Impact of Biochar and Phosphogypsum Addition on Soil Physical Properties, Physiological Traits and Productivity of Maize under Water Deficit Conditions

INTRODUCTION

Maize (Zea mays L.) is one of the most important grain crops cultivated worldwide and plays a crucial role in meeting global food needs. In Egypt, the total cultivated area of maize amounted to 2.8 million faddan, with an annual production of approximately 9.2 million ton, sufficient for 48–50% of our needs. This gap is filled through imports (Economic Affairs Sector, Agriculture Ministry). Water stress is considered one of the main obstacles to global agricultural production, especially in Egypt, in light of the increasing water challenges it faces due to population growth, climate change and the Ethiopian Renaissance Dam. Maize is one of the most sensitive to water shortage (Li et al., 2021), which can result in a yield reduction of 25–30% (Kimm et al., 2020).

                Drought stress is a series of abiotic stresses that induce morphological, physiological, and biochemical changes responsible for a substantial reduction in crop yield (Liang et al., 2020; Latif et al., 2022), which increases leaf senescence,  decreases chlorophyll synthesis and enhanced the overproduction  of radical oxygen species, ROS (Vijayaraghavareddy et al., 2022), that damages proteins, lipids, DNA and enzymatic reactions (Cui et al., 2017)  for this pervious reasons  photosynthesis and crop productivity were reduced a substantial  (Ma et al., 2021). Therefore, it is crucial to create techniques that may improve the soil's capacity for holding water and nutrients, increasing crop production under water deficit. Examples of such techniques are the use of biochar or Phosphogypsum.

Biochar (BC) is composed of plant-based materials that have been charred through a procedure known as pyrolysis in which there is no or less oxygen (Wu et al., 2023). It is abundant in carbon-based compounds. The use (BC) as a soil amendment improves plant development and nutrient use efficiency. It also improves the soil's ability to retain nutrients like calcium, phosphorus, and nitrogen while having a higher pH and greater moisture-holding capacity. In recent studies indicated that integrated application of (BC) with mineral fertilizer caused to improving soil structure and productivity of maize Tufa et al. (2022) and increasing soil physicochemical properties such as pH, cation exchange capacity, water retention capacity, and influencing microbial soil activity (Mosharrof et al., 2021).

Phosphogypsum (PG) is a by-product of the phosphate fertilizer industry, due to the manufacturing of phosphoric acid from rock phosphate (fluorapatite). Globally, around 160 Mt of phosphogypsum are manufactured yearly and it is mainly removed in big stocks or discharged into Waterways (Saadaoui et al., 2017). Given that it is primarily made up of CaSO₄ and 2H₂O, it can serve as a source of calcium for agricultural soils, which are one of the main sources of this element globally.

According to Mahmoud et al., (2017) reported that the combination of BC and PG at a rate of 10 Mg ha^-1 with recommended nitrogen fertilizer for maize plants could be considered as an ameliorating material to reclaim compacted soils such as some physical-chemical characteristics and to improve the yield of maize plants.

Therefore, the objective of this investigation was to determine whether drought harm can be minimized by using soil amendments like BC and PG to reduce water stress and thus improve physiological traits and the productivity, as well as WUE and WP.

MATERIALS AND METHODS

A field experiments was layout out at El-Gemmeiza Agricultural Research Station Farm (located between Latitude 30° 58′ 56″ N and Longitude 30° 57′ 8″ E), Egypt during the two summer seasons of 2021 and 2022 to study the influence of water stress and soil amendments i.e.biochar (BC) and Phosphogypsum (PG) on soil physical proprieties, some growth parameters and productivity of maize plants (Three Ways Cross 368, "TWC 368").The experimental unit area was 28.8 m² (4.8 x 6 m) including 6 ridges (6m length and 80cm width).Grains of the tested maize treatments were obtained from Maize Department, Field Crops Research Institute, Agriculture Research Center, Egypt. TWC 368 was sown on 20^th and 25^th May in the first and the second seasons, respectively, as recommended for maize in the area. The experiment was laid out in a split plot design with four replications where the irrigation treatments were allocatedin the main plots whereas the sub plots contained application of BC and PG, which mixed with the soil surface layer (0-30 cm depth) before cultivation. Every agricultural practice was implemented in accordance with the guidelines provided by Egypt's Ministry of Agriculture.

The treatments were as follows:

I - Main Plots (Irrigation Treatments)

A- Irrigation at 50 % of available soil moisture depletion (AVSMD) (moist, I₁).

B- Irrigation at 65 % of AVSMD (medium, I₂).

C- Irrigation at 80 % of AVSMD (dry, I₃).

II -Sub-plots Application of biochar (BC) and phosphogypsum (PG)

1-       Without treatment (control, T₁)            

2-       Biochar (2 ton BC fad^-1, T₂)

3-       Biochar (4 ton BC fad^-1, T₃)           

4- Phosphogypsum (2 ton PG fad^-1, T₄)

5-       Phosphogypsum (4 ton PG fad^-1, T₅)  

6-       (2 ton BC fad^-1 plus 2 ton PG fad^-1,T₆)

Meteorological tables play an important role in cases of water deficit of various crops due to their close connection to the processes of transpiration and evaporation from the soil surface (Table, 1).

Table 1: Meteorological data in 2021 and 2022 growing season Month for Gharbia Governorate.*

*Source: Water Requirement and Field irrigation Res., Dept.

The physical and chemical properties of the soil samples before application of soil amendments, where the soil samples (0-30 cm) were air dried, crushed and passed through a 2 mm sieve and kept for soil chemical and physical properties analysis as shown in Table (2 and 3).

Table 2: Chemical and physical properties of the experimental soils.

OM= organic matter, C.sand= corease sand, F.sand= fine sand, Hc= hydraulic conductivity. CEC= cation exchange capacity

Table 3: Field capacity, permanent wilting point, available moisture and bulk density were determined for the experimental sit.

FC= Field capacity, wp= water point, Aw= available water, Bd= bulk density.

Soil sampling analysis:

                Soil sample were randomly made in the experimental site to measure soil physical properties. Soil texture was determined using the pipette method (Gee and Bauder 1986) at 0-30 cm depths for soil. Bulk density was determined by the core method (Blake and Hartage 1986) for soil. Soil water content was determined from soil samples taken at the same locations using the gravimetric method. Field capacity and permanent wilting points were considered at 0.3 and 15.0 bars, respectively (Klute 1986). Hydraulic conductivity saturated (Ksat) was determined for each tested soil and calculated by Darcy, slow according to Black et al. (1965). Available NPK of soil were determined according to Page et al. (1982). Organic matter content was determined using Walkley and Black rapid titration method according to Soil Laboratory Staff (1984). Soil pH was determined in 1:2.5 (soil: water) suspension using Beckman pH meter as out lined by Soil Laboratory Staff (1984). Total soluble salts were measured as dS m^-1 using electrical conductivity (EC) in soil paste extract. Sample of BC and PG were air-dried and ground, 1.0 g weight of manure and digested then, the digest was diluted with distilled water to a volume of 100 ml. Aliquots from this digest was analyzed for the content macronutrients according to Cottenie et al. (1982). PH value was determined in 1:10 (soil amendments: water) suspension using glass electrode pH-meter according to Jodic et al. (1982).

Table 4: Some characteristics of biochar and phosphogypsum used in this study.

Growth and physiological traits:

Leaf chlorophyll content:

Chlorophyll a and b content in fresh leaves (as mg/g fresh weight) at 70 days after sowing were determined and calculated according to Moran (1982)

At 90 days after sowing five guarded plants from each plot were chosen randomly to determine plant height, leaf area and shoot dry weight, then the data were averaged and recorded. The leaf area in cm² (LA) was calculated as follows:

 Individual leaf area= Leaf length × Leaf width × 0.73 according to Stewart and Dwyer (1999).

 Leaf relative water content (LRWC %):

LRWC % was estimated according to (Salgado-Aguilar et al., 2020) as follows:

RWC % = (Fw- Dw)/ (Tw- Dw) X 100

Where Fw, Tw and Dw are fresh weight, turgid weight and dry weight, respectively.

Antioxidant enzymes activity of leaves

Peroxidase activity was according to Allam and Hollis (1972) and Polyphenol oxidase activity was determined as described by Matta and Dimond (1963).

Proline content of leaves:

Proline in leaves was determined according to Bates et al. (1973). The results were calculated in mg / g dry weight.

Days to 50 % silking (DTS): was determined.

Harvesting took place 7 October, 2021 and 12 October, 2022 in the first and second seasons, respectively. At harvest time, ten individual guarded plants were randomly taken from one row in each sub-plot to determine: Ear length (cm), 100- kernels weight (g) and Grain yield (GY) ard. fad^-1, was calculated from two ridges in each sub-plot.

Water consumptive use (WCU):

In order to determine the soil moisture content, soil samples were taken with a regular auger at planting time, 48 hours after each irrigation and at harvest time. Duplicate soil samples were collected at depths of 0–15, 15–30, 30-45, and 45–60 cm and their moisture contents were computed by weighting. 

Moisture content and water consumptive use per unit area was calculated according to the equation described by Israelsen and Hansen (1962).

Where: WCU = Water Consumptive use (WCU) (cm). Bd = Bulk density of soil layer (g cm^-3). 

Q1 = Soil moisture content (%,wt/wt) just before the next irrigation

Q2 = Soil moisture content (%, wt / wt) 48 hrs after irrigation. 

ERZ = Effective root zone depth (cm).  

Q = CA (2gH) 0.5

Where: Q = orifice flow discharge C = discharge coefficient t = 0.6 Range (0.6 & 0.8) A = cross-sectional area of orifice or pipe (ft²) g = acceleration due to gravity (32.2 ft/s²) H = effective head on the orifice (measured from center of orifice to water surface).

Water use efficiency (WUE):

Water use efficiency was calculated accordance with Jensen (1983) as follows:

WUE = Grain yield (kg fad^-1)/seasonal water consumption in m³ fad^-1.

Water Productivity (WP):

 Water productivity was calculated according to (Ali et al., 2007) as kg grains m^-3 water applied:  WP (kg m^-3) = Gy/I    Where: Gy = Grain yield (kg fad^.-1)    I = Irrigation water applied m³ fad^.-1.

Statistical analysis

                Data of the two seasons were subjected to statistical analysis of variance according to Steel and Torrie (1980) by using (Costat, 2005). Means of the studied traits were compared using LSD at 5% probability level.

RESULTS AND DISCUSSION

1- Impact of water stress, applications BC, PG either alone or in combination and their interaction on soil physical properties.               

Data presented in Table (5) show that irrigation treatments had a significant impact on Bd, Tp, and Hc efficiency in both seasons. According to the results, Bd significantly increased when soil depletion moisture was increased from (I₁) to (I₃), on the other side Tp and Hc were decreased in both seasons. Irrigation at (I₁) or (I₂) were similar in previous traits except for Hc in the second season. In comparison to I₃, irrigation treatment (I₁) resulted in a decrease in Bd by (3.48 and 3.31%) and an increase in Tp and Hc by (2.72, 3.31%) and (19.62, 25.63%), respectively, over the course of two seasons. The current study supports the findings of Zhang et al. (2019), who found that Bd in the 0–10 cm soil layer was increased, but Tp and Hc were significantly decreased by drought stress. This may be due to lower fine root biomass and residue input from understory vegetation in the surface layer.

Table 5: Effect of irrigation treatments, biochar and phosphogypsum, as well as their interaction on soil physical properties during 2021 and 2022 seasons.

Regarding BC and PG either alone or in combination had significant effect on Bd, Tp and Hc in both seasons (Table, 5). Adding (T₆) achieved the highest values of Tp by (7.70, 8.84 %) and Hc by (188.89, 185.29 %), but it recorded the lowest values of Bd by (9.02 and 10.83 %) respectively, in the first and second seasons compared to untreated plants (T₁). The results showed that the mixture of BC and PG led to increased soil porosity, water aggregate stability and decreased soil bulk density. Moreover, the generation of macrospores and channels by root penetration through soil tends to form preferential flow paths, thus enhancing soil infiltration (Benegas et al., 2014). These results agree with Mahmoud et al. (2017), who found that Bd and Hc significantly increased as a result of the addition of 10 Mg BC ha^-1 plus 10 Mg PG ha^-1. Even worse, there is little research about the extent of the effect of BC adding for short periods of time to soils with medium to high soil organic content (SOM). In this regard Lehmann et al. (2011) illustrated that BC can change soil physicochemical parameters that increase root biomass and crop productivity by improving the soils' hydrologic properties that include increasing the soils' water-holding capacity and available water content, changing the hydrophobicity of the soil and altering the hydraulic conductivity of the soil. Also, Agbede and Adekiya (2020) found that application of BC at 10, 20, and 30 t ha⁻¹ reduced Bd by 9.7%, 19.40%, and 28.8%, respectively, as the average for both seasons compared with the control. Filho et al. (2016) found that the combined application of lime and (PG) effectively increased the organic carbon content in different classes of aggregates as well as lower soil bulk density and penetration resistance.

The interaction effect between water stress and soil amendments was significant on Hc in the second season only. The maximum value of Hc were recorded in response to treating maize plants by (I₂×T₆), but (I₃×T₁) recorded the lowest value.

2- Impact of water stress, applications BC, PG either alone or in combination and their interaction on soil chemical properties.

Data obtained in Table (6) revealed that increasing soil moisture depletion from (I₁) up to (I₃) caused a significant reduction in OM, N, P and K available, but soil pH increased in both seasons. In this concern, the relative increases were 4.58 and 5.06% for OM, 12.89 and 9.22% for N available, 18.45 and 14.06% for P available and 7.54 and 7.73% for K available compared with I₃ in the first and second seasons, respectively. The corresponding decrease in soil pH was 0.75 and 1.00% with I₁ as compared to I₃ for the first and second seasons, respectively. These findings concur with El-Gamal et al. (2021), who observed that irrigation at 40% of water depletion improved pH, OM, available N, P, and K in soil when compared to irrigation at 60 and 80% of water depletion. This could be explained by the fact that as soil drought stress increased, microbial activity weakened and declined, changing the soil's structure and degrading soil ecosystem productivity.

It is clear that BC and PG mixture augmented significantly OM, N, P and K available over control by about 40.46, 49.38, 65.64 and 14.73% as compared to control in the first season, respectively. While, the second season increased by 39.42, 46.73, 87.66 and 11.71% with BC and PG mixture as compared to control at the same previous properties respectively. The results illustrated in Table (6) showed that the applied of BC with PG gradually decreased soil pH by 2.95 and 3.09 % as compared to control in the first and second season, respectively. These results concur with Yang et al. (2022), who reported that adding BC enhanced the amount of available nutrients (N, P, and K) and OM and improvements in these

indices were generally correlated with the amount of BC added; moreover, adequate moisture can also provide more nutrients from the root zone. 

It is known that soil pH affects the availability of nutrients and how the nutrients react with each other. The current investigation demonstrated that the addition of BC and PG has a positive effect on lowering PH. These results agree with Liu and Zhang (2012) who reported that adding BC produced a decreasing for pH trend. The alkaline soil used for the study had a pH of 7.9, which could have prevented any BC liming effect. Thus, the addition of BC to the soil may benefit the environment by preventing nutrients loss and thereby protecting water resources. Application of PG led to lowering soil pH that may be attributed to release of phosphoric acid and sulfuric acid contained by PG and that enhanced soil fertility, through improving soil available nutrients. These results were confirmed with Kimet al. (2021). Also Vicensi et al., (2016) reported that adding (PG) improving the chemical conditions enabled greater root development and improved root distribution throughout the soil profile to enhance their ability to take up water and nutrients.

As for interaction effect between water deficit and soil amendments (BC, PG) was found to be a significant effects on soil pH and OM in the two seasons and P and K available in the second season only (Table, 6). The data showed that the treatment (I₁×T₆) provided the lowest value for soil pH and the highest values for P and K. Irrigation of maize plants at I₁ or I₂ with T₆ gave the maximum value for OM.

3-Impact of water stress, applications of BC, PG either alone or in combination and their interaction on chlorophyll a, b and a/b ratio.

Data are given in Table (7) illustrated that Ch. a, Ch. b and Ch. a/b ratio were significantly affected by irrigation treatments in the two season. Increasing soil moisture depletion from (I₁) up to (I₃) resulted in significantly reduction in Ch. a, Ch. b but Ch. a/b ratio was increased. Irrigation at (I₁) gave the highest values of Chl. a and b this may be attributed to the abundance irrigation water which encourage the absorption of water and nutrients by cells that prompted their volume and photosynthesis efficiency. While water stress has a negative effect on chlorophyll due to damage to the chlorophyll mechanism and the destruction of the photosynthesis system due to the lack of water absorption and nutrients from the soil and their transfer to the various plant organs. Our results agreed with those obtained by (Ali and Abdelaal, 2020 and Rusmana et al., 2021). Kaya et al. (2020) confirmed that deficit irrigation led to lower RWC, which in turn caused stomatal closure, limiting CO₂ availability, and reduced rates of photosynthesis and antioxidant /reactive oxygen species. Furthermore under drought stress the reduction of Chl b is greater than that of Chl a, thus, transforming the ratio in favor of Chl a (Jaleel et al. 2009). On the other hand, Shafiq et al. (2021) found that under drought stress circumstances, the chl. a/b ratio remained constant.

Concerning the impact of application of BC, PG either alone or in combination, there were significant differences on Ch. a, Ch. b and Ch. a/b ratio as presented in Table 7 in the two season. Results pointed out that application of (T₆) on the soil scored the maximum values of Ch. a and b followed by treated with (T₃) with a significant difference between such two treatments. On the other side addition (T₆) or (T₃) gave the minimum value for Ch. a/b ratio. As well as BC and PG mixture improved significantly soil physical and chemical properties as shown in Tables (5 and 6).

                The increases in leaves chlorophyll content as a result of BC addition which may be due to what was reported by Wu et al. (2023) who referred that adding BC to soil improved soil structure, soil organic matter, soil aggregate stability, water and nutrient holding capacity, and the activity of both beneficial microbes and fungi, that improved leaf water

Table 6: Effect of irrigation treatments, biochar and phosphogypsum, as well as their interaction on soil chemical properties during 2021 and 2022 seasons.

Table 7: Effect of irrigation treatments, biochar and phosphogypsum, as well as their interaction on chlorophyll a, b and a/b ratio of maize hybrid TWC 368 during 2021 and 2022 seasons.

status and reduced ROS damage, which increased chlorophyll synthesis and photosynthetic rate, reducing the negative impacts of water shortage on carbon assimilation and photosynthesis, that is linked with boosted chlorophyll synthesis Wang et al. (2021). Also Bossolani et al., (2021) stated that PG improves root system by increasing rate of multiplication and expansion of the root throughout the soil profile which in turn increased plant uptake of water and nutrients. These changes are reflected in greater synthesis of chlorophylls that, it an important part on Calvin cycle and is responsible for harvesting sunlight during plant photosynthesis (Busch, 2020).

The interaction effects between water stress and application of BC and PG on chl. a, b and chl. a/b ratio are shown in Table 7. Results cleared that application of BC and PG had a significant effect

on chl. a and b in the two seasons. In both seasons, treatment of (I₁×T₆) produced the best value for chl. a, followed by (I₂×T₆) with presence insignificant differences. As well as, (I₁×T₆) recorded the highest value for chl. b followed by (I₁×T₃), which had insignificant differences between them in both seasons. Whereas, worst values of chl. a and b were observed by plants under water stress (I₃) and unfertilized (T₁) during the two seasons.

4-Impact of water stress, applications of BC, PG either alone or in combination and their interaction on shoot dry weight plant^-1, leaf area, plant height and leaf relative water content

Data presented in Table (8) showed that shoot dry weight plant^-1, LA ,plant height and LRWC % were significantly affected by irrigation treatments in both seasons. There are gradual reductions in each mentioned traits by exposing maize plants to drought stress (I₃) compared to the other treatments in both seasons .Irrigation treatments (I₁), increased shoot dry weight plant^-1 and LA by (38.81 and 46.95 %) and (30.14 and 27.13 %) in the first and second season, respectively compared to maize plants under drought stress (I₃). In the same time, increasing plant height by (25.42 and 29.44 %) and LRWC by (13.13 and 13.81 %) in the first and second seasons, respectively in response to irrigated plants (I₁) compared to (I₃). Reduction in soil water potential as a result of water stress caused the inability of the plant to absorb water and nutrients in the critical growth stages of plants, that led to the congestion of soluble carbohydrates, proline, and osmotic regulation (which helps cell division and elongation), thus a decrease in the number and length of nodes, which reflected negatively on plant height. On the other hand, the LA decreased due to water stress, that reduced the size of chloroplasts and deterioration of the internal chloroplast membranes, and thus decreased total chlorophyll, thereby resulted in lower photo-assimilates and less dry matter accumulation. These results are in accordance with those of (Laskari et al., 2022 and Seham Mohamad et al., 2023).

With respect the effects of applying soil amendments (BC & PG), data in Table (8) pointed out that shoot dry weight plant^-1, LA, plant height and LRWC were affected positively by BC and PG application either alone or in combination in the 1^st and 2^nd seasons. Where, (T₆) appeared significantly increasing in all mentioned traits compared with the other treatments in both seasons. Adding T₆ treatment to soil improved shoot dry weight plant^-1 and LA by (54.65 and 49.28 %) and (25.56 and 24.21 %) in both seasons, respectively compared to control (T₁). In the same trend, plant height was increased by (26.35 and 26.13 %) and LRWC by (12.88 and 12.90 %), in the two seasons, respectively compared to (T₁). The current study shows that maize plants treated with BC amended soil resulted in increased LRWC (Table 8), which could be attributed to the significantly increased for water uptake from soil to maintain the plants' water status and, as a result, encourage photosynthesis, which has positive effect on shoot dry weight plant^-1 and grain yield. The present results were in agreement with the findings by (Abideen et al., 2022; and Ali et al. 2021). Most plant growth parameters may have improved as a result of the application of BC to the soil, which enhances the biological, chemical, and physical properties of the soil that increases its ability to retain water and nutrients (Mavi et al., 2018). In the same trend, Gharred et al., (2022) reported that addition of BC to the soil may be caused  an improvement in plant nutrition rather than by increasing water uptake and increased soil-available potassium (K) and enhanced its uptake and then tolerance plant to water stress. Moreover, Bossolani et al. (2021) reported that application of Lime plus PG improved root development, which reflected on increasing water and nutrients uptake by plants, increased photosynthesis and better regulation of oxidative stress led to higher shoot dry matter and grain yield of maize.

As for interaction effect between water deficit and soil amendments (BC& PG) was found to be a significant effect on shoot dry weight plant^-1 and LRWC in the two growing seasons and LA and plant height in the first season only (Table 8). Data confirmed that the maximum values of shoot dry weight plant^-1, LA and plant height were recorded by treatments (I₁×T₆) or (I₁×T₃) compared to other treatments. On the other hand, the highest values of LRWC was obtained when soil treated with (T₆) under treatment (I₁) followed by (T₆) under irrigation treatment (I₂) with insignificant difference between them in the both seasons. It could be confirmed that growth parameters such as plant height, LA and shoot dry weight were significantly reduced under water deficit, while the addition of BC and PG improved such traits under normal irrigation and minimized the harmful impact of water stress.

5-Impact of water stress, applications BC PG either alone or in combination and their interaction on antioxidant enzymes and proline content.

Data are given in Table (9) illustrated that, antioxidants enzyme i.e., peroxidase and polyphenol oxidase increased significantly in response to increasing water deficit from (I₁) to (I₂), but by increasing water deficit up to (I₃), antioxidants enzymes began reduced in both seasons. Also, the accumulation of proline increased significantly in both seasons by raising the soil moisture depletion level from (I₁) to (I₃) in both seasons. It is known that antioxidants production increased in tissues under stress conditions such as drought in order to protect the plant from over production of ROS, which might damage different macromolecules and cellular structures, thus this plant is forced to secrete more amounts of total phenols and proline to resist these ROS (Gharibi et al., 2016 and Hafez et al., 2021) but with the continuing stress conditions for a long time, the production of antioxidant enzymes decline.

Regarding the effect of soil amendments of BC, PG and their combination, it cleared that soil amendments of BC, PG significantly increased peroxidase and polyphenol oxidase, but proline was decreased in leaves of maize plants as compared to other treatments. The highest values of antioxidants enzymes were achieved by maize plants fertilized at (T₆) followed by addition of (T₃) while lowest values was observed with untreated plants (control). In contrary the maximum value of proline was scored with untreated plant

Table 8: Effect of irrigation treatments, biochar and phosphogypsum,as well as their interaction on shoot dry weight plant^-1, leaf area, plant height and leaf relative water content of maize hybrid TWC 368 during 2021 and 2022 seasons.

Table 9: Effect of irrigation treatments, biochar and phosphogypsum, as well as their interaction on peroxidase, polyphenol oxidase and proline of maize hybrid TWC 368 during 2021 and 2022 seasons.

control followed by addition of (T₄). These findings confirmed those of Wu et al. (2023), who found that adding BC to soil enhances the production of antioxidant enzymes (peroxidase and catalase), which may be related to improved plant metabolic function, cell growth, and a decrease in ROS production, which protects the plants from the adverse effects of drought stress and thus improves plant growth under this condition (Zulfiqar et al (2022).

Data in Table (9) show that the interaction between soil moisture stress and application of BC, PG had a significant effects on peroxidase enzyme in both seasons and polyphenol oxidase in the second season while proline content in the first season only. The results indicated that maize plants treated with I₂×T₆ scored the highest values

of peroxidase enzyme and polyphenol oxidase. On the other hand, the lowest value of proline was recorded by (I₁×T₆) or (I₁×T₃).

6-Impact of water stress, applications BC, PG either alone or in combination and their interaction on days to 50 % silking, ear length, 100-kernel weigh and grain yield.

In both seasons findings showed that days to 50 % silking, ear length, 100-kernel weigh and grain yield were significantly affected by irrigation treatments (Table 10). It could be observed that increasing soil moisture depletion from (I₁) up to (I₃) resulted in reduction in former mentioned traits. Irrigation treatment (I₁) increased days to attain 50 % silking and ear length by (6.37 and 6.15%) and (27.66 and 28.58%) in both seasons, respectively as comparison to maize plants exposed to drought stress (I₃). In the same trend (I₁) caused to increasing 100- kernels weigh and grain yield by (18.00, 17.35 %) and (30.58, 30.82 %) in the first and the second, respectively compared with irrigation regime (I₃). Maize plants reduce the time it takes to reach 50% silking in order to escape unfavorable conditions. These findings are consistent with those of El-Gamal et al. (2021) and Seham Mohamad et al. (2023). The decrease in ear length under water stress during plant growth stages may be due to lowering speed of photosynthesis and decreased absorption of nutrients, which was negatively affected on cell growth, consequently declined ear length. These results are in accordance with (Sathish et al., 2022).

 The depression in 100- kernels weigh and grain yield obtained herein by prolonging the irrigation intervals which may be due to the significant reduction in the growth characters such as shoot dry weight plant^-1 and leaf area as well as the physiological constituents in the leaves (chlorophyll content and LRWC) discussed previously in Tables 5 and 6, respectively. Our results are in line with Hafez et al. (2021) who found that irrigation every 18 days decreased 100-grain weight and grain yield compared to irrigation every 12 days. These findings are consistent with those of (Dina Ghazi and El-Sherpiny, 2021) and Ariyanto et al. (2023).

Data shown in Table (8) demonstrated that days to 50% silking, ear length, 100-kernel weigh and grain yield were significantly impacted by the addition of BC and PG in both seasons. It is evident that fertilized maize plants with (T₆) increased days to 50 % silking by (4.44 and 5.73 %), ear length by (25.30 and 21.70 %) in the first and the second, respectively compared to untreated plants. In the same trend 100-kernel weigh and grain yield were increased by (18.05 and 17.53 %) and (20.24 and 21.16 %) in both seasons, respectively. Tufa et al. (2022) reported that delayed phenological parameters of maize as a result of adding BC with mineral NPS addition might be due to improving soil fertility, increasing essential nutrients uptake of plant, leading to production of more vegetative growth. According to Al-Kadem (2022), the increase in 1000 -grains weight is attributed to the effect of BC, which was the main store for nutrients and good moisture content, which encouraged the plant to form a large leaf area and then increasing the leaf area index, consequently elevating chlorophyll content, that resulted in a longer and larger reception of solar rays, increasing photosynthetic activity, flow speed, and the accumulation of vital matter downstream grains.

Results in Table (10) show that the interaction effect between soil moisture stress and soil amendments was found to be significant on all mentioned traits in both seasons, except for days to 50 % silking in the first season only. Days to 50 % silking and ear length, 100-kernel weigh and grain yield recorded the highest values in response to irrigation at (I₁) or (I₂) with fertilized maize plants at (T₆), however, unfertilized maize plants under water regime (I₃) gave lowest values for the same traits in both seasons.

8- Impact of water stress, applications BC, PG either alone or in combination and their interaction on water measurements.

                Data in Table (11) showed that the values of WA, WCU, water use efficiency (WUE) and water productivity (WP) were significantly affected by irrigation treatments. The irrigated plants at (I₁) and (I₂) gave the maximum values of WA and WCU, with significant variation between them. Similarly, irrigation at (I₁) or (I₂) resulted in the highest values for WUE and WP. On the other hand, irrigation at (I₃) had the lowest values for all the attributes listed. The high water consumptive use for the moist treatment is due to the abundance of moisture in the soil, so the plants tend to grow without stress. These results are similar to those of (Taha and Kasem, 2022), Who demonstrated that when maize was grown under sole cultivation, irrigation at 80% ETo (evapotranspiration) gave the lowest values for WA, WCU, WUE and WP compared to irrigation at 100 and 120% ETo.

                 In regard with the results presented in Table(11) application of soil amendments significantly affected on water measurements in both seasons. The combined of BC and PG decreased significantly WA and WCU by (9.80, 8.94 %), (8.66, 7.28%), while increased WUE and WP by (33.33, 32.38 %) and (32.17,30.07%) compared to control in the two seasons respectively. Results showed that the use of a mixture of PG and BC improved the soil's hydro-physical and chemical properties, resulting in less evapotranspiration losses, making water available for crops for a longer period which protecting the crop against water stress and consequently, increasing WUE and WP. Our results concur with (Faloye et al., 2020, Bossolani et al., 2021 and Zahra et al., 2021). Studies show that BC has a high porosity and surface area which leading to an increase in the general soil porosity and water content, reducing water stress for plants (Batista et al., 2018). The WUE was lowered by 45 and 50% by using 4% biochar and 40% plant water requirements (PWR) irrigation respectively. (Ngulube et al., 2018).

The interaction effect between water treatment and soil amendments were significantly on WA and WUE in the two seasons while WP significantly affected in the second season only. The maximum value of WA was obtained from (I₁×T₁) treatment, but when treated maize plants by (I₃×T₆) recorded the lowest value. Whereas treated maize plants by (I₂×T₆) resulted in the maximum value of WUE while, WP recorded the highest value in response to treated maize plants by I₁ or I₂ with T₆ but the lowest values were obtained when maize plants received (I₃×T₁) treatment.

Table 10: Effect of irrigation treatment , biochar and phosphogypsum, as well as their interaction on days to 50 % silking, ear length, 100- kernel weigh and grain yield of maize hybrid TWC 368 during 2021 and 2022 seasons.

Table11: Effect of irrigation treatments, biochar and phosphogypsum, as well as their interaction on water measurements of maize hybrid TWC 368 during 2021 and 2022 seasons.