Dr. David Barker, Professor – Horticulture and Crop Science, The Ohio State University
Dry weather in recent weeks throughout Ohio has raised several questions about how pastures should be managed during drought. Although the experts don’t all agree if this period of dry weather meets the definition of a drought (yet), there is no doubt that pasture growth will slow to zero. How should we be grazing our pastures in mid-summer?
Unfortunately, without rain or irrigation pastures will not grow, and close grazing will exaggerate this effect. Leaf removal by grazing (or mowing) results in a roughly similar proportion of root death. During moist conditions, roots can recover quite quickly, however, grazing during drought will reduce water uptake due to root loss. As a general rule of thumb, grazing below 2 or 3 inches will accelerate drought effects on pastures, and also, slow recovery once rain does come. Of course, optimum grazing height and management varies with pasture species. As summer progresses into fall we will increase pasture grazing heights and leave more residual, while increasing resting periods. More leaf means less water runoff.
Watch for endophyte poisoning on tall fescue and perennial ryegrass. Drought can result in a triple whammy in respect to endophyte i) ergovaline (the toxic alkaloid) levels are elevated compared to spring, ii) livestock graze nearer the base of plants where endophyte and alkaloids are the most concentrated, and iii) seed-heads typically have higher alkaloid levels than leaves. It would be best to utilize other forages during this period of growth, such as annual warm-season grasses or legumes where possible. You might also consider feeding hay or grain.
De-stock pastures. Livestock pressure on pastures can be reduced by selling unproductive livestock, feeding silage/hay/grain, and finally in extreme cases you might even consider selling productive livestock. In many cases, making the hard decisions early can be the best decision in the long-run.
Be ready with nitrogen
Pastures and livestock can make compensatory growth upon relief of drought. Strategic use of N, early in the recovery from drought can re-gain some of your losses. Don’t make applications too early, since volatilization losses could be high without rain to ensure incorporation of N.
Be wary of the potential for nitrate toxicity if grazing warm-season grasses during drought. More especially, grazing the first regrowth of warm season grasses that results from the first rainfall after drought can also have elevated nitrate levels. A forage nitrate test is highly recommended. The toxic limit can be lower for young stock. Most labs will offer a fast option for forage nitrate tests during summer.
Start planning for next year
The best drought strategy is to plan in advance, i.e., it’s not “if” it gets dry, but “when” it gets dry.
Spring-planted crops such as brassica, grazing corn, and sorghum-sudan grass (use brown mid-rib varieties) can fill the summer slump.
Warm-season grass stands (big-bluestem and switchgrass) are not high quality, but will be more than adequate to keep livestock maintained during summer.
Use drought tolerant pasture mixes — species including alfalfa, chicory, red clover, orchardgrass and tall fescue have good drought tolerance and can help during dry summers. Perennial ryegrass, kentucky bluegrass and white clover have poor drought tolerance, and go dormant very quickly.
Surplus spring growth can reduce tiller density and summer growth potential — there is evidence that closer spring grazing can benefit summer production.
Learn feed budgeting
Using a feed budgeting and monitoring system can identify feed deficits up to 3 weeks earlier than without such a system. This advance notice can give you critical time to think and plan your options before the effects of a drought actually hit.
Observe changes in your pasture
What has survived the drought? Are these the grasses and legumes you want? Does your management favor these forage species?
Maintain a sacrifice area, a heavy use pad or a paddock, which will be utilized in extreme situations while allowing pastures to re-grow. One of the best ways to weaken a stem is to overgraze during the summer through the killing freeze.
Maintain good fertility levels
Soil test and adjust pH, phosphorus, potassium and strategically apply nitrogen to support forage growth.
Consider frost-seeding legumes in February or March.
Evaluate the need for weed control. Consider carefully weed pressure and herbicide use next year. Some problem perennials may need to be controlled.