ISU Crop Performance Tests yield info on soybean herbicide traits

How do LibertyLink® soybeans compare to Roundup Ready® systems for yield and weed control?

Published on: Dec 7, 2015

  • The question comes up from time to time: “Is there an alternative to the Roundup Ready-based seed and herbicide system for soybeans?” Of course there is. “We have conventional soybean varieties with conventional herbicides and there is also the Liberty Link seed and Liberty herbicide system,” notes Paul Kassel, Iowa State University Extension field agronomist at Spencer in northwest Iowa. He talked to Wallaces Farmer about this topic at last week’s annual Integrated Crop Management Conference at ISU in Ames.
  • The interest in using an alternative herbicide/seed system occurs because of glyphosate resistant waterhemp weeds. The situation requires the use of conventional herbicides like Flexstar, Cobra or Ultra Blazer along with glyphosate applications. So if you have to use an additional herbicide along with glyphosate in your herbicide weed control strategy, should you change the whole system? Should you switch to a Liberty Link system rather than use a glyphosate or Roundup Ready system?

LIBERTY LINK VS. ROUNDUP READY: Which system yields better? It depends where you are planting them. If the right genetics are paired with the right agronomic characteristics and conditions and management in soybean fields, both systems can bring top yields.

  • One seed/herbicide system that can be considered is the Liberty system. That is, the Liberty tolerant soybean seed varieties and Liberty herbicide. “Part of this interest in Liberty Link occurs because there is no confirmed resistance to the group 10 herbicides,” says Kassel. “Liberty herbicide is the only Group 10 herbicide we have at this time.”
  • Liberty herbicide system requires a little more management Liberty herbicide is not glyphosate. “We have to use a little more management with Liberty herbicide,” he notes. Label guidelines for application of Liberty recommend a weed height of no more than 5-inch waterhemp, use of flat fan nozzles, a 40 PSI sprayer pressure and an application rate of 10 to 20 gallons per acre.
  • The available varieties and the performance of those varieties is always a big question. If you give up some yield performance, any cost savings and/or herbicide, cost savings is quickly erased.
  • The Iowa Crop Improvement Association and Iowa State University conduct corn and soybean performance tests. Reports, sortable spreadsheets, and data from individual locations are available at Following are some observations from Kassel regarding the soybean herbicide traits that illustrate the general performance of these varieties in the Iowa Crop Performance tests. The data listed here is general in nature, he points out, but it does show that the Roundup Ready trait soybean varieties and the Liberty trait varieties perform similar in this test.
Varieties in the north Iowa soybean tests
  BPA Number in test 
LibertyLink   61.5 11
Roundup Ready 1 62.5 7
Roundup Ready 2 Yield 63.0 87
North Iowa test Avg. 62.5 115
Varieties in the central Iowa soybean tests
  BPA Number in test
LibertyLink 56.0 13
Roundup Ready 1 55.7 11
Roundup Ready 2 Yield  55.7 78
Central Iowa test Avg. 55.0 110