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Roundup Ready® Xtend Crop System Weed Control Efficacy Comparison

January 12, 2021

The Roundup Ready® Xtend Crop System with XtendFlex® soybeans provides growers with soybean products that have herbicide tolerance to glufosinate, glyphosate, and dicamba.
In 2020, two herbicide tolerant soybean platforms launched Enlist E3® soybeans and LibertyLink® GT27™ soybeans.
- Enlist E3® soybeans confer tolerance to 2,4-D choline, glyphosate, and glufosinate that allows growers to use Enlist Duo® herbicide or Enlist One® herbicide to control weeds.
- LibertyLink GT27 soybeans have a tolerance to glyphosate, glufosinate, and isoxaflutole. To date, Alite 27® is the only group 27 herbicide product registered for use on GT27™ soybeans.
The objective of the trial was to evaluate the three soybean systems: Roundup Ready® Xtend Crop System with XtendFlex soybeans, the Enlist™ weed control system with Enlist E3 soybeans, and the GT27™ Soybean Performance with LibertyLink G27 soybeans.

Location Salina, KS
Gothenburg, NE Soil Type Silt loam

Previous
Crop Corn Tillage
Type Conventional
Strip tillage

Planting Date 5/20/20
5/8/205 Harvest Date 10/5/20
10/20/20

Potential Yield
(bu/acre) 50 Seeding Rate
(seeds/acre)
160,000

Single replication demonstrations were planted on sites with very high Palmer amaranth pressure.
Plot size was 10 by 243 feet at Salina, KS and 10 by 250 feet at Gothenburg, NE.
Three soybean products for each weed control platform were used. The maturity groups ranged from 3.6 to 4.2 at Salina and 2.5 to 3.0 at Gothenburg.
Herbicide application dates
- Salina
  - Pre-emergence (PRE): May 20
  - Early Post (EPOST): June 9
  - Late Post (LPOST): July 6
- Gothenburg
  - PRE: May 8
  - EPOST: June 18
  - LPOST: July 2

Table 1. Roundup Ready® Xtend Crop System, XtendFlex® soybeans.

Table 2. Enlist™ weed control system, Enlist E3® soybeans.

Table 3: GT27™ Soybean Performance System, LibertyLink® GT27™ soybeans.

Weed control efficacy ratings were taken on a scale of 0 to 100% with 0 indicating no control and 100% indicating compete control of the evaluated weed species.
Weed control efficacy ratings for each system were averaged across the three soybean products for each system for each rating date.
Yields were low at both sites due to late season moisture stress and were not reported.

The early POST (EPOST) applications were applied to soybeans at the V4 growth stage when Palmer amaranth plants were approximately 4.5 inches tall.
The late POST (LPOST) applications were applied to all soybeans prior the R1 growth stage when Palmer amaranth plants were approximately 2-12 inches tall. A disparity in weed height was observed in this trial because the EPOST Roundup Ready® Xtend Crop System with XtendFlex® soybeans treatment performed better than the other two EPOST systems.

Table 4. Percent Palmer amaranth control for each soybean crop production system (2020).

Figure 1. Images of the soybean weed control systems 26 days after late post application, July 28, 2020 at Gothenburg, NE.

Early season weed control efficacy initially appeared to be similar between the three weed control systems at both sites with a small advantage for the Roundup Ready® Xtend Crop System with XtendFlex® soybeans platform.
Differences in weed efficacy became more apparent as the growing season continued with the XtendFlex® platform showing better weed control efficacy at both the mid-season and pre-harvest observations.
Palmer amaranth is a difficult weed for farmers to control effectively. A system like the Roundup Ready® Xtend Crop System with XtendFlex® soybeans that can help provide season-long control by layering residuals is one way to help achieve effective weed control.
Farmers should visit with their local Bayer Crop Science Sales Representative about the possible benefits the Roundup Ready® Xtend Crop System with XtendFlex® soybeans platform can bring to their operation.

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