Comparing the Liberty Link^® to the Roundup Ready^® System in soybeans—how do you know which to choose?

With the onset of resistant weeds such as marestail, waterhemp and Palmer amaranth in soybeans, many growers are looking to move from depending on the Roundup Ready system to a Liberty Link system. We need to take into consideration the differences between them and carefully consider which system will be best suited for your farming operation. I feel there are three main questions to consider when making this decision.

The first question is whether there any differences in yield. In researching this, I found that at one time there seemed to be slight differences in yield, but after reviewing this falls’ data, I think those differences are minimal to none now and growers no longer have to consider that a risk. But still, do your due-diligence and select varieties that perform.

The second question is based on weed control. In this case, there are several differences between the two systems. Both systems exhibit good weed control as long the chemistries of each herbicide are understood. First and foremost, both systems need to have a good pre-emergence chemical put down early and then layered applications to keep control of the resistant weeds.

The major difference between these two systems is that glufosinate (Liberty) is a contact herbicide while glyphosate (Roundup) is a systemic herbicide, meaning that it translocates within the plant itself. As a contact herbicide, Liberty needs thorough coverage with at least 15 –20 gallons of water compared to the 10 gallons of water a glyphosate normally gets sprayed at. Weeds need to be 4 inches tall or less. Liberty kill weeds in days compared to a week or more with Roundup.

You cannot spray Liberty on tall weeds and expect to kill them, especially waterhemp and Palmer amaranth that have many growing points. Weed spectrum and application windows are also different—glufosinate is labeled for control of 140 species, while glyphosate is labeled for control of about 250 different weed species. Liberty can be sprayed up until R1 (bloom stage), while Roundup is R3 (pod set stage) and the rainfast period for Roundup is as short as 30 minutes, while Liberty’s is 4 hours.

The third question is the cost of each system. In the Liberty Link system, the cost per acre will be higher due to the cost of the Liberty herbicide itself compared to the cost of the Roundup. This amounts to $10 to $15 per acre higher on average. However, the seed costs between the two systems are virtually the same with maybe a slightly lower cost advantage for Liberty Link seeds.

Dawn Kielsmeier is an agronomy sales specialist with Pearl City Elevator in Baileyville, Ill. She has a B.S. in dairy science and an M.S. in agronomy, both from University of Illinois and has been a CCA since 1993. She started her career with Riverview FS and American Cyanamid and worked for a co-op in central Wisconsin as well as at Landmark Services Cooperative out of Durand, Ill., before joining Pearl City.