Discipline: environment; Keywords: drought, water shortages, veld and pasture, sediment, water infiltration, water quality.
The severe droughts in successive years in several parts of the country have suggested that more regular droughts and water shortages could become the norm in future farming. This, of course, is also predicted by climate change scientists and it implies that farmers will have to look at ways to make the most of the water they have. Soil management, rainwater harvesting and proper storage of water will determine how efficiently farmers make use of water resources. It is estimated that agriculture consumes about 75% of the precipitation in South Africa, of which 60% is utilized by veld and pasture, 12% by dryland crop production and 3% by irrigation. Livestock farmers to varying degrees make use of all three channels and should ensure that they manage every drop from these channels optimally.
It is common knowledge that ground water dams on farms and the large country storage dams lose water storage capacity due to sedimentation. Farmers, therefore, should manage their farm dam capacities carefully to ensure that they remain sediment-free. Also, while ground water dams have the advantage of volume, their evaporation area and rate are greater. Where practical, water should rather be stored in covered reservoirs as they minimize evaporation and algae formation. Water can also be stored underground depending on the geological formation. For example, bore holes can be drilled in the dam surface and covered with mesh to prevent sediment entering the hole. Clean water results which raise the underground water level and which can then be re-harvested from downstream bore holes or fountains.
In order to ensure that farmers take advantage of rain even when heavy downpours occur, it is imperative to ensure that there is no excessive run-off, resulting in soil erosion and poor water infiltration. The following measures should be considered:
- Catchment areas on farms should become storage areas using both mechanical means like weir construction, and vegetative means by creating wetlands in catchment areas by planting reeds and tough grasses which are adapted to the specific region.
- Vegetative cover in veld and pasture is the most important factor. This ensures that rainwater that otherwise would have run away is captured and utilized effectively for plant growth. Vegetative cover is primarily determined by grazing capacity and stocking rate; conservative stocking rates and comparatively long resting periods have the most significant effect on plant cover (even more than the variation in rainfall). Conservative stocking rate refers to the farm in total and does not mean that farmers should not have more animals than the calculated stocking rate in the camp or paddock that is presently grazed – in fact, intensive grazing under particular environmental conditions can be a good choice as it would assist in breaking the top soil (trampling) and provide more manure which supports moisture penetration, seeding and seed germination. This is as a result of the organic status of the soil being improved. However, the grazing period should be short and the resting period long to ensure recovery and vegetation thickening.
- In mixed farming systems where livestock farmers also produce crops, minimum tillage should become the norm rather than the exception. Minimum tillage ensures more organic matter which leads to better water capture and usage.
Apart from quantity, quality of water is important yet is often not considered on farms. It is important that effective measures be implemented to ensure that water is free from contaminants. Water tests should be done regularly for microbiological and chemical contents to ensure that the water complies with specifications for human, animal and crop use. All water sources such as borehole, river and canal water should be tested. If water is chlorinated on site, routine checking must be implemented. Storage tanks and reservoirs for water must be covered to prevent contamination by birds, rodents, organic and inorganic matter. The air vents to these tanks and reservoirs must also be insect and rodent proof. Where there may be effluent such as from an on-farm feedlot, it must be appropriately managed to ensure effective disposal with no contamination of water sources. If the effluent is applied to pasture, there must be a lapse of at least 21 days between application and grazing or harvesting of the pasture.
H.H. Meissner, 2019. In: RPO Newsletter March 2019, based on the RPO-NERPO and Dairy Codes of Best practices. Obtainable from the RPO and MPO offices, Pretoria.