By Sjoerd Willem Duiker and Justin Brackenrich
Many grazers and agricultural professionals will refer to the hot, dry part of summer, as the summer slump. The summer slump is when cool-season grasses, which compose the majority of Pennsylvania hay and pasture fields, slow in growth or essentially go dormant. The optimum temperature for cool-season grasses is between 60°F to 80°F, anything above this and growth dramatically declines. Since regrowth slows during this period, it is critical to avoid grazing too low during the summer months. Ignore this and serious soil degradation, nutrient loss, and weed invasion is usually the result. This article will outline a few practices that will promote stand health, and encourage regrowth when temperatures drop, and grasses begin to regrow.
First, maintaining 3-4 inches is the general rule of thumb for grazing practices, but it is especially important during this time for various reasons. Above ground biomass is so important to grazing systems because what you see above ground is reflected belowground. Research has shown that if grass is grazed very short repeatedly, the root system dies back significantly, and the stand declines. This is critical during the summer months as grasses try to scavenge for limited water sources. Most problematic pasture weeds have taproots, which makes them excellent water scavengers because that taproot grows deeper than the fibrous root system of grasses. Research shows, that grazing too short during the summer slump, as would occur in a continuous grazing system, results in increased weed populations and exposed soil which results in increased soil erosion and nutrient runoff. Further, soil health degrades because it depends in great degree on vigorous root systems. Grazing too aggressively negatively impacts the grass's ability to regrow as temperatures cool in the fall.
Second, just like tall, thick forage stands can help to protect crowns and tillers from freezing, these kinds of stands can also shade them from high temperatures. If grazed too low, tillers could be exposed to temperatures as high as 95°F compared to temperatures in the mid-70s°F under a well-developed canopy. Those high temperatures could cause tillers to die and result in thin stands.