Roundup Ready alfalfa: Where does it fit in eastern management?

It’s common to use cool-season grasses to establish a new alfalfa stand in the East. That requires different management strategies when incorporating Roundup Ready alfalfa in your forage rotation.

By Ev Thomas

Ev Thomas

Now that most of the legal dust has cleared, farmers are able to purchase and plant Roundup Ready alfalfa. This is great news for farmers in the Western U.S., where almost all alfalfa is seeded without a grass companion crop. The ability to apply glyphosate (Roundup) to alfalfa will allow these farmers improved control of many annual and perennial weeds. These weed problems are serious enough  that many California farmers have been harvesting their first cut of alfalfa abnormally early in order to permit the timely application of contact herbicides. With Roundup Ready alfalfa, glyphosate can be used not only during establishment, but between harvests to control summer annual grasses including green foxtail, yellow foxtail and barnyardgrass. It’s expected Roundup Ready alfalfa will quickly become very popular in alfalfa-growing regions of the West.

The situation in the Eastern U.S. is quite different, in that a much higher percentage of alfalfa is seeded with a cool-season grass such as timothy, orchardgrass or tall fescue. According to a survey several years ago, about three-fourths of alfalfa in New York is seeded with a grass, with a similar proportion likely in many New England states. Clear-seeded alfalfa will remain the norm where alfalfa is harvested and sold as dry hay, but the acreage of alfalfa-grass is reportedly increasing in a number of dairy farming areas, including the Midwest. Glyphosate will kill forage grasses; therefore, where does Roundup Ready alfalfa fit in the Eastern U.S?

 

Alfalfa vs. alfalfa-grass

Alfalfa has earned its title as “queen” of forage crops. Alfalfa’s taproot allows it to remain productive under moderately dry conditions, and few forage crops have the ability to produce more protein per acre. However, this “queen” has rich tastes, and alfalfa needs fertile, well-drained soils to be most productive. Fields with variable drainage may be better suited to alfalfa-grass. In many years of growing alfalfa-grass at Miner Institute we’ve learned the two species adapt to variable drainage conditions. Where soil drainage is good, the alfalfa dominates the stand; where drainage is moderate, we get a nice mixture of alfalfa and grass.

One place not to seed alfalfa-grass is in fields where soil fertility, particularly potassium, is poor. That’s because the root systems of cool-season grasses are much more efficient at finding and using potassium and other nutrients. Seeding alfalfa-grass into a field with low potassium levels may result in a good initial stand of alfalfa, but as the grass becomes well-established it will rob the alfalfa of this essential nutrient. The alfalfa may go into the winter in decent shape, but by spring what was an alfalfa-grass stand is now predominantly grass. If the field isn’t well-enough drained for clear alfalfa to be a good option, rather than seeding alfalfa-grass it may be better to use red clover even though clover stands don’t usually last as long as alfalfa.

 

Seed alfalfa, then grass?

One option being considered by agronomists is to seed Roundup Ready alfalfa, apply glyphosate postemergence, and then interseed a cool-season grass into the young alfalfa stand. Agronomists at Pennsylvania State University seeded orchardgrass 4 and 5 weeks after planting Roundup Ready alfalfa, immediately after glyphosate application. At the time of orchardgrass seeding the alfalfa was at the 2 to 3 trifoliate stage. While there was less orchardgrass during the seeding year, by the following year there was no significant difference between the yield of orchardgrass in the Roundup Ready alfalfa-orchardgrass stand vs. where alfalfa and orchardgrass were seeded at the same time with no application of glyphosate. While the Penn State research didn’t investigate the influence of different grass seeding rates, it’s possible that a slightly higher grass seeding rate 4-5 weeks after alfalfa seeding would produce even better results. Most grass seed (with reed canarygrass the notable exception) is pretty inexpensive.

 

Alfalfa dollars and sense

It doesn’t look like there will be any serious shortages of Roundup Ready alfalfa seed. However, this technology comes at a price. The cost of the Roundup Ready trait differs from East to West: $150 per 50-lb. unit in the West; $125 per unit in the East. This is in addition to the cost of the alfalfa seed, but farmers purchasing Roundup Ready alfalfa seed will know this because the “tech fee” will appear as a separate item on the invoice. In the East, the trait will add $2.50/lb. to the price of the alfalfa seed or, at a 16 lbs./acre seeding rate, an additional $40/acre. Add in the cost of an application of glyphosate and it’s over $50/acre. However, we have to amortize this cost over the life of the stand, and assuming even a moderately short 3-year stand life, it wouldn’t take much improvement in yield and/or forage quality to amount to at least $50/acre, especially with current alfalfa hay prices of $150 or more per ton.

Another factor to consider is that not all seed in a bag of Roundup Ready alfalfa is resistant to glyphosate. About 5% of the seed is not resistant, and the seedlings from this seed will be killed by the herbicide. However, in most cases the alfalfa seeding rates used by farmers are high enough that the loss of 5% of the seedlings shouldn’t be a problem.

 

The bottom line

There are several advantages of alfalfa-grass vs. pure alfalfa stands, including less susceptibility to certain insect pests, less alfalfa winterkill due to heaving, and in cases of severe alfalfa winterkill the presence of grass in the field may provide some early-season forage to harvest while you’re still figuring out what to do next. Many farmers in the Eastern U.S. will find that alfalfa-grass, even with limited weed control options, is their best alternative. However, those farmers who have the type of soils that pure alfalfa requires may find the combination of Roundup Ready alfalfa and a timely application of glyphosate will result in superior weed control at a reasonable cost.

 

FYI

Ev Thomas is president of Oak Point Agronomics Ltd., Hammond, N.Y. Reach him via phone: cell 518-570-7408; e-mail: ethomas@oakpointny.com or visit www.oakpointagronomics.com.

 

 

Two more lawsuits filed

Two lawsuits related to Roundup Ready alfalfa had been filed as Eastern DairyBusiness went to press.

Attorneys for the Center for Food Safety (CFS) and Earthjustice filed a lawsuit against USDA, arguing the agency’s unrestricted approval of Roundup Ready alfalfa was unlawful.

In late January 2011, USDA’s Animal and Plant Health Inspection Service announced the deregulation of Roundup Ready alfalfa, without conditions, one of three options outlined in a court-ordered Environmental Impact Statement (EIS). In approving the genetically engineered seed, USDA declared it “as safe as traditionally bred alfalfa.”

A second lawsuit, filed against Monsanto by the Public Patent Foundation (PUBPAT), challenges the company’s patents on genetically modified seed. Filed on behalf of organic plaintiffs, the organization said the lawsuit seeks preemptive protection from being accused of patent infringement, should their crops ever become “contaminated” by Roundup Ready alfalfa seed or pollen.

No court action regarding the sale or planting of Roundup Ready alfalfa had been announced at the Eastern DairyBusiness press deadline.

 

background_banner