Introduction

One of the world’s biggest challenges to food security today is the pressure on natural resources, for instance over 70% of the fresh water is used for irrigation. The irrigation requirements over the next few years will not be able to be implemented as a result of reduced water supplies and increased competition for clean water. There are wide variations in the duration and severity of environmental stress, which can be aggravated more as a result of climate change that will have a significant impact on the severity and frequency of future droughts (Manabe et al. 2004; Harte et al. 2006). Meanwhile, water stress can drastically reduce the optimum plant products that can be achieved and it has negative influences on the plants such as delaying plant growth, decreasing photosynthesis, and leading to a major inhibition of important biochemical processes in plants (Aimar et al. 2011). The plant’s response to stress is complex due it is determined by the characteristics of the constituents that connect and contrast in their individual reactions according to the intensity and duration of the water deficits and temperature. Since water stress continues, plants take certain protection strategies against these stress conditions include: A) a cascade of signs ranging from essential reactions to auxiliary reactions (Haggag Wafaa et al. 2017), B) at the cellular level biochemical restrictions can prevent the photosynthetic CO2 fixation (Ennahli and Earl 2005; Galmés et al. 2007). These responses enable plants to adapt to the temporary water stress in the short term, nonetheless, the effects of antioxidants and enzymatic activities cannot cope with severe or prolonged water stress (Tan et al. 2006).

Under these circumstances, despite there were reductions in yield as temperatures and evapotranspiration increased, the adoption of certain management practices (i.e., proper irrigation, optimum sowing date, compost, and tillage), capable to alleviate these negative impacts, improve yield and decrease ET (Attia et al. 2022). One of management practice is applying chitosan, which has been proposed to help reduce oxidative damage caused by stress caused by drought in crops (Yang et al. 2009; Mohammadi et al. 2021). The scavenging mechanism of chitosan can be linked to its structure, which has many available hydroxyl and amino groups interacting with reactive oxygen species (ROS) such as superoxide radicals, hydrogen peroxide, hydroxyl, and singlet oxygen that are toxic to plants (Li et al. 2002; Sun et al. 2004). Generally, chitosan is an N‑polysaccharide formed by the deacetylation reaction of chitin, it is a naturally degradable substance and derived from the crustacean shield (Bautista-Baños et al. 2006; Duan et al. 2019). Chitosan is divided into three reactive groups, and it should be noted that the amino group is generally preferred because it is more reactive than the other two hydroxyl groups (Jayakumar et al. 2008; Badawy and Rabea 2011). Recently it has attracted much attention owing to its unique biological and physiological properties, for example, it can increase the growth and development of plants under normal conditions and water deficiency which positively changes several characteristics (dos Reis et al. 2019). In addition, chitosan caused an increase in plant height, the number of shoot branches and leaves, leaf area, biomass characteristics, and cereal yield for several plant species, such as maize (Guan et al. 2009). Also, the recent results have shown that chitosan has the potential to work and acts as an antitranspirant agent and an efficient elicitor under agricultural stress conditions which allows fulfilling an important role in stimulating defense mechanisms (Hadwiger 2013).

On the other side, foliar potassium silicate application has some advantages for instance, increases growth and yield production improves strength, minimizes climate stress, and provides impedance to mineral stress (Shedeed 2018; Gomaa et al. 2020). Silicon (Si) is available in large quantities in the soil and on the earth’s surface, its concentrations in the plant vegetative parts (shoot) ranging from 0.1 to 10.0% of dry weight (Liang et al. 2006). Its importance has not been proven to be an essential element for the higher plants yet, although some recent studies indicated that Si amendments have some beneficial effects on the growth of crops, including enhancing the crop tolerance to either biotic or abiotic stress (Mustafa et al. 2021; Souri et al. 2021). In addition, Si applications increase the photosynthetic activity, the stomatal conductance, and nutrients uptake (Shaaban and Abou El-Nour 2014; Rao et al. 2018), which through the foregoing ultimately leads in turn to increasing the crop growth parameters, yield and yield quality (Ahmed et al. 2007; Laane 2018; Ali et al. 2019). Therefore, applying potassium silicate as foliar spraying on plants and as a cofactor has become a pioneering approach and it has a prominent effect in the agricultural uses to enhance the growth and ameliorate the deleterious effect of water stress (Gomaa et al. 2021).

Therefore, based on the foregoing, I assume that Ch or PS application has the potential for decreasing transpiration and enhancing corn yield.

Agricultural production is also affected by climate change, in this concern Ramírez and Thornton (2015) reported that maize production is expected to decline by 12–40% due to climate change in Africa. Among several influences of climate change, its effect on sowing date, which requires an urgent need to adjust and determine the better sowing date for each crop under current circumstances. Sowing date depends not only on the environment, but also on the extent to which insects, pests and diseases are prevalent, and selection should focus on allowing critical stages of growth to escape these conditions (Anjum and Arif 2022). Initial work indicated that for each location, there is an optimal planting date for corn to improve crop yield (Hassaan 2018; Maresma et al. 2019). In Egypt, the most appropriate sowing date is between May 10 and May 20 in the Gemmiza (Lower Egypt) and Sids areas (Middle Egypt) and through July in the Mallawy area (Middle Egypt) (El-Marsafawy et al. 2012), in the same context (Hassaan 2018; Abaza 2021) mentions that sown yellow maize hybrids in the second week of August successfully improved production of maize yield and its components under Toshka conditions which are located in the south of Egypt.

The efficiency of water use has been defined as the obtained grain yield per unit of water consumed or transpired by the crop (Hatfield and Dold 2019). In order to improve crop yield, it is essential to identify evapotranspiration to proper manage irrigation water and avoid the adverse effects of water stress on plants, where proper irrigation management may prevent nutrient and yield losses caused by inadequate irrigation (Kheir et al. 2021). In arid regions the adoption of the determination of irrigation amounts based on actual evapotranspiration has attracted less attention (Srivastava et al. 2018). In this concern, Attia et al. (2022) indicated that in arid regions, adoption combination of crop models and machine learning algorithms is a powerful tool for predicting yield and water use efficiency, that are especially susceptible to climate change and water scarcity. On the other side, Kheir (2013) revealed that the seasonal water consumptive use values were ranged between 2936.3 to 3295.0 m3 fed−1 when maize plants were irrigated at 20% depletion of soil water. Moreover, the maximum value of water productivity 1.43 kg m−3 was achieved by adding 120 kg N fed−1(fed = 4200 m2) to the North Delta soils (clay soil). While Abaza et al. (2016) investigated the impact of different irrigation systems, pulse technique and silicon on maize yield and water use efficiency under the same climatic conditions of the current study, they mentioned that the average maize water use efficiency values were (0.56, 0.52 and 0.52 kg m−3) for pulse technique, irrigation system and silicon application, respectively. In addition, Abaza (2021) studied the effects of irrigation water levels and applied the filter mud cake at different sowing dates on water use efficiency indicated that the seasonal values of the actual ETa of under toshka climatic conditions were ranged between 930 and 793 mm.

Maize hybrid (Zea mays L.) is one of Egypt’s most important cereal crops, and as all C4 type plants maize has a higher capability to use CO2, solar radiation, water, and N in photosynthesis than C3 crops which leads to increase the effectiveness of water use efficiency (Abideen 2014). The yellow maize variety is rich in vitamin A (carotenoid), whereas blue, purple, and red are rich in antioxidants and phenolic compounds (Flint-Garcia et al. 2009; Chaudhary et al. 2014).

However, there have been little studies that have examined the effects of Ch &PS applications to maize with a view toward assessing the effects of these applications on enhance plant tolerance to water stress under different sowing dates. Thus, I used maize plants to test the hypothesis that Ch &PS applications would enhance yield traits and grain yield and thereby ameliorate the deleterious influences of water stress and improve the efficiency of water use and irrigation water use efficiency of maize under a drip irrigation system in Toshka—Egypt.

Materials and Methods

Experimental Site

In the south of Egypt, field experiments were conducted during the spring (March) and fall (September) seasons of 2020 and 2021 at the experimental farm of Water Studies and Research Complex station, National Water Research Center, Toshka—City of Abu Simbel which is located at the latitude of 22°, 24′.11′ N longitude of 31°, 35′.43′ E and altitude 188 m. The texture of the experimental soil is sand, and the other main physical and chemical properties are given in Table 1. The main source of irrigation water is groundwater through a well that has been dug into the area under investigation, depending on the quality of the water it has been classified as C2S1, and the chemical properties of the irrigation water are given in Table 2.

Table 1 The physicochemical properties of soil at the experimental site, Egypt
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Table 2 Water chemical properties at the experimental site during the spring and fall seasons of 2020 and 2021
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Meteorological Data

The experimental site has an arid climate with a daily average temperature ranging from 40 to 45. The meteorological data from March to September in both growing seasons were obtained from the agrometeorological station at Toshka, approximately 100 m from the experimental site. The weather data of the monthly relative humidity (%), T maximum, and minimum temperature (℃) during the 2020–2021 growing season are given in Fig. 1 in the spring and fall. The T max during spring 2020 & 2021 ranged from 33.7 to 43.1 ℃ (39.4 ℃ as mean) and T min was ranged from 16.4 to 24.7 ℃ (21.6 ℃ as mean). While, the T Max for fall 2020 & 2021 ranges from 24.2 to 40.0 ℃ (31.6 ℃ as mean), the T Min was ranged from 8.4–23.3 ℃ (15.8 ℃ as mean).

Fig. 1
figure 1

The weather data of the monthly relative humidity (%), T maximum, and minimum temperature (℃) during the 2020–2021 growing season

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Experimental Details

In order to accomplish the purpose of this study two similar experiments were chosen, and the sowing dates (spring sowing date—Sd1 and fall sowing date—Sd2) were allocated in the main plot, then a strip-plot design with five replicates was used. The vertical plots were allocated to the two irrigation water levels, i.e., 100 and 70%, whereas the horizontal plots were devoted to the four foliar application rates, namely, 0 (control—spray with pure water), 250 (mg l−1) chitosan, 500 (mg l−1) chitosan, 1000 (mg l−1) potassium silicate, 2000 (mg l−1) potassium silicate. The foliar chitosan was sprayed four times every 15-day initiated after 4 weeks of emergence, while potassium silicate (K2SiO3) (10% K2O, 25% SiO2) as foliar spraying has been applicated three times at 40, 60, and 80, days after sowing. The experimental area of each plot was 5 × 3 m (15 m2) with five lines, the experimental site was irrigated by drip irrigation.

Management Practices

The fertilization recommendations and field practices of the Ministry of Agriculture in Egypt for the newly reclaimed soils were implemented as follows: with the preparation of the soil before sowing phosphorous fertilizer has been added at the rate of 710 Kg ha−1 with calcium super phosphate (15% P2O5), while at a rate of 235 Kg ha−1 potassium sulfate (48% K2O) has applied in three equal portions, at 60, 75, and 90 days of cultivation. Nitrogen as ammonium nitrate (33.5% N) was applied in equal portions on a basis of 950 kg ha−1, it started after 15 days of sowing and was repeated every 3–4 days at a rate of 50 kg per portion until it reached the flowering stage. The cultivar of maize (Zea mays L.) was Triple Hybrid Giza 352, which is resistant hybrid to late wilt, the most appropriate date for planting is during the month of May and lasts until August, and the harvesting takes place 110–120 days after planting. In the Sd1 and Sd2 seasons of 2020 and 2021 maize seeds were sown in hills at a rate of 35 kg ha−1 on the 15th of March and 15th of September, respectively. The maize seeds were sown on one side of the dripper’s jet. The spacing between the plants was 20 cm, the spacing between the rows was 50 cm, and the depth was 5 cm. Two seeds were drilled, and about 2 weeks after emergence, it was thinned to ensure a plant per hill to maintain the population density at 10 plants m−2 (100,000 plants ha−1).

Calculations Related to Irrigation

Crop Evapotranspiration (ETc)

The reference evapotranspiration of maize (ETo) was calculated using the weather data obtained from Toshka agrometeorological station by using Fao Penman-Monteith (Allen et al. 1998). While ETc was determined as the following equation:

$$\mathrm{ETc}=(\mathrm{ETo}\times \mathrm{kc}\,\text{stage})$$
(1)

Where

ETc:

= the crop evapotranspiration (mm day−1).

ETo:

= the reference evapotranspiration (mm day−1).

kc:

= the crop coefficient.

The irrigation water applied (100% Ir) was calculated according to the equation of James (1988) as follows

$$\mathrm{Ir}=\frac{\mathrm{ETc}+\mathrm{Lf}}{\mathrm{ER}}$$
(2)

Where

Ir:

= the irrigation water applied (mm).

Etc:

= the crop evapotranspiration (mm).

Lf:

= the leaching factor 10% (since electrical conductivity of soil solution is low, LR was neglected).

ER:

= the irrigation system efficiency% (the efficiency for drip irrigation = 85%).

The irrigation amounts for the other treatments were proportionally obtained from the (100% Ir) treatment. The ETc and Ir which are applied to maize crops at the different growth stages during the growing seasons 2020 and 2021 are presented in Table 3.

Table 3 The crop evapotranspiration and irrigation water applied for maize at different growth stages during the spring and fall seasons of 2020 and 2021
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Water Use Efficiency (Wue)

Mathematically the water use efficiency (Wue) can be represented as:

$$\mathrm{Wue}=\left(\frac{\mathrm{Y}}{\mathrm{ETc}}\right)$$
(3)

Where

Wue:

= water use efficiency (kg m−3)

Y:

= yield (kg ha−1) and

ETc:

= equals seasonal actual evapotranspiration (mm).

Irrigation Water Use Efficiency (Iwue)

The irrigation water use efficiency (Iwue) can be represented as:

$$\text{Iwue}=\left(\frac{\mathrm{Y}}{\mathrm{Ir}}\right)$$
(4)

Where

Iwue:

= irrigation water use efficiency (kg m−3)

Y:

= yield (kg ha−1) and

Ir:

= irrigation water applied (m3 ha−1).

Measurements

After 60 days of planting, composite plant samples were taken from each experimental unit to record the plant height, each consisting of five plants. To measure the growing parameters of maize, the three middle rows were harvested. After the border rows were excluded, the plants were harvested to determine the grain yield and yield components: number of ears plant−1, (thousand) grain weight, number of row/ears, ear length, and weight (g).

Statistical Analysis

Differences between treatments were analyzed through analysis of variance (ANOVA) and the significance of differences between the experimental treatment data means were analyzed and tested using the least significant difference (LSD) multiple range tests (at the p ≤ 0.05 level) with SAS version 9.1 (SAS Institute, Cary, NC, USA) using a factorial arrangement to assess individual effects and interaction.

Results

Maize Growth Yield Characteristics as Affected by Sowing Date, Water Levels and the Application of Ch and PS

The individual effect of the treatments for sowing dates, irrigation levels and foliar application rates of Ch and PS (p < 0.05), as well as the interaction effects of sowing dates × irrigation regimes × foliar application rates of Ch and PS (p < 0.05) on maize growth yield characteristics are given in (Table 4 and 5). Regarding the individual effect of the irrigation levels in Sd1, the results refer to a negative significant effect on most growth characteristics (comparison between C100 with C70) except for (ear weight and grain index). In the contrast, the results mention that in Sd2 there were fluctuated influences, the adoption of Ir70 has positive significant impacts on (ear length, number of ears/plant and number of rows/ear), as seen in (Fig. 2).

Table 4 Summary of combined F significance from analysis of variance
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Table 5 Continue
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Fig. 2
figure 2

Average plant height, ear length, number of ears per plant, number of rows per ear, ear weight and grain index of maize as affected by sowing date, irrigation levels, chitosan, and potassium silicate, during the spring and fall growing seasons of 2020/2021. Vertical bars represent ± standard error (SE) of the means. Bars with different letters are statistically significant at p ≤ 0.05. Abbreviations: Control (spray with pure water); Ch 250 (spray with 250 mg l−1 chitosan); Ch 500 (spray with 500 mg l−1 chitosan); PS 1000 (spray with 1000 mg l−1 potassium silicate); PS 2000 (spray with 2000 mg l−1 potassium silicate);100% Ir (applying 100% of irrigation water applied—represent full irrigation level); 70% Ir (applying 70% of irrigation water applied—represent limited irrigation scheme); Sd1(spring sowing date); and Sd2 (fall sowing date)

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By comparing the adoption of the same applications of Ch and PS treatment, it was found that under Ir100 in Sd1, the adoption of the higher concentration rates of Ch caused in significant improvements differences in (plant height, number of ears/plant and number of rows/ear), while under Ir70 there had no significant differences. Likewise, in the Sd2 season, it was found that under Ir100 the adoption of the higher concentration rates of Ch caused significant improvements in (ear length and grain index), while under Ir70 there had no significant differences in growth yield characteristics.

Maize Grain Yield, WUE, and IWUE as Affected by Sowing Date, Water Regimes, and the Application of Ch and PS

Based on the results illustrated in (Fig. 3a), by comparing the control treatment, the gained results mention that under Ir100 planting maize seeds in the Sd2 caused an increase in grain yield than spring Sd1 by 29.7%, also it was increased with using Ir70 by 33.0% under the same circumstances.

Fig. 3
figure 3

Average maize yield, water use efficiency, and irrigation water use efficiency as affected by sowing date, irrigation levels, chitosan, and potassium silicate, during the spring and fall, growing seasons of 2020/2021. Vertical bars represent ± standard error (SE) of the means. Bars with different letters are statistically significant at p ≤ 0.05. Abbreviations: Control (spray with pure water); Ch 250 (spray with 250 mg l−1 chitosan); Ch 500 (spray with 500 mg l−1 chitosan); PS 1000 (spray with 1000 mg l−1 potassium silicate); PS 2000 (spray with 2000 mg l−1 potassium silicate);100% Ir (applying 100% of irrigation water applied—represent full irrigation level); 70% Ir (applying 70% of irrigation water applied—represent limited irrigation scheme); Sd1(spring sowing date); Sd2 (fall sowing date); Wue (water use efficiency); and Iwue (irrigation water use efficiency)

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On the other side, the foliar application of Ch and PS leads to obtaining more enhancement on grain yield than the control treatment under each irrigation level, for instance, in the Sd1 under Ir100 it was raised by 37.2, 80.5, 6.9, and 59.0% for Ch250, Ch500 PS1000 and PS2000 treatments, respectively. In the same context, in the Sd2 under Ir100 it was raised by 17.4, 31.2, 17.4, and 27.7% for Ch250, Ch500 PS1000, and PS2000 treatments, respectively.

By comparing the control treatment, a lower maize yield was obtained with sowing maize seeds in the Sd1 season, as can be seen in (Fig. 3a). Furthermore, by comparing the application of Ch and PS treatment in Sd1 under Ir100, a higher maize yield was obtained with adopting Ch500 in contrast to adopting the other applications. Likewise, in the Sd2 season, it was found that under Ir100 or Ir70, a higher maize yield was obtained with adopting Ch500 which was significantly equaled adopting Ir70 × foliar applications of PS2000. In the same context, the superiority of the adoption of the higher concentration rates of Ch and PS under Ir100 or Ir70 irrigation level is still pronounced in attaining the highest maize yield in the Sd1 and Sd2 except with adopting higher concentration rates of PS in the Sd1 × the adoption of Ir100.

On those grounds, by comparing the control treatment, a lower maize Wue was obtained with sowing maize seeds in the Sd1 season, as can be seen in (Fig. 3b). Furthermore, the obtained results showed that the highest Wue values were attained by applying Ch500 or PS2000 as a foliar application and irrigating maize plants at Ir100 in the Sd2 which caused increases in Wue reach to 30.6% than the control treatment which were significantly equaled applying foliar applications of PS2000 × adopting Ir70 irrigation level for attaining the highest Wue in the second season—Sd2.

By sowing maize seeds in the Sd2 and applied Ch500 × the adoption of Ir70 irrigation level, caused in increases of Iwue by 63.0% than the control (C70), which allowed to confer irrigation water at par with attained the highest Iwue.

In this respect, adopting Ir70 × foliar applications of Ch250, PS2000 and PS1000 were significantly equaled control treatment under Ir70 for attaining the lowest Iwue in the Sd1. Likewise, in the Ir100, the adoption of PS1000 applications were significantly equaled the control treatment for attaining the lowest Iwue. In the same context, the results in (Fig. 3c) indicated that the highest Iwue values in the first season were obtained with adopting Ir100 or Ir70 irrigation level and applying Ch500 applications. While in the Sd2, it was obtained by adopting the limited irrigation level- Ir70 × foliar applications of Ch250 or Ch500.

Discussion

Agricultural policies that use less water must be adopted to improve the efficiency of water use in irrigation by focusing on agronomic management (Ghazy 2021). Maize is generally known to be heavily irrigated and sensitive to water stress, while having the ability to cope with a short period of water stress, however, water stress caused numerous influences on the morphological and the photosynthesis process which ultimately caused decreased dry matter accumulation (Rekaby et al. 2017; Gheysari et al. 2017). Thus, this study sought to find the equilibrium between maize water requirements and the current changes in the climatic situation and available irrigation issues.

The Effect of Sowing Date

Sowing date constitutes one of the prominent factors that limit maize crop yield and is also a fundamental factor in determining yield. Accordingly, determining the optimum sowing date is considered essential to crop production, as the planting date depends on the temperature since an increase in temperature affects crop yield due a shorter duration of different growing seasons (Harrison et al. 2011; Ahmad et al. 2018). The obtained results indicated that Sd2 leads to attaining a higher maize yield than the Sd1, this due to the suitable climatic condition in the fall which allows for maize plants to growing better such as (suitable temperature, humidity, less transpiration, etc), these results are closed to those obtained by (Hassaan 2018; Abaza 2021). In this concern, as the other crops maize plants are susceptible to climate change (high temperature, precipitation, and CO2), however, the temperature showed more negative impacts on crop yield than other variables (Ottman et al. 2012; Wheeler and Von Braun 2013). Moreover, increased mean temperatures have been shown to reduce the actual growth period between planting date and crop maturity due to accelerated crop development, and although that enhancing filling, the fill rate cannot compensate for these temporal constraints which leads to a decrease in biomass accumulation and yields (Dias and Lidon 2009; Wang et al. 2009; Asseng et al. 2011). Hence, it’s worth noting that the average climatic data which has been recorded in the spring and fall seasons of 2020 and 2021 indicated that the mean maximum and minimum temperatures were (40.0–23.3) in September, (35.9–20.3) in October, (30.4–15.0) in November, and (27.6–11.8) in December, respectively, while it was (33.7–16.4) in March, (38.1–19.3) in April, (40.9–23.5) in May, (41.3–24.3) in June, and (43.1–24.7) in July, respectively, as seen in (Fig. 1). Through the obtained results herein, it’s interesting to point out that at higher temperatures than 32 °C most significant effects occur on starch production and grain weight, resulting in lower fill rate and causing deterioration of the quality of maize cereals (Wilhelm et al. 1999; Siebers et al. 2017), furthermore according to (Waqas et al. 2021) they mention that stress caused by high temperatures limits pollen viability and silk receptivity, resulting in significant reductions in grain yield. In addition, referring to the obtained data that has been recorded for the mean maximum and minimum temperatures in the period from 2005 to 2007 reached (39.4–23.4) in September, (36.8–21.1) in October, (29.2–13.8) in November, and (34.2–18.6) in December, respectively, while it was (31.5–13.2) in March, (36.1–17.8) in April, (39.8–22.7) in May, (41.7–24.3) in June, and (42.3–24.5) in July, respectively. As such it is important to note that simply increasing the average seasonal temperature by 1 °C can reduce the economic production of the maize crop by 3% to 13% (Izaurralde et al. 2011). Thus, through the forgoing clarified the prominent impact of climate change which involves the importance of rearrangement of the common recommendations that related to the optimum sowing dates in south of Egypt and other similar areas.

The Effect of Water Levels

The obtained data indicated that the adoption of Ir70 provides better maize yield and wue than Ir100, particularly in the Sd2 sowing dates. I assumed that attribute to improvements in the yield characteristics, which were in agreement with those obtained by (Atta 2007; Rekaby et al. 2017; Wang et al. 2022). Furthermore, I concluded that with exposing maize plants to water stress in the fall season there were several interrelated factors that could partly ameliorate the impact of these circumstances among them the short span of time which plants have exposed to water stress, viz when the sowing date was shifted from the middle of March to the middle of September this status allowed plants to exceed the negative impact of water shortage by escaping strategy which based on the ability to complete its life cycle after exposure to water shortage as long as that didn’t exceed the critical point at par with availability of suitable climatic conditions for growth in the studying area, in this case, plants do not suffer from water deficiency due they are capable of modulating their vegetative and reproductive phenology according to the most favorable period, which is consistent with (De Micco and Aronne 2012). Moreover, planting maize seeds in the fall works in decreasing the growing period which reaches to 100–110 days approximately, conversely planting maize seeds in the spring the growing season reaches 135–140 days. These reasons are accompanied by the self-ability of maize to cope with short periods of water stress resulting in maintaining the yield profitability at acceptable values in the fall, these findings are in harmony with the study of (Kulczycki et al. 2022).

The Effect of Chitosan and Potassium Silicate

The current results showed that at Sd1 & Sd2 applying Ch and PS as a foliar application on maize plants fulfills pronounced improvements in yield, Wue, and Iwue under full irrigation (Ir100) or stress treatment (Ir70). The previous findings attributed to the numerous benefits that Ch and PS confer, this effect has been widely studied among them that Ch has an important effect on plant growth by catalyzing cell growth and development, increasing the activity of key enzymes in nitrogen metabolism, and enhancing nitrogen transfer, leading to increased yield (Guan et al. 2009; Mondal et al. 2013; dos Reis et al. 2019; Mohammadi et al. 2021). On other hand, applying PS not only improved physiological and agronomic features affecting crop growth and yield through optimum treatment of the water supply but has also mitigated the negative impacts of water stress. Generally, the application of PS enhances growth, seed yield, and WUE, thus it is an appropriate management strategy (Eyni-Nargeseh et al. 2022). In this regard, Artyszak (2018) hypothesized that such increases in yield, yield components, and WUE attributed to the promotion of photosynthetic activities and optimal growth conditions in PS-treated plants, moreover Li et al. (2018) indicated that plants treated with silicon produce respectively 35% more biomass and 24% more grain yield than untreated treatment.

Furthermore, the gained results clarified that the favorable impacts were rising steadily by using the higher concentrations of Ch and PS, such findings are in parallel with those obtained by (Chibu and Shibayama 1999; Mondal et al. 2013; Shedeed 2018) they demonstrated that the morphological and the physiological traits, and yield was improved by using the higher rates of foliar Ch and PS. In this regard, (Kamenidou 2005; Wang et al. 2022) recommended that a number of horticultural plants have been improved through supplementation in Si according to the source, the rate, the Si content, and its deposit in plant tissues which varied from one species to another. On the other side, the results point out to the immense improvements in yield by the adoption of Ch500 which were superior than the PS2000 under Ir100 and Ir70, these findings attribute to the butter solubility of Ch than PS particularly after adjustment pH of Ch by diluting acetic acid, this finding is corroborated by (Almeida et al. 2020).

On the other hand, the obtained results demonstrated that adoption of the higher Ch concentrations in Sd1, lead to better improving maize yield particularly under Ir70, while the adoption of the higher concentrations of PS in Sd2, lead to better improving maize yield particularly under Ir70 (Fig. 3a). In this concern, I conclude that in Sd1 due to the increments of the weather conditions, confer the educated amounts of water within the plant tissues are considered a crucial factor, while in Sd2 the main crucial factor is the reduction of the growing season (90–100 day). Therefore, with the adoption of the higher Ch concentrations under Ir70 although plants have severed of increasing climate conditions, it appears that Ch applications form a transparent layer reducing perspiration, which in turn worked on the maintenance of water within the tissues of plants that was useful for the mitigation of harmful effects of the reduction in soil moisture (Roychoudhury et al. 2022). Therefore, the multiple features of Ch500 work on ameliorating unfavorable effects of water stress in growth and yield, these findings are parallel to those obtained by (Malerba and Cerana 2015; Hidangmayum et al. 2019). Whilst, it appears that the adoption of higher PS applications in Ir70 treatment at (Sd2) attained better yield. In this context, I hypothesized that in Sd2 the higher humidity rates seems it worked on in more improvements in PS solubility, which perform some features such as improving the nutrients transportation and accumulation, which has led to the enhancements of yield.

From the foregoing, the impacts of Ch &PS applications on maize plants sowing in spring or in fall sowing dates and exposure to water stress were clear. It’s quite important noted that the obtained results indicated the positive impact of identify the optimum sowing dates and irrigation level. However, there are some obstacles facing that such as (the competition between crops, insects and diseases). The obtained results recommended sowing maize during the fall season, which will lead to the inability to sow an important crop (i.e., wheat, barley, faba bean etc.). Therefore, the competition between crops on the available cultivation area remains the main limitation, thus I suggest that the better crop for sowing will be identified, in accordance with the highest wue. Furthermore, by sowing maize during the fall season, as humidity increased, more insects and diseases arose, particularly fall armyworm insect. Where maize is the preferred host for fall armyworm insect in the countries (Rashed et al. 2022). It can decrease annual maize yield from 21% to 53% without control methods (Huang et al. 2020). However, in the current study noticed that it’s appearance and damage was more detected in the spring season. On the other side, regarding the enhancing of the diseases during the fall season, the current study noticed that the Ch &PS applications enhance maize tolerance. In this concern, Kocięcka and Liberacki (2021) demonstrates that this Ch is very effective against diseases and pathogens that are most dangerous to cereals, which have been broadly emerging at the Sd1 than Sd2.

Conclusion

As a consequence of water scarcity and severe changes in climate, the irrigation water conservation has become an urgent priority. This research provides new information about the impact of the separate foliar application of chitosan and potassium silicate on stressed plants and studies their reflection on the efficiency of water use. The main conclusions of this study include: (1) irrigate maize plant of 70% of irrigation water applied, provides better maize yield and water use efficiency than the adoption of the full irrigation level, particularly in the fall sowing date; (2) maize yield could be increased by applying foliar applications of chitosan at the rate of 500 mg l−1, or potassium silicate at the rate of 2000 mg l−1 particularly with the adoption of 70% of irrigation water applied. Nonetheless, sowing the seeds in the fall season showed a more positive increase; (3) the tested applications were similar in their influences on maize yield although the adoption of the higher Ch concentrations in the spring, lead to better improving maize yield particularly under 70% of irrigation water applied, while the adoption of the higher concentrations of potassium silicate in in the fall, lead to better improving maize yield particularly under 70% of irrigation water applied; (4) Also, the findings of this study indicated that there are some obstacles facing the identification of the optimum sowing dates and irrigation level such as (the competition between crops, insects and diseases), further studies are required to observe the obstacles on other similar areas. Overall, as a consequence that water is considered the crucial factor in arid regions, thus it seems to be logical for recommended sowing maize in the fall and applying chitosan four times as foliar applications with concentrations at 500 (mg l−1), which mitigates water stress impacts in the arid regions as this study and other similar areas and rises water use efficiency of the maize crop.