The perfect pasture? It’s an environmentally and economically sustainable forage system that meets the needs of the grazing livestock and the producer.
If a grass farmer intensively manages the pasture, production is consistent and reliable compared to continuously stocked pastures — even in stressful conditions such as drought. There is enough leaf material for photosynthesis to produce more sugars than are being used for plant maintenance within three weeks of grazing.
The forage canopy covers 95% of the ground surface, with a leaf area index ranging from 3 to 6. Good canopy cover optimizes transpiration, water uptake and evaporation through the plant and minimizes evaporation from the soil surface. That optimizes water-use efficiency.
The amount of canopy or leaf area remaining after grazing is critical for pastures to maintain good growth. We studied the light interception by orchardgrass in rotationally grazed irrigated pastures in south-central Idaho. Our conclusion was that orchardgrass needs 4-5” of stubble height to produce more forage for the next grazing cycle and maintain a vigorous root system to withstand stresses such as drought.
About 90% of the plant nutrition from the soil is provided by recycled nutrients from livestock, insects and soil organisms. The 10% of lost nitrogen (N) that is volatilized from the pasture is replaced by atmospheric N that is fixed into plant-available ammonia and nitrate by legumes. Legumes comprise 40% of the plant population, and at least half are non-bloating, such as birdsfoot trefoil. The perfect pasture will be sustainable with a minimum of fertilizer nutrients.
How do grass farmers manage to get the perfect pasture?
Herding, used for about 8,000 years, successfully provides most of the necessary actions to allow for the perfect pasture, except when another herder moves into the same area too soon. Pastures divided into paddocks and subdivided with temporary fencing can concentrate livestock and provide for high stock densities from 30,000 to 60,000 lbs of animal live weight per acre, which can replace herding.
The common thread in both systems is intensive management of forage allocation to the livestock.
Extraordinary fall management is necessary to provide conditions for the perfect pasture. Fall is critical for development of tillers the next spring. Too many grass farmers have the idea that efficiency is “no blade left behind.”
Besides leaving adequate photosynthetically active plant tissue, we need to consider the energy storage in the stubble of cool-season perennial grass plants. Maintaining a type of battery that stores energy for winter survival and tiller growth next spring is critical for optimum forage production.
Cool-season perennial grasses store energy as fructans in the lower parts of the stems and leaves, most below 4-5” of stubble. This energy storage is critical for next spring’s growth, as the roots first grow in late February and early March, before any growth of above-ground leaves, and before much photosynthesis occurs.
Each unit of the perfect pasture would not be managed the same. That’s because the perfect pasture system would allow early spring grazing on several paddocks that were not grazed much the previous fall.
Conversely, to extend the grazing season, some paddocks might be grazed late into fall, recognizing production will be reduced next spring. This also relates to the myth of the “perfect grass” species. A diversity of plants within and among pastures is desirable. Different tools are useful to meet specific goals.
The Lost Rivers Grazing Academy provides an annual four-day boots-on-the-ground training opportunity that can help graziers attain the perfect pasture. Forage publications and pasture tools are available from the academy site and from www.extension.uidaho.edu/forage.
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