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Alfalfa variety selection rates a closer examination from growers

Other than a few select breeders, practically no one can distinguish one alfalfa variety from another simply by viewing a stand, so it’s vital for a grower to investigate whether he’s growing the best variety for his location.

That was one of the tips offered by Dan Putnam, Extension agronomist, University of California, Davis, during an alfalfa and forage field day at Parlier.

“The only way you can tell one variety from the next for sure is to see them side-by-side growing in a field with the same conditions and cutting schedule,” he said, pointing across variety strip plots at the Kearney Research and Extension Center.

“Alfalfa is a very forgiving crop, and you can make lots of mistakes and still have something out there with green plants. That doesn’t mean you made an optimal selection, only that you were lucky enough to get a crop that survived the mistakes that were made.”

Putnam went through a list of dos-and-don’ts for growers, including a graph that depicts the greater importance of performance when compared to seed price.

The trial conducted at Kearney in 2003-2005 showed that even assuming the now quite modest price of $125 per ton on a three-year stand seeded at 25 pounds per acre, a $3 increase per pound of seed is equivalent to an increased gross return of $75 dollar per acre.

The idea, he said, “is not to look at the price of the seed, but consider as much data as you can about the potential performance of that variety in your region. You can imagine how the graph changes if you are looking at $250 hay.”

He advised growers to select a group, say the top one-third, of varieties from among the top performers in university and seed company trials for a given region, such as one planted at Kearney in March of 2005.

“They won’t always perform the same in all locations and soil types, but these are more likely to perform than the ones near the bottom. It’s good to look at as much multiple year data as you can. We do not recommend choosing a variety on the basis of one year’s data.”

The venerable CUF 101 is the standard for UC trials, which range from Tulelake to El Centro, and the bulk of California varieties released over the past five to 10 years are superior to it.

It will profit growers to also select for fall dormancy in their location. Fall dormancy, as measured by the relative height of varieties in October and indicated on an 11-point scale, generally speaking, has a relationship to plant persistence.

“Thus,” Putnam said, “generally, a fall dormancy rating of 9 is higher yielding and a little less persistent. So you have to decide whether you want the crop to be in three to four years, or five to seven years and decide if you are willing to give up growth potential for stand persistence.”

Even so, he added, some varieties with fall dormancy of 7, 8, or 9 are quite persistent, so the grower is advised to check all the data he can find.

Lower fall dormancy tends to have higher quality, when managed with the same cutting schedule.

“Under the current market conditions,” he said, “it would be a mistake to give up yield in favor of quality if you are a cash basis farmer.”

Growers are attracted to varieties that maximize cutting schedules and yields for the present, but there is no guarantee how long the market conditions will last.

For the San Joaquin Valley, for example, fall dormancy between 7 and 9 is recommended, along with high resistance for spotted alfalfa aphid, pea aphid, and blue alfalfa aphid, and high resistance to Phytophthora root rot, Fusarium wilt, and bacterial wilt.

Putnam urged growers to select varieties for resistance to pests of their region, including aphids and nematodes, and diseases such as Phytophthora root rot during stand establishment.

“Resistance doesn’t mean immunity,” he said. “It just means they have a higher resistance. They are good insurance for the one to two out of five to ten years when these pests are a problem.”

Genetically modified traits, particularly as Roundup Ready varieties, are another consideration in variety selection. Inserted in many field crops, the RR trait was modified in alfalfa in 1997 and commercialized in the crop in 2005.

However, alfalfa having resistance to Roundup herbicide, Putnam explained, is presently prohibited from additional commercial planting, pending completion of a review by USDA for an environmental impact statement due to a lawsuit concluded in March of 2007.

Although a date for resolution is uncertain, Putnam speculated it might be sometime in 2009. “We have about 80,000 acres of Roundup Ready alfalfa in California and about 350,000 acres across the nation. It has had a big effect on the way we approach weed control.”

In the future, he added, he expects to see other traits, particularly those that influence quality and fiber, and protein digestibility in alfalfa hay. Pest and disease resistance, as well as salt tolerance are also being developed.

“One of the things we have to get right with these crops is the issue of coexistence of genetically modified alfalfa varieties that can be grown near neighbors who do not want to have it.

“Researchers, seed companies, and growers all are wrestling with this to provide stewardship of these varieties, both for hay and seed production, to make sure people who don’t want the traits can grow the type of products that are important to them,” he said.

On quality, Putnam said there’s a good correlation between fall dormancy scores and forage quality such as ADF, NDF, and crude protein.

“In other words, we see the shorter, slower-growing varieties not putting on as much fiber and lignin as the more non-dormant lines. One trick is to produce higher-quality hay, but the key question is whether you can afford to go after high quality under the kind of economic conditions we have now.”

TAGS: Forage
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