Managing perennial pastures to withstand drought
Plan ahead to ensure grazing lasts as long as possible.
Effective graziers constantly assess and monitor their pastures forage inventory, and this is never more important than when rain is scarce. Pastures that are already vigorous, well fed, and managed to promote root and plant health will remain productive longer than neglected pastures going into a drought period.
Pastures that include a diverse mixture of grasses, legumes, and forbs (broadleaf plants that are not legumes) can often withstand drought better than monocultures if some deep-rooted and drought-tolerant species are included. Species with good drought tolerance for the Great Lakes region include alfalfa, smooth bromegrass, tall fescue, reed canarygrass, and chicory. A dense plant canopy and root system also improves soil water-holding capacity by providing organic matter to absorb water and keep it in the root profile, and by improving infiltration of any scarce rain that occurs. The plant canopy also shades the soil, keeping it cooler, and this helps cool-season plants last longer before the combination of hot soil and lack of water shifts them into dormant survival mode.
To help maintain soil fertility, Michigan State University Extension recommends that pastures be soil tested at least every three years, with lime, nitrogen, phosphorus, and potassium applied as needed. Potassium is an especially important nutrient for helping plants withstand stress like drought and winterkill. Keep in mind that moisture is needed to dissolve top-dressed fertilizers before they can move into the soil and then into the plant. This is one reason why it is so important to keep up with soil fertility. Deficits can be difficult to address in the middle of a drought crisis.
Managed grazing is essential to getting the most out of a pasture during drought. A well-managed pasture uses rotational stocking to build soil and plant health and vigor while maintaining good animal productivity. There are many variations of rotational stocking, but they all involve moving animals around the pasture within smaller paddocks, thus controlling animal access to plants and allowing plants to rest and recover from grazing. Rest is essential to pasture plant survival. When plants are stressed by lack of water, it is more important than ever to make sure regrowth is not grazed until enough new leaves have formed to support the root system.
As a general rule of thumb, this means animals should not be kept on a paddock for longer than four days and they should not be put back into the paddock until at least three new leaves have appeared on grass tillers or new flowers have appeared on legumes. This may only take three weeks during the fast growth of spring with adequate rain, or it may take months if grasses go dormant in drought. Shorter paddock occupations of one day or even less can also help encourage livestock to eat the available forage uniformly if enough stocking density is applied. Uniform grazing means that more of the available forage gets into the livestock. It also means that recycled nutrients in the form of urine and manure are distributed more evenly across the pasture.
Pasture utilization is a grazing term that refers to the percentage of grass production that is eaten by the grazing animal. In a forage shortage, it is tempting to leave livestock on the pasture until every scrap of green is eaten. This will slow down recovery of your pastures when the rains return. A normal utilization target is 50% (take half, leave half) of available forage, but this may range from 30-70% based on time of year, forage type, and grazing goals. In a drought, it is better to err conservatively and aim for utilization rates in the 30-50% range leaving at least four inches of stubble behind, when the animals are moved. This leaves more residual forage behind in the pasture to help the plants survive and will pay off in the long run because live plants can grow back.
To learn more about pasture growth, refer to this article on spring turnout. When pastures have not grown back enough to support viable grazing, it is best to confine animals in a small sacrifice paddock and feed hay or supplements. This will likely destroy the plants in that sacrifice paddock, but it will be less costly to renovate the small area than the whole pasture after the drought breaks. When choosing the sacrifice area, pick one that is already in poor condition instead of the best paddock.
During the spring growth flush, cool-season perennial pastures that contain more than 2500 pounds of forage dry matter (DM) per acre are not optimal for high-quality grazing because they are likely to be heading out or flowering. At flowering, nutritive value of forages declines sharply which means animals need to eat more bulk to get the same nutrients. It is also difficult to graze tall, overmature pastures without getting considerable levels of trampling. Trampled forage is not truly wasted because its nutrients and carbon recycle into the soil, but it does not help to keep the livestock fed in times of forage shortage. A thick layer of trampled mulch will also slow down regrowth and reduce tillering because light needs to reach plant crowns to trigger new growth. Therefore, paddocks that “get away” in the spring are best removed from the regular grazing rotation. These can be set aside for hay or baleage and returned to grazing later. Alternatively, they can be set aside for stockpiling and deliberately grazed later as mature “standing hay.” If there is adequate rain, new regrowth will come up through the old dead stems and provide green herbage for animals to select. This mature hay stockpiled in place will be relatively low in nutritional value but can be suitable for livestock with modest nutritional needs. Paddocks that are grazed through the end of June and then set aside for stockpiling will likely remain vegetative and can provide very high-quality grazing in the fall provided there is some rain to drive regrowth.
Another tip for extending perennial pasture life in drought is to reduce the stocking rate. If the forage budget is calculated out into the future and shortage looms, consider reducing herd or flock numbers early. A drought is not the time to carry unproductive animals. You may be able to get a better price if you are selling before necessity forces everyone to flood the sale barns with livestock they cannot feed.
Another way to reduce grazing pressure on stressed perennial pasture is to move stock elsewhere onto temporary annual pastures planted on idle cropland. Think about grazing drought tolerant annual forages like sorghum, sudangrass, millets, or cover crops. Graziers do not need to own the land—it can often be leased for grazing and fenced using portable electric wire or net. This can become a win-win for the livestock owner who gets extra forage and the landowner who gets the benefits of cover crops plus the grazing fee. Be aware that annual forage seed supplies may rapidly become limiting in a widespread drought.
When you plan, you can be better prepared for adverse weather conditions.