Importance of water in South African agriculture
Water is one of the globe’s most valuable resources, particularly in drought-prone agricultural hubs like South Africa. This is because both the quality and quantity of water directly affect all organisms, ecosystems, and biological processes, including agricultural production and sustainability.
Furthermore, according to code requirement 3.1 of the SIZA Environmental Standard, “Water abstraction and use is within legal limitations and is as efficient as it can be”. During the summer months in South Africa, efficient water management becomes crucial due to high water demand, increased evaporation and transpiration, and reduced rainfall, resulting in a decline in the replenishment of water resources.
This article highlights several water-efficient interventions that may be implemented on farms during the summer period to support water conservation efforts while complying with the SIZA Environmental Standard and market requirements. This includes efficient irrigation, reducing evaporation and transpiration losses via netting, reusing wastewater where possible, and harvesting rainwater.
Efficient irrigation methods
Micro-sprinkler irrigation is considered one of the most water-efficient irrigation methods globally. It is a low-volume irrigation device that sprays a fine mist, reducing potential runoff and improving water-use efficiency (WUE) towards optimal levels.
Drip irrigation is generally considered the most efficient irrigation method overall. This irrigation method targets the root zone of crops, reducing potential runoff and ensuring efficiency without the risk of saturated soils.
Compared to micro-sprinklers, drip irrigation uses lower pressures, which require smaller pumps, thinner pipes, and less energy, thereby reducing the fixed costs of the system. However, drip irrigation requires longer running times, and therefore, suppliers should carefully evaluate the costs and benefits of each irrigation system by considering their commodities’ irrigation requirements, their local power supply, and the prevailing climatic conditions.
Reduce water loss from evaporation and transpiration
Post-irrigation methods may also be implemented to reduce water evaporation directly from the soil or to reduce transpiration (the process by which plants release water vapour, primarily through their leaves).
Soil covering, such as crop residues or cover crops, may significantly reduce groundwater loss by minimising solar exposure of the soil, thus reducing evaporation of groundwater. This enhances the soil’s water retention and reduces the amount required for irrigation. Cover crops may also result in improved soil structure, improving the soil’s water-holding capacity and thereby further reducing irrigation needs.
Shade netting over orchards/vineyards is often used as a form of crop protection, but did you know that it also induces well-established water-saving benefits? In this scenario, shade netting significantly reduces solar radiation from reaching the soil and crops, thereby reducing water loss through evaporation and transpiration, and consequently reducing irrigation demand.
Irrigating at night has also proven to be an effective water-saving strategy for South African farmers, as it reduces water loss and allows more time for water to be effectively taken up by plants before it can evaporate from the soil.
Reuse of wastewater resources where possible
The reuse of wastewater may be done in line with the General Authorisations published under the National Water Act (NWA). The legal reuse of wastewater for irrigation purposes significantly reduces a business’s water demand, with potential associated cost savings.
When irrigating with wastewater, it is essential to determine the volumes of wastewater to be irrigated, which will dictate the aspects of the wastewater that need to be tested to ensure they are within legal limits, as outlined in Tables 1.1, 1.2, and 1.3 of the General Authorisation of the NWA. Here, it is essential to register the water use with the Department of Water and Sanitation to ensure that wastewater irrigation does not occur near water sources and that any storage of wastewater for reuse (i.e., section 3.7 of the General Authorisation) is also adhered to.
Methods to harvest rainwater
One method to ensure effective water management is by harvesting rainwater to reduce dependency on ground/surface water sources, which can be particularly beneficial during summer months when water sources are in high demand.
One example of this is harvesting runoff water from a roof, which is classified as a Schedule 1 water-use activity that does not require legal authorisation, not accounting for the individual storage parameters thereof, which should conform to the general authorisation published under the NWA. This strategy is a low-effort, low-risk method to ensure adequate water supplies throughout the summer months, particularly for dry, rural areas.
Measuring water-related aspects
The effective measurement of water-related aspects on-site facilitates their management, thereby reducing associated risks. Recordkeeping of water usage is crucial for assessing the efficiency of irrigation practices and establishing a baseline from which continuous improvement can occur. Therefore, using digital recordkeeping programmes, such as SIZATrack360, provides evidence of improvement that is of interest for auditing and market transparency requirements. The benefit of using digital recordkeeping is that you can also incorporate it into your journey to calculate your carbon footprint. Overall, effective and measurable water management strategies are key, not only to ensure seamless production and mitigate water-related risks throughout the summer, but also to support compliance with the SIZA Environmental Standard.
