July 09, 2002

LINCOLN, Neb. — It's a tough year for alfalfa due to hot, dry weather and increased insect populations, said a University of Nebraska forage specialist.

Producers must make good management decisions as new seedlings struggle to survive and mature plants grow more slowly, said Bruce Anderson, an NU Institute of Agriculture and Natural Resources forage specialist.

Seedlings can be sustained by reducing weeds and competition for moisture and light by applying herbicides or clipping fields, he said. Clippings help conserve moisture, reduce plant size and decrease water needs by acting as mulch, Anderson said.

"These are difficult days for alfalfa seedlings," Anderson said. "Anything you can do to reduce stress and competition will help. Even if there's not enough alfalfa to make hay, it still might be good to (use clipping to conserve moisture) so plants' water demand is less, enabling them to make it through the dry times a little bit easier."

Tall weed clippings can smother struggling seedlings and remove the weed canopy, suddenly exposing alfalfa plants to more sunlight, heat and humidity and increasing the risk of shock. Anderson recommended leaving tall stubble to help plants continue to metabolize and develop.

Increased insect problems have made scouting and early insecticide application more important, he said. Leafhoppers, aphids, grasshoppers and other insects can cause extra problems during stressful weather, Anderson said.

"If you add heat, dryness and insect injury to those seedlings, even the toughest alfalfa seedlings may not be able to make it through," he said.

Mature alfalfa can experience quality changes due to heat. Fine-stemmed alfalfa has high protein, but also has high fiber, which decreases feed value, complicates digestion and reduces feed intake, Anderson said.

Harvesting alfalfa at the right time for best quality and yield can be challenging during hot weather because alfalfa tends to mature more quickly, he said. This misleads many growers who use blooming as a signal to harvest, he said. Plants need about five to six weeks of regrowth time between cuttings, he said.

"During hot weather, the plants burn off more nutrients than they are able to put into the root system," he said. "We need to let plants get more mature than normal to keep the same healthy, vigorous regrowth we anticipated."

Anderson recommended taking advantage of rapid drying conditions when possible, harvesting when hay can quickly dry to less than 50 percent moisture before nightfall. At high moisture levels, nutrients respire away during the night to decrease yield and quality, he said. If hay won't dry to optimal levels before the first night, it's better to cut late in the day when plants are highest in quality, he said.

07/09/02-SH

Bruce Anderson - Ph.D
Agronomy
Professor
(402) 472-6237

Sandi Alswager Karstens
IANR News and Photography
(402) 472-3030

Department: Agronomy & Horticulture