Poor Management of Animal Wastes
in Grazing Systems and Mixed Farming Systems

The impact of animal wastes - manure - from grazing systems, largely relates to the intensity of production. The more intensive the production system, the more animal wastes become a potential problem, but the greater the potential for managing animal wastes to maintain soil fertility and hence productivity. | Pollution of Surface and Groundwater Protection of Surface and Groundwater Environmental Assessment: Pressure State Response Indicators Technology Options

Within grazing systems and low to medium intensity mixed systems, the impact on soils is generally beneficial, with improved soil fertility in grazing areas, and where cattle are also grazed on cultivated wastes or manure is deliberately managed as a fertiliser input, improved soil fertility on cultivated land.

However, there is a risk even with low intensity production systems, that manure contamination of surface and ground water sources can occur. This is both a direct contamination problem and results from leaching or run-off that can introduce nitrogenous compounds (ammonia, nitrates), phosphorous, and other nutrients and bacterial and viral agents.

Pollution of Surface and Groundwater

With increasing population density, the development of livestock and human drinking water supplies has been a key aspect of rangeland development in semi-arid zones where surface water is a constraint.

The development of water points based on limited and in some cases seasonal sources of surface water and local ground water sites results in a concentration of livestock pressure. The most obvious impact is often to vegetation, with the localised overgrazing resulting in degraded "sacrifice zones" around water points. However, the impact on water is through the direct contamination of the water sources, which due to their restricted availability are often shared between livestock and human consumption.

The main problem with surface water resources is this shared use. The direct contamination of water with faeces, urine and mud increases human (and livestock) health risks considerably.

Water quality in wells is often decreased as a result of the contamination of ropes and buckets used for withdrawing water. Animals may also fall into the wells and drown. The resulting contamination is less obvious than ground water sources, as the water may appear clean and therefore suitable for human consumption, while the obviously polluted surface water is avoided.

Covered wells and boreholes are generally well protected from direct contamination, however the high concentration of livestock in and around these watering points can result in pollution of the groundwater with nitrates and nitrites leached into the aquifer.

As the environment becomes more humid, the availability of water increases, and hence the competition for water sources decreases and watering pressure is spread over larger areas, with less risk of contamination.

In these areas, the major concern is often not contamination of the water source but the destruction of stream bank vegetation and potential loss of biodiversity. Stream bank vegetation typically receive 20 to 30% greater grazing pressure than neighbouring areas, and are often morphologically fragile.

Protection of Surface and Groundwater

Protection of water sources is not complex. Livestock watering can be restricted to areas below water extraction points for human consumption. Boreholes and wells can be covered. Water can be treated.

However, in many semi-arid areas, resources for development are limited, and water treatment comes well below the need to supply water in adequate quantities.

In the more populated areas associated with mixed farming systems, the treatment of domestic water supplies is likely to be standard procedure, and dealing with discharges from upstream inhabited areas, is capable of coping with the additional burden of livestock waste at little or no extra cost.

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