Recently I was asked to write this column for the Leopold Letter, the newsletter of the Leopold Center for Sustainable Agriculture.
Twelve thousand years ago, in the wake of a glacier, the land that would become Northern Iowa was a geologic wasteland. Glacial materials conveyed from the north had obliterated the biological diversity of the previous era. But then nature’s ecological processes began anew, creating-over twelve millennia-a prairie ecosystem with its fertile, productive soils.
How did that happen? Gradually, plants, animals and microorganisms colonized the desolate landscape, creating an increasingly diverse and complex ecosystem. The ecosystem’s plants and animals generated organic materials which soil microorganisms used to develop fertile soils from raw geologic materials.
It has been estimated that fifty million bison once roamed the prairies and plains of North America. Bison herds roving the prairie landscape are a useful model we can use to design animal production systems that are resilient, energy-efficient, and biologically diverse. (continues after the jump)
When bison herds grazed the tall, deep-rooted prairie plants, they reposited their manure nutrients back to the soil from whence the plant nutrients had come. And, their grazing activities stimulated regeneration and robustness of the ecosystem. When grazed, the now shortened plants had excess root mass and sloughed a portion of it into the soil as the plants began a new cycle of their perennial process of capturing sunlight to produce new shoots and roots. The root mass that was released into the soil after the bison had grazed the prairie plants became food to sustain soil microorganisms and produce humus. Repeated grazing cycles of the roaming bison herds increasingly added to the soil’s fertility and productivity.
Modern livestock production systems can be designed and managed to mimic the ecological processes that created the diverse prairie and its productive soils. And these systems can be much more energy-efficient than current industrial animal production methods. The key is to find ways to harness the energy, efficiency and organizing power of nature’s ecology.
A grass-based dairy farm provides a good illustration of one way this can be done. In a grass-based dairy, the landscape surrounding the milking barn is converted into a polyculture of grasses, legumes and forbs-some of which are planted and some that “volunteer.” The landscape of perennial plants is divided into segments (called paddocks) using inexpensive fencing materials, with cow lanes connecting all paddocks to the milking barn. After each milking (twice a day) the cows are allowed to graze a new paddock area that is just large enough to provide the cows’ forage needs until the next milking time. As the cows rotate through the paddock system, grazed paddocks have time for recovery to allow plants to regrow to a stage of optimum nutrition for the next grazing episode.
Management is important. If paddocks are allowed too much recovery time, the plants will become overly mature and will lose nutritional value. With too little recovery time, some plant species will not recover fully and will die, reducing pasture productivity and diversity. Under good management, plant diversity is maintained or increased and soil fertility is continuously regenerated.
Compare the energy efficiency of a grass-based dairy with a confinement dairy: When cows are kept in confinement, the cows’ forage has to be mechanically harvested in the field, hauled to the confinement facility, placed in storage, then mechanically removed from storage each day to feed the cows. And, the cows’ manure must be collected into a storage facility from where it eventually must be hauled back to fields and spread. All these operations require fossil fuel energy.
By contrast, in a well designed grass-based dairy the same objectives are accomplished by simply opening the gate to the next paddock. The cows harvest their own forage and spread their manure throughout the paddock at the same time. And, they enjoy their work!
The irony of modern confinement animal production has been summed up by Allan Nation, editor of the Stockman Grass Farmer in this way: It is the nature of cows to move about and the nature of grass to stand in one place. With confinement animal production we have turned it backwards and made the cows stand in one place and made the grass move to the cows.
Cows out grazing in their natural environment are healthier than when living in confinement conditions. Also, a diet high in freshly grazed forage is healthier for cows than diets that are normally fed in confinement dairy systems.
An additional benefit of grass-based dairies is that milk produced by grazing cows is higher in nutritional components found to be beneficial to humane health, including omega-three fatty acids, conjugated linoleic acids, beta carotene, and some vitamins.
Two major challenges loom on the horizon of tomorrow’s agriculture: 1) a growing scarcity and rising cost of fossil fuel energy, and 2) an intensification of the effects of climate change, particularly manifested as greater extremes of weather events, including intense rainfall events and flooding.
One way to meet both challenges is to reintegrate livestock back onto the landscape in ways that mimic nature’s ecology in order to create animal production systems that are resilient, energy-efficient, and biologically diverse.