Harvesting Stressed Alfalfa and Other Forages

Mark Sulc, Forage Specialist, OSU Extension

I have received several calls about harvesting alfalfa that appears to be under stress from dry weather. Alfalfa usually has a strong capacity to continue growth under dry conditions, and we would normally expect alfalfa to be growing better than it is at this stage in a dry cycle. The late spring frost injury combined with the first harvest taken before the crop had a chance to replenish taproot reserves has likely contributed to the weak regrowth now being observed.

Many alfalfa stands were cut in mid- to late-May, which in a normal year is ideal timing. Unfortunately, the late killing spring frost this year resulted in alfalfa plants having to initiate new growth all over again. That required a lot of energy from the plant at a time when taproot reserves were low. So the mid- to late-May cutting was actually like an early harvest stress in terms of the physiological condition of the plant. This has likely contributed to the weak regrowth of many alfalfa stands, especially those that were cut last autumn or have additional stress factors such as suboptimal fertility and pH.

Many stands don’t appear to be growing any more, but that does not mean the plants are sitting idle. Alfalfa stems stop elongating during the initial phases of moisture stress, but the plant continues to manufacture carbohydrates and protein that are stored in the root system since they are not being used to produce top growth. Allowing those reserves to accumulate a little longer will benefit alfalfa plant health and longevity. I encourage growers to allow the alfalfa to get close to full bloom stage before taking the second cutting this year. Allow at least a 35-day interval from the first harvest.

Once the alfalfa is well into bloom stage and there is enough harvestable forage to economically justify a hay cutting, then go ahead and harvest it. The forage will probably be higher in quality than normal growth in full bloom because of the stems are short and fine. If fencing is available, controlled grazing of drought-stressed alfalfa stands is a very economical way to utilize the forage that is present, but bloat prevention strategies should be employed.

Other forages are also showing signs of drought stress. Red clover is not as tolerant to the combined effects of drought and heat stress as alfalfa. Cutting during periods of hot and dry weather CAN WEAKEN RED CLOVER PLANTS and may cause stand reductions. If feed is badly needed, red clover stands can be lightly grazed during drought stress.

When cutting or grazing birdsfoot trefoil during periods of heat and drought stress, be extra careful to harvest when plants are at least in mid-bloom stage and leave a full 3-inch stubble. Birdsfoot trefoil maintains relatively low levels of reserve carbohydrates in the roots and crowns during the summer. Cutting or grazing when plants are well into bloom stage and leaving sufficient leaf area will improve its regrowth potential.

Grass growth has also been slowed by dry weather in many areas. Established orchardgrass and tall fescue have better regrowth after first harvest than species like ryegrass or timothy that are less tolerant of dry conditions. Established grass stands can survive through drought conditions and regrow once rains return.