There is the persistent question as to when to plant. UC forage specialist Dan Putnam learned at Kearney that the UC recommendations developed more than 20 years ago by his predecessor Vern Marble are still very valid.

It was in a certified organic alfalfa trial at Kearney that Putnam once again validated UC’s long standing recommendations.

Sixty to 80 percent of the success of an alfalfa crop occurs at stand establishment. This is more critical in organic alfalfa, due to the threat of weeds killing a stand. Putnam’s small trial had plenty of those, he said. The field was fallowed over the summer and tilled to control summer weeds.

A Sept. 23 planting date provided the highest first yields (10 tons per acre in four harvests) in the first season. An early spring (March 12) planting was the second most successful and “would be a good second choice if early fall planting was not feasible,” says Putnam.

A Dec. 9 seeding date was a disaster. This time frame is often used by growers to catch seasonal rains. It did not rain on the Putnam plots and the field had to be irrigated. It failed nevertheless, due not only to the lack of rain, but weeds and cold temperatures at stand establishment.

The late spring planting (April 24) was successful with fewer weeds, but yields were approximately half of the fall planting date.

Clipping in the fall-planted plots was beneficial in controlling winter weeds. “We clipped twice only the top one-third of the canopy to prevent windrows from smothering the crop from excessive herbage.”

An oat companion crop with the alfalfa was not “particularly effective preventing weeds,” Putnam reports.

Summer weeds like lambsquarter, pigweed and watergrass can be “extremely problematic” in organic or conventional stands of alfalfa.

“A vigorous alfalfa stand is the best defense against weeds,” Putnam emphasizes.