1995 Res. Prog. Rep. West Soc. Weed Sci.
Jointed goatgrass has become an especially troublesome weed in winter wheat. The current herbicides do not selectively control jointed goatgrass in winter wheat because the two plants are genetically similar. The objective of this study was to investigate the integration of common tillage regimes and herbicides for jointed goatgrass management. The experiment was initiated in the fall prior to a summer fallow season. Three common tillage regimes were evaluated; no-till, conservation tillage, and conventional tillage. Two herbicides were evaluated for jointed goatgrass control. Clomazone was applied in the fall as a preemergence herbicide. A 2,4-D plus glyphosate combination was applied in the spring as a postemergence herbicide at the three to five leaf stage of jointed goatgrass. Control plots were not treated with herbicide and followed a no-till regime. The experiment was set up as a split-split plot design with tillage in strips and herbicide treatments in strips across the tillage treatments. This design in strips and herbicide treatments in strips across the tillage treatments. This design allowed for common tillage equipment to be pulled through the plots at normal speeds.
Winter wheat was planted in the fall after the fallow season. No jointed goatgrass control strategies were implemented during the crop season. Wheat was harvested with an 8 foot wide plot combine. The combine was designed to determine harvest weights and distribute a sample for analysis from each plot. The percent of wheat and jointed goatgrass seed in the harvest bags was measured. Wheat yields and percentages were statistically analyzed. Wheat yields were five times higher in the conventional plots than in either no-till or conservation tillage plots. The samples consisted of approximately 5 to 10 percent jointed goatgrass in the conventional tillage. 55 to 75 percent jointed goatgrass in the conservation tillage, and 50 to 60 percent in the no-till regime. Conventional tillage treatments, which included three rodweedings at 3 week intervals during the summer fallow, provided the greatest control of jointed goatgrass. No statistical difference was found among herbicide treatments.
Table1. Percent jointed goatgrass in winter wheat harvest and wheat yields following three tillage regimes.
| Tillage Regime | Cloa 0.5 lb/A | Glya + 2,4-D 40 oz/A | Control | Wheat Yield |
| ————————-%————————– | –bu/A– | |||
| No-tillNon-tilled | 52.86 | 49.89 | 53.23 | 5.58 |
| Conservation tillageChisel plow (Fb) Skewtreader (Spb)Subsoiler (F) Skewtreader (Sp) | 60.36 71.36 |
58.41 73.70 |
60.24 73.73 |
6.29 6.92 |
| Conventional tillageChisel plow (F) Rodweeder (Sub)Chisel plow (Sp) Rodweeder (Su)
Subsoiler (F) Rodweeder (Su) |
8.54 8.54 9.57 |
8.03 5.58 7.00 |
12.27 5.96 5.40 |
30.32 34.69 30.52 |
| LDS @ 0.05 | ————- | ——–11.3———- | ———- | –6.86— |
aClo=Clomazone, Gly=Glyphosate
bF=Fall, Sp=Spring, Su=Summer
cThree summer rodweedings.