Effect of Some Soil Conditioners on Water-Use Efficacy, Growth, and Yield of...

[Full title: Effect of Some Soil Conditioners on Water-Use Efficacy, Growth, and Yield of Date Palm Siwi Grown in Sandy Soil under Different Irrigation Regimes to Mitigate Climate Change]

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Citation: Hassan, K.H.A.; Alamery, S.; El-Kholy, M.F.; Das, S.; Salem-Bekhit, M.M. Effect of Some Soil Conditioners on Water-Use Efficacy, Growth, and Yield of Date Palm Siwi Grown in Sandy Soil under Different Irrigation Regimes to Mitigate Climate Change Sustainability 2022 , 14 , 11421 https://doi.org/10.3390/ su 141811421 Academic Editors: Marc A. Rosen and Teodor Rusu Received: 31 May 2022 Accepted: 2 September 2022 Published: 12 September 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations Copyright: © 2022 by the authors Licensee MDPI, Basel, Switzerland This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/) sustainability Article Effect of Some Soil Conditioners on Water-Use Efficacy, Growth, and Yield of Date Palm Siwi Grown in Sandy Soil under Different Irrigation Regimes to Mitigate Climate Change Khairy H. A. Hassan 1, *, Salman Alamery 2 , Mohamed Farouk El-Kholy 1 , Shobhan Das 3 and Mounir M. Salem-Bekhit 4 1 Department of Tropical Fruits Research, Institute Horticulture Research, Agricultural Research Centre, Giza 12619, Egypt 2 Department of Biochemistry, College of Science, King Saud University, P.O. Box 22452, Riyadh 11451, Saudi Arabia 3 Department of Biostatistics Epidemiology, and Environmental Health Science, Georgia Southern University, Statesboro, GA 30460, USA 4 Department of Pharmaceutics, College of Pharmacy, King Saud University, P.O. Box 2457, Riyadh 11451, Saudi Arabia * Correspondence: kh 11191@ymail.com Abstract: A field experiment was carried out at Al-Bahariya Oasis, Giza, Egypt, during three successive seasons to find out the effect of application of bentonite (BN) as a natural clay deposit at either 6 or 12 kg/palm tree and humic substances (HS) as organic amendment at either 0.75 or 1.0 L/palm tree incorporated with Bacillus polymyxa (BP) as a biofertilizers at 14 and 28 mL/L rates on growth, yield, and fruit weight of 10-year-old Siwi date palm cv. ( Phoenix dectylifera L.). Siwi trees were cultivated in sandy texture soil at a distance of 8 × 8 m and were irrigated with 100%, 85%, and 70% of ET crop. Effects of the previous treatments on growth, date palm crop, soil properties, water relations, water-use efficiency (WUE), and economic return were also studied. The obtained results showed that the mean values of leaf length, leaflet length and width, fruit set%, bunch weight, yield/palm, yield/fed, fruit weight, flesh weight, and fruit pulp weight were increased in response to the different individual and combined treatments used in this study with various significance levels compared to the control treatment means in the studied three seasons. However, the superiority was for combining between amending the sandy soil with either low concentrations of BN (6 kg/tree) + HS (0.75 Liter/tree) + BP (14 mL/L) or high concentrations of BN (12 kg/tree) + HS (1.0 L/tree) + BP (28 mL/L) and irrigation with 85% of ETc water level, as such combinations attained the highest values in most of the mentioned values over both the sole and combined treatments in the studied three seasons. Furthermore, the results indicated that the highest monthly ETc values occurred during June and July months, while the lowest values occurred during December and January months. Additionally, water productivity (WP) increased considerably by reduction of water quantity (70% ETc) associated with soil conditioner treatment (BN.12 kg +HS 1 L + BP. 28 mL/L), and values were 2.17, 2.25, and 2.27 kg fruit/m 3 of water irrigation during the growing seasons, respectively. The highest net return was attributed to irrigation with 85% of ETc water level along with the application of soil conditioners at high rates. Accordingly, it is advisable to apply the soil conditioners of bentonite (at 6 or 12 kg/tree) and humic substances (at either 0.75 or 1.0 L/tree) with B. polymyxa (at either 14 or 28 mL/L) plus irrigation with either 85% or 70% of ETc water level to obtain the best growth, highest yield, (WP), and gross return from var. Siwi date palm grown under an oasis agro-system Keywords: date palm; Siwi cv.; Phoenix dectylifera ; growth; yield; fruit weight; bentonite; Bacillus polymyxa ; biofertilizers; irrigation water Sustainability 2022 , 14 , 11421. https://doi.org/10.3390/su 141811421 https://www.mdpi.com/journal/sustainability

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Sustainability 2022 , 14 , 11421 2 of 20 1. Introduction Due to the pressing water-deficit problem in Egypt, especially after building the Grand Ethiopian Renaissance Dam (GERD), it has become urgent to identify economical crops that consume the least water and their efficient management, among which may be date palm varieties. Date palm ( Phoenix dactylifera L.) is one of the most indispensable fruit trees in the world, especially in the arid and semi-arid regions. Egypt ranks as the first largest date producer among world countries, as its production is approximately 1.4 million tons The Siwi date palm variety is the most significant semi-dry date in Egypt. It represents approximately 13.2% of the overall production. Date palm fruits are marketed worldwide as a highly nutritious and cheap fruit as well as high gross return fruits, achieving valuable profit for farmers and the country alike in the desert-like regions [ 1 , 2 ]. There is a common misconception among farmers that dates palm trees can tolerate drought and can be grown well with small amounts of water supplies. However, such beliefs are not correct because date palm trees actually need adequate amounts of water to promote growth through maintaining all metabolic processes in a vital and vigorous way [ 3 ]. The yearly water requirement needed for a mature date palm tree varies from 115–306 m 3 depending on the climate conditions, soil type, and date variety [ 4 ]. In Egypt, the amount of water required for irrigating the date palm tree ranges between 86–124 m 3 /tree (10.28–14.88 m 3 /100 m 2 ) [ 4 ]. In this regard, ref. [ 5 ] emphasized that date palm trees need sufficient water of convenient quality to reach full potential [ 6 ]. Date palm trees are drought-resistant plants, but when they are exposed to prolonged drought, they become stunted and cease to grow. On the other hand, ref. [ 7 ] cited that although the highest yield of date palm tree is achieved by irrigation with its full water requirements, it can also be attained by only 50% of water requirements or less in the presence of the proper soil conditioners Therefore, the application of soil amendments of various soil types is considered a crucial factor for the sustainability of oasis agro-systems [ 8 ]. In dry land and oasis, water is considered the most affecting factor for crop production and soil amendments, such as organic matter (OM), e.g., bentonite and bacillus bacterium, which is the key factor for preventing water loss. Apart from the supply of N, P, K and other nutrients, OM application increases water-holding capacity, cation exchange capacity (CEC), soil fertility, and sustainability of the agro-system over time. In this regard, ref. [ 9 ] indicated that application of plant refuse compost at 100 t/hm 2 increased soil-moisture retention and fertility. Likewise, ref. [ 10 ] reported that OM content of 4–5% in sandy soil where date palm trees grow can hold ten times the amount of water and nutrients compared to sandy soil with lower OM content. This in turn, would greatly support water-saving efforts and increase water-use efficiency. Regarding date palm varieties, similar observations were also detected [ 11 , 12 ]. Bentonite as a valuable absorbent swelling clay is widely used alone or with humates to increase the CEC and improve the fertility of sandy soil. This truth was documented by ref. [ 12 ] on Deglet Nour date palm trees, ref. [ 13 ] on sugarcane, ref. [ 14 ] on aloe vera, ref. [ 15 ] and on wheat and peanut as well Likewise, microbial inoculation with some effective microorganisms such as Bacillus spp. plant growth-promoting rhizobacteria (PGPR) may hasten date palm production in oasis agro-systems, as such bacteria do not only increase the plant growth, but they also improve nutritional assimilation of plants, suppress pathogens in the rhizosphere, fix the root-associated N, solubilize P 2 O 5 compounds, produce plant growth-promoting substances, aggregate partial distribution, and improve soil porosity [ 16 , 17 ]. The abovementioned benefits were demonstrated by ref. [ 16 ] on wheatgrass, ryegrass, and white clover, ref. [ 18 ] on wheat, ref. [ 19 ] on Arabidopsis thaliana , ref. [ 20 ] on sugar beet, ref. [ 17 ] and on wheat. Applying deficit irrigation to palm trees that are grown in dry areas can maximize water productivity [ 21 ]. The increase in yield might be linked to the availability of optimum soil moisture, which promotes balanced root growth and nutrient intake. Ref. [ 12 ] determined the effect of sandy soil (S) mixed with farm manure (M) and bentonite clay (B) BSM on the soil characteristics and date palm trees morphological characteristics.

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Sustainability 2022 , 14 , 11421 3 of 20 Soil macroand micronutrient contents were improved after BSM. Retention of soil water in BSM was also elevated compared to an untreated soil (no amendment). The improvement of morphological characteristics was observed for the canopy diameter in BSM treatment compared to untreated palm trees. Likewise, the leaf number increased, and height of the palm trees increased as well However, this work aims to improve the growth and yield of Siwi date palms cultivated and grown in sandy soil through organic, inorganic, and bio treatments under various irrigation water levels 2. Materials and Methods A field experiment was conducted in a private orchard at Al-Bahariya Oasis district, Giza, Egypt, at (28 ◦ 19 0 10” N: 28 ◦ 57 0 35” E. 130 m a.s.l.) during the three successive seasons of 2018/19, 2019/20, and 2020/21 with the aim to study the effect of bentonite, humic substances, and Bacillus polymyxa plant growth-promoting rhizobacteria PGPR in combinations on WP, growth, and productivity of Siwi date palm cv., bearing in mind that palm trees were grown in sandy soil and were irrigated with different levels of water Therefore, 27 mature date palm trees ( Phonex dactylifera L.) var. Siwi of the same size and growth vigor (10 years old) were planted at a distance of 8 × 8 m. The layout of the experiment in the 3 studied seasons was split plot design with three replicates [ 22 ], where irrigation levels were devoted for the main plots, whereas soil amendments were devoted for the sub-plots. The treatments of both water levels and soil amendments were as follows: 2.1. Irrigation Treatments (Main Plots) Irrigation treatments as a percentage of crops evapotranspiration (ETc%) were applied at the following 3 levels: I 1 Irrigation with amount of water equals 100% of potential evapotranspiration (ETcrop) I 2 Irrigation with amount of water equals 85% of potential evapotranspiration (ETcrop) I 3 Irrigation with amount of water equals 70% of potential evapotranspiration (ETcrop) 2.2. Soil Conditioners Treatments (Sub-Plots) A combination of bentonite BN (as natural swelling clay) + humic substance HS (as an organic amendment) + Bacillus polymyxa BP plant growth-promoting rhizobacteria PGPR (as liquid biofertilizers, 109 c.f.u.) was applied at the following rates for each palm tree: A—Without soil conditioners (control); B—BN (6 kg/tree) + HS (0.75 L/tree) + “ Bacillus polymyxa ” biofertilizers BP (109 c.f.u.) plant growth-promoting rhizobacteria (PGPR at 14 mL/L); C—BN. (12 kg/tree) + HS (1.0 L/tree) + “ Bacillus polymyxa ” biofertilizers BP plant growth-promoting rhizobacteria PGPR (109 c.f.u.) at 28 mL/L 2.3. Soil Analysis Samples of soil were collected from the date palm rhizosphere zone at three different depths (0–30, 30–60, and 60–90 cm) and oven-dried at 55 ◦ C, and their physical and chemical properties were determined using the methods described by [ 23 , 24 ]. The constant soil moisture was measured by the pressure membrane apparatus explained by [ 25 ]. The analysis results are summarized in Tables 1 and 2 .

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Sustainability 2022 , 14 , 11421 4 of 20 Table 1. Physical characteristics of the experimental soil Soil Depth (cm) Particle Size Distribution % Textural Class Organic Matter (%) Bulk Density g/cm 3 Field Capacity (%) Wilting Point (%) Available Water (%) Coarse Sand Fine Sand Silt Clay 0–30 28.48 61.70 5.27 4.55 Sandy soil 0.52 1.60 12.6 3.3 9.3 30–60 27.81 60.55 6.23 5.41 0.45 1.63 12.3 2.9 9.4 60–90 26.72 60.04 6.97 6.27 0.39 1.66 12.0 2.6 9.4 Table 2. Chemical characteristics of the experimental soil Soil Depth (cm) EC (dS m − 1 ) pH CaCO 3 % Soluble Ions (meq/L) in Saturated Soil Paste Extract Na + K + Ca ++ Mg ++ Cl − HCO 3 − CO 3 = SO 4 = 0–30 2.31 7.48 5.51 10.39 1.51 7.17 4.79 8.3 2.87 - 12.69 30–60 2.22 7.53 3.95 9.27 1.43 6.86 4.11 7.98 1.95 - 11.74 60–90 1.81 7.61 2.37 7.51 0.69 5.59 3.46 5.99 1.84 - 9.42 2.4. Irrigation Water Quality The chemical analysis of irrigation water was evaluated according to the methods of [ 26 ] and is listed in Table 3 . Table 3. Chemical analysis of irrigation water Sample pH EC dS m − 1 SAR Soluble Cations, meq/L Soluble Anions, meq/L Na + K + Ca ++ Mg ++ CL − HCO 3 − CO 3 = SO 4 = Mean 7.93 0.46 1.95 2.02 0.57 0.77 1.36 2.29 1.74 - 0.69 The chemical analysis of bentonite and characteristics of humic substances were measured and are expressed in Tables 4 and 5 , respectively Table 4. The chemical analysis of bentonite Bentonite Composition (on a Weight Basis) SiO 2 Al 2 O 3 Na 2 O CaO MgO K 2 O Fe 2 O 3 73.20% 11.40% 0.31% 2.67% 1.05% 2.58% 0.29% Table 5. Characteristics of humic substances extracted from biogas manure Samples Humic Acid (%) Fulvic Acid (%) Total (mmol/100 g HS) Total Macro-Elements (%) Acidity Phenolic Groups Carboxylic Groups N P K HS-B 30.8 17.1 879 510 368 5.1 2.3 4.6 HS-B., humic substances extracted from biogas manure Regarding the above-mentioned substances, they were dark-yellow powder, and their pH was 7.22 and EC values were 2.95 dS · m − 1 . The substances were obtained from El-Basatin Industrial Zone, Cairo, Egypt In addition, the average of the month’s temperature ◦ C, wind speed (m/s), solar radiation, relative humidity (%), and rain fall from the Metrological Authority of Giza governorate are outlined in Table 6 .

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Sustainability 2022 , 14 , 11421 5 of 20 Table 6. Meteorological data in 2018, 2019, and 2020 seasons Season 2018 2019 2020 Month T.Max T.min. W.S R.H S.R R.F T.max T.min W.S R.H S.R R.F T.max T.min W.S R.H S.R R.F January 19.4 10.3 2.6 60 385 1.1 17.1 4.4 3.0 48.2 353 1.5 16.5 5.0 3.3 63.9 343 6.5 February 21.5 8.0 2.0 62 461 5.1 19.4 6.2 2.9 46.6 416 1.83 18.9 6.7 2.8 61.3 403 109.2 March 25.4 12.0 2.3 50 569 10.3 22.8 8.4 3.4 40.4 522 0.44 22.3 8.7 3.2 55.0 502 8.4 April 28.8 15.8 2.4 41 590 5.5 27.9 12.7 3.3 32.7 571 0.22 26.6 11.5 2.9 45.0 598 0.0 May 34.6 19.4 2.0 34 627 0.0 35.6 18.7 3.3 22.0 602 0 33.1 16.7 3.4 32.7 611 0.0 June 36.7 16.0 2.0 23 650 0.0 37.2 22.1 3.6 29.0 620 0 36.1 19.8 3.4 28.3 625 0.6 July 38.2 24.5 1.6 42 645 0.0 38.1 22.9 3.4 30.3 650 0 36.8 21.4 3.4 30.8 650 0.0 August 37.1 24.6 2.0 46 636 0.0 37.5 22.5 3.1 31.4 595 0 37.4 22.0 3.3 33.1 577 0.0 September 34.9 22.3 2.9 46 545 0.0 34.3 20.0 3.4 40.8 485 0 36.5 21.3 3.5 37.4 567 0.0 October 31.0 18.5 1.9 47 495 4.8 31.9 18.1 2.8 41.1 478 1.46 31.7 18.0 3.3 45.2 476 0.7 November 25.5 13.7 1.7 54 399 26.0 26.8 13.3 2.3 45.6 387 0 23.1 12.1 2.7 60.1 370 7.4 December 23.9 12.4 2.3 64 289 34.8 19.6 7.9 3.1 62.8 329 20.4 21.2 9.7 2.7 58.8 317 1.0 T.max and T.min, maximum and minimum temperature ◦ C; W.S, wind speed (m/s); S.R, solar radiation (Mg 2 /cal/m); R.H, relative humidity (%); R.F, rainfall (mm/month). (Data were obtained from the agrometeorological Unit at SWERI, ARC.) 2.5. Crop–Soil–Water Relations 2.5.1. Reference Crop Evapotranspiration (ETo) Water requirements were evaluated by meteorological parameters using the “WA- TER” computer model [ 27 ], based on calculation using the Doorenbos and Pruitt equation and the Kc values (Table 6 ). Ref. [ 7 ] adapted the radiation formula to predict potential evapotranspiration as follows: ETp = bwRs/L − 0.3 (1) where: ETp = daily potential evapotranspiration (mm/day); b = adjustment factor based on wind and mean relative humidity; W = weighting factor based on temperature and elevation above sea level; Rs = daily total incoming solar radiation for the period of consideration (cal/cm 2 /day); L = latent heat of vaporization of water (cal/cm 2 /day); and factors (b) and (w) could be obtained from the tables cited by [ 7 ]. 2.5.2. Crop Evapotranspiration (ETc) According to the following equation given by [ 28 ], the ETc values were calculated ETc = ETo × Kc (2) where ETc = crop evapotranspiration (mm day − 1 ); ETo = reference crop evapotranspiration (mm day − 1 ); Kc = crop coefficient. (The Kc values used in this study were 0.76, 1.07, 1.18, and 0.88 for the initial, development, mid-season, and maturity growth stages, respectively, as reported by Ref. [ 29 ].) 2.5.3. Amount of Applied Irrigation Water (AIW) The amount of applied water was measured by a flow meter and was calculated according to the following equation [ 30 ]: AIW = Sp × S 1 × ETo × Kc × Kr × I interval Ea + LR (3)

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Sustainability 2022 , 14 , 11421 6 of 20 where: AIW = applied irrigation water depth (liters/day); Sp = distance between plants in the same line (m); Sl = distance between lines (m); ETo = potential evapotranspiration (mm/day) values obtained by [ 7 ]; Kc = crop coefficient, and Kc ranged between 0.5 to 1.18 during the growing season as recorded by [ 29 ] and shown in Table 6 ; Kr = reduction factor that depends on ground cover. It equals 0.75 for mature trees [ 31 ]; Ea = drip irrigation system efficiency = 90%; I interval = irrigation intervals (days) = 1 day for the experimental site; LR = leaching requirements = the extra amount of applied water needed for salt leaching and is calculated according to [ 26 ] as follows: LR = ECiw/ECe (4) where ECiw = salinity of irrigation water (dS m − 1 ), and ECe = average soil salinity tolerated by the crop as measured by soil saturated extracts (dS m − 1 ). Under the current experimental conditions, no additional water was added for leaching to avoid any effect on stress treatments Data recorded: Leaf parameters such as values of leaf length (cm) and leaflet length and width (cm) were measured; percentage of fruit set: As for fruit set%, the number of flowers as full bloom and set fruitlets were recorded on the tagged limbs; then, the percentage of fruit set was estimated by the following equation according to [ 32 ]. Fruit set ( % ) = No. of set fruitlets Total No. of flowers at full bloom × 100 (5) Yield and its components: In October, when fruits reached the (tamer) date stage, the date palms were harvested during the study years. The average fruit yield (kg/palm) and bunch weight (ton/fed) were registered in kilograms. Moreover, samples were randomly collected from four different bunches to determine the values of fruit weight, flesh weight, and fruit pulp weight in gm 2.5.4. Crop Water Productivity (WP) WP is a crop yield per unit for applied irrigation water that investigates the effective use of applied irrigation water [ 33 ] and is formulated as follow: WP = Fruits yield ( kg/fed ) Applied irrigation water ( m 3 /fed ) (6) Statistical analysis: Data collected during the study period (three seasons) were subjected to variance analysis according to [ 34 ]. Using Duncan’s multiple range test, the significant differences amongst means were determined [ 35 ]. 3. Results 3.1. Effect of Soil Amendments, Irrigation Levels, and Their Interactions on 3.1.1. Palm’s Water Relationships The estimated crop evapotranspiration (ETc): Water use by mature palm trees crop (ETc) is determined by multiplying the reference ETo by the palm trees crop coefficient (Kc). The ETc was calculated using the climate data for three seasons to calculate water requirements for the palm trees. Results in Figure 1 illustrate the results of the ETc calculations for the experiment site. The highest monthly ETc was during June and July at (197.7 and 208.6), (197.7 and 215.8), and (198.0 and 213.3) mm/month for the first, second, and third seasons, respectively, while the lowest ETc value was in January and December and was (88.4 and 15.5), (75.3 and 75.3), and (72.5 and 74.7) mm/month in the three seasons, respectively. Generally, the ETc in the 2018 season was higher than ETc in both 2019 and 2020 seasons. These results agreed with those of [ 29 ].

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Sustainability 2022 , 14 , 11421 7 of 20 Sustainability 2022 , 14 , x FOR PEER REVIEW 7 of 20 Figure 1. The estimated evapotranspiration (ETc) during the three growing seasons (2018, 2019, and 2020) for experiment site. 3.1.2. Applied Irrigation Water (AIW) The effect of tested irrigation treatments on applied irrigation water, expressed as liters/tree/day, m 3 /fed/month, and m 3 /fed/year during the three growing seasons, are shown in Table 7. Results show that the least amounts of water requirements were during January and December regarding the three seasons and the greatest amounts of water requirements during June and July. As for the average amounts of applied irrigation water, they were 5664, 4815, and 3965 m 3 /fed/year (mean of the three seasons) for the 100%, 85%, and 70% Etc irrigation treatments, respectively. The obtained amounts were 1349, 1146, and 944 mm/fed/y for the same respective treatments, and they were consistent with the results concluded by [36]. The results show that the total irrigation water volume for the applied full irrigation treatment is (86, 80) m 3 palm-1 year −1 [37], as the total annual net water use in the regions ranged between 59.4 and 108 m 3 palm −1 year −1 , according to the geographical location, soil characteristics, and climate elements. The results of this study concluded that the amount of applied irrigation water with soil conditioner for a good yield of palm trees should be ≥4815 m 3 /fed/y (1146 mm/fed/y). Due to higher evapotranspiration and reduced groundwater recharge, climate change reduces the available quantities of water and increases the need for water in agriculture. Accordingly, the most efficient use of water resources is crucial to improving the provision of water [38]. Table 7. Irrigation treatments effect on the amounts of applied irrigation water for the three growing seasons. Month AIW Irrigation Levels (ETc) 70% 85% 100% 70% 85% 100% 70% 85% 100% 1 st Season 2018 2 nd Season 2019 3 rd Season 2020 January L/tree/day 81 98 116 69 84 98 66 81 95 m 3 /fed/month 160 195 229 137 166 195 132 160 188 February L/tree/day 102 124 145 89 108 127 85 103 122 m 3 /fed/month 182 221 261 160 194 228 152 185 218 Figure 1. The estimated evapotranspiration (ETc) during the three growing seasons (2018, 2019, and 2020) for experiment site 3.1.2. Applied Irrigation Water (AIW) The effect of tested irrigation treatments on applied irrigation water, expressed as liters/tree/day, m 3 /fed/month, and m 3 /fed/year during the three growing seasons, are shown in Table 7 . Results show that the least amounts of water requirements were during January and December regarding the three seasons and the greatest amounts of water requirements during June and July. As for the average amounts of applied irrigation water, they were 5664, 4815, and 3965 m 3 /fed/year (mean of the three seasons) for the 100%, 85%, and 70% Etc irrigation treatments, respectively The obtained amounts were 1349, 1146, and 944 mm/fed/y for the same respective treatments, and they were consistent with the results concluded by [ 36 ]. The results show that the total irrigation water volume for the applied full irrigation treatment is (86, 80) m 3 palm − 1 year − 1 [ 37 ], as the total annual net water use in the regions ranged between 59.4 and 108 m 3 palm − 1 year − 1 , according to the geographical location, soil characteristics, and climate elements. The results of this study concluded that the amount of applied irrigation water with soil conditioner for a good yield of palm trees should be ≥ 4815 m 3 /fed/y (1146 mm/fed/y). Due to higher evapotranspiration and reduced groundwater recharge, climate change reduces the available quantities of water and increases the need for water in agriculture. Accordingly, the most efficient use of water resources is crucial to improving the provision of water [ 38 ].

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Sustainability 2022 , 14 , 11421 8 of 20 Table 7. Irrigation treatments effect on the amounts of applied irrigation water for the three growing seasons Month AIW Irrigation Levels (ETc) 70% 85% 100% 70% 85% 100% 70% 85% 100% 1 st Season 2018 2 nd Season 2019 3 rd Season 2020 January L/tree/day 81 98 116 69 84 98 66 81 95 m 3 /fed/month 160 195 229 137 166 195 132 160 188 February L/tree/day 102 124 145 89 108 127 85 103 122 m 3 /fed/month 182 221 261 160 194 228 152 185 218 March L/tree/day 175 212 249 160 195 229 151 183 216 m 3 /fed/month 346 420 495 318 386 454 300 364 428 April L/tree/day 201 244 287 194 236 277 197 239 281 m 3 /fed/month 385 468 550 373 452 532 378 459 540 May L/tree/day 256 310 365 252 306 360 247 300 353 m 3 /fed/month 507 616 725 499 606 713 491 596 701 June L/tree/day 276 335 394 276 335 394 276 335 394 m 3 /fed/month 529 642 756 529 642 756 530 643 757 July L/tree/day 296 360 424 307 372 438 303 368 433 m 3 /fed/month 588 714 840 608 739 869 601 730 859 August L/tree/day 245 297 350 238 289 340 232 282 331 m 3 /fed/month 486 590 694 472 573 675 460 559 657 September L/tree/day 180 219 258 162 196 231 190 230 271 m 3 /fed/month 346 421 495 310 377 443 364 442 520 October L/tree/day 136 165 194 134 163 191 135 164 193 m 3 /fed/month 269 327 385 266 323 380 267 325 382 November L/tree/day 87 105 124 87 106 125 78 95 112 m 3 /fed/month 166 202 238 167 203 239 151 183 215 December L/tree/day 42 51 60 45 55 65 45 55 64 m 3 /fed/month 84 102 120 90 109 129 89 108 128 Total m 3 /fed/year 4050 4918 5786 3929 4771 5613 3915 4754 5594 3.2. Effect of Soil Amendments, Irrigation Levels, and Their Interactions on Growth Leaf Parameters It is obvious from data shown in Figures 2 – 4 that the mean values of leaf length (cm) and leaflet length and width (cm) significantly increased with the increasing percentage of soil amendments utilized in this experiment (bentonite, humic substances, and Bacillus polymyxa ) to reach the maximum results by utilizing the highest percentages of such amendments in the three studied seasons compared to the control ones. This may be attributed to conglomerating the benefits of the three used amendments, as mixing bentonite and humic substances with B. polymyxa was more effective in improving the physio-chemical characteristics and fertility of sandy soil. Thus, the growth of cv. Siwi date palm trees thereby improved.

[Find the meaning and references behind the names: Oil]

Sustainability 2022 , 14 , 11421 9 of 20 Sustainability 2022 , 14 , x FOR PEER REVIEW 9 of 20 water quantity to the recommended level does not usually improve all growth characteristics. Figure 2. Effects of soil amendments, irrigation levels, and their interactions on leaf length (cm) of Phoenix dactylifera L. var. Siwi tree during the three studied seasons. Note: The same letter are not significantly different at 5% level according to Duncan's Multiple range test 40.00 45.00 50.00 55.00 60.00 65.00 70.00 75.00 80.00 85.00 90.00 100% 85% 70% 100% 85% 70% 100% 85% 70% Firs t s e as on; 2018/2019 Se cond s e as on; 2019/2020 Third s e as on; 2020/2021 Without s oil conditioners BN 6 kg +HS 0.75 L + BP. 14 ml/ liter BN.12 kg +HS 1 L + BP. 28 ml/ liter Le afl et le ng th (c m ) c e a b d c e f a b d a b c c e f a b d a b d f g c a Figure 3. Effects of soil amendments, irrigation levels, and their interactions on leaflet length (cm) of Phoenix dactylifera L. var. Siwi tree during the three studied seasons. Note: The same letter are not significantly different at 5% level according to Duncan's Multiple range test. Figure 2. Effects of soil amendments, irrigation levels, and their interactions on leaf length (cm) of Phoenix dactylifera L. var. Siwi tree during the three studied seasons. Note: The same letter are not significantly different at 5% level according to Duncan’s Multiple range test Sustainability 2022 , 14 , x FOR PEER REVIEW 9 of 20 water quantity to the recommended level does not usually improve all growth characteristics. Figure 2. Effects of soil amendments, irrigation levels, and their interactions on leaf length (cm) of Phoenix dactylifera L. var. Siwi tree during the three studied seasons. Note: The same letter are not significantly different at 5% level according to Duncan's Multiple range test 40.00 45.00 50.00 55.00 60.00 65.00 70.00 75.00 80.00 85.00 90.00 100% 85% 70% 100% 85% 70% 100% 85% 70% Firs t s e as on; 2018/2019 Se cond s e as on; 2019/2020 Third s e as on; 2020/2021 Without s oil conditioners BN 6 kg +HS 0.75 L + BP. 14 ml/ liter BN.12 kg +HS 1 L + BP. 28 ml/ liter Le afl et le ng th (c m ) c e a b d c e f a b d a b c c e f a b d a b d f g c a Figure 3. Effects of soil amendments, irrigation levels, and their interactions on leaflet length (cm) of Phoenix dactylifera L. var. Siwi tree during the three studied seasons. Note: The same letter are not significantly different at 5% level according to Duncan's Multiple range test. Figure 3. Effects of soil amendments, irrigation levels, and their interactions on leaflet length (cm) of Phoenix dactylifera L. var. Siwi tree during the three studied seasons. Note: The same letter are not significantly different at 5% level according to Duncan’s Multiple range test.

[Find the meaning and references behind the names: Par, Better, Enough, Cases, Gave, Lite, Rate, General, Peak]

Sustainability 2022 , 14 , 11421 10 of 20 Sustainability 2022 , 14 , x FOR PEER REVIEW 10 of 20 2.20 2.40 2.60 2.80 3.00 3.20 3.40 3.60 3.80 4.00 100% 85% 70% 100% 85% 70% 100% 85% 70% Firs t s e as on; 2018/2019 Se cond s e as on; 2019/2020 Third s e as on; 2020/2021 Without s oil conditione rs BN 6 kg +HS 0.75 L + BP. 14 ml/ lite r BN.12 kg +HS 1 L + BP. 28 ml/ lite r Le afl et w id th (c m ) f b a f c b g e d f b a g c b h f d f b a f c b g e d Figure 4. Effects of soil amendments, irrigation levels, and their interactions on leaf width (cm) of Phoenix dactylifera L. var. Siwi tree during the three studied seasons. Note: The same letter are not significantly different at 5% level according to Duncan's Multiple range test. 3.3. Effect of Soil Amendments, Irrigation Levels, and Their Interactions on Yield and Its Components 3.3.1. Fruit Set and Bunch Weight Results listed in Figures 5 and 6 show that mixing the sandy soil with 12 kg bentonite + 1 L humates + 28 mL/L B. polymyxa achieved the highest percentage of fruit set over the other supplementation and control treatments in the three successive seasons. Irrigation with 100% of ET crop water level also registered higher fruit set percentage in the three growth seasons. However, interacting between mixing the sandy soil with the three amendments at high rates and irrigating with either 85 or 100% water level achieved the highest percentage of fruit set in the three growth seasons without significant differences among them. Bunch weight (kg) was found to be maximum by mixing the sandy soil with the three used soil conditioners at either low or high rates in the first and third seasons, while bunch weight (kg) was found to be maximum by mixing the sandy soil with the three used soil conditioners in the second season by applying the three conditioners at only the low rate. In addition, irrigation with 85% of ET crop water level registered the heaviest bunch weight in the first and third seasons. As for the second season, irrigation with both 85 and 100% water levels gave bunch weights on par with each other. Accordingly, combining between amending the sand with the low rate of bentonite (6 kg), humic substances (0.75 L), and B. polymyxa (14 mL/L) and the medium water level (85% of ETc) elevated the bunch weight to the highest values over all the other interactions in the three studied seasons. Figure 4. Effects of soil amendments, irrigation levels, and their interactions on leaf width (cm) of Phoenix dactylifera L. var. Siwi tree during the three studied seasons. Note: The same letter are not significantly different at 5% level according to Duncan’s Multiple range test Actually, leaf length was the longest with 85% of ET crop water level in the three experimental seasons, followed by 100% level, whereas the shortest leaf length in the three seasons was attained by 70% of ET crop water level. On the other hand, leaflet length and width means progressively increased with the increase of the irrigation water level to reach its peak by 100% water level. Nevertheless, date palm is considered drought-tolerant and can resist water shortage; it is preferable to provide it with enough water amounts for better growth and higher production Likewise, the interaction treatments had a considerable effect on leaf characteristics, where combining between soil supplementation with the highest percentages of the three used conditioners and irrigating with either 85 or 100% of ET crop water level gave the best results in general, with the prevalence of the three soil conditioners (at high rates) along with 100% water level combined with treatments that scored the highest means in most cases of the three growth seasons. However, irrigation of date palm trees amended with the three soil conditioners (at the high rates) with 85% water treatment attained the longest leaf length in the three growth seasons, followed by those grown in the same supplemented soil but irrigated with 100% of ETc water level, with significant differences among themselves in the three studied seasons. This means that increasing irrigation water quantity to the recommended level does not usually improve all growth characteristics 3.3. Effect of Soil Amendments, Irrigation Levels, and Their Interactions on Yield and Its Components 3.3.1. Fruit Set and Bunch Weight Results listed in Figures 5 and 6 show that mixing the sandy soil with 12 kg bentonite + 1 L humates + 28 mL/L B. polymyxa achieved the highest percentage of fruit set over the other supplementation and control treatments in the three successive seasons. Irrigation with 100% of ET crop water level also registered higher fruit set percentage in the three growth seasons. However, interacting between mixing the sandy soil with the three amendments at high rates and irrigating with either 85 or 100% water level achieved the highest percentage of fruit set in the three growth seasons without significant differences among them.

[Find the meaning and references behind the names: Few]

Sustainability 2022 , 14 , 11421 11 of 20 Sustainability 2022 , 14 , x FOR PEER REVIEW 11 of 20 35.00 40.00 45.00 50.00 55.00 60.00 65.00 70.00 75.00 80.00 100% 85% 70% 100% 85% 70% 100% 85% 70% First season; 2018/2019 Second season; 2019/2020 Third season; 2020/2021 Without s oil conditioners BN 6 kg +HS 0.75 L + BP. 14 ml/ liter BN.12 kg +HS 1 L + BP. 28 ml/ liter Fr ui t s et (%) a d g a c f b e g a d e f a c fg b e g a d h a c f b e g Figure 5. Effects of soil amendments, irrigation levels, and their interactions on fruit set (%) of Phoenix dactylifera L. var. Siwi tree during the three studied seasons. Note: The same letter are not significantly different at 5% level according to Duncan's Multiple range test. 8.00 8.50 9.00 9.50 10.00 10.50 11.00 11.50 12.00 12.50 13.00 13.50 100% 85% 70% 100% 85% 70% 100% 85% 70% Firs t s e as on; 2018/2019 Se cond s e as on; 2019/2020 Third s e as on; 2020/2021 Without s oil conditioners BN 6 kg +HS 0.75 L + BP. 14 ml/ liter BN.12 kg +HS 1 L + BP. 28 ml/ liter Bu nc h w ei gh t (k g) d d e c a b a b d d b f c a e b c e d c g b a e b e f Figure 6. Effects of soil amendments, irrigation levels, and their interactions on bunch weight (kg) of Phoenix dactylifera L. var. Siwi tree during the three studied seasons. Note: The same letter are not significantly different at 5% level according to Duncan's Multiple range test. 3.3.2. Yield Components In an identical response to that of leaf characteristics, fruit set and bunch weight were also obtained regarding yield components attributes shown in Figures 7 and 8, as yield of palm tree (kg/palm) and feddan (ton/fed) successively increased with increasing soil conditioners rates to reach the maximal values by amending the soil with 12 kg bentonite + 1 L humates + 28 mL/L B. polymyxa treatment, which achieved the highest yield either per palm tree or per feddan, with few exceptions in the three growth seasons. On the other hand, palm yield (kg) improved by raising irrigation water amount to either 85 or 100% of ET crop, with the superiority of 85% water level, which attained the highest yield in the three seasons. That was true for the yield of feddan (ton) in the first, Figure 5. Effects of soil amendments, irrigation levels, and their interactions on fruit set (%) of Phoenix dactylifera L. var. Siwi tree during the three studied seasons. Note: The same letter are not significantly different at 5% level according to Duncan’s Multiple range test Sustainability 2022 , 14 , x FOR PEER REVIEW 11 of 20 35.00 40.00 45.00 50.00 55.00 60.00 65.00 70.00 75.00 80.00 100% 85% 70% 100% 85% 70% 100% 85% 70% First season; 2018/2019 Second season; 2019/2020 Third season; 2020/2021 Without s oil conditioners BN 6 kg +HS 0.75 L + BP. 14 ml/ liter BN.12 kg +HS 1 L + BP. 28 ml/ liter Fr ui t s et (%) a d g a c f b e g a d e f a c fg b e g a d h a c f b e g Figure 5. Effects of soil amendments, irrigation levels, and their interactions on fruit set (%) of Phoenix dactylifera L. var. Siwi tree during the three studied seasons. Note: The same letter are not significantly different at 5% level according to Duncan's Multiple range test. 8.00 8.50 9.00 9.50 10.00 10.50 11.00 11.50 12.00 12.50 13.00 13.50 100% 85% 70% 100% 85% 70% 100% 85% 70% Firs t s e as on; 2018/2019 Se cond s e as on; 2019/2020 Third s e as on; 2020/2021 Without s oil conditioners BN 6 kg +HS 0.75 L + BP. 14 ml/ liter BN.12 kg +HS 1 L + BP. 28 ml/ liter Bu nc h w ei gh t (k g) d d e c a b a b d d b f c a e b c e d c g b a e b e f Figure 6. Effects of soil amendments, irrigation levels, and their interactions on bunch weight (kg) of Phoenix dactylifera L. var. Siwi tree during the three studied seasons. Note: The same letter are not significantly different at 5% level according to Duncan's Multiple range test. 3.3.2. Yield Components In an identical response to that of leaf characteristics, fruit set and bunch weight were also obtained regarding yield components attributes shown in Figures 7 and 8, as yield of palm tree (kg/palm) and feddan (ton/fed) successively increased with increasing soil conditioners rates to reach the maximal values by amending the soil with 12 kg bentonite + 1 L humates + 28 mL/L B. polymyxa treatment, which achieved the highest yield either per palm tree or per feddan, with few exceptions in the three growth seasons. On the other hand, palm yield (kg) improved by raising irrigation water amount to either 85 or 100% of ET crop, with the superiority of 85% water level, which attained the highest yield in the three seasons. That was true for the yield of feddan (ton) in the first, Figure 6. Effects of soil amendments, irrigation levels, and their interactions on bunch weight (kg) of Phoenix dactylifera L. var. Siwi tree during the three studied seasons. Note: The same letter are not significantly different at 5% level according to Duncan’s Multiple range test Bunch weight (kg) was found to be maximum by mixing the sandy soil with the three used soil conditioners at either low or high rates in the first and third seasons, while bunch weight (kg) was found to be maximum by mixing the sandy soil with the three used soil conditioners in the second season by applying the three conditioners at only the low rate. In addition, irrigation with 85% of ET crop water level registered the heaviest bunch weight in the first and third seasons. As for the second season, irrigation with both 85 and 100% water levels gave bunch weights on par with each other. Accordingly, combining between amending the sand with the low rate of bentonite (6 kg), humic substances (0.75 L), and B.

[Find the meaning and references behind the names: Pal]

Sustainability 2022 , 14 , 11421 12 of 20 polymyxa (14 mL/L) and the medium water level (85% of ETc) elevated the bunch weight to the highest values over all the other interactions in the three studied seasons 3.3.2. Yield Components In an identical response to that of leaf characteristics, fruit set and bunch weight were also obtained regarding yield components attributes shown in Figures 7 and 8 , as yield of palm tree (kg/palm) and feddan (ton/fed) successively increased with increasing soil conditioners rates to reach the maximal values by amending the soil with 12 kg bentonite + 1 L humates + 28 mL/L B. polymyxa treatment, which achieved the highest yield either per palm tree or per feddan, with few exceptions in the three growth seasons Sustainability 2022 , 14 , x FOR PEER REVIEW 12 of 20 second, and third seasons, where 85% water level registered 8.23, 8.41, and 8.69 ton/feddan compared to 7.37, 7.59, and 7.81 ton/fed for control treatment in the three growing seasons, respectively. This indicates that increasing the water amount to level 100% of ET crop does not result in additional growth increments in either palm or feddan yield. As for the effect of interactions, results in Figures 7 and 8 show that all interaction treatments significantly hastened both yield/palm and yield/fed compared to the control one in the three seasons, but the prevalence was for the combination of adding three soil conditioners (at the high rate) + 85% water level, which achieved the highest yield/palm and yield/fed compared to all the other combinations in the first, second, and third seasons. 60.00 70.00 80.00 90.00 100.00 110.00 120.00 130.00 140.00 150.00 160.00 100% 85% 70% 100% 85% 70% 100% 85% 70% First season; 2018/2019 Second season; 2019/2020 Third season; 2020/2021 Without s oil conditioners BN 6 kg +HS 0.75 L + BP. 14 ml/ liter BN.12 kg +HS 1 L + BP. 28 ml/ liter Y ie ld ( kg/ pal m ) d g a b g e c f c e h a b g d b f c e g a d f c b f c Figure 7. Effects of soil amendments, irrigation levels, and their interactions on yield (kg/palm) of Phoenix dactylifera L. var. Siwi tree during the three studied seasons. Note: The same letter are not significantly different at 5% level according t Duncan's Multiple range test. 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.00 11.00 100% 85% 70% 100% 85% 70% 100% 85% 70% First season; 2018/2019 Second season; 2019/2020 Third season; 2020/2021 Without s oil conditioners BN 6 kg +HS 0.75 L + BP. 14 ml/ liter BN.12 kg +HS 1 L + BP. 28 ml/ liter Y ie ld (T on /fe d.) c c g a b f d c e b c f a b e c b d bc d f a c e bc ab e Figure 8. Effects of soil amendments, irrigation levels, and their interactions on yield (ton/fed) of Phoenix dactylifera L. var. Siwi tree during the three studied seasons. Note: The same letter are not significantly different at 5% level according to Duncan's Multiple range test. Figure 7. Effects of soil amendments, irrigation levels, and their interactions on yield (kg/palm) of Phoenix dactylifera L. var. Siwi tree during the three studied seasons. Note: The same letter are not significantly different at 5% level according t Duncan’s Multiple range test Sustainability 2022 , 14 , x FOR PEER REVIEW 12 of 20 second, and third seasons, where 85% water level registered 8.23, 8.41, and 8.69 ton/feddan compared to 7.37, 7.59, and 7.81 ton/fed for control treatment in the three growing seasons, respectively. This indicates that increasing the water amount to level 100% of ET crop does not result in additional growth increments in either palm or feddan yield. As for the effect of interactions, results in Figures 7 and 8 show that all interaction treatments significantly hastened both yield/palm and yield/fed compared to the control one in the three seasons, but the prevalence was for the combination of adding three soil conditioners (at the high rate) + 85% water level, which achieved the highest yield/palm and yield/fed compared to all the other combinations in the first, second, and third seasons. 60.00 70.00 80.00 90.00 100.00 110.00 120.00 130.00 140.00 150.00 160.00 100% 85% 70% 100% 85% 70% 100% 85% 70% First season; 2018/2019 Second season; 2019/2020 Third season; 2020/2021 Without s oil conditioners BN 6 kg +HS 0.75 L + BP. 14 ml/ liter BN.12 kg +HS 1 L + BP. 28 ml/ liter Y ie ld ( kg/ pal m ) d g a b g e c f c e h a b g d b f c e g a d f c b f c Figure 7. Effects of soil amendments, irrigation levels, and their interactions on yield (kg/palm) of Phoenix dactylifera L. var. Siwi tree during the three studied seasons. Note: The same letter are not significantly different at 5% level according t Duncan's Multiple range test. 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.00 11.00 100% 85% 70% 100% 85% 70% 100% 85% 70% First season; 2018/2019 Second season; 2019/2020 Third season; 2020/2021 Without s oil conditioners BN 6 kg +HS 0.75 L + BP. 14 ml/ liter BN.12 kg +HS 1 L + BP. 28 ml/ liter Y ie ld (T on /fe d.) c c g a b f d c e b c f a b e c b d bc d f a c e bc ab e Figure 8. Effects of soil amendments, irrigation levels, and their interactions on yield (ton/fed) of Phoenix dactylifera L. var. Siwi tree during the three studied seasons. Note: The same letter are not significantly different at 5% level according to Duncan's Multiple range test. Figure 8. Effects of soil amendments, irrigation levels, and their interactions on yield (ton/fed) of Phoenix dactylifera L. var. Siwi tree during the three studied seasons. Note: The same letter are not significantly different at 5% level according to Duncan’s Multiple range test.

Sustainability 2022 , 14 , 11421 13 of 20 On the other hand, palm yield (kg) improved by raising irrigation water amount to either 85 or 100% of ET crop, with the superiority of 85% water level, which attained the highest yield in the three seasons. That was true for the yield of feddan (ton) in the first, second, and third seasons, where 85% water level registered 8.23, 8.41, and 8.69 ton/feddan compared to 7.37, 7.59, and 7.81 ton/fed for control treatment in the three growing seasons, respectively. This indicates that increasing the water amount to level 100% of ET crop does not result in additional growth increments in either palm or feddan yield As for the effect of interactions, results in Figures 7 and 8 show that all interaction treatments significantly hastened both yield/palm and yield/fed compared to the control one in the three seasons, but the prevalence was for the combination of adding three soil conditioners (at the high rate) + 85% water level, which achieved the highest yield/palm and yield/fed compared to all the other combinations in the first, second, and third seasons 3.4. Fruit Characteristics The results of fruit characteristics presented in Figures 9 – 11 are similar, and they indicate that the mean values of fruit weight (g), fruit pulp weight (%) and flesh weight (g), significantly increased in response to amending the sandy soil with bentonite, humic substances, and B. polymyxa soil conditioners at either a low or high rate compared to the control means in the three studied seasons. Although these two amending treatments switched their benefit effects in improving fruit characteristics characters in the three seasons, the dominant impact was that of applying the three soil conditioners at the low treatment rates (6 kg bentonite + 0.75 L HS + 14 mL B. Polymyxa ), which achieved better results in most fruit measurements than the high rate Sustainability 2022 , 14 , x FOR PEER REVIEW 13 of 20 3.4. Fruit Characteristics The results of fruit characteristics presented in Figures 9 – 11 are similar, and they indicate that the mean values of fruit weight (g), fruit pulp weight (%) and flesh weight (g), significantly increased in response to amending the sandy soil with bentonite, humic substances, and B. polymyxa soil conditioners at either a low or high rate compared to the control means in the three studied seasons. Although these two amending treatments switched their benefit effects in improving fruit characteristics characters in the three seasons, the dominant impact was that of applying the three soil conditioners at the low treatment rates (6 kg bentonite + 0.75 L HS + 14 mL B. Polymyxa ), which achieved better results in most fruit measurements than the high rate. The same results were also achieved regarding the effect of irrigation water treatments, where, increasing water quantity used for irrigation from 70% to either 85 or 100% of ET crop, the mean values of all fruit criteria significantly increased with various difference levels relative to the means of control level in the three experimental seasons. In addition, the medium (85%) and high (100% of ET crop) water treatments also achieved good results, but the upper hand in the three seasons was for irrigation with 85% treatment level, which achieved higher means than the 100% treatment level in most measured fruit parameters. Regarding the effect of interaction treatments, results in Figures 9 – 11 show that the means of fruit characteristics fluctuated due to the combination of the soil conditioners treatments used in this study with irrigation of both 85 and 100% of ET crop water level, achieving significant increments in different fruit parameters obtained in the three seasons in general. However, combining the amendment of the three soil conditioners at low rates (bentonite at 6 kg + HS at 0.75 L + B. polymyxa 14 mL/L) with the medium level of irrigation water (85% of ETcrop) achieved the best results and gave the maximum values in most fruit characteristics. 11.75 12.00 12.25 12.50 12.75 13.00 13.25 13.50 13.75 14.00 14.25 100% 85% 70% 100% 85% 70% 100% 85% 70% First season; 2018/2019 Second season; 2019/2020 Third season; 2020/2021 Without soil conditioners BN 6 kg +HS 0.75 L + BP. 14 ml/ liter BN.12 kg +HS 1 L + BP. 28 ml/ liter F ru it w ei gh t (g) a b-d d bc a c bc ab c ab d ef b-c bc cd b-d ab d a-c b-d e a-c ab cd b-d a d Figure 9. Effects of soil amendments, irrigation levels, and their interactions on fruit weight (g) of Phoenix dactylifera L. var. Siwi tree during the three studied seasons. The same letter are not significantly different at 5% level according to Duncan's Multiple range test. Figure 9. Effects of soil amendments, irrigation levels, and their interactions on fruit weight (g) of Phoenix dactylifera L. var. Siwi tree during the three studied seasons. The same letter are not significantly different at 5% level according to Duncan’s Multiple range test.

Sustainability 2022 , 14 , 11421 14 of 20 Sustainability 2022 , 14 , x FOR PEER REVIEW 14 of 20 8.75 9.00 9.25 9.50 9.75 10.00 10.25 10.50 10.75 11.00 11.25 11.50 100% 85% 70% 100% 85% 70% 100% 85% 70% First season; 2018/2019 Second season; 2019/2020 Third season; 2020/2021 Without s oil conditioners BN 6 kg +HS 0.75 L + BP. 14 ml/ liter BN.12 kg +HS 1 L + BP. 28 ml/ liter F le sh w ei gh t (g) a a b a a c c d e a bc d a-c ab e b c e b a c b b d a b c Figure 10. Effects of soil amendments, irrigation levels, and their interactions on flesh weight (g) of Phoenix dactylifera L. var. Siwi tree during the three studied seasons. Note: The same letter are not significantly different at 5% level according to Duncan's Multiple range test. 68.00 70.00 72.00 74.00 76.00 78.00 80.00 82.00 84.00 100% 85% 70% 100% 85% 70% 100% 85% 70% First season; 2018/2019 Second season; 2019/2020 Third season; 2020/2021 Without soil conditioners BN 6 kg +HS 0.75 L + BP. 14 ml/ liter BN.12 kg +HS 1 L + BP. 28 ml/ liter F ru it p u lp w ei gh t (%) b c d a b b a a e d d e a c d bc b f c d e c a d b c f Figure 11. Effects of soil amendments, irrigation levels, and their interactions on fruit pulp weight (%) of Phoenix dactylifera L. var. Siwi tree during the three studied seasons. Note: The same letter are not significantly different at 5% level according to Duncan's Multiple range test. 3.5. Effect of Soil Amendments, Irrigation Levels, and Their Interactions on Water Productivity 3.5.1. Crop Water Productivity (WP) Water productivity (WP) is used to describe the relationship between production and the amount of applied irrigation water. It is clear from Figure 12 that this characteristic was markedly profitable under the lowest amount of irrigation water (ETc 70%), as it registered 1.82, 1.92, and 1.98 Kg fruits/m 3 of irrigation water in the first, second, and third seasons, respectively. On the other hand, when increasing the amounts of the applied irrigation water (ETc 100%), they produced the smallest values (1.42, 1.45, and 1.43 kg fruits /m 3 ) of irrigation water in the first, second, and third seasons, respectively. Water conservation benefits can be obtained by allowing plants to experience moderate water stress. Supplying water to the crop at levels below evapotranspiration (ET) Figure 10. Effects of soil amendments, irrigation levels, and their interactions on flesh weight (g) of Phoenix dactylifera L. var. Siwi tree during the three studied seasons. Note: The same letter are not significantly different at 5% level according to Duncan’s Multiple range test Sustainability 2022 , 14 , x FOR PEER REVIEW 14 of 20 8.75 9.00 9.25 9.50 9.75 10.00 10.25 10.50 10.75 11.00 11.25 11.50 100% 85% 70% 100% 85% 70% 100% 85% 70% First season; 2018/2019 Second season; 2019/2020 Third season; 2020/2021 Without s oil conditioners BN 6 kg +HS 0.75 L + BP. 14 ml/ liter BN.12 kg +HS 1 L + BP. 28 ml/ liter F le sh w ei gh t (g) a a b a a c c d e a bc d a-c ab e b c e b a c b b d a b c Figure 10. Effects of soil amendments, irrigation levels, and their interactions on flesh weight (g) of Phoenix dactylifera L. var. Siwi tree during the three studied seasons. Note: The same letter are not significantly different at 5% level according to Duncan's Multiple range test. 68.00 70.00 72.00 74.00 76.00 78.00 80.00 82.00 84.00 100% 85% 70% 100% 85% 70% 100% 85% 70% First season; 2018/2019 Second season; 2019/2020 Third season; 2020/2021 Without soil conditioners BN 6 kg +HS 0.75 L + BP. 14 ml/ liter BN.12 kg +HS 1 L + BP. 28 ml/ liter F ru it p u lp w ei gh t (%) b c d a b b a a e d d e a c d bc b f c d e c a d b c f Figure 11. Effects of soil amendments, irrigation levels, and their interactions on fruit pulp weight (%) of Phoenix dactylifera L. var. Siwi tree during the three studied seasons. Note: The same letter are not significantly different at 5% level according to Duncan's Multiple range test. 3.5. Effect of Soil Amendments, Irrigation Levels, and Their Interactions on Water Productivity 3.5.1. Crop Water Productivity (WP) Water productivity (WP) is used to describe the relationship between production and the amount of applied irrigation water. It is clear from Figure 12 that this characteristic was markedly profitable under the lowest amount of irrigation water (ETc 70%), as it registered 1.82, 1.92, and 1.98 Kg fruits/m 3 of irrigation water in the first, second, and third seasons, respectively. On the other hand, when increasing the amounts of the applied irrigation water (ETc 100%), they produced the smallest values (1.42, 1.45, and 1.43 kg fruits /m 3 ) of irrigation water in the first, second, and third seasons, respectively. Water conservation benefits can be obtained by allowing plants to experience moderate water stress. Supplying water to the crop at levels below evapotranspiration (ET) Figure 11. Effects of soil amendments, irrigation levels, and their interactions on fruit pulp weight (%) of Phoenix dactylifera L. var. Siwi tree during the three studied seasons. Note: The same letter are not significantly different at 5% level according to Duncan’s Multiple range test The same results were also achieved regarding the effect of irrigation water treatments, where, increasing water quantity used for irrigation from 70% to either 85 or 100% of ET crop, the mean values of all fruit criteria significantly increased with various difference levels relative to the means of control level in the three experimental seasons. In addition, the medium (85%) and high (100% of ET crop) water treatments also achieved good results, but the upper hand in the three seasons was for irrigation with 85% treatment level, which achieved higher means than the 100% treatment level in most measured fruit parameters Regarding the effect of interaction treatments, results in Figures 9 – 11 show that the means of fruit characteristics fluctuated due to the combination of the soil conditioners treatments used in this study with irrigation of both 85 and 100% of ET crop water level, achieving significant increments in different fruit parameters obtained in the three seasons

[Find the meaning and references behind the names: Choice, Quite, Standing, Cost]

Sustainability 2022 , 14 , 11421 15 of 20 in general. However, combining the amendment of the three soil conditioners at low rates (bentonite at 6 kg + HS at 0.75 L + B. polymyxa 14 mL/L) with the medium level of irrigation water (85% of ETcrop) achieved the best results and gave the maximum values in most fruit characteristics 3.5. Effect of Soil Amendments, Irrigation Levels, and Their Interactions on Water Productivity Crop Water Productivity (WP) Water productivity (WP) is used to describe the relationship between production and the amount of applied irrigation water. It is clear from Figure 12 that this characteristic was markedly profitable under the lowest amount of irrigation water (ETc 70%), as it registered 1.82, 1.92, and 1.98 Kg fruits/m 3 of irrigation water in the first, second, and third seasons, respectively. On the other hand, when increasing the amounts of the applied irrigation water (ETc 100%), they produced the smallest values (1.42, 1.45, and 1.43 kg fruits/m 3 ) of irrigation water in the first, second, and third seasons, respectively Water conservation benefits can be obtained by allowing plants to experience moderate water stress. Supplying water to the crop at levels below evapotranspiration (ET) levels considerably allows crops to sustain some degree of water deficit without significant yield reduction but with significant water savings On the other hand, the control under all irrigation treatments gave quite lower water productivity, greatly lower than that given by the applied conditioners. The lowest water productivity (WP), 1.30, 1.36, and 1.38 kg fruits/m 3 of irrigation water by the control treatment, was obtained However, water utilization efficiency progressively increased with applied soil conditioners in comparison to the control one, which increased the WP by averages of 36.7 and 41.5% for BN 6 kg +HS 0.75 L + BP. 14 mL/L and BN 12 kg +H 1 L + BP. 28 mL/L, respectively Additionally, water productivity (WP) increased under the treatment of 70% of Etc combined with soil conditioners BN (12 kg) + HS (1 L) + BP. (28 mL/L), and values were 2.17, 2.25, and 2.27 kg fruits/m 3 as compared with the full irrigation (100% Etc) treatment values standing at 1.16, 1.25, and 1.31 kg fruits/m 3 , respectively 3.6. Economic Analysis Total cost, gross return, and net return of palm trees as affected by different amounts of irrigation water and organic and inorganic soil conditioners treatments are shown in (Table 8 ). The highest net return of 84144 EGP./fed and 79166 EGP./fed were obtained from 85%ETcrop with BN (12 kg) + HS (1 L) + BP (28 mL/L) and BN (6 kg) + HS (0.75 L) + BP (14 mL/L) (in average of the three seasons), respectively. These treatments represent the best choice for high net return under the study conditions compared with the control ones.

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Sustainability 2022 , 14 , 11421 16 of 20 Sustainability 2022 , 14 , x FOR PEER REVIEW 15 of 20 levels considerably allows crops to sustain some degree of water deficit without significant yield reduction but with significant water savings. On the other hand, the control under all irrigation treatments gave quite lower water productivity, greatly lower than that given by the applied conditioners. The lowest water productivity (WP), 1.30, 1.36, and 1.38 kg fruits/m 3 of irrigation water by the control treatment, was obtained. However, water utilization efficiency progressively increased with applied soil conditioners in comparison to the control one, which increased the WP by averages of 36.7 and 41.5% for BN 6 kg +HS 0.75 L + BP. 14 mL/L and BN 12 kg +H 1 L + BP. 28 mL/L, respectively. Additionally, water productivity (WP) increased under the treatment of 70% of Etc combined with soil conditioners BN (12 kg) + HS (1 L) + BP. (28 mL/L), and values were 2.17, 2.25, and 2.27 kg fruits/m 3 as compared with the full irrigation (100% Etc) treatment values standing at 1.16, 1.25, and 1.31 kg fruits /m 3 , respectively. ( a ) ( b ) Sustainability 2022 , 14 , x FOR PEER REVIEW 16 of 20 ( c ) Figure 12. Effect of irrigation water amount and soil conditioners rate on water productivity (WP) (kg fruits/m 3 water) of palm trees during ( a ) 2018, ( b ) 2019, and ( c ) 2020 seasons 3.6. Economic Analysis Total cost, gross return, and net return of palm trees as affected by different amounts of irrigation water and organic and inorganic soil conditioners treatments are shown in (Table 8). The highest net return of 84144 L.E./fed and 79166 L.E./fed were obtained from 85%ETcrop with BN (12 kg) + HS (1 L) + BP (28 mL/L) and BN (6 kg) + HS (0.75 L) + BP (14 mL/L) (in average of the three seasons), respectively. These treatments represent the best choice for high net return under the study conditions compared with the control ones Table 8. Economic analysis as affected by amount of irrigation water and organic and inorganic soil conditioners treatments (average yield and applied water of the three years). Treatments Cost of Production (EGP./fed) Income Profits (EGP./fed) Net Return (EGP/fed) Field Practices Cost of Add Soil Conditioner Water Total (EGP/fed) Fruit (EGP/Kg) Kg/fed Total (EGP/fed) 70% of ETc Without soil conditioners 7000 0.0 0.0 991 7991 10 5623 56,230 48,239 BN (6 kg) + HS (0.75 L) + BP. (14 mL/L) 320 1990 926 10,236 10 8273 82,730 72,494 BN (12 kg) + HS (1 L) + BP. (28 mL/L) 320 3980 894 12,194 10 8873 88,730 76,536 85% of ETc Without soil conditioners 7000 0.0 0.0 1204 8204 10 6677 66,770 58,566 BN (6 kg) + HS (0.75 L) + BP. (14 mL/L) 320 1990 1124 10,434 10 8960 89,600 79,166 BN (12 kg) + HS (1 L) + BP. (28 mL/L) 320 3980 1086 12,386 10 9653 96,530 84,144 100% of ETc Without soil conditioners 7000 0.0 0.0 1416 8416 10 6503 65,030 56,614 BN (6 kg) + HS (0.75 L) + BP. (14 mL/L) 320 1990 1323 10,633 10 8953 89,530 78,897 BN (12 kg) + HS (1 L) + BP. (28 mL/L) 320 3980 1277 12,577 10 8740 87,400 74,823 Figure 12. Effect of irrigation water amount and soil conditioners rate on water productivity (WP) (kg fruits/m 3 water) of palm trees during ( a ) 2018, ( b ) 2019, and ( c ) 2020 seasons.

[Find the meaning and references behind the names: Arabi, New, Renders, Makes, Large, Nile, Area, Shoot, Pounds]

Sustainability 2022 , 14 , 11421 17 of 20 Table 8. Economic analysis as affected by amount of irrigation water and organic and inorganic soil conditioners treatments (average yield and applied water of the three years) Treatments Cost of Production (EGP./fed) Income Profits (EGP./fed) Net Return (EGP/fed) Field Practices Cost of Add Soil Conditioner Water Total (EGP/fed) Fruit (EGP/Kg) Kg/fed Total (EGP/fed) 70% of ETc Without soil conditioners 7000 0.0 0.0 991 7991 10 5623 56,230 48,239 BN (6 kg) + HS (0.75 L) + BP. (14 mL/L) 320 1990 926 10,236 10 8273 82,730 72,494 BN (12 kg) + HS (1 L) + BP. (28 mL/L) 320 3980 894 12,194 10 8873 88,730 76,536 85% of ETc Without soil conditioners 7000 0.0 0.0 1204 8204 10 6677 66,770 58,566 BN (6 kg) + HS (0.75 L) + BP. (14 mL/L) 320 1990 1124 10,434 10 8960 89,600 79,166 BN (12 kg) + HS (1 L) + BP. (28 mL/L) 320 3980 1086 12,386 10 9653 96,530 84,144 100% of ETc Without soil conditioners 7000 0.0 0.0 1416 8416 10 6503 65,030 56,614 BN (6 kg) + HS (0.75 L) + BP. (14 mL/L) 320 1990 1323 10,633 10 8953 89,530 78,897 BN (12 kg) + HS (1 L) + BP. (28 mL/L) 320 3980 1277 12,577 10 8740 87,400 74,823 Note: L.E., Egyptian pounds. USD 1 = EGP. 18 4. Discussion Bentonite as a natural soil conditioner improves the coarse texture of soils; absorbs large amounts of water, giving a volume equaling approximately 15 times of its dry bulk; and also has a high cation exchange capacity [ 13 ]. Application of bentonite to sandy soil improves water movement downwards, prevents water loss, keeps the minerals from leaching out [ 39 ], and enhances the physiochemical properties and soil moisture cation exchange capacity in particular [ 5 ]. Humic substances influence the plant growth through either the amelioration of physical, chemical, and biological conditions of the soil or by promoting metabolic activity in plant growth [ 40 ]. In addition, humus improves soil fertility through raising the soil microbial population, including beneficial microorganisms, such as Bacillus polymyxa , which decomposes organic matter, renders nutrients, and makes them more available for plants [ 41 ]. This may be reasonable because sufficient water supplies the plants with their water requirements necessary for healthy growth [ 42 ]. Thus, the saving and maximization of WUE for date palm trees grown either in sandy soil or in arid and semi-arid regions through applying organic and biofertilizers has become the key for sustainable production [ 8 ]. The results of this current study are consistent with those results concluded by [ 13 ], who indicated that the amelioration of canopy diameter in Deglet Nour date palm trees reached 226 ± 0.6 cm in sandy soil mixed with farm manure and bentonite clay treatment compared to 172 ± 0.6 cm in untreated palm trees. The height of the palm trees increased by 69 ± 0.8 cm from 29 ± 0.1 cm under the control treatment, and the number of leaves increased from 40 leaves/palm tree in sandy soil mixed with only bentonite to 60 leaves/palm tree in sandy soil mixed with both farm manure and bentonite. Furthermore, [ 43 ] recommended to apply 2 kg of Nile fertile + 500 g K 2 SO 4 with irrigation level of 11 m 3 /tree/year to enhance the means of the number of the new shoots, the shoot length and diameter, the number of leaves/shoots, and leaf area parameters to the highest values in the Arabi pomegranate tree. Ref. [ 12 ] found that the highest irrigation level of 11 m 3 /tree/year and application of either Hundz soil at a rate of 10 kg/tree or the mixture of Nile fertile+ K 2 SO 4 at 2 kg + 500 g rate improved fruit set of 10-year-old Arabi pomegranate trees grown in sandy soil under drip irrigation. Similar observations were also obtained by [ 3 , 11 , 44 , 45 ] on various varieties of date palm. These results are in

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Sustainability 2022 , 14 , 11421 18 of 20 great accordance with those discovered by [ 12 ], who postulated that farm manure (M) and bentonite clay (B) noticeably improved the yield of the 3-year-old Deglet Nour date palms growing in sandy soil. The sand (S) mixed with either manure (M) or with both bentonite (B) and manure (M) obtained yields of 70 ± 0.9 kg/palm and 80 ± 0.5 kg/palm, respectively. This might partially alleviate the alternate-year bearing of this date palm variety. Likewise, [ 43 ] revealed that applying 2 kg/tree Hundz soil + 2 kg Nile fertile + 500 g K 2 SO 4 with irrigation level of 11 m 3 /tree/year produced the highest yield and good quality of Arabi pomegranate fruits, and applying the same three previous amendments at the same rates under an irrigation level of either 8.25 m 3 /tree/year or 5.5 m 3 /tree/year for saving 25–50% of water achieved the same yield as well. [ 12 ] On 3-year-old Deglat Nour date palms grown in sandy soil, the authors pointed out that sand amended either with farm manure or with bentonite clay and farm manure improved fruit quality compared to the untreated sand. Likewise, [ 43 ] pointed out that fruit quality (fruit weight, diameter, and length) of Arabi pomegranate trees greatly improved by supplementing the sand with either Hundz soil (5 or 10 kg/tree) or mixture of Nile fertile + K 2 SO 4 (1 kg + 250 g or 2 kg + 500 g) under irrigation levels of 50, 75, and 100% of ET crop water levels, which were 5.5, 8.25, and 11 m 3 /tree/year. Accordingly, the results are in agreement with [ 46 ], who indicated water productivity gains by decreasing the amount of used water; ref. [ 21 ] also indicated that applying deficit irrigation to palms in dry areas can maximize water productivity (WP); however, water productivity (WP) significantly increased with decreasing the irrigation water amount [ 47 ]. Earlier studies indicated that deficit irrigation strategies can improve WP and save irrigation water in several important horticultural crops, especially those that are typically tolerant of water stress [ 48 ]. Water productivity (WP) for date palms of many date-producing countries ranges as a general average of 0.18–0.37 kg · m − 3 [ 4 ]. Bentonite increased soil moisture and soil water storage as well as millet yield and water efficiency, and ref. [ 49 , 50 ] asserted that soil conditioners, whether natural or organic, contributed significantly to providing a reservoir of soil water to plants when needed in the upper layers of the soil, which is the zone where root systems normally grow. Likewise, shale sediments (bentonite) applied at different rates to sandy soil improved its physicochemical properties, including soil moisture [ 5 ]. 5. Conclusions Based on the previous results, it is recommended to apply bentonite, humic substances, and B. polymyxa at either low (BN (6 kg) + HS (0.75 L) + BP (14 mL/L)) or high (BN (12 kg) + HS (1 L) + BP (28 mL/L)) rates to the sandy soil and irrigate with 85% and 70% of ETc water level to obtain the best growth, highest yield, optimal quality, and water-use efficiency along with gross economic return from planting Siwi date palm trees in sandy soil under oasis agro-system conditions Author Contributions: Conceptualization, M.M.S.-B., K.H.A.H. and M.F.E.-K.; methodology, software, formal analysis, data processing, and writing—original draft preparation, K.H.A.H., M.F.E.-K and S.D. writing—review and editing, S.A., K.H.A.H. and M.F.E.-K.; funding acquisition, all authors All authors have read and agreed to the published version of the manuscript Funding: This research was funded by King Saud University (grant number RSP-2021/241) Institutional Review Board Statement: Not applicable Informed Consent Statement: Not applicable Data Availability Statement: Relevant data applicable to this research are within the paper Conflicts of Interest: The authors declare no conflict of interest.

[Find the meaning and references behind the names: Abd El, Eng, Dunn, Bartoli, Mlih, Vermeiren, Ibrahim, Olive, Local, Valley, Eds, Soc, North, Sahin, Asa, Gene, Marine, Mead, Mendel, Mini, Bot, Hall, Candy, Clin, Int, Brun, Hafidi, Abd, Sci, Bousnina, Zein, Shahib, Inter, Abdeen, Madison, Pereira, Aydin, Hashim, London, Latifa, Part, Syrian, Future, Marshall, Donmez, Hady, Cakmakci, Smith, Arab, Allen, Agron, Raes, Middle, Zazueta, Moussa, Keeney, Jordan, Baddi, Kassem, Groves, Brahim, Faiz, Benites, Soliman, Holl, Radley, Miller, Burtin, Cane, Obeed, Mattar, Chapman, Nelson, Zubi, Pore, Rome, Bana, Africa, Badr, Wagner, Mill, Bol, Florida, Ayers, Asli, Ait]

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[Find the meaning and references behind the names: Zhang, Liu, Abdul, Alex, Mohammad, Belmont, South, Drain, Press, Hamed, Silvestre, Zaghloul, Awad, Tuck, Ismail, Qurashi, Al-Mosawi, Cochran, York, Westwood, Salisbury, Rose, Kingdom, Mosawi, Chaves, Hernandez, East, Hort, Tejada, Baki, Hayes, China, Marzouk, Costa, Garcia, Mansor, State, Wadsworth, Culture, Kassam, Aslan, Chang, Nat, Ortuno, Clim, Mclaughlin, Syria]

Sustainability 2022 , 14 , 11421 20 of 20 30 FAO. Food and Agriculture Organization of the United Nations. FAOSTAT. Available online: http://foastat.fao.org./site/339/ default.aspx 1984 (accessed on 1 May 2022) 31 FAO Yield Response to Water, Irrigation and Drainage Paper, 33 ; Doorenbos, J., Kassam, A.H., Eds.; FAO: Rome, Italy, 1979 32 Westwood, M.N Temperate Zone Pomology, Physiology and Culture , 3 rd ed.; Himber Press: Portland, OR, USA, 1993; p. 523 33 Zhang, H. Improving water productivity through deficit irrigation: Examples from Syria, the north China Plain and Oregon, USA. In Water Productivity in Agriculture: Limits and Opportunities for Improvement ; CABI Publishing: Egham, UK, 2003; p. 332 34 Snedecor, J.P.; Cochran, W Statistical Methods , 7 th ed.; The Iowa State University Press: Aims, OR, USA, 1980; Volume 507, pp. 2033–2037 35 Duncan, D.B. Multiple Range and Multiple Ftests Biometrics 1955 , 11 , 1–42. [ CrossRef ] 36 Al-Mansor, A.N.; Nedawi, D.R.; Al-Mosawi, K.A. Effects of regulated deficit Irrigation on water productivity of date palm ( Phoenix Dactylifera L.) in the arid environment of South Iraq Nat. Volatiles Essent. OILS 2021 , 8 , 2164–2182 37 Alamoud, A.I.; Mohammad, F.S.; Al-Hamed, S.A.; Alabdulkader, A.M. Reference evapotranspiration and date palm water use in the Kingdom of Saudi Arabia Int. Res. J. Agric. Sci. Soil Sci 2012 , 2 , 155–169 38 Lelieveld, J.; Hadjinicolaou, P.; Kostopoulou, E. Climate change and impacts in the Eastern Mediterranean and the Middle East Clim. Chang 2012 , 114 , 667–687. [ CrossRef ] [ PubMed ] 39 Affifi, M.Y. Use of clay deposits in improving the physical properties of sandy soils J. King Univ. Agric. Sci 1986 , 8 , 255–262 40 Tejada, M.; Hernandez, M.T.; Garcia, C. Application of two organic amendments on soil restoration: Effects on the soil Biological Properties J. Environ 2006 , 35 , 1010–1017. [ CrossRef ] [ PubMed ] 41 Morard, P.; Eyheraguibel, B.; Morard, M.; Silvestre, J. Direct effects of humic-like substance on growth, water and mineral nutrient of various species J. Plant Nutr 2011 , 34 , 46–59. [ CrossRef ] 42 Salisbury, F.B.; Rose, C.W Plant Physiology ; Wadsworth Pub. Co.: Belmont, CA, USA, 1985; 185 p 43 Abd-Ella, E.K. Effect of soil conditioners and Irrigation Levels on Growth and Productivity of Pomegranate Trees in the New Reclaimed Region Alex. Sci. Exch. J 2011 , 32 , 550–575 44 Abdul-Baki, A.; Aslan, S Management of Soil and Water in Date Palm Orchards of Coachella Valley, California ; International Center for Agricultural Research in Dry Areas: Beirut, Lebanon, 2005 45 Marzouk, H.A.; Kassem, H.A. Improving fruit quality, nutritional value and yield of Zaghloul dates by the application of organic and/or mineral fertilizers Sci. Hort 2011 , 127 , 249–254. [ CrossRef ] 46 Al-Qurashi, A.D.; Ismail, S.M.; Awad, M.A. Effect of Water Regimes and Palm Coefficient on Growth Parameters, Date Yield and Irrigation Water Use of Tissue Culture Regenerated ‘Barhee’ Date Palms Grown in a Newly Established Orchard Irrig. Drain 2016 , 65 , 491–501. [ CrossRef ] 47 Leskovar, D.; Xu, C. Irrigation strategies and water use efficiency of globe artichoke Acta Hort 2013 , 983 , 261–268. [ CrossRef ] 48 Costa, M.; Ortuno, M.F.; Chaves, M.M. Deficit irrigation as a strategy to save water: Physiology and potential application to horticulture J. Integra. Plant Biol 2007 , 49 , 1421–1434. [ CrossRef ] 49 Mi, J.; Gregorich, E.G.; Xu, S.; McLaughlin, N.B.; Ma, B.; Liu, J. Effect of bentonite amendment on soil hydraulic parameters and millet crop performance in a semi-arid region J. Field Crop Res 2017 , 212 , 107–114. [ CrossRef ] 50 De Boodt, M. Application of polymeric substances as physical soil conditioners. In Soil Colloids and Their Association in Soil Aggregates ; De Boodt, M.F., Hayes, M.H.B., Herbillon, A., De Strooper, E.B.A., Tuck, J.J., Eds.; Planum Publishing Corporation: London, UK; New York, NY, USA, 1990; pp. 580–592.