How Summer Heat Affects Forage Growth
With temperatures in the 90s this week and humidity high, cool-season forages are suffering. Alfalfa and clovers, bromegrass, orchardgrass, fescues, needlegrasses, and wheatgrasses all struggle during hot weather.
When temperatures don't drop much below 80°F, 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, and our native bluestems, gramas, switchgrass, and other warm-season grasses thrive when the temperature is around 90°F degrees. Their metabolism runs at peak efficiency when it is hot so they grow rapidly while maintaining reasonable forage quality and good root growth.
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 weather is putting on your forage. When it’s too hot, allow plants to recover for a longer time before next use. And don’t expect high feed values or good animal gains when the nutritional goodies are burned right out of the plants.