Researchers Check Up on Herbicides

Soy and corn results available here.

In an effort to evaluate weed management strategies in corn and soybeans, researchers at the Southern Research and Outreach Center in Waseca conducted trials last year at six sites.

Trials were held in Waseca, Lamberton and Rochester. Weeds evaluated were giant foxtail, yellow foxtail, common ragweed, giant ragweed, velvet leaf, tall waterhemp and common lambsquarters. Researchers used Pioneer's corn hybrid 38H65 which has both the glyphosate tolerance gene and Liberty Link gene. They used Dairyland's DSR 199RR soybean which is Roundup Ready and has genetic sulfonylurea tolerance (tolerance to post herbicides Classic and HarmonyGT).

What researchers noted

Tom Hoverstad, University of Minnesota Southern Research and Outreach Center scientist, says they evaluated products using a systems approach, the same way they are marketed to growers.

In soybeans, returns per acre ranged from $182 (40.9 bushels per acre yield) for a pre- and post-plant application to $243 (50.4 bushels per acre) for a two post-plant application. Cost per acre ranged from $31.60 (43.4 bushels per acre) to $58.81 46.5 bushels per acre) for herbicides.

In corn, returns per acre ranged from $353 (160 bushels per acre yield) to $410 (188 bushels per acre), both under the pre-emergence/post system. Cost per acre ranged from $29.42 (157-bushel yield) to $60.07 (177-bushel yield).

For soybeans overall, Hoverstad says it has been difficult for conventional herbicides to compete with the Roundup Ready system in university trials.

"There are special markets for soybeans that are not Roundup Ready and there are herbicides available for this," he says. "However, cost is usually higher for conventional herbicides and that should be accounted for in the special soybean markets."

Hoverstad notes the two- pass glyphosate systems cost slightly more than one- pass systems, but they offer slightly better weed control and soybean yields than one pass systems.

"Returns for both systems are quite similar, but the advantage of a two-pass system is consistency," he says.
Corn growers have more choices when choosing weed control.

"In U of M trials, the conventional, Liberty and glyphosate systems in corn performed quite similar and there are good options in each system," Hoverstad says. "Corn producers can effectively rotate herbicides and hopefully reduce odds of selecting glyphosate tolerant weeds."

As growers compare corn herbicide evaluation data, Hoverstad says trying to pick the best one would be difficult, particularly in the pre/post approach.

"The two-pass programs usually did better than the one-pass programs," he says, "especially when you look at the post I (V2) corn treatments."

2006 Soybean Herbicide Evaluation

Giant Yellow Common Tall Redroot Common Giant
Rate foxtail foxtail lambsquarters waterhemp pigweed ragweed ragweed Velvetleaf Yield Cost Returns
- Number of locations -
  5 1 5 3 2 2 1 1 6   6
(pt/A) -----------(% control)---------- (bu/A) ----($/A)-----
43 oz / 4 oz + 0.3 oz + 0.25% + 3 qt 84 98 96 77 91 69 85 99 43.3 54.35 197
2.5 / 0.3 + 0.25% + 3 qt 79 95 96 80 80 75 93 94 44.9 43.63 217
43 oz / 3 pt + 0.125% + 3 qt 92 97 98 87 87 41 67 99 40.9 54.73 182
- 0 0 0 0 0 0 0 0 13.6 0.00 79
3 oz / 0.3 oz + 8 oz + 9 oz + 0.25% + 3 qt 91 95 75 93 99 97 95 98 46.5 58.81 211
3 oz / 0.3 oz + 8 oz + 9 oz + 0.25% + 3 qt 88 97 79 98 96 98 97 95 45.8 No Label
1.5 / 16 oz + 8 oz + 0.125 oz + 1% + 2.5% 93 93 95 98 99 86 89 92 43.0 57.79 191
4 / 22 oz + 3 qt 98 95 96 97 99 83 71 97 44.8 48.97 211
1 + 12.6 oz / 22 oz + 3 qt 98 95 98 97 99 81 73 98 45.3 56.38 207
1.8 oz / 22 oz + 4 qt 97 93 99 98 98 96 95 96 48.6 46.46 235
1 / 24 oz + 3 qt 98 97 99 98 99 89 90 98 47.3 48.13 226
1.5 / 24 oz + 3 qt 97 97 97 97 99 94 79 97 46.8 52.41 219
2 oz / 22 oz + 3 qt 95 88 98 98 99 81 73 97 45.8 45.37 220
1.5 oz + 0.5 oz / 22 oz + 3 qt 96 88 98 98 91 85 92 99 48.6 47.92 234
1.5 oz + 3 oz / 22 oz + 3 qt 95 85 98 98 92 80 75 96 45.3 45.99 217
0.5 / 24 oz + 3 qt 93 83 98 94 99 79 80 98 45.1 42.59 219
0.8 / 24 oz + 3 qt 92 83 98 94 89 86 86 99 46.0 45.42 221
0.3 / 24 oz + 3 qt 96 93 97 92 72 87 85 97 48.1 45.40 233
- 100 100 100 100 100 100 100 100 50.5 0.00 293
22 oz + 3 qt / 99 98 99 99 99 99 99 99 50.4 49.46 243
22 oz + 3 qt
24 oz + 3 qt / 24oz + 3 qt 99 98 99 99 99 99 99 99 49.4 No Label
0.5 oz + 22 oz 0,25% + 3 qt 94 84 97 94 99 76 71 94 44.0 34.75 221
0.5 oz + 0.33 oz + 22 oz 0.25% + 3 qt 97 85 98 93 95 78 70 98 44.9 38.97 222
22 oz + 3 qt 93 78 97 87 97 73 69 98 43.3 31.60 220
LSD(0.10) 4 4 4 5 9 13 10 3 2.2 13

2006 Corn Herbicide Evaluation

Giant Yellow Common Giant Tall Common
Herbicide Rate foxtail foxtail ragweed ragweed Velvetleaf waterhemp lambsquarters H2O Yield Cost Returns
- Number of locations -
    5 1 2 2 1 3 3 6 6   6
Preemergence (product/A) (% control) (%) (bu/A) ($/A) ($/A)
Keystone LA + Hornet WDG 2.2 qt + 4oz 96 85 99 72 99 98 99 18.4 164 42.65 364
Preemergence/POST III (V4 corn)
Surpass / Hornet + Callisto + atrazine + COC + AMS 2.75 pt / 3 oz + 0.75 oz + 8 oz + 1% + 3 qt 95 88 94 98 97 98 99 18.5 186 50.16 409
Outlook / Status + atrazine + NIS + AMS 21 oz / 5 oz + 16 oz + 0.25% + 2.5 lb 94 83 99 93 99 97 98 18.2 183 53.69 400
Define SC/ Liberty+atrazine+AMS 12 oz / 32 oz + 16 oz + 3.5 qt 91 91 98 84 99 92 97 18.5 179 47.69 393
Define SC/ Option+Distinct+MSO+28% 12 oz / 1.5 oz + 2 oz + 1.5 pt + 3 pt 90 91 97 88 99 88 97 18.9 166 49.90 355
Define SC/ Laudis+MSO+28% 12 oz / 3 oz + 1.5 pt + 3 pt 95 93 98 91 99 96 97 18.6 187
Cinch/ Steadfast+Callisto+atrazine+COC+AMS 1 pt / 0.75 oz + 2 oz + 16 oz +1% + 3 qt 94 94 99 91 99 96 99 18.7 180 58.35 384
Dual II Magnum/ Callisto+atrazine+COC+28%N 1 pt / 3 oz + 16 oz + 1% + 2.5% 89 84 94 94 99 99 99 18.2 177 60.07 377
Outlook / Aim+atrazine+Clarity+NIS 21 oz / 0.5 oz + 16 oz + 3 oz + 0.25% 90 83 98 73 99 98 99 18.3 160 44.28 353
Harness / Roundup WeatherMax+AMS 1.25 pt / 22 oz + 3 qt 98 93 97 89 99 97 96 18.5 181 50.75 395
Lumax / Touchdown Total+AMS 3 pt / 24 oz + 3 qt 98 95 99 95 99 97 99 18.2 188 54.89 410
Lumax / Liberty+AMS 3 pt / 24 oz + 3 qt 89 89 95 93 99 98 99 18.1 182 45.72 404
Keystone LA/ GlyphomaxXRT+AMS 1.1 qt / 24 oz + 3 qt 96 93 98 86 99 98 99 18.6 175 48.95 383
Outlook / Roundup WeatherMax+Status+AMS 12 oz / 14 oz+2.5 oz +3 qt 98 91 99 91 99 96 92 18.6 183 46.95 403
Dual II Magnum / Touchdown Total + Callisto + AMS 1 pt / 24 oz + 3 oz + 3 qt 97 93 99 94 99 96 99 18.7 190 63.32 403
Resolve / Atrazine + Roundup OriginalMax + NIS + AMS 1 oz / 16 oz + 22 oz + 0.25% + 3qt 94 90 97 92 99 93 98 18.7 181 44.31 400
GF 1834 / Glyphomax XRT + AMS 1.75 pt / 24 oz + 3 qt 98 94 99 92 99 98 99 18.4 179
Checks
Weedy Check - 0 0 0 0 0 0 0 18.6 49 0.00 119
Weed-Free Check - 100 100 100 100 100 100 100 18.6 187 0.00 460
POST I (V2 corn)
Stout + Lumax + NIS 0.5 oz + 2 pt + 0.25% 77 89 97 68 99 97 99 18.6 157 29.42 357
Lumax + Touchdown Total + AMS 3 pt + 24oz + 3 qt  81 92 97 80 99 93 99 17.9 167 47.89 368
Lumax + Liberty + AMS 3 pt + 20oz + 3 qt  81 92 99 76 99 98 99 18.0 163 38.72 367
POST III (V4 corn)
Steadfast+Callisto+atrazine+COC+AMS 0.75 oz + 2 oz + 16 oz +1% + 3 qt 82 84 99 91 99 82 98 18.4 175 37.40 395
Resolve + atrazine + Roundup OriginalMax + NIS + AMS 1 oz + 16 oz + 22 oz + 0.25% + 3 qt 94 84 95 91 96 78 96 18.9 179 37.31 400
LSD (0.10) 4 5 4 7 2 5 1 0.5 10 26
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