Farmers should examine forages as the crop emerges from dormancy to determine if they have been damaged from the recent sleet and ice storms, a Purdue Extension specialist says.
Forage crops specialist Keith Johnson estimated that one-fifth of the Indiana landscape was covered by the sleet and ice from the early February storm.
"The snow that fell was not the normal, powdery snow but a combination of ice and rain acting as a natural concrete," he said.
Ice can surround the crown 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.
Farmers won't know whether ice caused winter damage to their crops until they go out and check their fields, Johnson said.
"As a good management practice, producers should always check plants when crops break winter dormancy," he said. "Farmers who delay a field check until mid-April because they assume everything is okay can go into panic mode when they discover a winter-damaged crop. I want producers to have more time to make an informed decision if a crop is affected."
The key to a field check is to determine how many plants survived.
Around the third week in March is an excellent time to assess if alfalfa plants are coming back properly, Johnson said.
He encouraged using a spade for destructive sampling. Producers should start in the lower-lying portions of the field, as this is likely where damage is to be found, then fan out to areas with better drainage.
"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," Johnson said.
If weak alfalfa stands are found, producers should determine whether there is a need for added nutrients by soil testing. Johnson also recommends delaying harvest to beyond the late bud stage because reserves for regrowth will be higher than in an earlier harvest. Forage quality will be lower for this one cutting, but persistence of the stand 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," Johnson said. "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 by having residual growth and not clean cutting a fall-dormant alfalfa crop. This creates a vertical air channel and reduces the effects of ice.
"Leaving stubble after a dormant harvest last fall requires an equipment adjustment and loss of some yield, but it's a way to reduce chances of winter damage," Johnson said. "Farmers taking preventive measures before and after the ice occurs increase their chances of having a successful crop."
Source: Purdue University Extension