PEER-REVIEW ARTICLE PEER-REVIEWED ARTICLE bioresources.cnr.ncsu.edu Almutairi et al. (2025). “Irrigation, yield & date quality,” BioResources 20(3), 6019-6032. 6019 The Influence of Irrigation Regimes on the Yield and Fruit Quality of Date Palm Trees Khalid F. Almutairi,a,* Hussien A. Al dalwi,b Lidia Sas-Paszt,c and Walid F. A. Mosa d,* One of the big problems in Saudia Arabia is the scarcity of irrigation water, and this extremely affects the yield of plant components. Consequently, determination of the best water irrigation requirements for the growth and productivity of date palm trees is needed. The current study was performed on three date palm cultivars: ‘Khalas’, ‘Nabbut’, and ‘Rothana’ to investigate the effect of 100% (19.2 m3), 80% (15.36 m3), 60% (11.52 m3), and 40% (7.68 m3) irrigation on the yield and fruit quality characteristics. The results showed that irrigation with 100% and 80% significantly increased the fruit yield, marketable fruit number, and fruit weight. Moreover, these regimes also greatly increased the fruit content from total and reduced sugars, and soluble solids compared with 40% and 60% regimes. The 100% and 80% irrigation regimes reduced the fruit acidity but the differences between 100%, 80%, 60%, and 40% water irrigation were not significant in ‘Khalas’ or ‘Nabbut’. The effect of 100% was significant compared with the influence of 40%. The water footprint was significantly higher with 100% and 80% rather than with 60% or 40%. DOI: 10.15376/biores.20.3.6019-6032 Keywords: Irrigation regimes; Date palm; Total sugars; Fruit weight Contact information: a: Department of Plant Production, College of Food Science and Agriculture, King Saud University, P.O. Box 2460, Riyadh 11451, Saudi Arabia; b: National Date Palm Research Centre (NDPRC), P.O. Box 43, Al-Hassa-31982, Kingdom of Saudi Arabia; c: The National Institute of Horticultural Research, Konstytucji 3 Maja 1/3, 96-100 Skierniewice, Poland; d: Plant Production Department (Horticulture-Pomology), Faculty of Agriculture, Saba Basha, Alexandria University, Alexandria 21531, Egypt; * Corresponding author: walidmosa@alexu.edu.eg INTRODUCTION Date palm (Phoenix dactylifera L.) represents 74% of the fruit trees cultivated area in the Kingdom of Saudi Arabia (Kassem 2007), and it is dominant in the arid and semi- arid zones characterized by water resource shortage (Shadeed 2013; Abd Elgawad et al. 2019). The cultivated area in Saudi Arabia is ≈ 157 thousand hectares, which produces ≈ 1.643 million tons (FAO 2025). The shortage of available water is a significant environmental factor that restricts plant growth and photosynthesis. However, plants are known to use various strategies to cope with this challenge, and these strategies are linked to different adaptive traits. These traits can be seen through several responses, such as minimizing water loss and increasing water uptake, or maintaining significant internal water storage (Lambers et al. 2008). World water supplies are diminishing due to high temperatures, leading to abiotic stress in plants, especially when subjected to drought (Gamble et al. 2010). The crop coefficient for date palms varies throughout the growing season, ranging from 0.5 to 1.18 depending on the growth stage (Mazahrih et al. 2012). In arid Mediterranean countries, where water scarcity is prevalent, enhancing irrigation efficiency is crucial for sustaining date mailto:walidmosa@alexu.edu.eg PEER-REVIEWED ARTICLE bioresources.cnr.ncsu.edu Almutairi et al. (2025). “Irrigation, yield & date quality,” BioResources 20(3), 6019-6032. 6020 production (Sperling et al. 2014). Extreme weather events such as heatwaves, droughts, and intense rainfall are increasingly common worldwide, impacting agricultural areas that depend on rain due to limited sustainable groundwater resources (Huber et al. 2016). Sharma et al. (2020) noted that a lack of water can hinder chlorophyll production, resulting in its breakdown and lower chlorophyll levels, which may diminish the photosynthetic ability of plants. A lack of water leads to the closing of stomata, which decreases the photosynthesis process in plants and impacts the ratio of carbon dioxide to oxygen in their leaves (Vaz et al. 2016; Ortega-Farias et al. 2021). Drought affects the transport and availability of soil nutrients (Vurukonda et al. 2016) as well as the morphological, physiological, and nutritional traits of plants. This includes factors like water content, leaf water potential, photosynthetic pigments, stomatal conductance, and the uptake of phosphorus and nitrogen (Meddich et al. 2018). Furthermore, water deficit is a significant environmental factor that reduces plant growth and production (Arora 2019). In arid and semi-arid regions, water shortage and ineffective irrigation water utilization are still the predominant factors affecting date palm cultivation because they often reduce the available groundwater (Baig et al. 2020). Proper water consumption in the tree system likely enhances and improves nutrient uptake (Mohammed et al. 2020). Although resilient to extreme environmental factors such as drought and high summer heat, date palm is a water-demanding crop that needs sufficient water for optimal yield and quality production (Dhaouadi et al. 2021). Water stress can reduce transpiration rates and lead to stomatal closure, which in turn impacts the transport of calcium ions from roots to shoots, ultimately lowering the calcium levels in plants (Li et al. 2021). Besides, water scarcity and salinity stress greatly affect the productivity of date palms, particularly in arid regions. This situation arises from low rainfall, excessive evapotranspiration, and inadequate irrigation practices. A major concern for agriculture in Saudi Arabia is water shortage, exacerbated by its dry, arid, to hyper-arid climate. Most regions receive under 100 mm of rainfall yearly, except the southwest area (Mohammed et al. 2021; Alnaim et al. 2022; Alotaibi et al. 2023). Drought conditions (40% and 60%) led to a significant reduction in leaf growth, plant dry biomass, and other physiological and biochemical traits. However, date palm cultivars can thrive in moderate drought (80% ETc), demonstrating minimal effects on their phenotypic, physiological, and biochemical characteristics, which supports water conservation (Ali-Dinar et al. 2023). Cultivating date palms in the area is difficult because of factors including water scarcity and salinity in the soil and water (Hammami et al. 2024). The amount of irrigation water applied was 50%, 65%, 82%, and 100% of the water needed by ‘Nab-but-Saif’ date palms to optimize irrigation efficiency, yields, and quality characteristics while grown on sandy loam soil in arid conditions. The research revealed that supplying 65% of the total water needed for irrigating date palms maximized yield at 46.1 kg per tree, resulting in the most efficient irrigation water use (IWU) of 0.8 m3/kg. Furthermore, reducing IWU while achieving production of 45.5 to 46 kg per tree increased water availability to 82% and 100% of the overall requirement. The results suggest that providing 34 m3 per tree annually in western Saudi Arabia significantly enhances the water use efficiency, productivity, and quality of the ‘Nab-but-Saif’ date palm variety (Ismail et al. 2014). The current study aimed to investigate the impact of water levels on the yield and characteristics (both physical and chemical) of three date trees grown in the arid region of Saudi Arabia. PEER-REVIEWED ARTICLE bioresources.cnr.ncsu.edu Almutairi et al. (2025). “Irrigation, yield & date quality,” BioResources 20(3), 6019-6032. 6021 EXPERIMENTAL Experimental Site Description and its Design The present study was carried out during the two successive seasons of 2022 on 10- year-old date palm trees (Phoenix dactylifera L.) cvs. ‘Khalas’, ‘Nabbut’, and ‘Rothana’, planted at 10×10 m apart and grown under a drip irrigation system in sandy soil at Palm and Dates Research Center in Al-Ahsa, Saudi Arabia. The date palm cultivars were irrigated by 100% (19.2 m3), 80% (15.36 m3), 60% (11.52 m3), and 40% (7.68 m3). The gross water requirements (GWR) were calculated using the following equation, GWR = ETc× 𝑆𝑒 (1 −LR)×Effir (1) where GWR = gross water requirement (m3/ha), ETc = crop evapotranspiration (m3/ha), Effir = efficiency (%), 90%, LR = leaching requirements, and Se = the percentage of evapotranspiration area. The crop evapotranspiration (ETc) can be calculated as, ETc = Kc ×ETr (2) where Kc = crop coefficient ranged from 0.8 to 1.0 depending on the month of the year, as noted in (Allen et al. 1998), ETr = ETo = Reference crop evapotranspiration (mm/day), ETc = Crop evapotranspiration (mm/day). The percentage of evapotranspiration area (Se) is derived from the shaded area observed at noon in June, which signifies the peak net radiation period, and the actual area of each tree based on the equation detailed by Hellman (2010), 𝑆𝑒 = Shaded area per tree Actual area × 100 = µ𝑅2 10𝑚×10𝑚 × 100 (3) where Se is the percentage of evapotranspiration area, R is the radius of the tree (m), and shaded area = area of the shade of one tree measured at noon. LR = (1 + 𝑥)𝑛 = ECiw 2MaxECe × 1 Ef (4) In Eq. 4, LR represents the fraction of water that permeates the entire root zone and drains below. ECiw denotes the electrical conductivity of irrigation water measured in dS/m. ECe indicates the electrical conductivity of the soil saturation extract relevant to the crop, reflecting the allowable yield reduction (dS/m). Max ECe refers to the highest acceptable electrical conductivity of the soil saturation extract for that specific crop (dS/m). Ef signifies leaching efficiency, which is 90% for sandy and loamy sands. The palm trees were uniformly selected as healthy and nearly the same in vigor and size. The physical and chemical analysis of the experimental soil is shown in Table 1. The data of the analysis of the irrigation water is shown in Table 2, and the average values of the climatic variables are in Table 3. Table 1. The Physical and Chemical Features of the Experimental Soil Texture Mechanical Analysis Soil Constants CaCO3 O.M Hydraulic Conductivity (cm/h) Sandy loom Sand Silt Clay W.P% F.C% SP% 67.5 17.5 15 8.3 16.6 33.2 14.1 1.88 4.2 W.P%: Wilting Point; F.C%: Field Capacity; SP%; Saturation Point; O.M: Organic matter PEER-REVIEWED ARTICLE bioresources.cnr.ncsu.edu Almutairi et al. (2025). “Irrigation, yield & date quality,” BioResources 20(3), 6019-6032. 6022 Table 2. Analysis of the Irrigation Water TDS (mg/L) SAR pH µS/cm Mg2+ Na+ K+ CO3 - HCO3 - Cl- SO4 2- 998 3.66 7.5 1560 3.0 7.5 0.25 0 2.6 7.0 6.5 TDS (mg/L): Total Dissolved Solids; SAR: Sodium Adsorption Ratio; EC (dS/m): Electrical Conductivity Table 3. The Average Values of the Climatic Variables Stat T-mean (°C) T-max (°C) T-min (°C) Rainfall (mm) Radiation (MJ/m2) Average 25.60 34.28 18.81 0.40 6.98 Wind speed (m/s) ET0 (mm) Kc ETc (mm) RH-min (%) Average 2.08 6.30 0.91 5.88 20.96 ETc: Crop Evapotranspiration (mmday-1); ETo: Reference Evapotranspiration (mmday-1); Kc: Crop coefficients; Rh = Relative humidity The treatments were arranged in a split plot with five replicates (five trees). The quantity of the irrigation water effect was investigated by studying their effects on the following parameters: The palm yield It was assessed in kg/tree and by the marketable and non-marketable fruit in kg. The differences between marketable and non-marketable fruits were measured based on the weight, size, and color Fruit sampling At fruits ripening (fruit reached full maturity and 100% yellow coloring), a sample of 50 fruit/replicate was randomly collected from each treatment to measure fruit physical characteristics and another sample of each treatment was collected to measure fruit chemical characteristics. Fruit physical characteristics Fresh fruit weight (g), dry weight (g), and then the wet percentage Average fruit weight, and Flesh weight (g) were measured. The wet percentage was calculated according to Eq 5: 𝑊𝑒𝑡 % = 𝐹𝑟𝑒𝑠ℎ 𝑤𝑒𝑖𝑔ℎ𝑡−𝑑𝑟𝑦 𝑤𝑒𝑖𝑔ℎ𝑡 𝐹𝑟𝑒𝑠ℎ 𝑤𝑒𝑖𝑔ℎ𝑡 × 100 (5) Fruit chemical characteristics The total soluble solids (TSS) percentage in the fruit juice was measured using a hand refractometer. The acidity of the fruit, expressed as malic acid units, was analyzed in the fruit juice through titration with 0.1N sodium hydroxide, with phenolphthalein as the indicator, following the method outlined in (AOAC 2005). Additionally, the total sugars and reducing sugars in the fruit were assessed using the phenol sulfuric acid method described in (Nielsen 2010). Non-reducing sugars were calculated by subtracting the amount of reducing sugars from the total sugars. PEER-REVIEWED ARTICLE bioresources.cnr.ncsu.edu Almutairi et al. (2025). “Irrigation, yield & date quality,” BioResources 20(3), 6019-6032. 6023 Statistical Analysis The results were statistically analyzed with One-way analysis of variance (ANOVA) via CoHort Software (Pacific Grove, CA, USA), employing the least significant difference (LSD) at a 0.05% level to compare treatment means (Heiberger et al. 2015). RESULTS The data in Table 4 show that giving date palm 100% water percentage was more effective in increasing the fruit yield in date palm cvs. ‘Khalas’, ‘Nabbut’, and ‘Rothana’ in comparison to the addition of 80%, 60%, or 40%, respectively. Additionally, increasing the quantity of the given water was more effective than the small quantities of water. The water footprint (WFp) was high with the ‘Nabbut’ cultivar when the date palm trees were irrigated 100% compared with the other date palm cv. ‘Khalas’, ‘Nabbut’, and ‘Rothana’. The WFp with the three-date palm cvs. ‘Khalas’, ‘Nabbut’, and ‘Rothana’ were higher with the addition of 100% compared to 80%, 60%, and 40%. The results showed that the irrigation of date palm with 100% increased the quantity of marketable fruits, while the quantity of unmarketable fruits was reduced in the ‘Khalas’ date palm cultivar. Although using 100% water significantly increased the marketable fruit in ‘Rothana’ cultivar, the differences between using 100% and 80% were insignificant. Table 4. The influence of the Water Irrigation Regimes on the Water Footprint, Yield, Marketable and Non-Marketable Fruit in Three Date Palm cvs. ‘Khalas’, ‘Nabbut’ and ‘Rothana’ during 2022 Season Cultivar Irrigation (%) Water quantity (m3/palm) WFp (water (L)/ fruit (kg)) Yield (kg/palm) Marketable fruit (kg) Non- marketable fruit (kg) Khalas 100 19.2 0.34bc 57.25ab 48.00a 9.25b 80 15.36 0.33bcd 46.00cd 34.50cd 11.50ab 60 11.52 0.26efg 44.25cde 33.00cd 11.25ab 40 7.68 0.19h 41.25ed 31.25cde 10.00ab Nabbut 100 19.2 0.43a 45.00cd 35.50cd 9.50b 80 15.36 0.37b 41.50cde 32.25cde 9.25b 60 11.52 0.29de 40.25de 28.75de 11.50ab 40 7.68 0.21gh 36.50e 25.00e 11.50ab Rothana 100 19.2 0.29cde 65.12a 50.87a 14.25a 80 15.36 0.27ef 57.37ab 44.37ab 13.00ab 60 11.52 0.24fg 49.50bc 37.75bc 11.75ab 40 7.68 0.18h 42.00cde 32.50cde 9.50b The same letters in each column indicated no significant differences between the treatments. The results in Table 5 show that the irrigation of date palm cultivars with the percentages of 100% increased the fruit content from TSS in the three date palm cultivars under study increased more than in the irrigated trees with 80%, 60%, and 40%. Additionally, 80% was also more effective in increasing the fruit content from TSS% % than the addition of 60% or 40%. Regarding fruit content of acidity, the results indicated that irrigating the date palm by 40% resulted in significantly reduced acidity compared to PEER-REVIEWED ARTICLE bioresources.cnr.ncsu.edu Almutairi et al. (2025). “Irrigation, yield & date quality,” BioResources 20(3), 6019-6032. 6024 using 100% in the date palm cv. ‘Rothana’. In date palm cvs. ‘Khalas’ or ‘Nabbut’, the differences between 40, 60, 80, or 100% were insignificant. The fresh weight of fruit was significantly increased by the irrigation of date palm trees by 100% in ‘Rothana’. The quantity of water did not significantly affect the fruit weight in ‘Khalas’. Fruit dry weight remarkably increased with the irrigation of date palm cv. ‘Rothana’ with 100%. In date palm cvs. ‘Khalas’ or ‘Nabbut’, the fruit dry weight did not significantly differ by the quantity of the irrigation. The percentages of irrigation did not differ substantially with the quantity of water in the three date palm cultivars. Table 5. The Influence of the Water Irrigation Regimes on Fruit Content in Three Date Palm cvs. ‘Khalas’, ‘Nabbut’, and ‘Rothana’ during 2022 Season Cultivar Irrigation (%) TSS (%) Acidity (%) Fresh Weight (g) Fruit Dry Weight (g) Fruit Wet Weight (%) Khalas 100 74.25a 0.422c 11.53bc 9.96bc 13.72a 80 74.25a 0.422c 11.63bc 9.91bc 14.80a 60 73.95ab 0.462c 12.04bc 10.32bc 14.26a 40 73.50ab 0.462c 11.83bc 10.02bc 15.37a Nabbut 100 73.80ab 0.654ab 11.92bc 10.88b 8.68b 80 69.95bc 0.721ab 11.97bc 10.36bc 13.43a 60 67.70cd 0.694ab 10.46c 9.59bc 13.18a 40 65.62de 0.727ab 11.05bc 8.89c 15.02a Rothana 100 74.55a 0.628b 15.31a 13.10a 14.40a 80 72.90ab 0.724ab 12.73b 11.01b 13.56a 60 70.35abc 0.699ab 11.25bc 9.69bc 13.75a 40 62.85e 0.742a 10.94bc 9.39bc 14.11a The same letters in each column indicated that there are no significant differences between the treatments. The results in Fig. 1 indicate that the irrigation of date palm cultivars with 100% increased the fruit content from total sugars compared to using 40 or 60% in the three date palm cultivars under study. The differences between 100, 80, 60, and 40% reduced sugar percentages in date palm cv. ‘Khalas’ were insignificant. Using 80 or 100% of water significantly increased the in ‘Nabbut’ date palm in contrast with using 40%. Sugar content of ‘Rothana’ date palm was increased extremely by adding 100% water rather than adding 40, 60, and 80%. Non-reduced sugar percentages were greatly increased using 100% water over 40 or 60% in ‘Khalas’ date palm cultivar. There were no significant differences between the usage of 40, 60, 80, and 100% water on the fruit content from non-reduced sugars in ‘Nabbut’ or ‘Rothana’ date cultivars. The fruit content from glucose was notably increased by the addition of 100 or 80% water rather than the using of 40 or 60% in ‘Nabbut’ date cultivar or using 40% in ‘Rothana’. Fructose content in the fruits was markedly increased by using 100% compared to 60 or 40% in ‘Khalas’, Nabbut’ or ‘Rothana’. The differences between the effect of using 100 and 80% in ‘Khalas’ and ‘Nabbut’ on the fruit content from Fructose were not significant. PEER-REVIEWED ARTICLE bioresources.cnr.ncsu.edu Almutairi et al. (2025). “Irrigation, yield & date quality,” BioResources 20(3), 6019-6032. 6025 PEER-REVIEWED ARTICLE bioresources.cnr.ncsu.edu Almutairi et al. (2025). “Irrigation, yield & date quality,” BioResources 20(3), 6019-6032. 6026 Fig. 1. The influence of water irrigation regimes on fruit content from total, reduced, non-reduced sugars, glucose and fructose in three date palm cvs. ‘Khalas’, ‘Nabbut’ and ‘Rothana’ during 2022 season DISCUSSION The results showed that the irrigation regimes controlled the performance of the date palm trees. The previous findings showed that improved soil water accessibility may have improved balanced root development and soil nutrient absorption, leading to an increase in production and its constituent parts (Bainbridge 2006). Hura et al. (2007) documented that the shortage of water lowered the leaf chlorophyll content, which consequently minimizes the process of photosynthesis and that consequently transforms the light energy into chemical energy. Shao et al. (2008) noted that changes in carbon allocation typically follow a decrease in water intake, which enhances fruit development and output. Under well-irrigated conditions, the fruit yield in apple was increased (Naor et al. 2008), as well as almond (Egea et al. 2010), and plum (Intrigliolo et al. 2013) compared to deficit irrigation. Lawlor and Tezara (2009) reported that under water deficit, plants adapt physiologically by adjusting stomatal behavior to water potential and recycling carbon dioxide during photosynthesis. The total productivity and fruit quality of many fruit species are adversely affected by limited amount of water available during the various PEER-REVIEWED ARTICLE bioresources.cnr.ncsu.edu Almutairi et al. (2025). “Irrigation, yield & date quality,” BioResources 20(3), 6019-6032. 6027 stages of fruit development, including flowering, fruit setting, and maturation (García- Tejero et al. 2010). Water limitation impacts fruit yield and quality, which varies according to the stages of vegetative and reproductive growth, the length and intensity of the water deficit, and the variation of species (Intrigliolo and Castel 2010). Moreover, the same authors also stated that the plants with lower water levels had higher concentrations of solutes and had collected more sugars, which raised the total soluble solids. Additionally, fruit tree productivity is also highly dependent on the quantity of irrigation (Ruiz-Sanchez et al. 2010). When water stress levels in Amri and Shamia date palm cultivars increased, water use efficiency also increased (Helaly and El-Hosieny 2011). Water stress reduced the photosynthetic rate and stomatal conductance in citrus but significantly enhanced water use efficiency under moderate water shortage (Ávila et al. 2012). The results presented in this study indicate that the highest growth parameters and marketable yield for date palm fruit were observed at 100% crop evapotranspiration (ETc), followed by 75% ETc, and 50% ETc. This may be due to the fact that water supplied at 100% ETc adequately meets the crop's water requirements, whereas the other amounts do not (Ibrahim et al. 2012). Additionally, crop evapotranspiration is improved by increased irrigation, which raises crop productivity to some degree (Steduto et al. 2012). In areas with limited water resources, irrigation systems that are both modern and effective are necessary to preserve water without sacrificing crop quality and yield (Tindula et al. 2013). By providing the date palm with roughly 65% of its total water needs, the yield was increased, and a high CWP was attained (Ismail et al. 2014). Although the date palm grows well in areas with limited water supplies, it needs enough irrigation to sustain all of its metabolic processes and yield fruits of superior quality (Al-Yahyai and Khan 2015; Dhaoudi 2019). Proper irrigation water scheduling enhances crop yield and water use efficiency (Wen et al. 2017). Salazar et al. (2015) reported that limited water availability can influence hormones including abscisic acid and ethylene, which play crucial roles in leaf growth regulation. The differences in the rate of stomatal conductance, carbon absorption, and the pressure of turgidity of plant tissues account for the impact of water accessibility on plant growth (Mohamed et al. 2018). Al-Khateeb et al. (2019) found that in date palm, the water deficit significantly minimized the water use efficacy, photosynthesis process, rates of stomatal opening or transpiration. Besides, the absorption of minerals greatly increased by providing the quantity of water to the trees (Mohammed et al. 2020). CONCLUSIONS 1. The fruit yield and fruit characteristics of date palm were greatly improved by raising the irrigation regimes, where 100% (19.2 m3) greatly increased the fruit yield and its components compared with 60% (11.52 m3) or 40% (7.68 m3) in the three-date palm cvs. ‘Rothana’, ‘Nabbut’, and ‘Khalas’. 2. The water footprint was greatly higher when the date trees were irrigated with 100% or 80% than that with 60% or 40%. 3. It is recommended to use materials such as manure and humic acid to reduce the required quantity of water and raise the rate of preservation of water, as well as spraying antitranspirant materials, such as kaolin, to reduce the rate of evaporation from date palm trees. PEER-REVIEWED ARTICLE bioresources.cnr.ncsu.edu Almutairi et al. (2025). “Irrigation, yield & date quality,” BioResources 20(3), 6019-6032. 6028 Data Availability Statement All the required data are included in the manuscript. ACKNOWLEDGMENTS The authors extend their appreciation to Ongoing Research Funding program, (ORF-2025-561), King Saud University, Riyadh, Saudi Arabia. Funding This research was funded by Ongoing Research Funding program, (ORF-2025- 561), King Saud University, Riyadh, Saudi Arabia. Conflicts of Interest The authors declare no conflicts of interest. REFERENCES CITED Abd Elgawad, H., Saleh, A. M., Al Jaouni, S., Selim, S., Hassan, M. O., Wadaan, M. A., Shuikan, A. M., Mohamed, H. S., and Hozzein, W. N. (2019). “Utilization of actinobacteria to enhance the production and quality of date palm (Phoenix dactylifera L.) fruits in a semi-arid environment,” Sci. Total Environ. 665, 690-697. DOI: 10.1016/j.scitotenv.2019.02.140 Allen, R.G., Pereira, L.S., Raes, D., and Smith, M. (1998). “Crop evapotranspiration,” FAO Irrigation and Drainage Paper no. 56, FAO, Rome, Italy Ali-Dinar, H., Munir, M., and Mohammed, M. (2023). “Drought-tolerance screening of date palm cultivars under water stress conditions in arid regions,” Agronomy 13(11), article 2811. DOI.10.3390/agronomy13112811 Al-Khateeb, S. A., Al-Khateeb, A. A., El-Beltagi, H. S., and Sattar, M. N. (2019). “Genotypic variation for drought tolerance in three date palm (Phoenix dactylifera L.) cultivars,” Fresenius Environ. Bull. 28, 4671-4683. Alnaim, M. A., Mohamed M.S., Mohammed, M., and Munir, M. (2022). “Effects of automated irrigation systems and water regimes on soil properties, water productivity, yield, and fruit quality of date palm,” Agriculture 12, article 343. DOI: 10.3390/agriculture12030343 Alotaibi, K. D., Alharbi, H. A., Yaish, M. W., Ahmed, I., Alharbi, S. A., Alotaibi, F., and Kuzyakov, Y. (2023). “Date palm cultivation: A Review of soil and environmental conditions and future challenges,” Land Degrad. Dev. 34, 2431–2444. DOI: 10.1002/ldr.4619 Al-Yahyai, R., and Khan, M. M. (2015). “Date palm status and perspective in Oman,” in: Date Palm Genetic Resources and Utilization, J. Al-Khayri, S. Jain, and D. Johnson (eds.), Springer, Dordrecht. DOI: 10.1007/978-94-017-9707-8_6 Association of Analytical Chemists (AOAC) (2005). Official Methods of Analysis of the Association of Analytical Chemists International, AOAC, Gaithersburg, MD, USA. Arora, N. K. (2019). “Impact of climate change on agriculture production and its sustainable solutions,” Environ. Sustain. 2(2), 95-96. DOI: 10.1007/s42398-019- 00078-w https://doi.org/10.1016/j.scitotenv.2019.02.140 https://doi.org/10.3390/agronomy13112811 https://doi.org/10.3390/agriculture12030343 https://doi.org/10.1002/ldr.4619 https://doi.org/10.1007/978-94-017-9707-8_6 https://doi.org/10.1007/s42398-019-00078-w https://doi.org/10.1007/s42398-019-00078-w PEER-REVIEWED ARTICLE bioresources.cnr.ncsu.edu Almutairi et al. (2025). “Irrigation, yield & date quality,” BioResources 20(3), 6019-6032. 6029 Ávila, C., Guardiola, J. L., and Nebauer, S. G. (2012). “Response of the photosynthetic apparatus to a flowering-inductive period by water stress in Citrus,” Trees-Struct. Funct. 26, 833-840. DOI: 10.1007/s00468-011-0657-4 Baig, M. B., Y. Alotibi, G. S. Straquadine, and Alataway, A. (2020). “Water resources in the Kingdom of Saudi Arabia: Challenges and strategies for improvement,” in: Water Policies in MENA Countries, Global Issues in Water Policy, S. Zekri (ed), Springer, Cham., Vol. 23, 135-160. DOI: 10.1007/978-3-030-29274-4_7 Bainbridge, D. A. (2006). “Beyond drip irrigation–Hyper-efficient irrigation,” in: 2006 ASAE Annual Meeting (p. 1), paper: 062073. DOI: 10.13031/2013.20692 Dhaouadi, L., Besser, H., Karbout, N., Al-Omran, A., Wassar, F., Wahba, M. S., Yaohu, K., and Hamed, Y. (2021). “Irrigation water management for sustainable cultivation of date palm,” Appl. Water Sci. 11, article 171. DOI: 10.1007/s13201-021-01507-0 Dhaoudi, L. (2019). “Water saving in arid irrigated lands: A comparison between different irrigation techniques adopted under date palms in the Tunisian Oasis,” Desalin. Water Treat. 176, 190-196. DOI: 10.5004/dwt.2020.25516 Egea, G., Nortes, P. A., González-Real, M. M., Baille, A., and Domingo, R. (2010). “Agronomic response and water productivity of almond trees under contrasted deficit irrigation regimes,” Agric. Water Manag. 97(1), 171-181. DOI: 10.1016/j.agwat.2009.09.006 FAO. (2025). “Food and agriculture organization of the United Nations. FAO Statistical Databases,” available online: http://faostat.fao.org/site. (accessed on February 27, 2025). Gamble, D. W., Campbell, D., Allen, T. L., Barker, D., Curtis, S., McGregor, D., and Popke, J. (2010). “Climate change, drought, and Jamaican agriculture: Local knowledge and the climate record,” Ann. Am. Assoc. Geogr. 100(4), 880-893. DOI: 10.1080/00045608.2010.497122 García-Tejero, I., Romero-Vicente, R., Jiménez-Bocanegra, J., Martínez-García, G., Durán-Zuazo, V., and Muriel-Fernández, J. (2010). “Response of citrus trees to deficit irrigation during different phenological periods in relation to yield, fruit quality, and water productivity,” Agric.Water Manag. 97(5), 689-699. DOI: 10.1016/j.agwat.2009.12.012 Hammami, Z., Mahmoudi, H., Al Janaahi, A., and Singh, R. K. (2024). “Evaluation of date palm fruits quality under different irrigation water salinity levels compared to the fruit available in the market,” Front. Sustain. Food Syst. 7, article 1322350. DOI: 10.3389/fsufs.2023.1322350 Heiberger, R. M., Heiberger, R. M., and Burt Holland, B. H. (2015). “Statistical analysis and data display,” An Intermediate Course with Examples in R., Springer Texts in Statistics ISBN 978-1-4939-2121-8. DOI:10.1007/978-1-4939-2122-5 Helaly, M., and El-Hosieny, A. (2011). “In vitro selection and photosynthetic characterization of date palm regenerated seedling as affected by water stress,” Amer. J. Plant Physiol. 6(3), 126-143. DOI: 10.3923/ajpp.2011.126.143 Hellman, E (2010). “Irrigation scheduling of grapevines with evapotranspiration data,” Texas A&M University, Texas AgriLife extension service: College Station, Texas. http://wineg rapes. tamu.edu/ grow/irrigationscheduling.pdf https://doi.org/10.1007/s00468-011-0657-4 https://doi.org/10.1007/978-3-030-29274-4_7 https://doi.org/10.13031/2013.20692 https://doi.org/10.1007/s13201-021-01507-0 https://doi.org/10.5004/dwt.2020.25516 https://doi.org/10.1016/j.agwat.2009.09.006 https://doi.org/10.1080/00045608.2010.497122 https://doi.org/10.1016/j.agwat.2009.12.012 https://doi.org/10.1016/j.agwat.2009.12.012 https://doi.org/10.3389/fsufs.2023.1322350 https://doi.org/10.1007/978-1-4939-2122-5 https://doi.org/10.3923/ajpp.2011.126.143 PEER-REVIEWED ARTICLE bioresources.cnr.ncsu.edu Almutairi et al. (2025). “Irrigation, yield & date quality,” BioResources 20(3), 6019-6032. 6030 Huber, A. E., and Bauerle, T. L. (2016). “Long-distance plant signaling pathways in response to multiple stressors: The gap in knowledge,” J. Exp. Bot., 67, 2063-2079. DOI: 10.1093/jxb/erw099 Hura, T., Hura, K., Grzesiak, M., and Rzepka, A. (2007). “Effect of long-term drought stress on leaf gas exchange and fluorescence parameters in C3 and C4 plants,” Acta Physiol. Plant. 29, 103-113. DOI: 10.1007/s11738-006-0013-2 Ibrahim, M. M., Ouda, S. A., Taha, A., El Afandi, G., and Eid, S. M. (2012). “Water management for wheat grown in sandy soil under climate change conditions,” J. Soil Sci. Plant Nutr. 12(2), 195-210. DOI: 10.4067/S0718-95162012000200001 Intrigliolo, D. S., and Castel, J. R. (2010). “Response of plum trees to deficit irrigation under two crop levels: tree growth, yield and fruit quality,” Irrig. Sci. 28, 525-534. DOI: 10.1007/s00271-010-0212-x Intrigliolo, D. S., Ballester, C., and Castel, J. R. (2013). “Carry-over effects of deficit irrigation applied over seven seasons in a developing Japanese plum orchard,” Agric. Water Manag. 128, 13-18. DOI: 10.1016/j.agwat.2013.06.009 Ismail, S. M., Al‐Qurashi, A. D., and Awad, M. A. (2014). “Optimization of irrigation water use, yield, and quality of 'NABBUT‐SAIF' date palm under dry land conditions,” Irrig. Drain. 63(1), 29-37. DOI: 10.1002/ird.1823 Kassem, M. (2007). “Water requirements and crop coefficient of date palm trees Sukariah CV,” Misr J. Agric. Engin. 24(2), 339-359. Lambers, H., Chapin, F. S., and Pons, T. L. (2008). Plant Physiological Ecology, 2nd Ed., Springer, New York, p. 604. Lawlor, D. W., and Tezara, W. (2009). “Causes of decreased photosynthetic rate and metabolic capacity in water-deficient leaf cells: A critical evaluation of mechanisms and integration of processes,” Ann. Bot. 103(4), 561-579. DOI: 10.1093/aob/mcn244 Li, L., Xing, J., Ma, H., Liu, F., and Wang, Y. (2021). “In Situ determination of guard cell ion flux underpins the mechanism of aba-mediated stomatal closure in barley plants exposed to PEG-induced drought stress,” Environ. Exp. Bot. 187, article 104468. DOI: 10.1016/j.envexpbot.2021.104468 Mazahrih, N. T., Al-Zubi, Y., Ghnaim, H., Lababdeh, L., Ghananeem, M., and Ahmadeh, H. A. (2012). “Determination actual evapotranspiration and crop coefficients of date palm trees (Phoenix dactylifera) in the Jordan Valley,” Am.-Eurasian J. Agric. Environ. Sci. 12(4), 434-443. Meddich, A., Ait El Mokhtar, M., Bourzik, W., Mitsui, T., Baslam, M., and Hafidi, M. (2018). “Optimizing growth and tolerance of date palm (Phoenix dactylifera L.) to drought, salinity, and vascular fusarium-induced wilt (Fusarium oxysporum) by application of arbuscular mycorrhizal fungi (AMF),” in: Root Biology. Soil Biology, Vol. 52, Springer, Cham., B. Giri, R. Prasad, and A. Varma (eds.). DOI: 10.1007/978- 3-319-75910-4_9 Mohamed, A. S., Ali, A. A., El-Ghany, A., and Yosri, A. (2018). “Irrigation water management of date palm under El-Baharia Oasis conditions,” Egyptian J. Soil Sci. 58(1), 27-44. DOI: 10.21608/ejss.2017.1609.1123 Mohammed, M. E.A., Alhajhoj, M. R., Ali-Dinar, H. M., and Munir, M. (2020). “Impact of a novel water-saving subsurface irrigation system on water productivity, photosynthetic characteristics, yield, and fruit quality of date palm under arid conditions,” Agronomy 10(9), article 1265. DOI:10.3390/agronomy10091265 https://doi.org/10.1093/jxb/erw099 https://doi.org/10.1007/s11738-006-0013-2 https://doi.org/10.4067/S0718-95162012000200001 https://doi.org/10.1007/s00271-010-0212-x https://doi.org/10.1016/j.agwat.2013.06.009 https://doi.org/10.1002/ird.1823 https://doi.org/10.1093/aob/mcn244 https://doi.org/10.1016/j.envexpbot.2021.104468 https://doi.org/10.1007/978-3-319-75910-4_9 https://doi.org/10.1007/978-3-319-75910-4_9 https://doi.org/10.21608/ejss.2017.1609.1123 https://doi.org/10.3390/agronomy10091265 PEER-REVIEWED ARTICLE bioresources.cnr.ncsu.edu Almutairi et al. (2025). “Irrigation, yield & date quality,” BioResources 20(3), 6019-6032. 6031 Mohammed, M., Sallam, A., Munir, M., and Ali-Dinar, H. (2021). “Effects of deficit irrigation scheduling on water use, gas exchange, yield, and fruit quality of date palm,” Agronomy 11(11), article 2256. DOI:10.3390/agronomy11112256 Naor, A., Naschitz, S., Peres, M., and Gal, Y. (2008). “Responses of apple fruit size to tree water status and crop load,” Tree Physiol. 28(8), 1255-1261. DOI: 10.1093/ treephys/28.8.1255 Nielsen, S. S. (2010). “Phenol-sulfuric acid method for total carbohydrates,” in: Food Analysis Laboratory Manual, Food Science Texts Series, S. S. Nielsen (ed), Springer, Boston, MA, USA, pp. 47-53. DOI: 10.1007/978-1-4419-1463-7_6 Ortega-Farias, S., Espinoza-Meza, S., López-Olivari, R., Araya-Alman, M., and Carrasco-Benavides, M. (2021). “Effects of different irrigation levels on plant water status, yield, fruit quality, and water productivity in a drip-irrigated blueberry orchard under Mediterranean conditions,” Agric. Water Manag. 249, article 106805. DOI: 10.1016/j.agwat.2021.106805 Ruiz-Sanchez, M. d. C., Domingo, R., and Castel, J. R. (2010). “Review. Deficit irrigation in fruit trees and vines in Spain,” Spanish J. Agric. Res. 8(S2), S5-S20. DOI: 10.5424/sjar/201008S2-1343 Shadeed, S. (2013). “Spatio-temporal drought analysis in arid and semi-arid regions: A case study from Palestine,” Arab. J. Sci. Eng. 38, 2303-2313. DOI: 10.1007/s13369- 012-0504-y Sharma, A., Kumar, V., Shahzad, B., Ramakrishnan, M., Singh Sidhu, G. P., Bali, A. S., Handa, N., Kapoor, D., Yadav, P., Khanna, K., et al (2020). “Photosynthetic response of plants under different abiotic stresses: A review,” J. Plant Growth Regul. 39, 509- 531. DOI: 10.1007/s00344-019-10018-x Shao, H.-B., Chu, L.-Y., Jaleel, C. A., and Zhao, C.-X. (2008). “Water-deficit stress- induced anatomical changes in higher plants,” C. R. Biol. 331(3), 215-225. DOI:10.1016/j.crvi.2008.01.002 Salazar, C., Hernandez, C., and Pino, M.T. (2015). “Plant water stress: Associations between ethylene and abscisic acid response,” Chil. J. Agric. Res. 75, 71-79. DOI: 10.4067/S0718-58392015000300008 Sperling, O., Shapira, O., Tripler, E., Schwartz, A., and Lazarovitch, N. (2014). “A model for computing date palm water requirements as affected by salinity,” Irrig. Sci. 32, 341-350. DOI: 10.1007/s00271-014-0433-5 Steduto, P., Hsiao, T. C., Fereres, E., and Raes, D. (2012). “Crop yield response to water,” Irrigation and Drainage Paper 66, United Nations FAO, Rome. Tindula, G. N., Orang, M. N., and Snyder, R. L. (2013). “Survey of irrigation methods in California in 2010,” J. Irrig. Drain. Engin. 139(3), 233-238. DOI:10.1061/ (ASCE)IR.1943-4774.0000538 Vaz, M., Coelho, R., Rato, A., Samara-Lima, R., Silva, L. L., Campostrini, E., and Mota, J. B. (2016). “Adaptive strategies of two Mediterranean grapevines varieties (Aragonez syn. Tempranillo and Trincadeira) face drought: Physiological and structural responses,” Theor. Exp. Plant Physiol. 28(2), 205-220. DOI: 10.1007/ s40626-016-0074-6 Vurukonda, S. S. K. P., Vardharajula, S., Shrivastava, M., and SkZ, A. (2016). “Enhancement of drought stress tolerance in crops by plant growth promoting rhizobacteria,” Microbiol. Res., 184, 13-24. DOI: 10.1016/j.micres.2015.12.003 https://doi.org/10.3390/agronomy11112256 https://doi.org/10.1093/%20treephys/28.8.1255 https://doi.org/10.1093/%20treephys/28.8.1255 https://doi.org/10.1007/978-1-4419-1463-7_6 https://doi.org/10.1016/j.agwat.2021.106805 https://doi.org/10.5424/sjar/201008S2-1343 https://doi.org/10.1007/s13369-012-0504-y https://doi.org/10.1007/s13369-012-0504-y https://doi.org/10.1007/s00344-019-10018-x https://doi.org/10.1016/j.crvi.2008.01.002 https://doi.org/10.4067/S0718-58392015000300008 https://doi.org/10.1007/s00271-014-0433-5 https://doi.org/10.1061/%20(ASCE)IR.1943-4774.0000538 https://doi.org/10.1061/%20(ASCE)IR.1943-4774.0000538 https://doi.org/10.1007/%20s40626-016-0074-6 https://doi.org/10.1007/%20s40626-016-0074-6 https://doi.org/10.1016/j.micres.2015.12.003 PEER-REVIEWED ARTICLE bioresources.cnr.ncsu.edu Almutairi et al. (2025). “Irrigation, yield & date quality,” BioResources 20(3), 6019-6032. 6032 Wen, Y., Shang, S., and Yang, J. (2017). “Optimization of irrigation scheduling for spring wheat with mulching and limited irrigation water in an arid climate,” Agric. Water Manag. 192, 33-44. DOI: 10.1016/j.agwat.2017.06.023 Article submitted: January 28, 2025; Peer review completed: March 29, 2025; Revisions accepted: May 27, 2025; Published: June 6, 2025. DOI: 10.15376/biores.20.3.6019-6032 https://doi.org/10.1016/j.agwat.2017.06.023