Set stocking & over grazing

Christine Page

There’s an old saying, “Never leave the sheep in the same field long enough to hear the church bell ring twice”. In other words, move them every week. 

This old practice of regularly moving animals to small fields of fresh grazing has all but disappeared. After the second world war, food security was a major concern and the government pushed farmers to increase production. Cheap fossil-fuel fertilisers were readily available and hedgerows were ripped out to make fields bigger and more productive. In fact, the intensification of agriculture since the 1950s has led to the disappearance of over 100,000 miles of hedgerows in the UK. So the traditional way of grazing has long since been replaced with ‘set stocking’, where a ‘set’ number of animals is left in a field for a long period of time, sometimes all year. Set stocking has now been the accepted norm in most conventional farming systems for almost three generations, the old ways mostly forgotten.

However, more recent understanding of the impacts of set stocking has shown that it leads, more often than not, to a degradation in soil quality and ecology, water management and pollution problems, as well as animals with chronic health issues that have a potential impact on the nutrient value of their meat. 

Selective grazing

Given the opportunity, grazing animals are highly selective in what they eat. We use this natural trait to their benefit with our Fields of Herbs here at Smiling Tree Farm.  But in situations where animals remain on a large area of land for an extended period of time, this trait can have severely detrimental consequences. In extensively grazed fields, animals spend more time walking around picking and choosing the plants they like the best, and then grazing them the hardest. Those plants can be so heavily grazed that they eventually weaken to the extent that neighbouring, less desirable plants encroach and push them out. This reduces plant species diversity and results in ‘weedy’ fields. Reaching for a herbicide is often the solution of choice but, of course, has further consequences that, together with declining diversity, begins a downward spiral. 

Short grass and hard, compacted ground

A healthy soil containing robust deep-rooted plants should have an open, porous texture allowing oxygen and rain to penetrate easily. It acts like a sponge, soaking up excess water and making it available to plants over a long period. But all that walking around selecting the best to eat compacts the soil (imagine the pressure of an 80kg sheep on two toes the size of a 50p coin). Water can't infiltrate the hard, compacted ground of over-grazed pasture. So rain runs off leaving frail and thirsty plants, causing erosion and leading to potential flooding and water pollution further down the catchment. The compacted ground also alters soil structure, creating the anaerobic conditions that favour the growth of more weeds.

Lack of nutrients

Plants use their leaves to absorb the sunlight needed to generate energy, just like solar panels. When a plant is continually bitten down over a period of time it gets weaker through not having enough ‘solar panels’ to generate the energy it needs to grow. The lack of energy also means it can't support a deep, healthy root system and is eventually forced to slough off an extensive part of its roots. This loss of deep roots exacerbates soil compaction and limits the plant’s ability to soak up water and draw nutrients up from deep down in the soil. So its capacity for nutrient exchange in the soil food web’s 'poop loop' is severely diminished and the downward spiral continues. 

Chemical fertilisers

The discovery of a way to make cheap fossil-fuel fertilisers, a consequence of explosives manufacture in WW1, was hailed as part of the Green Revolution that promised to feed a growing population. Decades later, however, this 'solution' has been found to have a nasty sting in its tail. 

Chemical fertilisers encourage faster plant growth by side-stepping the ‘poop loop’ and feeding plants nutrients artificially, taking the place of the main nutrients normally provided by the micro-organisms in a healthy soil food web. In a symbiotic relationship with the plants, those micro-organisms, especially the bacteria and fungi around the root zone, respond rapidly to changes in the available food sources. If the exudates from the plant roots suddenly decline, as they will when a plant is ‘fed’ chemical fertiliser, so will the corresponding numbers and species of bacteria and fungi. 

Downward spiral

In this way, the circle of life beneath the soil starts to break down and the organisms that normally provide other essential nutrients decline. The soil starts to lose its resilience and the plants become dependent upon the chemical fertilisers. Over years, a downward spiral intensifies as levels of organic matter decrease, topsoil starts to erode and both total numbers and diversity of species of micro-organisms decline. 

Fast food

And there’s yet another problem: Applying quick-release, soluble chemical fertilisers to soil is like feeding our children a fast food diet. It might fill them up and give them an energy burst in the short term, but in the long term it is nutrient-poor and their health begins to suffer. Like people, plants also need at least 42 essential nutrients and trace minerals to perform key functions and stay healthy. Chemical fertilizers, however, usually provide only three – nitrogen, potassium and phosphorus. 

We can survive for quite some time (on our fast food diet) without the other essential nutrients, but eventually our health starts to fail - we are effectively over-fed but undernourished. And this is exactly what happens to fields that are over grazed and ‘fed’ chemical fertilisers. In turn, this effects the health of the animals that graze them.

Disease and medication

Grazing sheep and cattle are converting grass to meat and milk. The animals can only get the nutrients that go into this produce from the food they eat. So the quality and nutrient value of the meat and milk they produce, as well as their own health, are directly effected by the diversity and nutrient value of the pasture they eat. Fields that are grazed continuously get sick and when the land gets sick, the animals get sick. This leads to an increase in diseases and parasites, like maggots, intestinal worms and fungal foot rot, so that the animals then need regular treatment with vaccines, chemicals and drugs. And to add insult to injury, almost all of the medications given to animals to rid them of these afflictions, also have the knock-on effect of killing off beneficial dung beetles as well as earthworms and other ‘friendly’ organisms, further weakening the soil’s ecosystem.

Who would have thought your pleasant Sunday drive in the country, passing those bucolic views of open fields of sheep or cattle, could harbour such hidden horrors! 

Topsoil regeneration

On a more optimistic note, although it’s often said that it takes 500 years to grow and inch of topsoil, recent research by pioneering soil micro-biologists, such as Dr Elaine Ingham in America and Dr Christine Jones in Australia, shows that topsoil can be grown relatively quickly - an inch within a handful of years - so long as the right farm management practices are followed.  And one of those is mob grazing.

Mob grazing - a modern version of a successful traditional farming practice – is one of the numerous sustainable farming methods we've introduced at Smiling Tree Farm.