We are in what is typically the hottest part of the summer, and we need to consider how these temperatures affect our pasture and forage plants.
The two primary plant classifications are warm-season and cool-season, and this is based on basic plant physiology and their specific photosynthetic pathway. Practically speaking, and as their names suggest, every plant species has a specific temperature range in which it maintains growth.
When it gets hot, 90-plus degrees F, cool-season plants such as bromegrass, orchard grass, fescues, needlegrasses and wheatgrasses all struggle and will have a very slow growth rate, even if there is plenty of moisture. When it is very dry, these cool-season grasses may completely stop growth and have gone into a summer dormant state.
Warm-season grasses are just the opposite. Millet, sudangrass, sorghums, bluestems, gramas, switchgrass and other warm-season grasses thrive when the temperature is around 90 F. Their metabolism runs at peak efficiency when it is hot, so they grow rapidly while maintaining reasonable forage quality and good root growth. With drought conditions, also be aware of the potential for the seeded summer annual grasses to accumulate nitrates.
As you graze or hay, be aware of the stress weather is putting on your forage. When it’s too hot, allow plants a longer recovery period before the next grazing. And don’t expect high feed values or good animal gains when the nutritional goodies are burned right out of the plants.
Proper expectations and management adjustments can limit the stress from hot weather.— Jerry Volesky, Nebraska Extension educator
