Dr. Mark Sulc, Forage Specialist, Ohio State University
As winter releases its grip, forage crops initiate new spring growth. April is a good time to walk hay fields and pastures to assess stand density and plant vigor. I don't expect any major problems with winter survival this year, but there are always isolated cases where stand density is less than desirable. Take a close look at stands that were marginal at the end of last year and summer seedings that were planted late.
As forage stands greenup, walk your fields and estimate the number of live plants per square foot. Actual counts in several spots can be made with a 2 x 2 foot square. If the planting is in rows, measure off a known area and make plant counts in the rows. Second year stands should have 8 to 12 plants per square foot, and third year or older stands should have 5 to 6 plants per square foot.
Visually estimating ground cover of desirable forage plants is also a useful way to assess stands. This should be done when there is about six inches of growth. Stands with more than 80% ground cover should produce excellent yields, 60 to 80% ground cover should produce normal yields, 40 to 60% ground cover will likely yield in the 60% range of normal, and 20 to 40% ground cover will yield less than half the normal potential. Weeds will be a problem in thinner stands, so over seeding with grass and clover or destroying the stand and rotating out of it should be considered.
It is useful to dig up alfalfa plants and split the crown and taproot lengthwise to evaluate general root health. This gives some indication of stand vigor and future life span. Very healthy plants have creamy and firm internal root and crown tissue. Some crown rot (dark discoloration of inner tissue) will be present in older stands. Healthy stands have fewer than 30% of the plants with significant discoloration and rot in the upper taproot and crown region. Stands showing more than 50% of the plants with significant rot across the entire diameter of the taproot or crown are likely to go downhill during this coming growing season.
Chickweed and other winter annuals can be a real problem in late summer seedings, especially those with poor vigor. So walk those fields and be prepared to make necessary herbicide applications in a timely manner, before the winter annuals get too big.
While it is important to evaluate forage stands in early spring, recent research in Ohio and Missouri has shown that more alfalfa plants die during the growing season (between spring and fall) than during the winter. Of course, there are some winters when catastrophic heaving causes complete stand loss. But during most years, alfalfa stand density changes more during the growing season than during the winter. Winter injury and other stresses during the growing season can accumulate and weaken plants, causing them to die at some point during the growing season. So as you walk your fields this spring, make a mental note to walk them again in the fall.