Residual Effects on Cotton

from Broadstrike + Treflan Applied to Soybean and Broadstrike SF + Dual Applied to Corn

Contents

Introduction

Materials and methods

      Cotton was planted during 1995 in plots that had grown Broadstrike-treated corn and soybean for 1 year. In 1996 and 1997, cotton was planted in plots that had grown Broadstrike-treated corn and soybean for 1 year or 2 consecutive years.

      All herbicides were applied with a tractor-mounted sprayer delivering 20 gallons total broadcast volume per acre. Row cultivation and postemergence-directed herbicides were applied with a four-row cultivator equipped with spray shields leaving a 12-inch undisturbed band centered on the crop row. Table 1 presents a list of the mechanical tillage operations, and Table 2 describes the herbicide applications for each crop during the 4 years. Cultivation for corn was performed on May 19, 1994, and May 10, 1995; for soybean, May 19 and June 20, 1994, and May 10 and 30, 1995; and for cotton, May 10 and 30, 1995, June 5, 1995, May 15, 1996, June 10, 1996, and June 5, 1997.

      Corn (Deltapine brand `8695') was planted April 8, 1994, and March 21, 1995. Soybean (Pioneer brand `9592') was planted May 6, 1994, and April 10, 1995. Two cotton varieties were grown: Deltapine brand `DES 119' was planted in 1995, and Suregrow brand 'SG 125' was planted in 1996 and 1997. Cotton was planted April 27, 1995, April 19, 1996, and April 21, 1997; it was replanted May 14, 1997. Cotton was grown without supplemental irrigation. A four-row John Deere 7100 planter was used for all crops. Crops were grown on a Bosket silt loam soil (30% sand, 53% silt, 17% clay, 1% organic matter, and pH 6.3). All areas were subsoiled at 45 degrees to the row direction in October or November each year.

      In addition to the herbicide treatments described in Table 2, a lay-by application of Bladex (cyanazine -- 1 pound ai per acre), Goal (oxyfluorfen -- 0.5 pound ai per acre), and COC 1% was made to cotton on July 21, 1997. Roundup D-Pak (glyphosate -- 0.75 pound ai per acre) and Induce at 1% v/v was applied to control winter vegetation on February 18, 1997.

      Granular in-furrow fungicide (Terrachlor Super X) was applied to cotton. An insecticide (Force 3G) was applied to corn at planting, and other insect control was provided according to Mississippi State University Extension Service recommendations.

      Nitrogen was applied as urea ammonium nitrate (UAN, 32% N) solution in early side-dress applications 10 inches to each side of the corn and cotton rows. No nitrogen was applied to soybean. A total of 150 pounds of N per acre was applied to corn in 1994, and a total of 180 pounds per acre was applied in 1995. Cotton received a total of 90 pounds of N per acre in 1995 and 100 pounds per acre in 1996 and 1997. In 1995, the growth regulator Pix (mepiquat) was applied to cotton on June 26 at 1 pint per acre and again on July 11 at 0.5 pint per acre.

      Cotton was harvested once each year with a mechanical picker adapted to harvesting plots. Corn and soybean were harvested with a two-row Massey 8 plot combine, with a header attachment for corn.

      The experiment was designed as a randomized complete block with six replicates. Individual plots consisted of four crop rows, 40 inches wide by 40 feet long. All data were obtained from the two center rows of each plot. Cotton response was measured by determining the stand, plant height, and yield each year. Cotton height was determined by measuring from the soil surface to the terminal of the plant. In May 1995, every 20th plant (8 to 12 plants total) in the two center rows of each plot was measured; in July 1995, every 10th plant (total of 14 plants) was measured. In 1996 and 1997, 15 consecutive plants in a selected row planted with the same planter unit were measured. An average was calculated for each plot and analyzed for treatment differences.

      The field was infested with a scattered population of ivyleaf, pitted, and willowleaf morningglory; nodding spurge; and annual grasses. Herbicide treatments, combined with hoeing, were effective in controlling weeds on the row, and cultivation controlled weeds between the rows. Purple nutsedge gradually increased each year but did not affect stand or yield. Zorial (norflurazon) was applied in 1997 to help in suppressing nutsedge.

      Weed control was evaluated in 1994 and 1995. On May 27, 1994, morningglory control was evaluated by counting plants on a 12-inch-wide band centered on each of two center rows for their entire length of 40 feet. On May 17, 1995, a visual estimate of broadleaf weed control was recorded (0 = no control; 100 = complete control).

Results

Weed Control

      In 1996 and 1997, weeds were controlled with uniform applications of herbicides to all treatments as needed (Table 2). Herbicides were augmented with hand hoeing and mechanical cultivation to prevent yield reductions due to weed competition.

Crop Response

      Corn and soybean yields were not affected by the application of Broadstrike + Treflan or Broadstrike SF + Dual, when compared with Treflan, Dual, or Canopy applied alone (Table 6). The low soybean yields in 1995 reflect the low plant population.

      Cotton -- In 1995, cotton stand was not affected by any treatment. In 1996, a marginal stand in May was evident with some treatments (Table 4). When determined again in early August, cotton stand was reduced in plots that had been planted in soybean treated with 2 pints per acre of Broadstrike + Treflan, as compared with plots where Broadstrike was not used. In 1996, after 2 years of applying Broadstrike SF + Dual to corn at 2 pints per acre, cotton stand was reduced, when compared with Dual alone. In 1997, cotton stand was marginally adequate because of extended cool, wet conditions. These conditions were considered responsible for the few treatment differences that occurred.

      Generally, cotton stand was not different in 1997 following corn or soybean. With one exception, this finding was true for cotton stands after 1 or 2 consecutive years of application of Broadstrike to corn or soybean. The exception was cotton planted in plots that had grown soybean treated with 2 pints per acre of Broadstrike + Treflan for 2 years.

      Cotton plant height in late May 1995 was reduced with Broadstrike + Treflan applied at both 1.6 and 2 pints per acre to soybean in 1994 (Table 5). Broadstrike SF + Dual (2 pints per acre) applied to corn in 1994 also reduced cotton height in 1995. When measured in May 1995, cotton height was less in plots that had been planted in soybean treated with Treflan alone in 1994, as compared to plots that had been planted in corn treated with Dual alone in 1994. July 1995 measurements revealed a similar cotton plant height reduction for Broadstrike + Treflan applied to soybean in 1994 at 2 pints per acre. However, cotton height was intermediate in plots that had received the 1.6-pint-per-acre Broadstrike + Treflan treatment in 1994; this finding indicates some plant compensation. Broadstrike SF + Dual applied to corn in 1994 at either rate did not reduce cotton height in July 1995. It is thought that the added plant residue from corn may have had a positive influence for reducing cotton injury.

      In 1996, cotton height in June was not affected by Broadstrike + Treflan applied to soybean in 1994. When compared with the Treflan-only treatment, Broadstrike + Treflan applied to soybean at 1.6 pints per acre in both 1994 and 1995 resulted in reduced cotton height, and the reduction was even greater with the 2-pint-per-acre treatment. This relationship also was true for Broadstrike SF + Dual applied to corn in 1994 and 1995, when compared with Dual alone.

      In 1997, cotton height in July was not affected by Broadstrike + Treflan applied to soybean or Broadstrike SF + Dual applied to corn in 1994, when compared with the standard herbicides. Likewise, cotton height was not affected by the applications of Broadstrike SF + Dual to corn in both 1994 and 1995. However, Broadstrike + Treflan applied to soybean at 2 pints per acre in both 1994 and 1995 reduced cotton height in July 1997, when compared with Treflan alone. On the other hand, the 1.6-pint-per-acre Broadstrike + Treflan treatment applied in 1994 and 1995 did not reduce cotton plant height in 1997, when compared with Treflan alone.

      Cotton yield in 1995 was not affected by Broadstrike SF + Dual applied to corn in 1994 (Table 6). However, when Broadstrike + Treflan was applied at 1.6 or 2 pints per acre to soybean in 1994, cotton yield in 1995 was reduced, when compared with Treflan alone. Cotton yields in 1996 and 1997 were not affected by any of the treatments, regardless of the timing of the applications.

Conclusion

References

Hurst, Harold R. 1997. Non-irrigated cotton following the application of Broadstrike SF + Dual to corn or Broadstrike + Treflan to soybean for 1 or 2 years. Proceedings of the Southern Weed Science Society. 50:46-47.

Jennings, Katherine M., Alan C. York, Roger B. Batts, and A. Stanley Culpepper. 1997. Sicklepod (Senna obtusifolia) and entireleaf morningglory (Ipomoea hederacea var. integriuscula) management in soybean (Glycine max) with flumetsulam. Weed Technology 11:227-234.

Johnson, III, W. Carroll, and Benjamin G. Mullinix, Jr. 1996. Phytotoxicity of flumetsulam on peanut. Weed Technology 10:481-487.

Jordan, David L., and Stephen H. Crawford. 1997. Rice (Oryza sativa) response to soil residues of selected herbicides. Weed Technology 11:379-383.

Sprague, Christy L., Edward W. Stoller, and Stephen E. Hart. 1997. Preemergence broadleaf weed control and crop tolerance in imidazolinone-resistant and -susceptible corn (Zea mays). Weed Technology 11:118-122.

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