Andy Kleinschmidt, Extension Agriculture and Natural Resources Agent
Gary Prill, Extension Associate, Farm Focus/Research Coordinator
To evaluate weed control effectiveness of three different postemergence herbicides based on the time of day in which applications were completed in soybeans. This study will help to show farmers the effect different time of the day applications can have on weed control when these specific herbicides are used.
| Cooperator: | Marsh Foundation/ | Fertilizer: | None applied |
| Farm Focus | Herbicides: | ||
| County: | Van Wert | POST: | 8 oz/A Fusion + |
| Nearest Town: | Van Wert | (June 24) | 1% v/v COC |
| Soil Type: | Hoytville silty clay loam | POST: | Variable |
| Drainage: | Tile - nonsystematic | (July 1) | (see Methods) |
| Previous Crop: | Corn | Insecticide: | None applied |
| Tillage: | Fall disk/ripper, spring | Variety: | Seed Consultants |
| field cultivate (2 times) | SC9302 RR | ||
| Soil Test (2002): | pH 6.1, P 45 ppm | Row Width: | 15 inch |
| K 161 ppm | Planting Rate: | 200,000 seeds/A | |
| Planting Date: | June 1, 2002 |
There are a total of 18 different treatments in this study involving three different post-emergence herbicide programs applied at six different times during the day. The study is set up in a randomized complete block design with four replications. The study was planted using a John Deere 7000 Maxemerge six-row planter with a splitter attachment to obtain a 15-inch row spacing. Herbicide treatments are:
Seven days prior to the application of the treatments, a postemergence application of Fusion @ 8 oz/A was sprayed perpendicular to all the plots with a 45’ Great Plains field sprayer to control grasses. Applications of the treatments were made on July 1 at 6 a.m., 9 a.m., 12 noon, 3 p.m., 6 p.m., and 9 p.m. The following weeds were present at the time of application (weed size in parenthesis): lambsquarters (4 to 6”), velvetleaf (4 to 6”), common cocklebur (4 to 6”), and common ragweed (2 to 4”). All herbicides were applied in 15 gallons of spray solution per acre with 36 to 40 psi pressure using flat fan nozzles with a CO2 delivery system on an ATV. Plot spray size is 12.5 feet wide by 535 feet long with a 2.5 foot running check between each plot. The plots were visually evaluated on August 29 for control of lambsquarters, velvetleaf, and pigweed. Each weed species in a plot was evaluated on its percent control between 0 and 100. One hundred percent represents perfect control, while 0 represents no control. Ohio State University Extension personnel conducted the evaluations.
Table 1. Environmental Conditions and Visual Evaluation of Control of Velvetleaf in Soybeans.a
| Application | Wind Speed, | Air | Roundup | |||
| Time of Day | Dew | Direction | Temperature | Flexstar | FirstRate | UltraMax |
| (mph) | (oF) | (%) | (%) | (%) | ||
| 6:00 a.m. | no dew | 0-5, west- | 77 | 69 c | 59 d | 100 |
| southwest | ||||||
| 9:00 a.m. | no dew | 0-5, west | 85 | 77 ab | 63 cd | 100 |
| 12:00 p.m. | no dew | 0-5, west | 93 | 75 abc | 75 b | 100 |
| 3:00 p.m. | no dew | 4-8, west | 94 | 80 a | 76 ab | 100 |
| 6:00 p.m. | no dew | 5-10, west | 96 | 76 abc | 81 a | 100 |
| 9:00 p.m. | no dew | 0-5, west | 90 | 60 d | 67 c | 99 |
| LSD (0.05) | 7.6 | 5.6 | NS | |||
| F-test | 8.2 | 20.3 | 1 | |||
| a Means followed by the same letter in the same column are not significantly different. | ||||||
NS = not significant
Only velvetleaf control was summarized in the results section, as velvetleaf distribution was very consistent throughout the plots. Pigweed distribution was much lower than that of velvetleaf, and several plots could not be rated for pigweed control, so it was not included in the results. Lambsquarters control was also not included in these results, since the use of FirstRate and Flexstar do not provide effective control of lambsquarters.
FirstRate and Flexstar showed similar trends for velvetleaf control based on time of day for herbicide application. For Flexstar, application times between 9 a.m. and 6 p.m. provided greater control of velvetleaf than the application times of 6 a.m. and 9 p.m. For FirstRate, application times between noon and 6 p.m. provided greatest control of velvetleaf compared to application times of 6 a.m., 9 a.m., and 9 p.m. Roundup Ultra-Max performance on velvetleaf was unaffected by time of day of application for this study.
The authors express appreciation to Jeff Stachler and Ed Lentz for their cooperation with weed ratings, and Mark Loux and Anthony Dobbels for their assistance with the study design.
For additional information, contact:
Andy Kleinschmidt or Gary Prill
Ohio State University Extension, Van Wert County
1055 South Washington Street
Van Wert, OH 45891
419-238-1214
kleinschmidt.5@osu.edu or prill.1@osu.edu