Checking Alfalfa For Winter Injury March 10, 2017
Alfalfa had started to green up and grow in many areas prior to this cold spell. When growth begins again, stands need to be evaluated soon.
Alfalfa usually comes through winter in pretty good shape in our area and serious losses are rare, but this has been an unusual winter. The lack of snow cover during cold temperatures this winter may have permitted cold injury or more likely, enabled dry winter winds to dry out and kill some exposed plants. High temperatures in February and early March caused much alfalfa to break dormancy early until growth was set back with the recent cold.
Evaluate your alfalfa stands early this spring. Older, dryland fields that have fewer than 30 new shoots per square foot coming from two or three plants may need to be rotated soon to a different crop and new fields planted to alfalfa. Very productive sites, such as irrigated and sub-irrigated fields, should have at least 40 shoots per square foot from four to six plants. Anything less is a strong candidate for rotation. We tend to lose about one tenth of a ton in yield potential for every shoot below these numbers.
When assessing your fields, check plant densities in several areas when the early shoots are 4 to 6 inches tall. Since some shoots begin growing later than others, stands with enough plants but slightly low shoot density may be all right, especially if shoot height and distribution is fairly uniform. But, if plant density is low, or shoot growth is not uniform, yields probably will be lowered.
Checking your alfalfa stands soon after growth begins should allow time to make any needed changes in your cropping plans.