MANAGING SUMMER SLUMP

On hot summer days, you are not the only one that wants a shade tree and a drink. The majority of our pastures in the Northeast and Upper Mid-Atlantic are comprised of cool season perennial plants, which grow optimally in temperatures of 60-80 F. There is a good reason for this. Cool season perennials offer high quality feed when harvested at the appropriate time. They grow during the many cool days experienced in this area, and they hold their quality fairly long into the winter. However, by the time the corn is starting to stretch to the sun, these plants are slowing their growth, or going dormant. For pasture-based cattle and small ruminant producers, this can be a challenge. You may want to reap the benefits of reduced forage costs that can come with grazing, or if you are a certified organic producer: you may need to graze through the summer to meet your pasture requirements. Thankfully, seasonal changes also offer seasonal opportunities.

The first management technique to look towards would be rotational grazing with the aim of conserving pasture through the season. Success in this is dependent on you stocking appropriately for your total acreage, rotating with the appropriate stocking density and rest times. These will be dependent on your stock requirements and pasture productivity.

Rotational grazing will also help keep your pastures healthy, summer slump and beyond. The technique of rotational grazing can be combined with clipping. As the cool season grasses are attempting to go to head in the summer heat, clipping them will keep them more palatable and digestible. You would set your mower high, leaving a generous amount of leaf to photosynthesize and support new growth. The goal is just to keep a vegetative state by clipping off the top portion and seedheads. You would then plan for a period of regrowth, which could take from 2 weeks to a month, depending on the conditions.

Another consideration is cool-season species selection. Although, they all fit into the general category of cool-season species, some grow better into the hotter periods of the season. Orchard grass, for example, is more likely to maintain growth and quality into the summer, as well as clovers. It may be tempting to consider tall fescue in this conversation as it has good drought resilience, and can persist through tough grazing situations, but this would be the best time to avoid endophyte infected fescue (Kentucky-31), as this is typically when its toxins are at their peak. Novel endophyte or endophyte free fescue could be grazed at this time, but, if possible, tall fescue would be best grazed after the frost, when it is more palatable, and when the majority of the toxins have dissipated from the leaves of the endophyte infected variety.

Unfortunately, even under careful rotational management, cool season pasture regrowth in the summer is still limited by the temperatures and moisture availability. For farmers who are reliant on good quality pasture through the growing season, choosing plants that thrive in the heat is a reliable option. Most commonly the Mid-Atlantic and Northeast area, this would be summer annuals.

The summer annuals that are commonly used for forage in this area are primed for heat and moisture-use efficiency. They germinate best in soils at 65o F, and grow well into the heat of the summer, even when temperatures surpass 90 F. There is a wide variety of options here. The most common are sorghum-sudan grass, millet, forage sorghum, corn, soybeans, cowpeas, and sunflower. Nutritionally, when taking high performance into consideration, you would want a mix that included a legume.

A mix of sorghum-sudan and cowpeas is a great place to start. The cowpeas will climb the sorghum-sudan well, offer protein to the animal and nitrogen to the soil. A study done by the University of Tennessee showed no dry matter losses when 50 lb/acre cowpeas were added to a sorghum-sudan pasture seeded at 30 lb/acre, and an increase of 2% crude protein over the sorghum-sudan alone1.

Before picking a summer annual species or species mix, do your research! There are management considerations to many of these, including prussic acid in the sorghum species and their hybrids, and nitrate accumulation in many of the annual summer grasses.

Summer annuals are a ideal option for quick dry matter in the summer heat, but there are native grasses to consider as well.

These native warm-season perennial grasses have the benefit of being poised to grow when the temperatures warm and produce deep root systems along with tons of dry matter. Switchgrass, for example, averages 4-6 tons acre in Pennsylvania2 and 5-6 tons in the Mid-South3. They can also be harvested for hay, and if left to grow back in late summer, they can provide cover for wildlife in the fall and winter (if that is one of your goals). Their deep root systems make them great for soil building, and great at scavenging nutrients. They aren’t warm season miracle plants, though. Warm season perennials take longer to establish, and once established, they need to be managed with a bit more care. They are more sensitive to over-grazing and are best left with 6-8 inches of residue after harvest or grazing. You will also have to consider what stock will be utilizing them, as they are lower in protein and quicker to lignify than your cool season grasses. Native warm season grasses average 8-12% crude protein at optimal harvest time, and the NDF of samples in this protein range are over 60%3. This may mean using these pastures for heifers, dry cows, bulls, or cows in maintenance. The pastures could also be maintained with interplanted clover or other legumes to increase the protein of the sward.

These above ideas are with the goal of maintaining forage availability throughout the season’s higher temperatures. However, there is nothing “wrong” with developing a hybrid system, where the animals are fed in the barn through the hottest parts of the summer.

If you are certified organic, work with your certifier to define your particular “grazing season,” and make sure you are aiming to meet your dry matter requirements from pasture. Under NOP guidelines, the “grazing season” does not have to be continuous, so you have the space to be flexible with your timeline, and work-in some breaks for the summer heat.

However you chose to face the summer slump, remember that pasture is an important resource that should be used wisely. Know your pasture, plan around its bounty and scarcity. With a little planning, I hope you get a moment to enjoy watching well-conditioned cattle grazing in early fall. As the orchard grass pops back into steady growth, you can be confident that you brought your stock through the worst of the summer heat.

Works Cited:

Nave RLG, Quinby MP, Griffith AP, Corbin MD, Bates GE. Forage mass, nutritive value and economic viability of cowpea overseeding in tall fescue and sorghum-sudangrass swards. Crop, Forage & Turfgrass Mgmt. 2020;6:e20003. https://doi. org/10.1002/cft2.20003

Jacobson, M. Ph.D. NEWBio Energy Crop Profile: Switchgrass. Pennsylvania State Extension. 2013. https://extension. psu.edu/newbio-energy-crop-profile-switchgrass.

Harper CA, Bates GE, Hansbrough MP, Gudlin MJ, Gruchy JP, Keyser PD. Native Warm Season Grasses. University of Tennessee Extension. 2007: PB1752. https://extension.tennessee.edu/publications/Documents/PB1752.pdf