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  • Author or Editor: Wayne C. Porter x
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Black polyethylene, perforated clear polyethylene, double-slitted clear polyethylene, spunbonded polyester, and a bare soil control were evaluated for their effect on the number, size, and distribution of production of sweet potato transplants. The perforated and double-slitted bed covers increased the weight and number of sweet potato transplants compared with the control or with black polyethylene at the first harvest in 1986 and 1987, Seed roots covered with the spunbonded polyester bed cover produced more plants of greater weight than seed roots covered with bare soil at the first harvest in 1986 only. Black polyethylene treatments produced the greatest weight and number of transplants at the second harvest (8 to 12 days later) in both years. There were no significant differences in total weight and number of transplants among black polyethylene, perforated or double-slitted clear polyethylene treatments in 1986. Total transplant number and weight from plots covered with spunbonded polyester were lower than those from plots with any other bed covers.

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Oxyfluorfen was evaluated for weed control in sweet potatoes. In 1989, applications were made overtop transplants immediately after transplanting. The 1990 applications were made just prior to transplanting. Oxyfluorfen applied post-transplant at 0.38 lb ai/A and greater rates caused a significant reduction in crop vigor. A 1.0 lb ai/A rate of oxyfluorfen reduced crop vigor when applied pretransplant. All rates of oxyfluorfen controlled Brachiaria platyphylla, Digitaria sanguinalis, Cyperus iria, and Sesbania exaltata. Oxyfluorfen rates of 0.5 lb ai/A and greater were needed to consistently control Sida spinosa and Echinochloa crus-galli. Mollugo verticillata was controlled at all rates in 1989 but not controlled at all in 1990. Yields of all grades of sweet potato roots from plots treated with oxyfluorfen were not different from yields from plots treated with currently labeled herbicides. However, in 1989 yields from all oxyfluorfen-treated plots were lower than yields from the hoed check. In 1990, plots treated with oxyfluorfen at 0.25 or 0.38 lb ai/A had lower yields of No. 1 grade roots than the hoed check.

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Four bed covers (black polyethylene, perforated clear polyethylene, double-slitted clear polyethylene, and spunbonded polyester) and a bare soil control were evaluated for their effect on the number, size, and harvest time of sweetpotato [Ipomoea batatas (L.) Lam. cv. Travis] transplants. The perforated and double-slitted bed covers increased the weight and number of sweetpotato transplants compared with the control or with black polyethylene at the first harvests in 1986 and 1987. Seed roots covered with the spunbonded polyester bed cover produced more plants of greater weight than seed roots covered with bare soil at the first harvest in 1986 only. Black polyethylene treatments produced the greatest weight and number of transplants at the second harvest (8 to 12 days later) in both years. There were no significant differences in total weight and numbers of transplants among black polyethylene, or perforated or double-slitted clear polyethylene treatments in 1986. Total transplant count and weights from plots covered with spunbonded polyester were lower than those from plots with any other bed covers.

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High annual rainfall and frequent torrential deluges have always made weed control a tenuous affair in Louisiana. Herbicide leaching and soil erosion often take preemergence herbicides to the nether regions. Before the time of postemergent grass herbicides, frequent cultivation was the only method to try to salvage the sweetpotato crop when preemergence weed control was lost. For many years, the most serious weed problems were prickly sida, cocklebur, and purple nutsedge with occasional hotspots of morning-glory. However, due to the change in herbicides used, the species of problem weeds have shifted to rice flatsedge, yellow and purple nutsedge, carpetweed, and various pigweeds. Before the registration of Command herbicide for use in sweetpotatoes, many sweetpotato growers used herbicides that effectively controlled or suppressed the current problem weeds. With the widespread use of Command, prior problem weed species are effectively controlled, but these other problem weeds are released.

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Studies were conducted to evaluate metolachlor for weed control and crop tolerance in sweet potatoes. Metolachlor was applied posttransplant at rates of 0.5, 1.0, or 2.0 lb/A. Tank-mix combinations of metolachlor + clomazone were also evaluated. Clomazone was the standard herbicide used for comparison. Metolachlor alone or in combination with clomazone did not cause any serious reduction in sweet potato plant vigor when applied posttransplant. Metolachlor provided excellent control of Brachiaria platyphylla, Cyperus iria, Cyperus esculentus, and Amaranthus hybridus. Tank-mixes with clomazone did not improve the weed control of metolachlor alone. Yields of No. 1 and marketable roots from metolachlor treated plots were equal to or greater than yields from plots treated with clomazone.

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Metolachlor herbicide is being evaluated for preemergent weed control in sweetpotatoes due to its ability to control yellow nutsedge (Cyprus esculentus) and rice flatsedge (C. iria). Registration of metolachlor has been delayed because of reports in North Carolina of injury to sweetpotato roots. This study was initiated to determine the response of sweetpotato cultivars to metolachlor rates. Metolachlor at 1.12, 2.24, and 3.36 kg·ha–1 was applied to `Beauregard', `Hernandez', `Jewel', and `Darby' sweetpotatoes after transplanting. All rates of metolachlor provided good control of sedges. No significant cultivar × metolachlor interactions were found in the yield of no. 1, canners, marketable, or percent no. 1 sweetpotatoes. In plots treated with metolachlor at 2.24 kg·ha–1, only `Beauregard' sweetpotatoes produced jumbo grade roots. No evidence of misshapen roots due to any herbicide rate was noted.

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Rye, wheat, hairy vetch, ryegrass, and Austrian winterpea were evaluated for effects on weed control and sweetpotato production. Sweetpotatoes were transplanted into these cover crops after the cover crops had been killed with glyphosate and mowed. One-half of each plot was treated with clomazone herbicide and one-half was not treated. Plots with rye residues contained fewer goosegrass, rice flatsedge, ground cherry, and smooth pigweed plants than other cover crop plots. Sweetpotato plant vigor was greatest in the rye plots. Goosegrass, crabgrass, groundcherry, and eclipta were controlled in cover crop plots treated with clomazone. Sweetpotato plant vigor was better in the plots treated with clomazone than in plots with a cover crop only. Highest yields of no. 1 grade and total marketable sweetpotatoes were in rye and ryegrass cover crop plots, with or without clomazone. Sweetpotatoes grown in Austrian winterpea plots without clomazone produced the lowest yields. There was an increase in yield of sweetpotatoes in all cover crop plots treated with clomazone.

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Selected herbicides, alone or in combination with polyethylene bed covers, were evaluated for preemergence weed control in sweet potato plant beds. No injury to sweet potato transplants was found when the herbicide was applied to the soil surface of freshly bedded sweet potato roots before application of the polyethylene or was applied to newly emerged transplants immediately after the bed cover was removed. Some foliar chlorosis was observed in transplants from beds treated with clomazone, but after the first transplant pulling, no reappearance occurred. Clomazone, chloramben, and napropamide provided excellent control of all annual grasses. Herbicides, regardless of timing of application, did not adversely affect number or weight of sweet potato transplants. Beds covered with polyethylene film produced more transplants at the early and total harvests than the uncovered beds.

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Clomazone was evaluated for reemergence weed control in summer squash, watermelon, cantaloupe, cucumber, and pumpkin. Clomazone was applied preplant incorporated or surface-applied after planting. All crops exhibited varying degrees of chlorosis in the cotyledonary stage and first one to three true leaves. Cucurbit tolerance to clomazone was pumpkin = squash > cucumber > watermelon > cantaloupe. Method of application did not affect crop vigor. Some pumpkin cultivars were more tolerant than others. Clomazone controlled Brachiaria platyphylla and Portulaca oleracea with both methods of application. Surface application provided better control of Amaranthus hybridus and A. spinosa. Mollugo verticillata was not controlled. Preplant incorporated application of clomazone tended to reduce the yield of watermelon.

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The initial investment of a precision seeder is cost prohibitive to many small vegetable growers. This study was initiated to evaluate the use of a relatively inexpensive bulk seeder to plant cabbage (Brassica oleracea L. Capitata). Cabbage was direct-seeded with a precision seeder or a relatively inexpensive bulk seeder. Treatments with the bulk seeder consisted of blending viable hybrid seed with nonviable, nonhybrid seed at several ratios to reduce hybrid seed cost and optimize plant spacing. Seed ratios represented 10, 20, 30, 40, 50, and 100% viable seed. Pre-thin plant stands of 30 and 40% hybrid seed treatments were similar to precision-seeded plant stands. Average head size was greatest with 10, 20, and 30% hybrid seed ratios. Marketable yields were similar for all hybrid seed ratios except the 10% ratio. Production costs per acre for the precision seeder were between that of the 40 and 50% ratios. Net income for 40% hybrid seed was similar to that of the precision seeder.

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