C.O.R.N. Newsletter 2011-11

After a 46 month environmental impact assessment process, the ruling by the USDA means that U.S. farmers are free to plant genetically altered alfalfa without restrictions. I found it worthwhile to browse the documents outlining the USDA’s position and assessment of the issues surrounding glyphosate-tolerant (GT) alfalfa, available at http://www.aphis.usda.gov/biotechnology/alfalfa_documents.shtml.

Opponents to this ruling have been vocal in their disapproval. They are concerned that without any restrictions, genetically modified alfalfa might contaminate organic and conventional alfalfa seed production and increase the occurrence of glyphosate-resistant weeds. The USDA concluded these issues were not of sufficient impact to justify placement of restrictions on use of Roundup Ready Alfalfa. Further court battles have already been initiated by groups opposing the USDA’s decision.

Whether you agree or disagree with the decision, the fact remains that Roundup Ready Alfalfa has been approved for planting this spring. Many producers will find it to be useful on their farms, while others will not adopt the technology for practical or philosophical reasons. For those considering its use, what factors should be considered? Where might Roundup Ready Alfalfa be of benefit?

We know that good managers have been able to control weeds in alfalfa to acceptable levels with current herbicide optons and best management practices; however, glyphosate is effective on many types of weeds, so it adds another tool to the toolbox in the battle for high quality alfalfa. Glyphosate may be especially helpful during stand establishment because it causes less injury to seedling alfalfa than most other herbicides used during stand establishment. It also controls a broader range of weeds than other alfalfa herbicide options.

We participated in a 5-year study evaluating Roundup Ready Alfalfa across six states. Glyphosate was compared with an alternative herbicide program and a no herbicide check. At all locations, glyphosate controlled weeds with no crop injury during the establishment year. Controlling weeds with either glyphosate or alternative herbicides resulted in greater alfalfa yield and greater forage quality compared with not using herbicides. Controlling weeds increased crude protein content by 3 percentage units and decreased NDF by 3.8 units on average across all locations in the seeding year.

During the seeding year of our study, alfalfa yield was 0.44 ton/acre higher in the glyphosate treatment than in the alternative herbicide treatment, but total forage (alfalfa + weed) yields and forage quality did not differ between the glyphosate and alternative herbicide treatments.

After the seeding year at most locations, herbicides were NOT needed for weed control, even into the fifth year. The alfalfa stand was vigorous and provided sufficient competition to keep weeds from re-invading for the remainder of the stand life, through the fifth year.

Keep in mind that those studies were conducted with small plot equipment so wheel traffic was not an issue. Under normal farm production practices, alfalfa stands tend to be weakened by wheel traffic and weeds can re-invade sooner than under experimental plot conditions. This is particularly true with the large equipment used on many farms today. The Roundup Ready technology will be especially useful where troublesome perennial weeds take hold later in the life of the stand. Examples include thistles, curly dock, and dandelion, which are hard to control with other herbicides labeled for alfalfa. Winter annual weeds can also be controlled well by glyphosate.

Roundup Ready Alfalfa is being marketed by several companies. Variety tests established in 2006 showed the yield of Roundup Ready Alfalfa varieties compared very well with yield of conventional elite alfalfa varieties.

Roundup Ready seed will be more expensive, so the need for glyphosate in weed control should be weighed against the extra seed cost to use this technology. Consider your goals and the importance of weed-free alfalfa in your particular situation.

Glyphosate tolerant alfalfa should be grown judiciously because of the risk of developing glyphosate-resistant weeds. Resistant weeds are likely to develop more rapidly if glyphosate is used on all crops. Just as crop rotation is important, so is rotation of herbicide chemistries. In addition, some customers won’t buy genetically engineered crops, so you need to know what your customers will accept.

As genetically modified alfalfa use increases, we will learn the degree to which glyphosate tolerant genes occur in conventional and organic alfalfa.  In the USDA’s Record of Decision, this and other concerns are discussed in detail. It is well worth the read. I hope the concerns with contamination by genetically modified alfalfa can be adequately addressed so conventional and organic alfalfa production can continue without undue additional cost and effort by producers choosing those systems.

There are other genetically engineered alfalfa traits in development that are likely to be more useful than glyphosate tolerance. A good example is the development of alfalfa varieties with lower lignin concentrations, that have been shown to increase milk production in lactating dairy cows.

In summary, Roundup Ready alfalfa has been deregulated and will be planted this spring. If you decide to use this technology, I encourage you to read through the USDA’s “Record of Decision”, found at http://www.aphis.usda.gov/brs/aphisdocs/04_11001p_rod.pdf. Be informed and use this technology wisely as part of an overall well-managed system. Respect your neighbor’s desire and right to produce organic crops on his/her farm and work together so both of you can achieve your goals.