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Article

Comparison of the Effects of Olive Tree and Date Palm Waste Biochar on Water Stress Measurements and Hydrophysical Properties of Sandy Soil

by
Abdulaziz G. Alghamdi
Department of Soil Sciences, College of Food and Agricultural Sciences, King Saud University, P.O. Box 2460, Riyadh 11451, Saudi Arabia
Water 2025, 17(17), 2612; https://doi.org/10.3390/w17172612
Submission received: 4 June 2025 / Revised: 18 August 2025 / Accepted: 2 September 2025 / Published: 3 September 2025
(This article belongs to the Special Issue Evapotranspiration and Plant Water Stress Measurements as the Driving Standard for Agricultural Irrigation)
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Abstract

The impact of biochar pyrolyzed at 450 ± 10 °C and made from date palm (D) and olive tree (O) wastes on the hydrophysical characteristics of sandy soil was assessed in this study through a laboratory column experiment. Two different application rates (wt/wt) were tested: 1% and 5%. The prepared biochars were added at 25 °C to the upper 10 cm layers of the soil columns. The outcome showed that, in comparison to O, D biochar possessed slightly less alkalinity and more salinity. The corresponding values for pH and EC in D and O biochars were 8.99 and 4.10 dS/m and 9.42 and 2.17 dS/m. Therefore, these biochars should be used cautiously as soil amendments in saline–sodic soils because of their excessive salinity, especially D biochar. On the other hand, they are safe to employ as amendments in acidic and non-saline soils. Cumulative evaporation (CE) decreased with all treatments, and the highest decrease of 10.2% (compared to control treatments after five cycles) was observed for D biochar and 5% application rate (D450, 5%). Moreover, the available water increased by 182%, 158%, 153%, and 29% for D450, 5%, D biochar and 1% application rate (D450, 1%), O biochar and 5% application rate (O450, 5%), and O biochar and 1% application rate (O450, 1%), respectively. The saturated hydraulic conductivity decreased by 94.8%, 87.0%, 76.6%, and 35.1% for D450, 5%, D450, 1%, O450, 5%, and O450, 1%, respectively. It was also found that the date palm biochar was more efficient than olive waste biochar in decreasing the cumulative infiltration and infiltration rate. Finally, this study showed the superiority of biochar prepared from date palm trees over that prepared from olive tree waste for improving the hydrophysical properties of sandy soil.

1. Introduction

Date palms and olive trees are grown extensively in the Kingdom of Saudi Arabia (KSA). There are currently 32 million date palms and 18 million olive trees in the Kingdom [1]. The production of date palms and olive trees generates a large amount of waste that can be recycled to improve soil productivity instead of discarded, thereby alleviating environmental problems. Because of the high temperatures and lack of precipitation, the majority of the Kingdom’s soils are sandy and contain a high percentage of calcium carbonate [2]. Poor fertility, poor organic matter content, and low accessible fresh water are further characteristics of the KSA’s soils [3]. Due to limited freshwater resources, the KSA mostly uses groundwater for irrigation [4]. Moreover, the Kingdom is affected by high rates of soil infiltration, resulting in low water use efficiency. The application of soil conditioners is consequently crucial to increasing the amount of water used for agriculture [5]. Soil conditioners can enhance the water-holding capacity, bulk density, texture, structure, and other physical and chemical characteristics of the soil. Furthermore, some types of soil conditioners can increase soil cation exchange capacities, which boosts the soil’s capability to retain nutrients and increase productivity [6]. An appropriate method for effectively managing and discarding excess agricultural wastes is the thermochemical process of pyrolysis, which turns agricultural residue byproducts into valuable materials called biochar [7]. Biochar is a carbon-rich product that can act as a soil conditioner. It was found that the quality of the soil and crop productivity are improved by using biochar as a soil conditioner [6,8,9,10,11,12]. However, it should be noted that the biochar effects are contingent on the feedstock’s supply, the pyrolytic temperature, and the rate of application. The soil fertility, aeration, porosity, distribution of pore size, bulk density, and specific surface area are among the soil properties improved by biochar [5,6]. According to Alkhasha et al. [13], applying 2% date palm biochar enhanced soil’s ability to retain water by 68%. Additionally, the application of biochar enhanced soil water retention and reduced hydraulic conductivity and the infiltration rate in sandy soils. These significant improvements in the physical and chemical properties of soil can lead to improved crop yields and increased resilience during dry periods. Additionally, the presence of biochar can foster beneficial microbial activity, further enhancing soil health and productivity [9,10,11,12]. According to Ibrahim et al. [14] and Ibrahim et al. [15], the application of Canocarpus biochar (Canocarpus sp.) to a sandy loam soil enhanced the soil’s capability to retain water and decreased the cumulative evaporation rate. Alghamdi et al. [5] and Al-Omran et al. [16] investigated how the hydrophysical characteristics of sandy loam soil were affected by the addition of date palm biochar, compost, and a combination of the two. They found that when addition rates were increased, daily and cumulative evaporation, saturated hydraulic conductivity, and cumulative infiltration decreased for all treatments, while the soil water retention capacity increased. Moreover, Igalavithana et al. [17] reported that corn (Zea mays) residue biochar enhanced sandy loam soil’s hydraulic characteristics. Furthermore, Randolph et al. [18] found that certain municipal organic wastes, such as newspaper, cardboard, landscaping, and woodchip residues, were utilized as feedstocks for biochars either separately or in a 25% mixture of all four waste streams. Biochar was prepared using three pyrolysis temperatures (350, 500, and 750 °C) and three pyrolysis residence times (2, 4, and 6 h). The authors found that the feedstocks and manufacturing circumstances affected important biochar characteristics such as pH, electrical conductivity, bulk density, and surface area. The pH, electrical conductivity, aggregate stability, water retention, and micronutrient levels of soil were all raised by biochar in general. Alghamdi et al. [19] found that olive-waste-derived biochar reduced the cumulative evaporation, cumulative infiltration, and infiltration rate; on the other hand, it increased the available water contents of sandy soil. In this study, we hypothesized that the feedstocks of biochar can affect its efficiency and impact on the physical and chemical properties of soil. Consequently, the main objective of this study was to compare and evaluate the effect of date palm and olive tree biochar and its application rate on sandy soil hydrophysical characteristics, such as infiltration rate, cumulative evaporation, water retention, and saturated hydraulic conductivity.

2. Materials and Methods

2.1. Soil Sample Collection and Preparation

Sandy soil was taken from the soil surface (0–30 cm) at King Saud University’s Agricultural Research Station in Dirab. The station is situated at longitude 46°44″ and latitude 24°39″ and is roughly 35 km from the city of Riyadh. A 2 mm diameter sieve was used to prepare the soils for laboratory analysis. Following the removal of organic matter and lime, the soil texture was determined using the hydrometer method [20].

2.2. Gathering Date Palms and Olive Tree Wastes and Biochar Production

Date palm (Phoenix dactylifera L.) leaves and petiole bases (fronds) were gathered from Riyadh City. The date palm was chosen for biochar production because it is widely available in the KSA. Olive debris, including leaves and branches, was gathered from olive orchards owned by the National Agricultural Development Company (Nadec) in northern KSA in the Al-Jawf region. After being allowed to air dry in the sun, the date palm and olive tree wastes were chopped into tiny pieces (20–30 cm) and then moved to the lab at King Saud University in Riyadh. The wastes were dried for 48 h at 70 °C then packed into a biochar kiln and pyrolyzed for three hours at a temperature of 450 °C ± 10 °C in an oven with an absence of oxygen [7,19]. Nitrogen gas was utilized in order to eliminate and displace oxygen gas from the pyrolysis reactor and to create an inert atmosphere [19]. Following pyrolysis, an electrical grinder was used to smash and grind the biochar bits. A 2 mm sieve was used to grind and sift the biochars that were produced. After being passed through a 2 mm screen, the prepared biochars were combined with the soil at application rates of 1% and 5% (wt/wt). The biochars were added to the upper 10 cm layers of the soil columns at a lab temperature of 25 °C (Table 1) [7,14,19].

2.3. Biochar and Soil Analyses

The biochar and soil pH and electrical conductivity (ECe) were measured in 1:10 biochar/water extract (wt/wt) and saturated soil paste extract, respectively, using EC and pH meters (Hanna, HI 9811-5, Bedfordshire, UK) (Table 2 and Table 3). The hydrometer method was used to determine the soil texture, which was sandy [21]. The percentages of silt, clay, and sand were 0.02%, 8.6%, and 91.3%, respectively (Table 2). The organic matter (OM%) in the soil was determined with an oxidation method as described by Walkley and Black (Table 2) [22]. Moreover, the calcium carbonate content was measured using the calcimeter method [23] (Table 2).

2.4. Proximate and Specific Biochar Surface Area Determination

A proximate analysis of the biochar samples (stable carbon, volatile matter, ash, and moisture) was carried out using the standard American Society for Testing and Materials (ASTM) procedure (number: D1762-84) [24].
The specific surface area and porosity were determined using the Accelerated Surface Area and Porosimetry System (ASAP 2020, Micromeritics, Norcross, GA, USA).

2.5. Setup of Column Experiment

Acrylic columns were used in this experiment. Filter paper was used to seal the bottoms of acrylic columns that were 45 cm long and 5 cm in diameter (Figure 1). The biochar treatments were introduced and blended through the top 10 cm of the soil in the columns after the sandy soil had been filled to a 30 cm height (Figure 1). The application rates of biochar for different biochar types (date palm and olive wastes) were 0.0%, 1.0%, and 5.0% (0, 10 g, and 50 g biochar per kilogram of soil) (Table 2). The experiment was carried out at a laboratory in King Saud University with an average temperature of 25 °C. Each treatment had four replicates, along with a control treatment.

2.6. Evaporation and Wetting Cycles

Over the course of the five wetting/evaporation cycles, 63.69 mm (25 mL each week) of tap water (EC = 0.76 dS m−1 and pH = 7.2) was supplied into the soil columns. The columns were weighed every day, and the evaporations were calculated by subtracting the weight of the column after adding water on the first day of the week from the weight of the column on each of the seven days of the week. During the five weeks of the experiment, cumulative evaporation was calculated for each treatment by collecting the evaporation from each column over time.

2.7. Distribution of Soil Moisture

The columns were divided into top-to-bottom portions immediately by the end of the experiment. Then, 2.5 cm portions were added at the top of the columns at a depth of 10 cm, followed by sections that were 5 cm thick at the bottom of the column. After that, the soil was dried for 24 h at 105 °C in an oven to measure the water content in each region. Each column’s water content was computed.

2.8. Soil Water Retention

The pressure plate method was used to measure the soil’s water retention for all treatments [25]. Rubber rings of 5 cm in diameter and 1 cm in height were used to hold the samples. Each treatment was soaked for 24 h in three replications. The matric potentials at which the retained soil water was measured were −0.3 and −15 bars. The field capacity (FC) was defined as having a −0.3 bar matric potential. A matric potential of −15 bars was thought to be the permanent wilting point (PWP). The FC and PWP were used to calculate the available water (AW) content as follows:
AW = FC − PWP

2.9. Measurement of Hydraulic Conductivity

The hydraulic conductivity (Ks) was determined using the constant head method approach and Darcy’s Equation (2):
Q A t = K s h + L L
where Q is the volume of water extracted from the soil (cm3), and A is the soil’s cross-sectional area (cm2). The time is represented by t (min) in the equation, whereas hydraulic conductivity, expressed in cm min−1, is denoted by Ks. The water head above the saturated soil is denoted by h (cm). Finally, the L is the soil’s length in centimeters.

2.10. Measurement of Infiltration Rate

Infiltration rates were measured using a mini-disk infiltrometer (3 cm diameter and 100 cm3 water holding (Model ML1, 0.5 cm suction; Mini-disk Infiltrometer, Decagon Devices, Inc., Pullman, WA, USA). The mini-disk infiltrometer was filled with distilled water and then placed on the soil surface for each column. Four measurements of the infiltration rate were conducted for each treatment. Beginning at time zero, the water quantity infiltrated was determined every minute [26]. The Philip Equation (3) [27] was used to calculate the cumulative infiltration as follows:
I = S   t 0.5 + A 1 t
where t is time (min), I is cumulative infiltration (cm), S is sorptivity (cm min−0.5), and A1 is a constant associated with hydraulic conductivity (cm min−1).
Plotting I against t0.5 provided a mathematical representation of Equation (3), and the calculated data was fitted to a second-order polynomial.

2.11. Statistical Studies

The average parameter values and standard errors were computed for range determination (X ± S.E.). The collected data was statistically analyzed using the analysis of variance (ANOVA). Duncan’s multiple range test (DMRT) and the least significant difference (LSD) were computed [28] using SAS software, version 9.4 (Cary, NC, USA).

3. Results

3.1. Chemical Properties of Biochar

The pH was alkaline for both date palm (D) and olive waste (O) biochars (Table 3). The pHs of these biochars were 8.99 and 9.42, respectively, with a pyrolytic temperature of 450 ± 10 °C. Accordingly, these biochars should be applied cautiously to alkaline soils due to their excessive alkalinity, especially in the case of olive biochar. On the other hand, due to the high buffering capacity of the soil, 5% biochar application rate could be suitable. A consistent nutrient supply and a healthy soil microbiota are supported by soils with a high buffering capacity, which improves resistance to pH variations with biochar application. In general, following biochar addition, the soil’s pH stabilized within 1–3 days [29,30]. These biochars are safe and suitable for use in acidic soils. It was also found that D biochar is 47.1% more saline than O biochar. The EC of D and O biochars was 4.10 and 2.17 dS/m, respectively (Table 3). Likewise, the cation exchange capacity (CEC) (Table 3) [31] and specific surface area (m2/g) of D biochar were 133.3% and 48.5% greater than those of O biochar, respectively. In addition, the total porosity, stable carbon, ash, and moisture content of D biochar are higher than those of O biochar; however, the volatile matter content of O is higher than that of D biochar (Table 3) [13,19].

3.2. Wetting, Cumulative Evaporation, and Evaporation Cycles

The soil columns received 63.69 mm of water over the course of five cycles of evaporation and wetting. The water recovered (maintained + evaporated) at the end of the experiment varied from 97.46% to 99.86% (Table 4). All biochar treatments showed a significant decrease in cumulative evaporation when compared to the control treatment yet also exhibited an increase in retained water (Table 4, Figure 2). After 35 days, the D450, 5% and O450, 5% treatments showed the greatest reduction in cumulative evaporation, with scores of 44.20 and 46.44 mm, respectively [5,13] (Table 4).

3.3. Water Infiltration into the Soil

Applying biochar to the soil at different rates resulted in a considerable decrease in cumulative infiltration when compared to the control treatment (Figure 3A). The D450, 5% treatment showed the largest reduction, followed by the D450, 1% treatment (Figure 3). Additionally, biochar reduced the infiltration rate (Figure 3C). The D450, 5% and D450, 1% treatments significantly reduced the infiltration rate in comparison to the control and other treatments. Accordingly, the retained water—a reliable measure of the quantity of water in the soil available for uptake by the plant—improved compared to the control (Table 4). Al-Omran et al. [16], Alghamdi et al. [19], Ibrahim et al. [15], and Alghamdi et al. [7] all reported similar findings. Because the fine biochar particles remain in the soil’s pores, they restrict water flow and lower soil water infiltration [32,33,34]. Moreover, the development of intraparticle porosity associated with small-sized biochar can help reduce wetting and enhance trapped air, which in turn can reduce cumulative infiltration of soil [35,36]. The results also showed that the soil treated with biochar led to a considerable decrease in sorptivity when compared to the control (Table 5 and Figure 3B). The term sorptivity is defined as the soil’s capability for water absorption or desorption via capillarity [27]. It combines the effects of soil capillarity and adsorption at the soil particle surface. Water is drawn into soil more quickly when sorptivity is low, which may explain the increase in water retention with the increasing rate of biochar application [5,7,13,19]. In this study, the highest decrease in sorptivity compared to the control was recorded as 97.8% for D450, 5%, followed by 84.3%, 68.9%, and 36.8% for D450, 1%, O450, 5%, and O450, 1%, respectively.
Table 5. Effect of biochar treatment on available water content of the soil.
Table 5. Effect of biochar treatment on available water content of the soil.
Ψ (Bar)Soil Water Content (cm cm−3)
ControlD450, 1%D450, 5%O450, 1%O450, 5%
−0.3 (FC) 1 0.073 d 50.155 b0.167 a0.100 c0.163 a
−15 (PWP) 20.0280.0390.0400.0420.049
AW 30.045 d0.116 b0.127 a0.058 c0.114 b
Sorptivity 4
(cm min−0.5)		5.790.910.133.661.80
1 Field capacity. 2 Permanent wilting point. 3 Available Water (AW) = Field Capacity (FC) − Permanent Wilting Point (PWP) 4 Sorptivity was calculated by fitting a second-order polynominal to the plot of cumulative infiltration versus the square root of time (Figure 4). 5 Duncan’s multiple range test (DMRT) means separation within each column at the 5% level (values with alike letters are not significant).
Water 17 02612 g004
Figure 4. Impact of biochar application on hydraulic conductivity of the soil (n = 4).
Figure 4. Impact of biochar application on hydraulic conductivity of the soil (n = 4).
Water 17 02612 g004

3.4. Soil Hydraulic Conductivity

All treatments showed a considerable decrease in saturated hydraulic conductivity (Ks) values when compared to the control. This is because the particles of biochar reduce the average size of the soil particles and can also fill or clog soil macropores with their fine particles (Figure 4) [8,17]. Furthermore, the platelike biochar particles may obstruct soil micropores according to Novak et al. [32]. The D450, 5% treatments in this investigation showed the largest Ks drop. The average values of this decline for D450, 5%, D450, 1%, O450, 5%, and O450, 1% were 94.8%, 87.0, 76.6, and 35.1%, respectively. This result is consistent with the findings of Ni et al. [33], Liu et al. [34], and Alghamdi [6]. Additionally, according to Barnes et al. [35], biochar decreased sandy soil’s hydraulic conductivity by about 90%.

3.5. Retention of Water

The application of either date palm or olive biochar improved the capacity of the soil to retain water when compared to the control treatment, especially at a water potential of −0.3 bar (Table 5). In comparison to the control treatment, the water content (WC) increased significantly at −0.3 bar, and the water retention increased with the increase in the biochar application rate (Table 5). The WC at field capacity (FC) increased by 129%, 123%, 105%, and 37% in D450, 5%, O450, 5%, D450, 1%, and O450, 1%, respectively. The findings of Ibrahim et al. [15] and Alghamdi et al. [19] were comparable. Because biochar is very hydrophobic and has more small holes than sandy soils, which mostly have large pores, it may have an impact on improving soil water retention. Less water enters the aggregate pores due to biochar’s hydrophobicity, increasing the aggregate stability and availability of water [36].
According to our findings, the application of biochar increased WC at both the FC and PWP. However, the amount of AW is the most significant figure for WC in the soil. The growth and development of plants are positively impacted by AW. In this study, the AW increased by 182%, 158%, 153%, and 29% for D450, 5%, D450, 1%, O450, 5%, and O450, 1%, respectively [5,18,37]. The amount of soil AW increased most at a high biochar application rate (5%) for both date palm and olive tree waste. The O450, 1% treatment had the least effect. Because of its high pH and salinity, biochar should only be used as a soil amendment in arid regions under stringent guidelines, even though high rates of biochar were found to produce the highest levels of AW (Table 5). Given that it has medium salinity, the biochar made from olive residues is not predicted to increase soil salinity as much as the biochar made from date palm wastes (Table 3) [5,7,19]. Subsequently, the use of these types of biochar is suggested with some restrictions in alkaline soils and with no restrictions in acidic soils.

4. Discussion

4.1. Biochar’s Impacts on Soil

When applied in arid conditions, biochar with a high salinity, such as that prepared from the date palm feedstock, can significantly increase the salinity of soil. Therefore, this type of biochar should be used with a high degree of restriction in saline environments [5,6,13]. On the other hand, the olive tree-derived biochar exhibited a medium salinity, which means that it could be used with a low degree of restriction under saline soil conditions. The same results were found by Alghamdi et al. [19].
Biochar’s cation exchange capacity (CEC) refers to its capacity to exchange cationic nutrients. A high CEC value means that the soils can retain more cationic nutrients (such as Cu2+, Zn2+, K+, and NH4+) in the root zone and prevent the nutrients from being lost by leaching. Table 3 showed that D biochar has a greater CEC (80.2 cmol/kg) than O biochar (30.37 cmol/kg). This suggests that D biochar might be a useful soil amendment for sandy soil [38]. Additionally, biochars with high CEC, such as D biochar, might be a viable choice for environmental management when cleaning up water or soil that has been contaminated by heavy metals [39].

4.2. Intermittent Evaporation

It is clear from this study that adding either date palm or olive waste biochar to sandy soils reduced soil column evaporation. It is evident that the addition of biochar improved the soil’s ability to hold water, which led to increased water savings. Applying biochar decreased cumulative evaporation for D450, 5%, O450, 5%, D450, 1%, and O450, 1% by 10.2%, 5.6%, 4.1%, and 2.2%, respectively. Many other studies on the addition of biochar have found comparable results [15,38,40,41,42].

4.3. Infiltration

According to the findings, applying D and O biochars limited the amount of water that could pass through the soil. Cumulative infiltration noticeably decreased by 58.1%, 33.8%, and 25.7% in the case of the D450, 5%, D450, 1%, and O450, 1% biochar treatments, respectively; however, there was no considerable decrease with the O450, 1% treatment. Infiltration is reduced due to tiny biochar particles entering soil pores and obstructing water movement, which explains why the lowest infiltration levels were observed with larger concentrations of D biochar [43,44,45,46,47]. Furthermore, the findings of Ibrahim et al. [15] and Busscher et al. [48] showed that adding biochar to sandy soils with a coarse texture can reduce water infiltration through the soil, preserving soil moisture and increasing water availability to plants. Alghamdi et al. [7] revealed that date palm biochar decreases the infiltration rate of calcareous sandy soil and improves its hydrophysical properties.

4.4. Soil Water Retention Capacity

The application of biochar enhanced various qualities of soil, such as its ability to hold water at high and low application rates. Furthermore, the water content at the FC increased. The highest increase in the FC was 129% for D450, 5%. There was also a substantial increase in AW, with the highest increase for D450, 5% being 182%. Kinney et al. [49] and Suliman et al. [50] similarly reported that the amount of water retained at the FC rose by 25% after adding pine wood, pine bark, and poplar wood biochar using sandy soil at a 2% application rate. The increased number of tiny pores in the soil following the addition of biochar may be the cause of the increase in water retention [47]. Furthermore, the high soil water retention of biochar-treated sandy soil may be explained by the large surface area of biochar [6,51]. Therefore, the results suggest that adding biochar may have increased the impact of soil pores on soil water content in comparison to untreated soil. This result agrees with the findings of Chen et al. [52], Rasa et al. [53], Chen et al. [54], and Ghazouani et al. [55]. It is also important to clarify that biochars such as D biochar have a high organic matter content, which typically improves the soil’s ability to retain water. This is due to the fact that organic matter either “glues” soil particles together or creates favorable living circumstances for soil organisms, which increases the number of micropores and macropores in the soil [56,57].
It was found in this study that biochar application decreased saturated hydraulic conductivity (Ks), and the highest decrease was for the D450, 5% treatment. The same result was recorded by Hussain et al. [12], Ibrahimi et al. [51], and Alghamdi et al. [19]. Novak et al. [32] stated that the platelike biochar particles could clog soil micropores, thus decreasing the Ks.

5. Conclusions

The efficacy of biochar made from date palm and olive wastes as a soil amendment was examined in this study. The findings indicated that while the pH of both types of biochar was high, the olive biochar had a higher alkalinity. However, date palm biochar had a higher salinity than olive-waste-based biochar. Date palm biochar should be used with extreme caution when applied to saline soil. All biochar treatments enhanced the quantity of water retained in the soil while decreasing cumulative evaporation. The addition of biochar hindered the saturated hydraulic conductivity; the treatments that involved the application of date palm biochar at the highest rate (5%) saw the greatest delay. Biochar application considerably reduced cumulative infiltration into soil as compared to the control treatment. Additionally, the results demonstrated that soil available water increased by 182%, 158%, 153%, and 29% for D450, 5%, D450, 1%, O450, 5%, and O450, 1%, respectively, in comparison to the control treatment. According to the results, among the studies conducted, the optimal type and application rate of biochar for enhancing the hydrophysical properties of sandy soil were date palm-prepared biochar and a rate of 5%. This biochar can be utilized as a soil supplement with limitations in saline–sodic soils and without limitations in acidic soils. Light-textured soils can be irrigated with less water if the suggested biochar is used.

Funding

This research was funded by the Ongoing Research Funding program (ORF-2025-825), King Saud University, Riyadh, Saudi Arabia.

Data Availability Statement

The raw data supporting the conclusions of this article will be made available by the authors on request.

Acknowledgments

The author would like to thank the Ongoing Research Funding program, (ORF-2025-825), King Saud University, Riyadh, Saudi Arabia for funding this investigation.

Conflicts of Interest

The author declares no conflicts of interest.

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Water 17 02612 g001
Figure 1. The columns and application rates of biochar used in the study.
Figure 1. The columns and application rates of biochar used in the study.
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Water 17 02612 g002
Figure 2. The distribution of water content in the columns with applied date palm and olive tree waste biochars after 35 days of evaporation/wetting cycles.
Figure 2. The distribution of water content in the columns with applied date palm and olive tree waste biochars after 35 days of evaporation/wetting cycles.
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Figure 3. Impact of biochar addition on cumulative infiltration (A), mathematical representation of cumulative infiltration obtained via fitting a second-order polynomial toward determined cumulative infiltration against time0.5 (t0.5) (B), and infiltration rate (C).
Figure 3. Impact of biochar addition on cumulative infiltration (A), mathematical representation of cumulative infiltration obtained via fitting a second-order polynomial toward determined cumulative infiltration against time0.5 (t0.5) (B), and infiltration rate (C).
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Table 1. The symbols used for different treatments.
Table 1. The symbols used for different treatments.
SymbolApplication Rate (%)Pyrolytic Temperature (°C)Type of Residue
Cont.0--
O450, 1%1450Olive trees
O450, 5%5450Olive trees
D450, 1%1450Date palm
D450, 5%5450Date palm
Table 2. Physicochemical properties of the soil used in the experiment.
Table 2. Physicochemical properties of the soil used in the experiment.
SamplePHECeCaCO3%O.M%%Soil
Texture
dS.m−1SandSiltClay
Soil8.21.19.20.1091.30.028.6Sand
Table 3. Surface area and chemical characteristics of biochar.
Table 3. Surface area and chemical characteristics of biochar.
SampleCodeType of ResiduepH
(1:10)		EC
(dSm−1) (1:10)		CEC
(cmol kg−1)		Specific Surface Area
(m2/g)		Total Porosity (%)Proximate Analysis (%)
Stable CarbonVolatile MatterAshMoisture
1D450Date palm pyrolyzed at 450 °C8.994.1080.2228.878.660.322.6213.843.33
2O450Olive pyrolyzed at 450 °C9.422.1734.37154.165.459.527.759.63.15
Table 4. Evaporation and water retention following five weeks of cycles of wetting and evaporation.
Table 4. Evaporation and water retention following five weeks of cycles of wetting and evaporation.
TreatmentAdded WaterEvaporation (mm)Cumulative EvaporationWater
Retained		Cumul. Evapo. +Recovery %
(mm)Week 1Week 2Week 3Week 4Week 5(mm)Water Retained (mm)
Control63.698.069.210.4410.511.0049.20 a *14.10 f63.399.39
O450, 1%63.698.108.709.6010.5011.2048.10 b15.50 d63.6099.86
O450, 5%63.697.548.309.3010.3011.0046.44 d16.95 b63.3999.53
D450, 1%63.697.508.009.5911.0011.0947.18 c16.10 c63.2899.36
D450, 5%63.697.007.509.2010.5010.0044.20 f17.87 a62.0797.46
* Duncan’s multiple range test (DMRT) means separation within each column at the 5% level (values with alike letters are not significant).
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Alghamdi, A.G. Comparison of the Effects of Olive Tree and Date Palm Waste Biochar on Water Stress Measurements and Hydrophysical Properties of Sandy Soil. Water 2025, 17, 2612. https://doi.org/10.3390/w17172612

AMA Style

Alghamdi AG. Comparison of the Effects of Olive Tree and Date Palm Waste Biochar on Water Stress Measurements and Hydrophysical Properties of Sandy Soil. Water. 2025; 17(17):2612. https://doi.org/10.3390/w17172612

Chicago/Turabian Style

Alghamdi, Abdulaziz G. 2025. "Comparison of the Effects of Olive Tree and Date Palm Waste Biochar on Water Stress Measurements and Hydrophysical Properties of Sandy Soil" Water 17, no. 17: 2612. https://doi.org/10.3390/w17172612

APA Style

Alghamdi, A. G. (2025). Comparison of the Effects of Olive Tree and Date Palm Waste Biochar on Water Stress Measurements and Hydrophysical Properties of Sandy Soil. Water, 17(17), 2612. https://doi.org/10.3390/w17172612

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