life situation. The work was not an experimental design with replications intended for in-depth statistical analyses. The mechanisms of degradation of the herbicide were not studied. The fact that motivate degrades over time was the key issue. The goal was to track the spatial and temporal environmental fate, not the various degradation mechanisms, of the herbicide parent compound molinate. Aqueous molinate residue was transported by circulating (lotic) water. Molinate dissipation was a logarithmic function of time; however, the hourly rate was erratic. Molinate applied into paddy water dissipated to non-detectable levels 35 days after application and to less than the detection limit within 16 days. Molinate life-half averaged 1.4 days in three fields indicating an average loss rate of 35 percent per day. Large field dissipation was about twice dissipation rates reported in controlled laboratory studies. The fourth field had a loss rate of about 13 percent per day, equating to a half-life of 3.9 days. Mild weather conditions were probably responsible for decreasing volatilization shortly after molinate application. Approximately 88 percent of terrestrial molinate residue was found in the 0-25 mm (0-1 in.) soil depth. Molinate soil residue was either not detected, or was less than the detection limit, at the lower soil depth (25-50 mm or 1-2 in). |
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| Item Description: | Vita. "Major Subject: Agricultural Engineering". |
| Physical Description: | xii, 222 leaves : illustrations, map ; 28 cm. Issued also on microfiche from University Microfilm Inc. |
| Bibliography: | Includes bibliographical references (leaves 98-105). |