Fire is a tool that livestock farmers must use wisely and carefully, argues Craig Morris, senior researcher at Agricultural Research Council – Animal Production. He is researching the ecology of mesic grassland in South Africa and how these grasslands could provide sustainable grazing for livestock while enhancing their biodiversity.
Fire is an ancient natural force on the Earth – it has burned vegetation for hundreds of millions of years, promoting the spread of flowering plants and the subtropical grasses common in grassland (veld) in the wetter areas of South Africa.
When fire is suppressed, like the colonial authorities tried to do in many parts of Africa, grasslands degenerate and become encroached with bush, degrading their value for livestock farming and reducing the diversity of plants, animals, and insects that call grassland their home.
Grasses and the numerous species of wildflowers that grow amongst them have evolved with fire over many thousands of years and are superbly adapted to being burned periodically. Grasses escape fire by having their growing points close to the ground whereas wildflowers store their regrowth resources safely underground (in bulbs, rhizomes, corms, etc).
Burning stimulates many grasses and wildflowers to produce new shoots and leaves, which grow rapidly in the bright light after a burn in late winter or spring. If grasslands are not burned or grazed for a lengthy period, the light-loving, productive grazing grasses are shaded out by the dead leaves and litter that builds up over time. Fire is the most effective tool to remove this moribund grass material and to rejuvenate fresh growth.
Burning in the drier regions of the country (below about 600mm of annual rainfall) is not necessary and can cause long-term damage to the veld. In these “sweetveld” areas, forage is palatable to livestock throughout the year so extra grass seldom accumulates except in very wet years. However, in the wetter and more productive “sourveld” regions of the country, grass leaves become unpalatable in winter and provide very little useful forage for livestock.
Grazing, even by a large “mob” of cattle or sheep, is not an effective or efficient alternative to burning for removing old sour grass because, unlike fire, animals are selective and will avoid the most unpalatable grasses. Dense herds of livestock also trample sensitive wildflowers, eventually reducing the overall diversity of sourveld. Therefore, the cow cannot completely replace the “match”.
Managing fire and grazing together
Livestock farmers can use fire and grazing very effectively together to regenerate sourveld and provide excellent forage for livestock. The young grass that resprouts after a burn in late winter or spring is short, palatable, and easily digested, with a high protein (nitrogen) content. Livestock will gain weight faster if they are allowed to graze the nutritious regrowth after a burn.
Sheep especially like and do well on such short, fresh grass swards. Birds and insects that prefer short, open grassland are also attracted to burned areas. Livestock will stay on newly burned patches for as long as they can and graze grass species, even the unpalatable ones, relatively evenly.
Multiple paddocks are useful for controlling the movement of livestock between burned and unburned areas on the farm. When the grass in the burned areas is used up, animals would need to be given access to forage in unburned paddocks, returning to the burned areas once enough forage has built up.
An ‘open-gate’ fencing system could also be used to let livestock choose when to move onto and off the burned paddock or area according to availability of forage and their needs. Where there are no fences, herders could control the movement of flocks and herds.
Repeated grazing after a fire, although best for livestock, will reduce the vigour and productivity of forage grasses. Therefore, careful grazing management is required to keep the grassland productive.
Rotational burning and resting is a useful, adaptive tool for managing sourveld areas. About one-quarter to one-third of the grazing area is burned then repeatedly grazed each year (as described above) while a similar sized area is completely rested from grazing for a whole growing season to allow it to fully recover. The rest of the grazing area is not burned and available for when there is insufficient grass to graze in the burned paddocks.
Because burning and resting is rotated to a different part of the farm each year, each area gets burned and grazed and also fully rested every three to four years. Research has shown that such a burn-rest rotational system will keep sourveld productive and in good condition.
In this rotational burn-graze-rest system, the paddocks that are being fully rested from grazing during the summer growing season could be used, together with a lick, for winter grazing. Rested grassland could also be a useful drought reserve. Rested areas should be burned in the spring following the rest to remove old grass and rejuvenate fresh growth.
Fire is a tool that livestock farmers must use wisely and carefully. Burning and grazing out of season (in summer or autumn) or too often (every year) could degrade grassland and create bare areas. Burning too infrequently will allow fuel to build up, proving plenty of fuel for a destructive unplanned wildfire.
Burning firebreaks in autumn or early winter to protect the farm and grazing areas is a legal and sensible requirement. Firebreaks also allow planned fires to be set and carefully controlled, to the overall benefit of the grass, livestock, and the farmer.