– Mark Sulc, Extension Forage Specialist, The Ohio State University
The dry weather combined with high temperatures and low humidity across many regions of Ohio this summer has limited summer growth of many hay fields. This is especially true of grass and mixed grass-legume hay stands. There are fields where very little regrowth has occurred since the second cutting. In some pockets of the state, regrowth has been insufficient for hay harvesting since the first cutting taken in May. How should those very drought stressed hay fields be managed where the limited growth present is old and mature now? Will mowing help to stimulate fall growth — assuming we get sufficient rainfall soon?
(photo taken 8/25/12 of the total regrowth from first cutting made on May 23 in West-Central Fairfield Co.)
I really don’t think mowing will help stimulate regrowth that much, especially in grasses. In alfalfa, mowing off old growth might help a little, but new growth will probably occur from crown shoots regardless of mowing, if the plant is released from drought stress.
With predominant alfalfa stands, if there is enough growth right now to make an economically viable harvest and the alfalfa is dormant and dropping leaves, then cutting and harvesting that forage will gain some salvage feed. Cutting the stand now should not hurt the stand, assuming it has already shut down due to drought stress. If hay harvest is not economical, an option would be to graze the stand, but precautions need to be taken to prevent bloat.
For new seedings of alfalfa or grasses made this spring, I recommend refraining from mowing them if they are severely drought stressed. If weeds are a problem, then consider mowing high to remove seed heads before the seeds mature.
For predominant grass stands that are established, if you don’t get significant rainfall soon, then cutting the crop will likely intensify the stress and could do more damage to the stand. The little bit of growth present is helping to shade the soil surface and preventing even worse drying. The leaf area present is probably transpiring just a little bit in the morning hours, which helps cool the plant. By removing the growth with clipping or mowing, plant transpiration will be reduced, decreasing its ability to cool. The soil will be more exposed to the sun, causing more drying and intensifying the drought stress on the root system and the plant.
If we get enough rain in the coming week or two to stimulate good fall growth of established alfalfa and mixed alfalfa-grass stands, no harvesting should be made until at least mid- to late October. This will allow time for the plant to accumulate the energy reserves needed for winter survival and regrowth next spring. Even, then late fall cutting runs the risk of increases in heaving damage later in the winter, especially on heaving prone soils. I recommend NO fall cutting of new seedings made this spring or late summer.
Finally, autumn is a good time to soil test and add recommended topdress fertilizer to your permanent hay and pastures. This too will enhance plant survival through the winter and productivity next year.