A weed management study on organic alfalfa has led University of California (UC) Davis researchers to recommend seeding organic or conventional alfalfa in September or October.

“Growers are starting to realize that early fall is a better time to start their alfalfa crops,” says Dan Putnam, UC Extension forage specialist. “With organic growers, it is even more important to pay attention to time of seeding because they have so few weed-control options.

“Many farmers plant in late November and wait for rain to bring the crop up. Other options are irrigating the crop up in early fall or waiting till early or late spring to plant. All of these strategies have implications for weed management,” adds Putnam.

His alfalfa weed management trial – at the UC Kearney Agricultural Research and Extension Center – was conducted with Carol Frate and Shannon Mueller, farm advisors in Tulare and Fresno counties, respectively. They experimented with seeding timing and early clipping to manage organic alfalfa in a weedy field.

The late November plantings failed in the experiment. “We had a lot of weed intrusion at that point as well as cold conditions for alfalfa growth, so the stands were poor,” Putnam says.

The earlier planting also had weeds intrude, but the researchers clipped the field in early spring when the alfalfa was 10-12” high. That cut back weeds that were overtopping the alfalfa, giving vigorous young alfalfa seedlings an advantage.

An early spring planting after tillage to destroy weeds also resulted in a good stand, but some production was lost in the first year compared to production of early fall plantings.

Although the research was conducted on organic alfalfa, its results are also applicable to conventional alfalfa production, Putnam points out.

“Timing has a profound effect on the first-year yield and health of the crop and its ability to compete with weeds,” he says.

Putnam, Frate and Mueller will share more about their research during a Sept. 5 field day at the Kearney station. Alfalfa variety trials, sorghum silage and nitrogen trials, how to optimize small grain yields, alfalfa pest management, irrigation and stand establishment are other topics to be discussed.

For more on late-season alfalfa establishment, read August Alfalfa Seedings Fool Weeds, Diseases.