Around the third week in March, Indiana alfalfa producers should assess whether alfalfa plants are coming back properly from a sleet and ice storm that hit the state in early February (see Feb. 22 eHay Weekly Indiana State Report), says Keith Johnson, Purdue University Extension forage specialist.
Ice can surround the crowns of alfalfa plants and allow toxic metabolites to build up, preventing the natural exchange of carbon dioxide and oxygen during respiration – essentially smothering the plant, Johnson points out.
He estimates that the February storm covered a fifth of the state’s landscape and that farmers won’t know whether their crops are winter-damaged until they check fields.
Start monitoring lower-lying portions of a field, where damage is most likely to be found. Then fan out to areas with better drainage, he recommends. Using a spade to sample, look for a minimum of 30 vigorous tillers per square foot. More is better.
“Cut into the taproot and crown to see if the color is a healthy whitish-beige, not brown, and that green crown buds are appearing evenly around the crown at ground level.”
If weak alfalfa stands are found, soil test to determine whether nutrients are needed. Johnson also recommends delaying harvest to beyond the late bud stage to shore up regrowth reserves. Forage quality will be lower for this one cutting, but stand persistence should be improved.
“It’s possible to overseed a moderately injured alfalfa field with red clover before, or as, alfalfa winter dormancy breaks to recover some forage yield for this year and next,” he warns. “It may be best to switch the field into corn, if it is too damaged, to get some nitrogen credit from the alfalfa crop. Seeding alfalfa into the old stand would not be recommended due to a self-imposed toxicity to germinating seeds.”
Forage producers can help prevent ice damage to their alfalfa crop in the future by having residual growth and not clean-cutting a fall-dormant alfalfa crop. This creates vertical air channels, which reduce the effects of ice.
“Leaving stubble after a dormant harvest in the fall requires an equipment adjustment and loss of some yield,” he says. “But farmers taking preventive measures before and after the ice occurs increase their chances of having a successful crop.”