DES MOINES, Iowa — Timing the final alfalfa cutting before mid-September offers regrowth opportunities to reduce the risk of winter injury, say experts at Pioneer Hi-Bred, a DuPont business.
“Whether a grower is in a three- or four-cut alfalfa program, cutting from Sept. 10 to Oct. 1 in most northern climates rarely allows the crop enough regrowth time to withstand winter months,” says David Miller, Pioneer alfalfa research director. “Poor fall harvest timing can negatively affect stored root food reserves, which can lead to poor winter survival.”
Generally, an alfalfa stand needs about six weeks of regrowth time after the last cutting to gain appropriate nutrients to avoid winterkill. During winter months and the following spring, alfalfa utilizes regrowth nutrients gathered by the roots.
“It’s a matter of arithmetic,” Miller says. “Depleting the energy source prior to dormancy will not allow the plant enough energy for adequate spring growth. If a final cutting is a necessity for ample feed, growers should wait until two consecutive days of a hard freeze — 24 to 26 degrees.”
According to the University of Wisconsin, the hardening process in preparation for cold weather begins when temperatures drop below 40 F. This process allows the plant to tolerate freezing temperatures for extended periods.
“Following a hard freeze, growers have the opportunity for a final cutting,” Miller says. “Leaving more stubble than typical summer cutting is recommended. For all fall cuttings, leave at least 4 inches of stubble to help catch insulating snows.”
Fall is also an excellent time to start reviewing fertilizer and weed management options.
“Growers should make sure soil fertility is adequate, especially potash,” Miller says. “An application in the fall or spring is fine. Typically, the best time is after the third or fourth cutting — depending on yield levels during summer months — to help maintain conditions for winter survival.”
Weed management is applicable in the fall as well. Autumn is an optimal time to control perennial weeds. “It’s smart to kill weeds before they establish,” Miller says.
“The majority of the time, a great spring alfalfa stand is due to applying weed control measures in the fall or early spring while the alfalfa is still dormant.”