With temperatures below 25 degrees for several nights in April, alfalfa in Illinois has suffered injury. Jim Morrison, Rockford Crops Educator, provided the following guidelines.

· With spring seedings, new plants are very cold tolerant at emergence. At the 2nd leaf stage and older, the plant is more susceptible to cold temperatures and may be killed by four hours or more at 26 degrees F. or colder. If alfalfa was seeded with a companion crop, damage from exposure to cold temperature may be less as a result of protection provided by the cover crop, as temperature at the soil surface is warmer than at the top of the canopy.

· On established alfalfa stands, a light frost will cause the top growth to look wilted. If there was only leaf damage and the stem tip is recovering, harvest as normally planned.

· If a high percentage of the stem tips are permanently damaged on taller alfalfa, regrowth will occur from axillary buds below the damaged portion of the stem. Regrowth will also arise from crown buds. Waiting on this regrowth will delay the first harvest. If the decision was made to harvest the damaged stand earlier than normal, this will place an added stress on the plant and recovery from harvest may be slower than normal.

Once livestock producers have made a decision on their alfalfa stand, forage yields may be reduced and forage inventory for the 2007-2008 could be short. The following alternatives can be considered.

1. If your alfalfa stand did not respond or plants did not survive, planting a warm season crop such as sorghum-sudan hybrid can be done in May or later. Harvesting at 20 to 24 inches (height) can produce high quality forage (over 14% crude protein and over 0.60 megacalorie of net energy (Mcal) per pound of dry matter) for high producing cows. If forage is needed for older heifers and dry cows, harvest at 30 inches or taller (more tonnage but lower in quality—10-12 percent crude protein and under 0.60 Mcal). Additional crops can be harvested every month if moisture is adequate.

2. Corn silage can be planted in late May and early June which is another choice to replace lost alfalfa forage. Ration balancing will be required if higher levels of corn silage are fed. Corn silage can lead to heavy heifers and dry cows as energy levels can be too high.

3. Fall seeded small grain forage (such as oats for oat silage) can be an alternative crop that can be harvested as silage in late fall. Growing and drying conditions can be a management challenge. Jim Morrison has collected data in Northern Illinois for this approach.

Forage needs for a high producing dairy cow and her associated replacement heifer(s) is 10.8 tons of dry matter per cow equivalent per year. For example, if you have 100 milk and dry cows, your inventory needs will be 1080 tons of forage dry matter for next year.