Steve D. Ruhl, Agriculture and Natural Resources Extension Agent
To evaluate the effect of Cobra herbicide on yields of Roundup Ready soybeans.
| Cooperator: | Tom Weiler | Soil Test: | pH 7.0 |
| County: | Morrow | P 23 ppm | |
| Nearest Town: | Chesteville | K 154 ppm | |
| Drainage: | Systematic | Fertilizer: | None |
| Soil Type: | Sloan silty clay loam | Planting Date: | May 1 |
| Tillage: | Conventional | Planting Rate: | 199,500 seeds/A |
| Previous Crop: | Corn | Row Width: | 10-inch |
| Variety: | Golden Harvest H-3414RR | Harvest Date: | October 19, 2001 |
| Herbicides: | |||
| POST | Roundup Ultra 1 qt/A + AMS |
The field was alternately sprayed in 45-foot strips throughout the field. Six ounces of Cobra plus 0.25% v/v of nonionic surfactant was sprayed when the soybeans were at the V5 - V6 stage. The treatments were replicated six times. The soybeans were just beginning to bloom. The Cobra was sprayed at 20-gallons per acre and 30 psi on June 27. Yields were measured by harvesting a 20-foot-wide strip out of the centers of the sprayed and untreated strips that were 460 feet long. Yield was measured by a weigh wagon. The size of the harvested portion of each strip was 0.211 acre.
| Table 1. Soybean Yield | |
| Treatment | Yield |
| (bu/A) | |
| Cobra | 56.1 |
| None | 56.8 |
| LSD (0.05) | NS |
| F | 6.0 |
| CV (%) | <1 |
Cobra has been shown to increase soybean yield through disease suppression, especially for Sclerotinia stem rot (white mold). However, the results of this study showed no yield benefit to the use of Cobra. Conditions in July and August greatly reduced the opportunity for Sclerotinia stem rot to be present. The application of Cobra did delay maturity by four to five days.
The author would like to thank Golden Harvest for providing the soybeans and Valent for the Cobra and nonionic surfactant used.
For additional information, contact:
Steve Ruhl
Ohio State University Extension, Morrow County
871 W. Marion Rd., Suite 102
Mt. Gilead, OH 43338
419-947-1070
ruhl1@postoffice.ag.ohio-state.edu