## 3 Results
### Systematic Review
(2016) recommended that RDI be applied with caution to avoid the carry-over effects of deficit irrigation. Even though the cv. Black Gold possesses these attributes, [PERSON] et al. (2018) identified the cv. Black Star as the most tolerant cultivar for deficit irrigation because it maintains a good water status. The late maturing cv. Angeleno was the second most studied, as well as the cv. Red Beaut. The Angeleno cultivar was grafted onto the Mariana 2624 rootstock with 6 \(\times\) 4 m spacing in all three studies included in this review ([PERSON] and [PERSON], 2018; [PERSON], 2019). Additionally, all orchards had cv. Larry-Ann and cv. Fortune trees planted, used as pollinators along with beehives. Studies have been conducted frequently to establish new water stress strategies more adapted to Angeleno. [PERSON] et al. (2019) concluded that water stress intensity extensively impacts the final fruit size. This conclusion was confirmed in a study by [PERSON] et al. (2020). The relevance of fruit size has been used to justify the adoption of expensive thinning practices ([PERSON] and [PERSON], 2018). Similar to the cv. Angeleno, the cv. Red Beaut was grafted onto the Marianna 2624 rootstock in a study by [PERSON] et al. (2022). The Marianna 2624 rootstock is known for tolerating wet soils and moderately resisting diseases and oak root fungus ([PERSON] et al., 2019). The Black Diamond and Ambra cultivars were used as pollinators, while beehives ensured optimal pollination. Regarding the geographical distribution, the studies included in this review were conducted in nine countries, as displayed on the map in Figure 4. These include four African countries (Morocco, Tunisia, South Africa and Egypt), two European (Spain and Poland) countries, two countries in the Americas (the United States of America and Chile) and an Asian country (Iran). All the articles were small-scale studies which involved experiments being undertaken at the farm or orchard level. In assessing the frequency of publication per country, the study observed that most of the studies were conducted in Spain (8), followed by South Africa (2). Egypt, Tunisia, Morocco, Iran, the United States of America (USA), Chile and Poland conducted a study each. Spain, which recorded the most studies, is the seventh plum producer in the world and third in the European Union (2018). Plum production is of economic importance to Spain (2019), as the cultivation of this fruit tree covers broad and climatically diverse regions within the country (2020). Spain is not exempted from the global effects of climate change and climate variability. An increase in high temperatures, especially in the regions characterized by the Mediterranean, causes a reduction in the accumulated chill, therefore affecting plum  
Figure 4: Geographical distribution of the studies conducted on the estimation of plum crop water requirements per country. phemology. This is due to several influencing factors, including the importance of plums (_Prunus salicina_ [PERSON]) among the stone fruit species grown in Spain [29]. For the country to meet international standards and demands, the water demands of this fruit tree must be understood. A few studies have been conducted on the water requirements of _Prunus salicina_; thus, more studies need to be conducted to fill in this gap while sustaining the fruit industry. This same applies in South Africa and Morocco. Both countries have Mediterranean climates characterized by hot and dry summers, which require accurate information on crop water requirements for efficient irrigation scheduling. These climatic conditions have caused South Africa to be considered one of the driest countries globally [31]. Although South Africa is a water-scarce country, it is one of the major global exporters of plums [24], which is why more studies are being conducted to sustain the vibrant plum industry [32].