## 3 Results
### Water Requirements of Japanese Plum Orchards
Moderate water stress (75% RDI) improved fruit yield and saved water without an undesirable effect on plum fruit quality. After two years of testing, the automated system could \"simulate\" the irrigation scheduling programmed by a human expert without human intervention. After eight years of applying the RDI strategies, no carry-over effects on the orchard yield were observed. Based on these results, RDI appears to be a sustainable practice for the cv. Angeleno and the growing conditions. The RDI treatments were suitable for reducing the total pruning weight. In the long term (five seasons), the effect of post-harvest RDI had no negative cumulative impact on tree productivity. This study suggests that allowing some degree of water stress during stage II and post-harvest appears to offer an effective management strategy for saving water and controlling vegetative growth without negatively affecting crop yield or farmers' economic return. Crop load regulation is a valuable tool allowing plum trees to quickly recover from the detrimental effects of long-term deficit irrigation. Deficit irrigation strategies should be used with caution in developing orchards. Only slight restrictions can be imposed to avoid the long-term carry-over effects of deficit irrigation on tree performance. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Reference Location** & **Method** & **Cultivar** & **Water Use (mm a\({}^{-1}\))** & **Water Use (mm** & **Key Findings** \\  & & & **(mm a\({}^{-1}\))** & **season\({}^{-1}\))** & **(m\({}^{-1}\))** \\ \hline \multirow{4}{*}{[24]} & South Africa & HYDRUS-2D & Fortune, African & 858–864 & Initial basal crop coefficients varied from 0.98 \\  & & & & (September-March) & to 1.01, whilst basal crop coefficients for the \\  & & & & Delight & 534–641 & mid-stage averaged between 1.11 (cv. African \\  & & & & (September-January) & Delight) and 1.18 (cv. Fortune). \\  & & & Santa Rosa, & & \\  & & & Timhdit, Red & & \\  & & Beaut, Black & & & \\  & & & Amber, Black & & \\  & & & [PERSON], Black & & \\  & & & [PERSON], Obilnaja, & & \\  & & & Fortune, Black & & \\  & & & Star & & \\  & & & Black Diamond, & & \\
[18] & Tunisia & FAO-56 Kc & Black Gold and & & \\  & & & Black Star & & \\  & & Press, & & & \\  & & Grabarczyk & & & \\
[51] & Poland & and & & 455-718 & \\  & & & Rzekanowski & & \\  & & and Treder & & & \\
[26] & Egypt & FAO-56 Kc & African Rose & & \\
[21] & Spain & SWB & Angeleno & 1011–1187 & \\
[25] & Iran & CROPWAT & Methyl & & \\  & & Soil & & & \\
[23] & Spain & Moisture & Red Beaut & & \\  & & & ISRX & & \\
[20] & Spain & FAO-56 Kc & Angeleno & & \\
[22] & Spain & FAO-56 Kc & Red Beaut & 835–1159 & \\
[19] & Spain & FAO-56 Kc & Angeleno & 962–1211 & \\
[16] & Spain & FAO-56 Kc & Black Gold & & \\
[15] & Spain & FAO-56 Kc & Black Gold & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Summary of annual and seasonal plum water use estimates from literature. In South Africa, [PERSON] and [PERSON] [52] reported water use of 921 mm a\({}^{-1}\) (1006 mm total irrigation) for a well-water drip-irrigated African Delight orchard (3 ha) in Robertson. This is \(\pm\)30% lower than the figures reported for well-watered late-maturing orchards in Spain despite having a higher plant density (2667 trees ha\({}^{-1}\)) and a markedly drier climate. [PERSON] et al. [24] observed similar water use figures for the same cultivar. [PERSON] et al. [24] estimated the water requirements of four full-bearing Japanese plum orchards (cvs. African Delight and Fortune) in Robertson and Wellington (South Africa). The late-maturing African Delight orchards in both regions displayed higher water usage figures of 858 and 864 mm in Wellington and Robertson, respectively, compared to 534 and 641 mm for the mid-maturing Fortune orchards. The differences in water use were attributed to the more extended growing season of African Delight (September-March) than that of Fortune (September-January).