ISU Crop Performance Tests yield info on soybean herbicide traits

ISU Crop Performance Tests yield info on soybean herbicide traits

How do Liberty Link soybeans compare to Roundup Ready systems for yield and weed control?

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.

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.

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?

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

                                                Bu./a     Number in test       

Liberty Link                              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

                                                Bu./a    Number in test       

Liberty Link                              56.0        13

Roundup Ready 1                   55.7        11

Roundup Ready 2 Yield          55.7        78

Central Iowa test Avg.             55.5      110

Earn soil and water CCA credits at Soil Health Conference
In addition to weed control and many other crop topics, soil health was also discussed at last week's 2015 ICM meeting in Ames. It was pointed out that you can earn soil and water Certified Crop Adviser credits by attending the Iowa Soil Health Conference on February 2-3, 2016 at ISU in Ames.

"The upcoming soil health conference in Ames, Iowa, February 2-3, 2016 is fast approaching," notes Mahdi Al-Kaisi, ISU Extension soil management specialist. This Inaugural Soil Health Conference will provide a unique opportunity to Certified Crop Advisers (CCA) who are seeking soil and water credits. The conference has been approved for a total of 17 soil and water credits during the two days.

Interesting topics, speakers to provide information you can use
A wide range of topics addressing principles and management practices that are essential for building soil health and productivity will be covered by well-established scientists from ARS-USDA and land grant universities. Topics will include soil management practices and cropping systems that are effective in reducing weather variability effects on yield and soil quality, cover crops establishment and their role in reducing soil erosion, cropping systems effect on soil biology, and many other topics will be presented during the conference.

"The conference is designed to provide research-based information for professional agronomists, farmers and the public who are interested in building and sustaining soil health," says Al-Kaisi. "Take advantage of this opportunity and visit the conference website for more information." Go to The registration deadline is January 16, 2016.

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