The Mediterranean climate of the Western Cape province of South Africa is characterised by dry summers and wet winters. The average rainfall in some of the mountainous areas in the south and eastern regions is well over 1000 mm, while parts of the Karoo and the northwest regions can receive less than 150 mm per annum. This great variation in rainfall, along with vast differences in soil types, contributes to the production of a wide variety of crops in the province, including grapes, deciduous fruit, citrus, grain, fynbos, vegetables and pastures for livestock and dairy production.
Cool air from the ocean and warmer onshore air interacts with high mountain ranges which serves as a water harvesting system. The harvested water forms run-off that holds potential for use in irrigating crops along the coast and the semi-desert regions of the Karoo on the other side of the mountains (Vink & Tregurtha, 2005). Hence, irrigation accounts for nearly half (43% or 186 m3 million) of the Western Cape’s water use (WWF, 2018, Partridge et al., 2020).
Besides being a large consumer of water, the province’s agricultural sector is invaluable in its contribution to the economy and food security of the country. Exports of deciduous fruit, citrus and wine from the Western Cape contribute 2 % of South Africa’s GDP (Zwane, 2019), with the province’s agricultural sector sustaining a total economy of R530 billion (WWF, 2018). Besides its critical role in South Africa’s economy, agriculture in the Western Cape (including the agri-processing sector) employs nearly 180 000 people and approximately 15% of the province’s labour force (WWF, 2018).
The Smart Agri brief for the deciduous industry explains that climate modelling predicts a high chance of continuously increasing temperatures and decreasing winter rainfall in the western regions of the Western Cape in the future, and thus some of the major regions of deciduous fruit, citrus and wine production (Green Agri, 2023). Increased warming of the province will increase evaporation (and thus the loss of water), increasing future instances of water scarcity and drought. The very real possibility exists of dam levels becoming depleted to such an extent that irrigation restrictions will once more become a reality for crop growers in the province, as it did during the recent 2017/2018 drought (WCDoA, 2017). Reducing pressure on water resources in the present is non-negotiable to ensure the sustainability of the Western Cape’s crop production in the future.
What can be done to reduce pressure on water resources for agricultural production as climate changes?
With South Africa being a dry and water-stressed country, the production of many crops simply cannot exist with rainfall alone and needs to be supplemented with irrigation. Considering the impact of climate change on water availability for agricultural production, along with the continuous growth in population and pressure to produce more food (FAO, 2015), the efficient use of water by primary crop growers becomes essential. Crop growers should utilise all innovative ways to their disposal to increase their production while using less fresh water for irrigation (WWF, 2018).
Remote sensing technology can support crop growers with an extra layer of information on their fields so that more informed decisions about resource application can be made, particularly the efficient use of irrigation to produce “more crop per drop”. FruitLook is one such technology that has been supporting crop growers in the Western Cape to achieve greater water use efficiency since 2011.
What is FruitLook and how can it be used to achieve greater water use efficiency?
FruitLook is a freely available remote sensing data platform in the Western Cape that is fully funded by the Western Cape Department of Agriculture. It is set up to provide an extra layer of information at a field level that supports management practices and sustainable water and nutrient usage. FruitLook can provide crop growers with field-specific growth, water, and mineral information to guide better management decisions and thereby achieve greater water use efficiency. For example, a sudden decrease in FruitLook’s biomass water use efficiency of a particular field, especially during the vegetative stages of a crop’s growing cycle, is often the result of over-irrigation. This means the crop is being supplied with more water than it can effectively use. Over-irrigation results not only in unnecessary water loss but also damage the crop and its potential yield.
Alan Hall, a citrus grower from Citrusdal (Latjeskloof farm), has been monitoring water use efficiency in FruitLook over the past few years. He has managed to improve it (Figure 1) by reducing his irrigation application from every day to every second day. “With the data, I strive to improve the irrigation schedule to continue to improve water use efficiency and minimize deficit to obtain superior production, fruit set and quality. This in turn leads to water saving, healthier trees and less insect control. Because I had historical data from quite a few years back, I could look at different irrigation scenarios and determine what worked best for me. I try to achieve better values every week. FruitLook enables me to get really objective feedback on what I am doing in my fields.”
Figure 1: The biomass water use efficiency (kg/m3) readings (higher is better) for the 2018-2019, 2020-2021 and 2022-2023 irrigation seasons respectively for a 28-year-old block of Satsumas at Latjeskloof farm.
FruitLook’s spatial maps are particularly useful to identify irrigation problems within a field. A farmer in Devon Valley noticed a constant wet spot in one of his fields. The spot in question never seemed to dry out like the rest of the field (circled in Figure 2). The vineyard was due for renewal and the vines were removed after the 2016 season. After the plant material was removed, the wet spot was dug up to try and identify the problem. They found that the drainage system never linked up to the mainline. Hence, all water drained into that spot. The drainage system was then linked to the mainline and the field started drying uniformly (as can be seen in the 2016/2017 season (Figure 3)).
Figure 2: A higher water use (Actual Evapotranspiration) in one section of a vineyard during peak season (2015/2016 season), detected in FruitLook.
Figure 3: The water use (Actual Evapotranspiration) of a vineyard during peak season (2016/2017) shown to be relatively uniform after a drainage issue was resolved.
In general, better irrigation practices will improve water use efficiency, reduce the unnecessary use of water and consequently relieve some pressure on water resources. In addition, the use of less water is associated with lower electricity and fertilizer use that not only saves the grower on costs, but it also reduces his/her carbon footprint and thereby makes for a more attractive product to market.
Equipped with the extra layer of information provided by FruitLook, a crop grower can focus his/her time and management efforts on achieving the best quality produce at the lowest cost to the environment and maximum financial returns.
Are you a crop grower and not using FruitLook yet? Have a look at the portal at www.fruitlook.co.za and get in touch with the FruitLook Team to help you get set up.
Partridge, A., Morokong, T. & Sibulali, A., 2020. Western Cape Agricultural Sector Profile 2020. Available from: https://www.elsenburg.com/wp-content/uploads/2022/02/Western-Cape-Agricultural-Sector-Profile-2020.pdf [ Accessed 24 July 2023].
WWF, 2018. Farming for a drier future. WWF Agricultural Water File. Available from: http://awsassets.wwf.org.za/downloads/wwfwaterfiles_19july2018.pdf [ Accessed 24 July 2023].
Zwane, E.M., 2019. Impact of climate change on primary agriculture, water sources and food security in Western Cape, South Africa. Jàmbá: Journal of Disaster Risk Studies, 11(1), pp.1-7.
Green Agri,3. Last visited on July 24, 2023. https://www.greenagri.org.za/assets/documents-/SmartAgri/Briefs-/9-Brief-for-the-Deciduous-Fruit-sector.pdf
Vink, N. & Tregurtha, N., 2005. Western Cape Agricultural Sector: Structure, Performance and Future Prospects. An Overview. Department of Agricultural Economics. University of Stellenbosch. Available from: https://www.westerncape.gov.za/other/2005/10/final_first_paper_overview_agriculture.pdf [ Accessed 24 July 2023].
WCDoA, 2017. Informing the Western Cape agricultural sector on the 2015-2017 drought. Available from: https://www.greenagri.org.za/assets/documents-/Drought-in-Agriculture/Drought-Fact-Sheet/DROUGHT-FACT-SHEET-PDF.pdf [Accessed 24 July 2023].