January 15, 2020
TRIAL OBJECTIVE
- This trial compared the effect of four different weed control systems, LibertyLink® GT27™ soybeans, Enlist E3® soybeans, Roundup Ready 2 Xtend® soybeans, and XtendFlex® soybeans on glyphosate-resistant (GR) Palmer amaranth control, soybean injury, and soybean yield potential.
RESEARCH SITE DETAILS
Location - Gothenburg, NE
| Soil Type | Silty loam | Planting Date | 5/13/19 |
| Previous Crop | Corn | Harvest Date | 10/18/19 |
| Tillage Type | Conventional | Seeding Rate (seeds/acre ) | 160K |
For each trait system, three soybean products were planted in strips that were four rows wide and 200 feet long per soybean product.
LibertyLink® GT27™ soybean product RMs ranged from 2.2 to 2.9, Enlist E3® soybean product RMs ranged from 2.4 to 3.0, Roundup Ready 2 Xtend® soybean product RMs ranged from 2.4 to 3.2, and XtendFlex® soybean product RMs ranged from 2.3 to 2.7.
Each soybean product for a given trait received the same herbicide treatments (Table 1).
Preemergence (PRE) treatments were applied one day after soybean planting and postemergence (POST) treatments were applied at the V3 soybean growth stage when Palmer amaranth plants were four to six inches tall.
Plots were visually evaluated for percent GR palmer amaranth control and soybean injury.
UNDERSTANDING THE RESULTS
At 42 days after the PRE treatments, Palmer amaranth control ranged from 30 to 50% across systems (Figure 4), which led to heavy pressure at the POST application timing at this location.
No soybean injury was observed from the PRE treatments, but soybean injury from the POST treatments was significantly (p<0.001) higher in the Enlist E3® soybean system compared to other 3 systems at this location (Figure 5).
At 37 days after the POST treatments, Palmer amaranth control was significantly (p<0.001) higher in the Roundup Ready 2 Xtend® (98%) and XtendFlex® (97%) soybean systems compared to the Enlist E3® (78%) or LibertyLink® GT27™ (50%) soybean systems (Figure 6).
Roundup Ready 2 Xtend® and XtendFlex® soybean yields were significantly higher than LibertyLink® GT27™at this location (p<0.001) (Figure 7).
KEY LEARNINGS
To manage tough-to-control weeds like Glyphosate-resistant Palmer amaranth, it is essential to choose a herbicide program that provides effective foliar and residual control.
Glyphosate resistant Palmer amaranth control was significantly higher in the Roundup Ready 2 Xtend® and XtendFlex® soybean systems than in the Enlist E3® and LibertyLink® GT27™ soybean systems at this location in 2019.
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