Research discoveries in the USA in recent years have demonstrated how livestock grazing affects soil health. While factors influencing agricultural environments may vary from country to country, the basic principle of using highdensity
livestock grazing to improve soil health is universally applicable.
“Farming is a business, so any purchase of a soil health amelioration product, such as fertiliser or lime, should be seen as a capital investment and not an annual expense,” says USA based soil scientist Doug Peterson, who visited S0outh Africa recently. “An investment should generate good returns for many years to come. Instead of being considered as regularly required and blanketapplied, soil health amelioration products should only be used strategically once in a while.
“A farmer should ask himself how he can improve soil health without the cost of these additional inputs.” World-renowned Zimbabwean researcher and proponent of holistic farming practices, Allan Savory, has had a major influence on Doug’s thinking on how animal activity affects the land. This includes grazing and drinking, hoof action, dunging, urinating, rubbing and salivating.
Depending on management, animal activity can be either positive or negative. For example, overgrazing and excessive hoof action can cause soil erosion. However, animal activity can be used as a biological alternative to the mechanical
equipment and chemicals used to improve some aspects of soil health.
“Animal impact is the most powerful tool we have to manage grassland,” says Doug. “It affects utilisation, reduces spot grazing, controls weed and brush competition, improves manure distribution, boosts mineral cycling and water
infiltration, and promotes seed-to-soil contact.”
The old west
He explains that the central USA is a highly agriculturally productive region. Before the advent of commercial agriculture, herds of herbivores roamed the land, resulting in areas of the central USA being subjected to alternating
periods of heavy grazing and rest. Large predators have a dramatic impact on the behaviour of prey animals on the
landscape. Herds will often stampede when predators are present, with profound hoof action on the soil surface.
Based on this natural system, sustainabilityminded farmers around the world are increasingly implementing highdensity
grazing and rest to improve soil health, and thereby increase productivity. “Even crop farmers are now asking how they can integrate livestock into their operations to improve soil health,” says Doug.
“One of the factors that plays a huge role in how livestock impact soil health is stocking density (SD),” says Doug. “SD influences grazing uniformity, dung distribution and many other key factors.” For example, a herd of 396 cattle averaging 567kg each collectively weigh 224 532kg. If this herd were to be kept in a 40ha camp, each hectare would be subject to an average 5 613,3kg on-the-hoof beef load.
By reducing the camp size to 4ha, the load increases to 56 133kg/ ha. An SD of 224 532kg in a 1ha camp would result
in a load of 224 532kg/ha. “SD, as I use it, has nothing to do with time. It’s simply a numeric value of how concentrated a group of animals is in a particular area,” says Doug. “The length of time a herd is allowed to graze in a camp will vary according to the SD. This can be from hours to days.”
He relates the experience of Canadian farmer, Neil Dennis, who moves his high-SD herds between grazing camps up to eight times daily. “Yes, it’s management-intensive but Neil and others like him are seeing that the positive results outweigh the effort involved,” he says.
Livestock farmer Mark Brownlee, who farms in south Missouri, USA, found that high-density livestock grazing has increased beneficial plant diversity in his camps. For example, many desirable native plant species that had previously been outcompeted by introduced and almost mono-cultured grass species, are now reappearing. This is as a result of hoof action trampling decomposing plant matter and dung into the soil.
According to Doug, this organic matter has a neutralising effect on soil acidity, increasing the pH of acidic soil and reducing it in alkaline soil. These pH-balanced soils and the organic matter become the ideal home and food for beneficial soil micro-organisms, which promote the growth of many important plant species.
Correctly managed high-density grazing results in the appropriate quantity of plant material being left until the camp has been allowed to recover. Livestock never totally consumes all of the standing plant material. In addition, the litter layer and dung patches, are trampled into the soil, providing organic matter to the soil while the camp is resting. This
decomposing material boosts soil health and moisture penetration and retention, promoting strong plant regrowth.
“I recently had the opportunity to talk to a US department of agriculture soil microbiologist,” Doug says. “He explained that it typically takes a few years for the soil micro-organisms to fully respond to the increase in decaying plant material. The mulch is a food source for the micro-organisms in the soil. So it’s important to feed the above-ground animals to feed the below-ground animals.”
This presentation was given at the OASIS Farmers’ Workshop held near Underberg, KwaZulu-Natal, from
6 to 7 August 2014..
Email Doug Peterson at [email protected].