It’s hard to tolerate waste in agriculture. We find ourselves in a craft where efficiency has been a core goal for at least the past 90 years. As such, it’s understandable that we might expect to minimize waste when grazing and cutting hay. That desire for extra forage can become quite pressing as we get into slumps in our forage programs.
Grazing sticks, disc mowers and dry summers push us to look out on stands and ask if we can take a lower cut or a longer graze. It’s understandable that we might want to get more out of a pass over the field or that we might need to push a stand in harder times. Our agents and our forage specialists tell us to leave some residual leaves, but we need some forage now. What’s the real value of cutting or grazing a little lower?
Here's a real-world math problem from a farm in Faulkner County, Arkansas. There’s a 13-head herd on 32 acres of mixed pasture with a lot of fencing and water infrastructure that makes rotational grazing and hay production easy for the owner. There have been some issues with bulls hopping fences, but the herd is generally in a similar plane of nutritional demand.
Let’s say that cattle generally go into a new paddock when the grass is 8 inches tall and leave when the grass is 4 inches tall. What’s the value of trying to graze down to a 2-inch stubble?
Here are some givens:
- Paddocks are approximately 5 acres.
- Grazing efficiency is 75% because cattle are moved through a lot of paddocks that get a fair deal of rest.
- The herd is 13 head, ingesting 2.5% of their bodyweight and weighing 1,200 pounds on average.
- Mixed pastures in excellent condition have about 400 pounds per acre per inch in forage, whereas fair-condition pastures only have 200 per acre per inch in forage.
The number of days a paddock can support grazing is estimated in Table 1.
Shorter stubble, longer grazing – with a price
If the pasture is in excellent condition, leaving a 4-inch stubble allows the paddock to support 15 days of grazing, and leaving a 2-inch stubble allows the paddock to support 23 days of grazing. Occasionally grazing a little lower will provide a little over an extra week of grazing. After three to five years of strong grazing, fertility and weed management, our pastures will forgive this occasional intense grazing event. We can build up the resilience of our grazing systems when our plants are allowed to recover from grazing or haying events.
However, these calculations obscure the fact that repeatedly grazing to lower stubble heights will degrade the stand over time. There was a study conducted in Virginia on orchardgrass and orchardgrass-alfalfa stands cut to different stubble heights. While yield was high in the stands cut to 2-inch stubbles, the stands degraded starting at the end of the first season. A 4-inch stubble balanced forage production and stand persistence. Whether warm season or cool-season, leaving a 4-inch stubble seems to be a great starting point for managing our pastures and hayfields.
Leaving less stubble after multiple grazing or haying events will slow down plant regrowth and can even shift the composition of a pasture away from more productive species. Think about the spread of common crabgrass, broadleaf weeds and bare soil where aggressive harvesting removes the root reserves of more desirable bermudagrass or tall fescue. Stubble heights can set the long-term trajectory of our plant pasture community in terms of its composition and productivity. In our example, the mixed pasture might move from excellent condition to fair condition.
Repeated shorter stubble equals shorter long-term grazing potential
When we account for the stand degradation typically seen when we leave short stubbles repeatedly, we can calculate that while our 4-inch stubble still provides 15 days of grazing, the 2-inch stubble only offers 12 days of grazing. When we compare the canopy architectures in those stands, those 12 days of grazing also provide less nutrition to the herd.
Our pastures and hayfields can be extremely forgiving when we graze or cut a little too aggressively, so long as those occasions are infrequent. In the long term, we will reduce the productive potential of our stands. The stubble left behind has been described as a solar panel, but it’s really a battery of energy to help our forage plants recover from grazing, grow new leaves and start building up energy reserves for the next grazing event. Crucially, a battery can only go down to zero. The stubble left in a field might be seen as waste, but that stubble is the source of our next grazing or hay crop.
We need to be especially judicious in pastures and hayfields where we are correcting years of mismanagement. The cushion of plant root reserves, soil nutrients and organic matter, as well as the productive plant community, will not have the resilience for overgrazing or aggressive haying.
When it comes down to it, leave the stubble, keep the stand.
