A plant growth regulator used primarily on apples could someday help alfalfa growers produce more dairy-quality hay.

That possibility is being studied by Michael Rethwisch, University of California extension vegetable and field crops advisor at Blythe, CA. He's been working with the regulator, BASF's Apogee, for more than four years.

“A change in alfalfa hay quality from good to premium and the associated increase in net dollars/acre is the desired outcome of the product's use,” says Rethwisch.

In the low desert area where he works, growers typically get only three cuttings of dairy-quality alfalfa. In the hot summer months, the irrigated crop grows fast and yields are high. But the stems are long, and the hay isn't dairy-quality.

Rethwisch thinks the growth regulator may enable growers to increase the number of dairy-quality cuttings to six.

Apogee's active ingredient is gibberellic acid. When applied shortly after a cutting, it shortens stem internodes, resulting in less stem and more leaves, says Rethwisch.

His first trials were conducted in 1997 and '98, when he was a University of Arizona extension agent at Parker, AZ. He has expanded the research since he moved to California.

In 2001 field trials, Apogee was commercially applied to ¾-acre plots. Very high rates (up to 0.25 lb active ingredient/acre) were used on three cuttings: late May, June and late July-early August.

“A significant quality increase was noted in late May, but not in later cuttings when temperatures in the low desert were often 110° or more,” says Rethwisch. “In 2002, I hope to test lower rates of product on higher-yielding fields.”

The California advisor says reaction by local growers has been mixed so far, primarily because the product is not yet registered for use on alfalfa.

“Growers and alfalfa hay brokers are still waiting for further testing on high-yielding fields, which is necessary for economic analysis and potential profitability,” he says.

Jerry Minore, BASF's manager of marketing strategy, says the company hasn't decided whether to seek registration of Apogee for use on alfalfa.

“We see some initial benefits, but the key is to determine if these benefits will give the grower a good return on his Apogee investment,” says Minore. “While the number of cuttings isn't expected to increase, we hope that Apogee will give the grower some additional cuttings of high-quality hay.”

The major drawback, according to Rethwisch, has been lower yield due to the shorter stems — consistently about 350 lbs less per cutting at the high rates tested last summer.

Another potential drawback, according to Rethwisch: Shorter alfalfa may be less effective at suppressing weeds.

He thinks the product will be economical only in fields yielding at least 1.5 tons/acre/cutting, and where plants aren't stressed by extreme heat or other problems.

He figures the regulator might be more beneficial in other areas of the U.S. and Canada than in the low desert.

“Alfalfa yield is relative to day length,” says Rethwisch. “The farther north you go in the Northern Hemisphere during the summer, the longer the day length and hence increased yields per cutting.”