By Sjoerd Willem Duiker & Justin Brackenrich
Most grazers rely on cool season pastures to sustain their animals. Growth of cool season grasses nearly come to a standstill when temperatures hit 80°F, which often causes a problem for grazers. This condition of slowed growth is referred to as the ‘summer slump’ in pasture production. Farmers should watch for overgrazing in these pastures because it can lead to many problems.
- overgrazing reduces the ‘solar panel’ for regrowth. Meaning that once temperatures decrease again, your regrowth will be slower. The solar panel of a plant refers to the leafy areas and the plants ability to capture energy from the sun to produce the needed carbohydrates for regrowth.
- overgrazing damages the root system. Because the small leaf area cannot capture the photosynthetic energy to sustain a healthy root mass, pastures are more susceptible to drought – further increasing your exposure to the summer slump.
- the weak, overgrazed pasture will be highly susceptible to interrill, rill and gully erosion, which can lead to: loss of valuable topsoil; reduction in soil organic matter; and reduction in nitrogen pool to feed your forage.
- overgrazing increases soil compaction. With limited grazing sources, animals tend to congregate leading to higher risk of soil compaction due to hoof pressure. This, coupled with the already damaged root systems, will almost certainly lead to compaction issues.
By having animal numbers that reflect plant production during this summer slump, you can avoid most of the negative effects resulting from over grazing. You can also supplement with hay or haylage, but remember that the cost of harvested feed is at least twice that of grazed forage (even if you make it yourself), increasing your yearly feed bill dramatically. Intensifying your grazing management is another way to increase productivity of your pasture. By concentrating the animals in small paddocks and letting the paddocks rest, will reduce issues related to compaction and allow your forage to regrow to a desired height before re-grazing.
Part of good grazing management is also to leave an appropriate amount of vegetation for regrowth - guidelines vary but in general you should leave 5 inches or more. Diversification of forage species is another strategy for beating the summer slump. This involves either using warm season annuals or perennials adapted to temperatures up to and exceeding 90°F, which are species like switchgrass or mixes of big bluestem and indiangrass. Warm season perennial species take some effort to establish when compared to cool season species and should be allowed to grow for around a year before grazing. However, once established, warm season species offer the added benefits of low-maintenance and drought tolerant, and stand longevity – under proper management, warm season perennials can be productively grazed for 20 years or more. Warm season annuals that can help alleviate the summer slump are sorghum-sudan, sudan grass, pearl millet, or Japanese millet, which is adapted to poorly drained soil. Warm season annuals can be planted now or even after small grain harvest. By using Management Intensive Grazing that includes warm season annuals and perennials, your farm can become more productive and profitable.