Author
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Richard Jr, Edward |
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Submitted to: Weed Technology Journal
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 2/14/1997 Publication Date: N/A Citation: N/A Interpretive Summary: In Louisiana, approximately 25% of the acreage devoted to sugarcane production is fallowed during the spring and summer. During the fallow period, fields are subjected to frequent diskings to destroy rhizomatous johnsongrass which can not be selectively controlled during the 3-yr crop cycle. Beside promoting erosion, the effectiveness of tillage in eliminating these rhizomes is rainfall dependent. In studies to evaluate the use of various preemergence and postemergence herbicide treatments during the fall period, it was found that johnsongrass can be controlled between row formation in the fallow and cane planting 90 d later using fallow management systems of either sulfometuron at 140 to 280 g/ha immediately after row formation followed by spot applications of glyphosate or sequential postemergence applications of glyphosate at 2240 g/ha each time. Utilization of these management programs would result in improved sugarcane yields and reduced dependence on in-crop methods of suppressing johnsongrass development within the crop. It was also found that weed residues present at planting negatively influenced crop establishment by reducing available soil moisture and by releasing allelopathic compounds during the decaying process. Since tillage was eliminated, erosion was minimized, soil moisture at planting was adequate and the presence of residues of all weed species was reduced with the programs developed. Technical Abstract: Soil surface applications of metribuzin at 1680 g ai/ha, pendimethalin plus atrazine each at 2240 g ai/ha, terbacil at 1680 g ai/ha, and sulfometuron at 36 and 69 g ai/ha, and an incorporated application of trifluralin at 2240 g ai/ha followed by atrazine at 2240 g/ha to the surface of newly formed beds in fallow sugarcane fields failed to control seedling johnsongrass. Infestations of rhizome johnsongrass originating from seedling johnsongrass that escaped the fallow treatments were lowest in the fall after planting and the plant-cane crop the following year for soil surface applications of sulfometuron at 140 to 280 g/ha and when glyphosate was applied POST at 2240 g ai/ha as either a single and sequential treatment or as a spot treatment at 2 % by volume following soil treatments of metribuzin, terbacil, or pendimethalin or trifluralin with atrazine. Sugarcane shoot populations in the fall after planting and sugar yields at the end of the crop's first growing season were highest for treatments tha minimized johnsongrass development during the fallow. Results suggest that fallow fields should be kept weed free not only to insure that newly planted fields are free of rhizomes but to limit the production of weed residues. Physical presence of these residues may limit moisture availability and/or by decaying produce allelopathic chemicals; both of which could hinder crop establishment. |
