Drought conditions, high leafhopper numbers, and a more frequent harvest schedule are common factors for alfalfa fields this year in many parts of the state. All of these factors can contribute to shorter stand life. In general, 5 or more cuttings of alfalfa per year can shorten stand life. Where rainfall has been adequate for growth, growers have harvested on a more frequent cutting schedule this year and are planning to take a fall harvest to boost forage quantity on the farm. The last harvest or cutting date of alfalfa is yet another factor that can influence stand persistence. If stand persistence is a goal, then growers need to carefully plan the last cutting date. According to the Ohio Agronomy Guide, the risk to alfalfa stands is minimized when the last harvest of the year is completed by September 7 in northern Ohio, September 12 in central Ohio and September 15 in southern Ohio. Harvesting later than this can limit the accumulation of carbohydrate and protein reserves that plants need for winter survival and to initiate early growth in the spring.
After that last cutting, growers can do a stand evaluation to assess how their stand has come through this difficult year and what might be expected next spring. Look at the stand density as measured by plants per square foot. The guidelines are:
– Seeding year: 25-30 plants per square foot
– Second year: 10-15 plants per square foot
– Third year and older: 5-6 plants per square foot
Next, dig and count the alfalfa plants in a 1 to 2-square foot area in several random locations in the field. Split open alfalfa roots lengthwise to observe tissue health. In healthy stands, fewer than 30% of plants will show significant discoloration and rot in the crown and taproot, and vigorous crown shoots are symmetrically distributed around the crown. If greater than 50% of the plants show symptoms of crown or root rot, plan to interseed with a legume other than alfalfa, interseed with an improved grass species, or rotate to another crop.