Interference and control of johnsongrass [Sorghum halepense (L.) Pers.] in corn (Zea mays L.) /
Field experiments were conducted at the Texas Agricultural Experiment Station, Agronomy Field Laboratory near College Station, TX, to investigate several aspects of johnsongrass interference and control in corn. The effects of seedling and rhizome johnsongrass densities on the magnitude of interfer...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
1995.
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| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=742534801&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | Field experiments were conducted at the Texas Agricultural Experiment Station, Agronomy Field Laboratory near College Station, TX, to investigate several aspects of johnsongrass interference and control in corn. The effects of seedling and rhizome johnsongrass densities on the magnitude of interference in corn were evaluated in two experiments. Corn grain yield was significantly reduced at relatively low rhizome johnsongrass densities. Grain yield losses of 5 % were predicted at rhizome johnsongrass density of 3 plants/9.8 m of row (9.8 m). Seedling johnsongrass growing at densities up to 128 plants/9.8 m of row (9.8 m2) did not affect corn grain yield. Experiments conducted to investigate seedling johnsongrass in corn planted at five densities did not affect corn grain yield. Grain yield was significantly affected by crop density, with the highest yield occurring at a crop density of 59300 corn plants ha-'. The effect of johnsongrass interference duration on corn grain yield was examined for three seasons. The critical period of johnsongrass control, which represents a specific interval during which the crop must be free of weeds, was determined to be between 2.5 to 6.5 weeks after crop emergence. This critical period of johnsongrass control is necessary to avoid losses above 5 % of yield produced by full-season weed-free corn. Johnsongrass control systems that included commercially available corn herbicides applied to continuous corn or corn-cotton-com rotation were evaluated over a 3-year period. Nicosulfuron provided the best johnsongrass control among the herbicides evaluated in all three years. The combination of metolachlor and glyphosate provided acceptable levels ( > 80 %) of johnsongrass control in the third year of the experiment in both cropping sequences. Johnsongrass control and grain yield harvested from corn planted after cotton were greater than values observed in continuous corn plots. Maximum economical net return was achieved from continuous corn plots treated with nicosulfuron for three years. Lower, but statistically equal, total economical net returns were obtained from plots planted to corn-cotton-corn and treated with either nicosulfuron, EPTC + R-25788, or metolachlor. |
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| Item Description: | Vita. "Major Subject: Agronomy". |
| Physical Description: | xii, 100 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilms Inc. |
| Bibliography: | Includes bibliographical references. |