Alfalfa variety choice keyed on performance

When it comes to selection of a new alfalfa variety, remember first and foremost: performance, performance, performance.

That was the essence of Dan Putnam’s advice to growers during a recent alfalfa field day at the Kearney Agricultural Center at Parlier.

“Performance, not the cost of the seed, is the most important economic feature of a new variety,” said the University of California Cooperative Extension agronomist.

Putnam, who conducts the independent, continuing variety testing program based at UC, Davis, said selection of a new, improved variety could mean as much as $400 per acre additional revenue over the life of a three-year stand.

Multi-year data is compiled from the program’s plots from Tulelake to El Centro, and statistics from Davis plots show yield differences by variety can range about 2.5 tons per acre over a three-year period.

But detection of relative performance of new varieties in the field depends on side-by-side comparison with an older, standard variety. “You can’t see the difference by just walking into a field of the new variety,” he noted.

He suggested growers set out their own strip trials for a close comparison of existing varieties and potential replacements.

And, he added, growers should be willing to spend a bit more for seed having higher performance. A gain of 200 pounds per acre can eclipse the additional costs of $1 to $2 per pound of seed of the new variety, and many varieties can produce improved yields of up to a ton per acre.

As he discussed results of his program’s 2003-2004 trials and growers viewed strip trials at the Kearney station, Putnam said a good gauge of a variety’s performance is comparison with the venerable CUF 101. Bred for the low desert and released nearly 30 years ago, it is resistant to blue aphid and is adaptable throughout the state.

For example, in 2003-2004 at Kearney, two-year comparative data showed (based on a price of $110 per ton, with no additional seed cost) CUF 101 posted about $220 per acre more revenue than the lowest producer, while several new varieties yielded in excess of $300 more per acre.

Multi-year records

Putnam stressed the need to compare multi-year production results when considering new varieties. Some new ones do well the first year and then decline, but others are slow during the establishing season and then produce quite well.

“We urge growers to look at two-year data, or three- or four-year data if they can find it,” he noted, adding that at Kearney many high fall-dormancy varieties deteriorate more rapidly than their moderate fall-dormancy counterparts.

In general, he reminded, high fall-dormancy varieties tend to be higher yielding, somewhat lower in persistence, and lower in quality under a given cutting schedule.

Many northern San Joaquin Valley growers have elected to sacrifice yields for higher quality. This, Putnam said, presents “a fairly challenging issue,” although it makes more sense in a lower-price year than a year like this.

He developed a table to help calculate options for the yield-quality tradeoff. It considers both yield for the season and average ADF content. As a rule of thumb, he said, the difference in quality must be worth over 33 percent more in price to justify the reduction in yield.

He recommended that growers looking for new varieties consider those in the top third of the results. From that group they can further examine for disease resistance.

‘Resistance not absolute’

“But remember that disease resistance is not absolute. Alfalfa is a widely adapted crop with a wide variation between plants and is not as uniform in this respect as a corn hybrid or a wheat variety. We consider a 50 percent or greater resistance to a disease or insect as highly resistant. Even highly resistant plants can be overwhelmed if the pest population is great enough.”

He went on to explain that an ideal “package” for resistance, by region of the state, would include strength against the aphid complex, Phytophthora, bacterial wilt, and root knot nematode.

Since chemical controls are not available for many of these pests on alfalfa, plant resistance and cultural practices are the only management tools.

Growers calculating the seed costs for resistance need to consider it an insurance issue, weighing whether the cost is worth protection in perhaps one year out of ten. A couple of years ago, Sacramento Valley alfalfa growers were caught unprepared for a root knot nematode outbreak of proportions not experienced for a decade before.

Putnam also has strip trials with “Roundup Ready” alfalfa varieties, planted in 2003 at Davis and this year at Kearney.

Roundup Ready alfalfa was de-regulated by USDA in June, and it can now be legally grown in commercial fields. Specific varieties developed through biotechnology are tolerant of glyphosate herbicide, which can be applied, over the top, without harm to the crop.

He will present results at the 35th California Alfalfa & Forage Symposium Dec. 12-14 at Visalia, but he offered preliminary comments on observations on stand establishment only. These trials do not include applications of Roundup.

The University of California’s Publication 8153, “Roundup Ready Alfalfa: An Emerging Technology,” details extensive investigation and trials on the concept throughout the state.

“Generally speaking, the yield potential of these varieties, at least in the Davis trial, looks very close to what we would expect from a similar line in the same fall dormancy class. We are seeing a 20 to 25 percent yield difference between the top and the bottom entries in the Davis trial. We will be analyzing the Kearney trial this fall.”

He said 2 to 5 percent of the seed (nulls) of Roundup Ready varieties is not resistant to the herbicide and will be stunted by applications.

“This is not a particular problem, however, especially if you spray during stand establishment, since a lot of seed do not become plants anyway. The stands look good but typically only about 30 percent, maybe less, of the seed becomes plants.”

Monsanto technical representative Barbara Kutzner of Fresno said Roundup WeatherMAX and Original MAX are registered for use on Roundup Ready varieties.

“It is very important to identify the three to four trifoliolate leaf stage of the alfalfa because we recommend application of 22 ounces at that stage to eliminate most of the weed pressure during stand establishment,” she said.

Up to 132 ounces of the product can be applied each year, and applications can be made up to five days before cutting.

Cost of the Roundup Ready seed includes a $3 technology fee per pound, and growers must sign an agreement that their crop will be used domestically.

Kutzner said Roundup Ready alfalfa varieties have been accepted, as were the Roundup Ready corn varieties, by dairymen.

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