With temperatures 90 degrees F and above and high humidity this summer, cool-season forages suffer. Alfalfa and clovers, bromegrass, orchardgrass, fescues, needlegrasses and wheatgrasses all struggle during hot weather.
When temperatures don’t drop much below 80 degrees, even at night, it results in very slow growth, lower forage quality as plants burn up the good nutrients and limited recovery of root reserves after defoliation. And, when it’s also dry, these conditions can even become deadly. Proper expectations and management adjustments can limit the stress from stressful weather.
Warm-season grasses have the opposite response. Millet, sudangrass, sorghums, our native bluestems, gramas, switchgrass and other warm-season grasses thrive when the temperature is around 90 degrees. Their metabolism runs at peak efficiency when it is hot, so they grow rapidly while maintaining reasonable forage quality and good root growth.
Sufficient moisture key
Of course, this assumes these plants have adequate moisture. Once they dry up, these grasses will overheat too — just like cool-season grasses do at lower temperatures.
As you graze or hay, be aware of the stress that weather is putting on your forage. When it’s too hot, allow plants to recover for a longer time before the next use. And don’t expect high feed values or good animal gains when the nutritional goodies are burned right out of the plants.
Anderson is a Nebraska Extension forage specialist.