Don’t select an alfalfa variety like you would a discount-priced entree from a restaurant menu, recommends Shannon Mueller, Fresno County farm advisor.
There’s much more to it than price of the seed, she reminded growers during a alfalfa and forage field day at the University of California’s Kearney Research and Education Center at Parlier.
“Variety decisions you make when establishing an alfalfa stand are the first and foremost you can make, because they affect the yield, persistence, quality, and pest management results for many years down the road,” she said as growers viewed the current variety trials at the Parlier site.
The UC multi-year variety trials at locations from Tulelake to El Centro are a convenient source of information and demonstrate how new varieties compare with established favorites. They serve as a clearinghouse for the some 300 varieties introduced each year.
Armed with guidance from these trials, considered the most comprehensive in the West, growers can make informed and profitable decisions.
It takes less than one-tenth of one ton in yields to justify even a $2 increase in the price of seed, she said, adding that many varieties may produce yield differences 10 times that amount. That’s why seed price – and promotional gifts – should be the last consideration.
“The only legitimate way to compare varieties is with side-by-side, replicated trials where the alfalfa is grown under uniform conditions and we have good control of the data used in the analyses,” Mueller noted.
Pointing to the currently available yield trial results for some 50 released and experimental varieties for 2005 through 2007 at the Kearney site, she said, “Don’t make decisions on any single year. Some varieties may perform very well in the first year and then not do well in the subsequent two seasons. Or they may start slow, but move toward the top later.”
An example is Magna 995, which came in 29th in 2005, only to ascend to first place the following year and sixth place in 2007, all for an average of fourth place for the three years.
Beyond yields, varieties adapted to a particular area of the state are designated by ratings for fall dormancy, or the physiological response of the variety to shortening days and cooler temperatures. In the SJV, those with a fall dormancy rating of 7 to 9 offer the greatest productivity.
However, along with higher yields, there is also diminished quality. Consequently, growers in the Valley often select varieties that are more semi-dormant, perhaps those with a rating of 6, if they believe they can manage them for a margin of higher quality.
Mueller added that the true test of this approach is whether those growers can achieve a higher price for that quality.
Turning to host-plant resistance, she said, “In many cases, it is the only help you will get in managing certain diseases, insects, or nematodes in alfalfa.”
UC trial results list the various ratings from highly resistant to tolerant for the varieties in a particular range of fall dormancy. Growers can compare these with the history of pests in their fields.
“One thing to remember is that pest-resistance ratings for alfalfa are not uniform like wheat or corn,” she continued. An alfalfa stand is a population of many plants, and they are genetically diverse, so even highly-resistant varieties express only 50 percent or so resistance. Once yield, fall dormancy, and pest resistance are considered, growers can investigate a variety’s biotechnical traits, such as herbicide resistance.
Complete details on varieties and other useful information are available at http://alfalfa.ucdavis.edu.
In another presentation at the event, Dan Putnam, alfalfa and forage specialist at UC Davis, discussed the issues and potentials involved in production of switchgrass and alfalfa as irrigated sources of cellulose for processing into biofuels.
Switchgrass, a perennial warm-season grass native to North America, is adapted to droughty conditions and high temperatures and can grow on marginal soils with little fertilizer. Results of four-year UC trials suggest it can produce 10 to 15 tons per acre at Five Points, Davis and El Centro.
Alfalfa might be grown for multiple uses: separating its leaves for forage and its stems for cellulose. A 10-ton alfalfa crop might yield a 4- to 5-ton leaf fraction and the remainder as cellulose. Or one or more cuttings could be used for forage and the rest for cellulose, Putnam said.
Interest in biofuels is mounting, he explained, because of demand for fuels by a global population that is both expanding in numbers and in affluence. Biofuels can be regenerated and are not “the one-way street” of fossil fuels. However, there is a need for improved cellulosic technology.
Citing the pros-and-cons of perennial crops for biofuel production, Putnam said crops for that purpose fall into three categories. The first includes corn, as well as soybeans and canola, two sources not presently considered economical. The second is crop residue and municipal waste, and the third is dedicated energy crops, such as fast growing trees and perennial grasses, that require full management systems.
Advantages for perennial crops are high yields, use of the full growing season, reduced nutrient run-off and soil erosion, efficient water use, and carbon sequestration.
“They also have disadvantages. There is less flexibility in location, rotation, and water use. You have to keep the crop alive, whether is it economical or not,” he added. Putnam cautioned that growers should not “jump on the band wagon” before giving biofuel production careful thought. “It you are considering a new crop, you shouldn’t necessarily start with the answer. You should keep asking questions. It’s likely we will see multiple answers depending on your location, what direction you take, and the available technology.”
Putnam and others have been evaluating various species of grasses. Miscanthus, a grass from China, produces well but is not adapted for use with existing hay equipment. Switchgrass, however, can be handled by typical implements.
One of the chief issues for cellulosic feedstocks presently is the yield of fuel per pound of material. Water-use efficiency and flexibility is an issue now and will continue to be in the future. Another question is how much energy is required to produce the crop itself.
“And a very important political issue,” Putnam said, “is the impact on food production from adapting a biofuel crop. There’s been much criticism of adapting corn for biofuel and its impact on worldwide food prices.”