Evaluating and Maintaining Pastures in Dry Conditions

During droughty periods, we need to make adjustments to our pasture management. In a typical Pennsylvania spring, there is adequate moisture and ideal temperatures for our cool-season forages to thrive. Our pastures often have surplus forage that allow for easy grazing management with long rotations, short rest periods and the potential for hay production. When conditions turn dry, at any time of the year, especially if temperatures are high, those pasture grasses will start to shut down or go dormant. This dormancy is a stress response to conserve energy, where the top growth may start to brown. This browning may be alarming and look like the plant is dying but energy is being diverted to the crown or roots rather than the leaves.  

Well-established grasses with deep root systems will bounce back after some moisture. Treat spring drought-stressed pastures like you would during the summer months. Do not allow livestock to continuously graze an entire pasture, continue to stick with a rotational grazing plan. After a grazing event, grasses will be slow to regrow and will need longer rest periods. Fully dormant grasses will not be able to regrow after grazing or mowing. This may mean that a sacrifice area will need to be utilized, like a barnyard, indoor feeding area, or paddock that needs remediated, while waiting for pasture regrowth. Heavily damaged pastures can be evaluated once the drought breaks and assessed for a replanting or overseeding. Once temperatures cool and moisture returns, you will be tempted to graze too short or too soon, don’t! Pastures need time to regrow above and below ground before grazing resumes. Deeper roots help ensure the plant can continue to scavenge for water and nutrients. Grazing too soon after a drought will further deplete any energy the grasses had stored causing roots to die off. Allow grasses to reach a height of at least 8-10 inches like normal when rotationally grazing and avoid overgrazing even after moisture returns. Do not graze less than 4, preferably 6, inches if drought conditions are to continue. For more information on grazing during the summer months, check out: Grazing During the Summer Slump.  

New seedings may not have the energy reserves to survive a drought. Do not graze new seedings during a drought and an evaluation will have to be done later in the season after moisture returns to determine if a follow-up planting is needed to thicken the stand.

Alternative Forages

As a drought persists, it is common to start thinking about emergency forage plans. Keep in mind, however, that under heavy drought conditions, new seedings will not be able to germinate. So any of our common emergency summer perennial warm season grasses like, switchgrass, big bluestem or any of the annuals like sorghum or sorghum x sudangrass hybrids would sit in the ground without adequate moisture. Switchgrass and big bluestem should be planted by mid-June and many of the warm season annuals can be planted as late as mid-July in certain areas of Pennsylvania, so waiting for forecasted rain would be recommended. More immediate adjustments like supplemental hay, baleage, haylage, etc. will be needed before those grasses are ready for grazing. Keep in mind when feeding warm season annuals that there is a risk of high nitrate levels, particularly during a drought.

Evaluating Available Pasture Forage

Estimations on pasture forage can be difficult compared to hay because the grasses are not collected and baled making them easy to weigh and count. This can be a time-consuming process because of that but can be of particular value during drought conditions to know if, and when, you’ll need to start using stored forages as supplemental feed.

Many methods exist such as hand clipping or utilizing a pasture ruler or rising plate meter. Hand clipping is precise but will be the most time consuming and impractical. A pasture ruler will evaluate based on plant height and its relationship to yield. The rising plate meter will look at both height and density. For more information on how to perform these tests, check out Determining Pasture Yield.

When assessing pasture yields, also be sure to look at the composition of the available forage. Is it a majority desired grasses? Are there some weeds in there? Is it mostly weeds that the livestock avoid? Just like with soil testing, irregular areas should be avoided when doing a pasture evaluation for available forage.  Don’t evaluate available forge from areas that contain heavy amounts of weeds or species that the livestock aren't eating on an annual basis. If there is heavy weed presence, consider some methods of weed control after the moisture returns. This will vary based on the time of the year and the weeds present.

For additional information on stored forage inventories like silage and hay, check out this article: Thoughts for Drought: Forage Inventorying.

Livestock Needs

The amount of forage that you need for your livestock will be determined by a variety of factors including, stocking rate, type and growth stage of livestock, the time of year, species of forages available, etc. The goal being that you need to meet the nutritional requirements of the livestock you have based on whatever stage of life they happen to be in and determining if you have enough quality forage to feed them. This may or may not be met with pasture alone, especially during drought conditions with minimal to no grass growth. Supplemental forages will be required as pasture availability declines and animals need moved onto dry lots.

"Pasture Species Selection by Animal Group", can help determine the best grass species for your pasture based on the type of livestock you have.  

Pasture Maintenance

Typical pasture maintenance includes mowing and fertility. These practices reduce grass seedheads, encouraging tillering and vegetative growth, and prevent weeds from developing viable seeds and spreading. So how does this change in droughty conditions?

Mowing under drought conditions can still be beneficial because it reduces the overall surface area of the plants thus decreasing the amount of water that is lost by the plant through transpiration. The stubble height should remain as high as possible, around 6 inches to maintain adequate ground cover and reduce water losses from the soil through evaporation. This will help to conserve and hold moisture in the soil when it does eventually rain.  

Maintaining soil fertility on an annual basis is often better than making an emergency application when plants are stressed. During a drought, grasses will be slow to take up any added nutrients because the plants take up those nutrients when they take up water, so water is the limiting factor in this case. There is also the potential for nitrogen losses without rainfall when paired with warmer temperatures, so careful considerations on type of nitrogen fertilizer and the addition of ways to inhibit volatilization will be necessary. Check out "Forage Fertility and Quality Issues During Spring Drought" for more details on nitrogen applications during a dry spell. Animals should also not be allowed back onto pasture with surface applied fertilizers until about ¼ inch of rain has fallen to wash residue from plants and incorporate the fertilizer into the soil.  

In general, fertilizer applications are not recommended when grasses are dormant, so waiting until rainfall is in the more immediate forecast and then continuing with your usual pasture fertility program. It is possible that decreased nitrogen applications will be needed if lower production is expected.

As a final thought, always remember that overgrazed grasses with shallow root systems will become drought stressed faster so implementing a rotational grazing plan that allows for adequate stubble heights will help the grasses tolerate a drought better and recover more quickly after rain. Taking care of pastures each year will ensure that we have a grass stand which will quickly regrow in the spring and persist for several years without requiring reseeding.