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Replicated experiments were conducted on three soils in northeast Louisiana to address questions concerning potential effects of Zorial residues on fall-seeded crops following application in cotton. Zorial was applied broadcast and incorporated to a depth of 0-2 inches with a reel-and-harrow bed conditioner one or two days prior to seeding fall crops. Rates of application were 0, 0.125, 0.@5, 0.5, and 0.75 lb ai/A. Coker 916 wheat, Bob oats, Gulf annual ryegrass, Dixie crimson clover, hairy vetch, and Austrian winter peas were drill-seeded in November 1988 so that each crop was subjected to each rate of Zorial. Sites were located on Commerce silt loam and Sharkey clay at St. Joseph and Gigger silt loam at Winnsboro. Considerable variability occurred in visual injury ratings and dry forage yields when evaluations were made in the spring of 1989. Much greater injury occurred in poorly drained areas of the experiments as compared to the well drained areas. Injury ratings at the two St. Joseph locations were generally similar and less severe than those at the Winnsboro site. Visual ratings indicated wheat was not tolerant to the lowest rate of Zorial (0.125 lb/A) at either St. Joseph location, however, no appreciable injury occurred at this rate at the Winnsboro site. Oats were not significantly injured at rates up to 0.25 lb/A at either location. Ryegrass was not injured at rates up to 0.25 lb/A at both St. Joseph locations and 0.125 lb/A at Winnsboro. Crimson clover was tolerant to maximum rates of 0.125 and 0.25 lb/A on silt loam and clay soils, respectively, at St. Joseph. A stand failure occurred with crimson clover at the Winnsboro location. Hairy vetch was tolerant to the highest rate of Zorial (0.75 lb/A) at both St. Joseph locations but a maximum of only 0.25 lb/A at Winnsboro. Austrian winter peas were tolerant to Zorial 0.5 lb/A and less at the St. Joseph locations but only 0.125 lb/A at Winnsboro. In terms of dry forage yield, the maximum rates of Zorial which wheat tolerated without yield loss were 0.5 lb/A on commerce silt loam, 0.25 lb/A on Sharkey clay, and 0.125 lb/A on Gigger silt loam. Oats were tolerant to Zorial rates of 0.75 lb/A and less on silt loam at St. Joseph, but only 0.25 lb/A or less at the other two sites. Ryegrass was tolerant to Zorial 0.5 lb/A and less on Sharkey clay, 0.25 lb/A and less on Commerce silt loam, and 0.125 lb/A on Gigger silt loam. Crimson clover was tolerant to Zorial at a maximum rate of 0.25 lb/A on both soils at St. Joseph. Hairy vetch was tolerant to Zorial 0.75 lb/A and less on Commerce silt loam and 0.5 lb/A or less on Sharkey clay; however, forage yield was reduced even at 0.125 lb/A on Gigger silt loam. Austrian winter peas tolerated Zorial rates of 0.25 lb/A and less without yield loss on commerce silt loam and 0.125 lb/A on Sharkey clay, but the lowest rate reduced yield at the Winnsboro location. |
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©National Cotton Council, Memphis TN |
Document last modified Sunday, Dec 6 1998
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