Grazing in dry pastures

By Matt Reese

Dry conditions are hit and miss around Ohio, but by mid-July areas of “moderate drought” were starting to show up in northwest (Williams, Defiance, Paulding, Van Wert) and west central (Hardin, Logan and Champaign) counties. Along with hurting corn and soybeans, pasture ground around the state was really starting to suffer.

“Once it gets dry, the best option you’ve got is to pull your stock off. Most farms have some woods or marginal areas you can graze that would help a little bit. You can de-stock and cull surplus livestock. Or, you can design your system so that you have got stock that can be sold off,” said David Barker, Ohio State University grazing specialist. “It all takes planning. Without planning, people will graze the pastures down to the dirt. Once the pasture is that short, the ability to recover isn’t there. If a rain does come there is no vegetation to hold the water there. The ground heats up when it is grazed down and you can expect the soil surface temperature to be 10 or 15 degrees hotter than the air temperature. Vegetation acts like a mulch layer that is going to keep the ground cool. When it gets dry, it is easy to make it worse if you leave animals on pasture.”

Over-grazing can have long-term implications.

“We all know that without rain or irrigation pastures will not grow, and close grazing will exaggerate this effect. Leaf removal by grazing 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,” Barker said. “As a general rule of thumb, grazing below 2 to 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.”

During drought conditions is it also important to monitor the potential for the “triple whammy” of endophyte poisoning on tall fescue and perennial ryegrass. First, levels of the toxic alkaloid ergovaline are elevated in summer drought conditions. When there is less to graze, livestock bite nearer the base of plants where endophyte and alkaloids are more concentrated. In addition, seedheads 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,” Barker said. “You might also consider feeding hay or grain.”

Another key concern is how to manage grazing when rains do come after extended dry conditions.

“There is a risk of nitrates with drought, so people have to know how to manage it. It is very simple. You have to manage for nitrates and if you get it wrong, it could be devastating. The problem is not so much grazing it in the drought, but when you get rain, there is nitrate in the soil that has continued to mineralize in the dry conditions. The plants take up all of that nitrate at once and you can get toxic levels of nitrate in the flush of growth that follows a rain,” Barker said. “All you have to do is wait a week and the plants metabolize that down and will be safe. You can send a sample to any testing labs in Ohio and forage nitrate tests often have priority for analysis. You just put some forage in a bag and send it in. They test it and call you with results in 24 or 48 hours. It is better to get a test if you are unsure.”

Barker said the temptation is high to get livestock grazing with new growth after a rain.

“It is the worst situation because everyone is desperate for feed. You get rain and ‘Praise the Lord. We’re safe now. Let’s put the cows out there.’ That is the worst thing to do. That is when forage is at the maximum toxicity,” he said. “It probably will involve some hay for the next week. Then you can put them out there perfectly fine. You just hear a lot of sad stories of putting livestock on forage one week too soon.”

Barker said the greatest concerns with nitrate toxicity problems are sorghum-Sudan grass, pearl millet, teff, and others in the warm-season family.

Once the drought has ended, nitrogen applications can help to boost forage recovery.

“Strategic use of N, early in the recovery from drought can re-gain some of your losses,” Barker said. “Don’t make applications too early, since volatilization losses could be high without rain to ensure incorporation of N.”

In terms of better preparing for future droughts, there are a number of good options to consider, Barker said.

“A lot of these things take planning and some math to figure out the best plan,” Barker said. “Every farm grazing plan needs many strategies on how you’re going to get through summer.”

Barker offered these tips for setting pastures up for success during droughts in the future.

  • 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.
  • Early calving could get calves weaned and off the property before the drought hits — dry cows on a maintenance diet have a much lower feed requirement.
  • 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 options before the effects of a drought actually hit.
  • Observe changes in the pasture. What has survived the drought? Are these the grasses and legumes you want? Does the management favor these forage species?
  • Maintain a sacrifice area, a heavy-use pad or a paddock, which will be used in extreme situations while allowing pastures to re-grow.
  • 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.

And, though Ohio is facing some tough conditions in 2020, properly managed pastures have recovered from more severe situations in the past.

“There are places this year where the pasture growth rate is zero, but we are still above average rainfall for the year. We had very high rainfall for March, April and May. Even June was up a little. It has only been these last few weeks we are looking at this dry period. We are right on the brink of having a problem. It depends on what pop-up showers you’ve had,” Barker said. “2012 was the worst drought we’ve had in a while. We have had as much rain in the first half of 2020 as all of 2012 in total. This year we have had 29.6 inches so far and 2012 had 30 inches of rain all year. We are not looking at a 2012, but if we don’t get rain for another few weeks it could still be a real challenge.”

 

 

 

 

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