1 Introduction

Ensuring food security is an enormous challenge for the world due to insufficient crop yields for direct human consumption, diminished water supplies, and the deterioration of agricultural lands (Hemathilake and Gunathilake 2022). The agricultural economy has been significantly impacted by climate change in recent years due to water scarcity and the resulting desertification especially in dry and semi-dry regions (Oladosu et al. 2022; Junaid and Gokce 2024). Food security depends greatly on wheat cultivation. Wheat is considered a strategic crop that contributes to bridging the food gap for the world population. For approximately 35% of the world’s population, wheat is the staple crop, and more than two thirds of the wheat produced worldwide is consumed for food (Grote et al. 2021). Wheat is an important food crop next to rice in terms of consumption (Senbeta and Worku 2023). Nowadays, wheat is cultivated more extensively than any other crop, accounting for 20% of our protein and carbohydrates and over 25% of the world’s total output (Langridge et al. 2022). In Egypt, it is necessary to expand wheat cultivation on newly reclaimed soils to cope with population growth. The soils of most newly reclaimed areas are coarse-textured and have a higher proportion of sand fraction comparing to the other fractions (silt and clay). These soils are generally characterized by poor physical and chemical properties such as rapid permeability, low capacity of water holding, low cation exchange capacity (CEC), inherent poor fertility, low content of organic matter (OM), and low productivity (Huang and Hartemink 2020). Various soil amendments could be added these characteristics. Super absorbent polymers (SAPs) and biofertilizers have become significant agricultural amendments for enhancing the soil quality and health as well as crop productivity (Zhang et al. 2018; Zheng et al. 2023).

As soil conditioners, Superabsorbent polymers (SAPs) are indeed a type of hydrogel, they consist of hydrophilic polymers, such as polyacrylic acid (PAA) and polyacrylamide, which are 3D crosslinked to form a network structure (Takahashi et al. 2023). The crosslinking agents used in SAPs can be polycations or other chemicals that help to create a stable network structure (Lee et al. 2020). SAPs have the ability to absorb and retain large volumes of water. Through their water retention and controlled release properties, SAPs help reduce irrigation requirements, enhance water use efficiency, and stop rapid water loss through evaporation and drainage (Dingley et al. 2024). As the soil dries, the water that has been held in the SAPs is released gradually through a diffusion mechanism, allowing the soil to stay wet for a longer period of time, thereby promoting plant growth and soil microbial activity (Khodadadi Dehkordi 2018; Albalasmeh et al. 2022). By adding SAPs to the soil, aggregate stability and soil structure are improved. This has the benefit of increasing soil porosity, which improves soil microbial and plant root oxygen circulation (Oladosu et al. 2022). SAPs work as agents for slow-release fertilizers, improve soil nutrient retention, and raise plant nutrient availability. Water-soluble nutrients are more readily available for plant uptake due to SAPs’ superior ability to absorb and retain water. This reduces nutrient loss by leaching in the soil and minimizes the groundwater contamination risk (Singh et al. 2021). In order to increase sustainable agricultural output in the event of soil water challenges and as a soil conditioner, using hydrogel will be a productive choice (Sri et al. 2019).

Due to the increased awareness of the usage of sustainable tools that pose less risk in the agricultural sector, biofertilizers have emerged as a safe and efficient alternative to the chemically manufactured fertilizers in recent times (Sharma et al. 2023). Biofertilizers are preparations in laboratory containing beneficial and efficient strains of living microorganisms such as bacteria, fungi and actinomycetes (Zambrano-Mendoza et al. 2021; Farhad et al. 2023). These microorganisms are applied to soil, seeds, or plants, they play an important role in the sustainable agriculture by their ability to colonize the rhizosphere or the inside of plants, promoting nutrient mobilization, improving soil fertility and plant growth (Khan et al. 2023). Biofertilizers can contain one or more microbial strains and are added in a variety of formulations, including liquids (suspensions), powders, and granules (Díez-Méndez et al. 2024). They can improve plant nutrient availability, increase productivity, enhance the agroecological environment, replenish the soil’s beneficial bacteria and microbial population (Zhang et al. 2018; Fasusi et al. 2021; Nosheen et al. 2021). Biofertilizers based on Bacillus sp., Trichoderma sp., and Actinomycetes sp. have shown significant benefits in agriculture. They can nourish plants and protect them from a variety of plant diseases and stressful environments through natural processes such as nitrogen fixation, hormone generation, siderophore synthesis, potassium and phosphorus solubilization, and the development of several hydrolytic enzymes (Zambrano-Mendoza et al. 2021; Chaudhary et al. 2022; Shankar and Prasad 2023).

In Egypt, the use of biofertilizers as a cheap and clean substitutional to chemical fertilizers is still not widespread, especially in the recently reclaimed soils of arid and semi-arid regions that suffer from coarse texture, low moisture holding ability, high temperatures, and evaporation rates, as these factors together constitute a threat to the survival and functioning of biofertilizer microbes. This study was carried out in the research farm of Sohag University, New Sohag City, southwest of Sohag governorate in Egypt. Climatically, Sohag Governorate is a part of the arid belt of Egypt which has warm winter with scarce or no rainfall and hot summer (Elbeih et al. 2011; Omran 2008). Our hypothesis is that when using biofertilizers in the coarse-textured soils of the dry and semi-dry regions, adding polymers increases the efficiency and effectiveness of biofertilizer microbes because these polymers increase water retention in the soil for a longer period, which is a crucial factor for the activity and proliferation of beneficial microbes. In addition to the role of these polymers in improving soil structure and aeration, which reflect positively on the performance of those microbes. This study aimed to investigate the effect of super absorbent polymers addition in combination with some biofertilizers such as Trichoderma sp., Actinomycetes sp. and Bacillus sp. on soil chemical characteristics and fertility as well as the wheat’s growth and productivity in sandy loam soil.

2 Materials and Methods

2.1 Soil Characterization

The experiment was carried out in the Sohag University’s agricultural farm in New Sohag City, which is situated at the western boundary of the Nile valley, approximately 15 km southwest of Sohag City (26°28’ 13” N and 31°40’ 20” E). The used soil air dried, grinded in a wooden mortar, and then sieved using 2 mm sieve. The sieved soil was analyzed for some properties as follows; the particle size distribution was determined based on the international pipette procedure (Piper 1950). The pressure plate membrane apparatus (Soilmoisture Equipment Corp, USA) was used for field capacity (FC%) and wilting point (WP%) determination in the studied soil (Black 1965), and the available water (AW%) calculated by subtracting the WP percentage from FC percentage. A 1:2.5 soil to water suspension was prepared for measuring soil pH by using pH meter (pH 211 microprocessor, HANNA Instruments, UK) and a glass electrode (McLean 1982). The electrical conductivity (EC) of soil was determined using the EC meter (Orion 150, USA) in a 1:5 soil to water extract (Jackson 1973). The organic matter (OM) % in the studied soil was determined according to the wet oxidation of Walkley and Black procedure (Jackson 1973). The alkaline permanganate method (Subbiah and Asija 1956) was used for available nitrogen (N) determination by Kjeldhal equipment (Automatic distillation system Rapidstill II, Labconco, USA). The sodium bicarbonate (0.5 M, with pH = 8.50) solution used for extraction the available phosphorus (P), and the extractable P was analyzed calorimetrically using the spectrophotometer (Jenway 7305 Bibby Scientific Ltd, UK) according to Olsen et al. (1954) method. The ammonium acetate (NH4OAc) solution (1 M) was used for extraction the available potassium (K) (Carson 1980), the extractable K was measured using the flame photometer (Clinical PFP7 Buck Scientific, USA). The available micro-nutrients (Fe, Mn, Zn, and Cu) were extracted by using the DTPA solution (DTPA 0.005 M, 0.1 M triethanolamine, 0.01 M CaCl2 at pH = 7.30) (Lindsay and Norvell 1978) and measured using atomic absorption spectroscopy (210VGP, Buck Scientific, Inc., USA). The characterization of the studied soil is shown in Table 1.

Table 1 Characterization of the studied soil
Full size table

2.2 Soil Amendments

2.2.1 Superabsorbent Polymers (SAPs)

Two types of superabsorbent polymers (P) were employed in this study. The first type (P1), named “Barbary Plant G3”, obtained from Lucky Star TG, Egypt. Barbary Plant G3 is composed of hydro polymer enriched with macro-nutrients (N, P, and K) and micro-nutrients (Fe, Mn, Zn, Cu, Br, and Mo), and growth regulators. The second type (P2) named Aqua Gool (AG), it is a Russian production and composed of hydro potassium polymer (90%) and polyacrylamide allylamine hydrochloride. Table 2 shows the characteristics of these polymers. These polymers were thoroughly mixed with the studied soil at a level of 0.2% (w/w) in our pot experiment.

Table 2 Characterization and elemental composition of the used superabsorbent polymers (SAPs)
Full size table

2.2.2 The Studied Biofertilizers

Four microbial isolates, selected as biofertilizers, were obtained from the stock cultures of the Plant Pathology Department, Faculty of Agriculture, Sohag University, Egypt. These isolates included one strain of the fungus Trichoderma (Trichoderma harzianum Rifai), two strains of Actinomycetes sp. (Streptomyces rochei and Streptomyces atrovirens), and one strain of the bacterium Bacillus (Bacillus subtilis).

2.2.3 Preparation of Microbial Inoculants

The microbial inoculants preparation involved growing the microbial isolates in 250 ml conical flasks containing 200 ml of specific nutrient media. For Bacillus subtilis and Actinomycetes sp. (Streptomyces rochei and Streptomyces atrovirens), nutrient glucose agar (NGA) broth medium (5.0 g pepton, 3.0 g beef extract, 5.0 g glucose, 20.0 g agar in 1 L of distilled water, pH 7.0) was used (Dowson 1957), while Trichoderma harzianum was grown in potato dextrose agar (PDA) broth medium (200.0 g potato infusion, 20.0 g dextrose, 15.0 g agar in 1 L of distilled water, pH 6.0) according to Anonymous (1968). Incubation was carried out on a rotary shaker (150 rpm) at controlled temperatures and durations (25 °C and 3 days for Bacillus and Actinomycetes, 28 °C and 14 days for Trichoderma). After incubation, the resulting microbial suspensions were adjusted to specific concentration (5 × 104 CFU ml− 1 for Trichoderma and 5 × 106 CFU ml− 1 for Actinomycetes strains and Bacillus) using sterilized distilled water (SDW) and a hemocytometer (Precicolor HBG, Germany).

2.3 Pot Experiment

The pot experiment was carried out in a completely randomized design with three replicates. Plastic pots of 35 cm (diameter) and 30 cm (depth) were utilized. Every pot was filled with 8.5 kg of the studied dried soil. The experiment consisted of 15 treatments in 3 replicates, these treatments are summarized as the following:

  1. 1.

    Control soil (CK).

  2. 2.

    Soil + Polymer 1 (P1).

  3. 3.

    Soil + Polymer 2 (P2).

  4. 4.

    Soil + Trichoderma (Trichoderma harzianum) (T).

  5. 5.

    Soil + Actynomicetes1 (Streptomyces rochei) (AC1).

  6. 6.

    Soil + Actinomycetes 2 (Streptomyces atrovirens) (AC2).

  7. 7.

    Soil + Bacillus (Bacillus subtilis) (B).

  8. 8.

    Soil + Polymer1 + Trichoderma (Trichoderma harzianum) (P1T).

  9. 9.

    Soil + Polymer1 + Actynomicetes1 (Streptomyces rochei) (P1AC1).

  10. 10.

    Soil + Polymer1 + Actinomycetes 2 (Streptomyces atrovirens) (P1AC2).

  11. 11.

    Soil + Polymer1 + Bacillus (Bacillus subtilis) (P2B).

  12. 12.

    Soil + Polymer 2 + Trichoderma (Trichoderma Harzianum) (P2T).

  13. 13.

    Soil + Polymer 2 + Actynomicetes1 (Streptomyces rochei) (P2AC1).

  14. 14.

    Soil + Polymer 2 + Actinomycetes 2 (Streptomyces atrovirens) (P2AC2).

  15. 15.

    Soil + Polymer 2 + Bacillus (Bacillus subtilis) (P2B).

The studied polymers thoroughly mixed with soil before cultivation at a level of 0.2% (w/w). The wheat seeds treated with the prepared microbial suspensions, and then another 50 ml of each suspension was added per pot during cultivation in all treatments that received microbes. Wheat seeds (Shandaweel 1 local variety) were sown in each pot on November 29, 2021. After 10 days from sowing, the wheat plants were thinned to uniform and healthy 10 plants in each pot and irrigated every 8-day intervals to the field capacity moisture level until the experiment end. After 90 days from cultivation, three plants were taken from each pot for measuring the growth parameters, including shoot length, plant fresh and dry weights, tillers and leaves number per plant, and leaf area index per plant. After that, the remained wheat plants in the pots were harvested after 160 days from cultivation and the weight of 1000 grains was determined. As regard to the climatic conditions during the growing season of the pot experiment, the average maximum temperature recorded in May 2022 was 35 °C, while the lowest recorded temperature in January 2022 was 19 °C with almost no precipitations (0.0 to 0.1 mm as monthly average). Wind speeds reaching 9 knots by May 2022 after averaging 6.6 knots in December 2021. The relative humidity decreased from 51% in January 2022 to 19% in May 2022 (https://weatherspark.com/).

2.4 Plant Analysis

The plants that taken after 90 days after cultivation were oven-dried at 70 °C until reaching a constant weight. The dried plants were grounded by using a stainless-steel mill. A 0.5 g of the grounded straw was digested using sulfuric and perchloric acid according to Chapman and Pratt (1961), then the macronutrients (N, P, and K) and micronutrients (Fe, Mn, Zn, and Cu) contents were analyzed for all treatments, following the methods outlined by Jackson (1973), to assess the effects of different applied amendments on the wheat’s nutritional status.

2.5 Soil Analysis After Wheat Harvest

After harvesting, the soil of each pot was well mixed and a soil sample was collected from each pot. Then, these collected soil samples were analyzed. The assessed soil parameters included soil pH in 1:2.5 soil to water suspension, electrical conductivity (EC) in 1:5 soil: water extract, organic matter (OM) percent, available N, P and K contents, and the DTPA-extractable micronutrients were determined in all soil samples according to the above-mentioned methods. All soil and plant analyses were carried out in soil and water department laboratory, Faculty of Agriculture, Sohag, Egypt.

2.6 Statistical Analysis

Using SPSS version 27 software, the analysis of variance (ANOVA) was performed on all of the obtained results. For comparing between means in the studied treatments, post-hoc comparisons using Duncan’s Multiple Range test was performed at a significance level of p < 0.05 (Gomez and Gomez 1984).

3 Results

3.1 Soil Chemical Properties

3.1.1 Soil pH

Data in Table 3 demonstrates that the application of polymers and microorganisms, whether individual or in combination, had considerable effect on the chemical properties of the investigated soil. Soil pH decreased in all treatment comparing with the untreated control. The highest value of 8.45 was recorded in the control (CK) treatment which significantly decreased to 8.20 and 8.36 with applying P1 and P2 treatments individually. Similarly, inoculation of soil with T, AC1, AC2, and B microbes had a clear and significant effect in reducing the pH value to 8.12, 8.27, 8.01 and 8.20, respectively compared to the control. The lowest pH value of 7.77 was observed in the P1AC2 interaction treatment.

Table 3 Effect of applied super absorbent polymers (SAPs) and microbial treatments on some soil chemical properties
Full size table

3.1.2 Soil EC

The effect of super absorbent polymers and biofertilization on soil electrical conductivity (EC) was illustrated in Table 3. It is noticeable that soil EC decreased throughout all treatments in comparison with the control soil (CK). The control treatment had the highest soil EC value of 0.61 dS m− 1. Addition of P1 and P2 polymers alone decreased the EC value significantly to 0.48 and 0.50 dS m− 1, respectively. While, amending soil with T, AC1, AC2, and B microbes only significantly reduced EC to 0.53, 0.52, 0.51, and 0.52 dS m− 1, respectively, relative to the untreated control (0.61dS m− 1). The lowest soil EC of 0.48 dS m− 1 with obtained from P1-treated soil.

3.1.3 Soil Organic Matter (SOM)

Regarding soil organic matter (SOM) content results in Table 3, a considerable enhancement was observed in SOM content as a result of polymers and micro-organisms application comparing with the control. The soil organic matter percentage increased significantly from 0.48% in control soil to 1.02 and 0.96% in P1 and P2-amended soils, and to 0.90, 0.92, 0.87 and 0.75% in T, AC1, AC2 and B inoculated soil with, respectively. For the interaction effect, treating soil with polymer P1 and Actinomycetes AC2 (P1AC2) resulted in the highest content of SOM (1.22%).

3.1.4 Available N Content in soil

The data illustrated in Table 4 showed that the hydro-polymers and biofertilizers application caused a significant improvement in the soil available N content, addition of polymers P1 and P2 only raised the average available nitrogen to 24.73 and 20.53 mg kg− 1, respectively, compared to 18.03 mg kg− 1 in the control treatment. Similarly, the T, AC1, AC2 and B microbes enhanced the available N to 21.67, 23.33, 24.10 and 19.60 mg kg− 1 by 20.19, 29.40, 33.67 and 8.71%, respectively more than the control soil. The maximum content of available N (28.03 mg kg− 1) was observed in P1AC2 treatment.

Table 4 Effect of applied super absorbent polymers and microbial treatments on some soil available macro- and micronutrients contents
Full size table

3.1.5 Available P Content in Soil

Concerning the effect of hydro-polymers and the different biofertilizers addition on the content of available phosphorus in the investigated sandy loam soil, the data in Table 4 illustrated a significant improvement in the available P status in all treated soils compared to the control soil that didn’t receive polymers or microbes. The maximum available P content (6.09 mg kg− 1) was observed in P1AC2-treated soil, while the lowest one (3.15 mg kg− 1) was recorded in control soil. Regarding to the individual effects of the studied treatments and in comparison with control, the soil available P significantly increased to 4.70 and 3.97 mg kg− 1 in P1 and P2-amended soils, respectively, and to 4.08, 3.69, 3.97, and 3.22 mg kg− 1 as a result of T, AC1, AC2, and B microbes application, respectively.

3.1.6 Available K Content in Soil

A significant increase occurred in the soil available potassium content from 84.67 mg kg− 1 in control (CK) to 120.0 and 113.00 mg kg− 1 after amending soil with the studied P1 and P2 super absorbent polymers. While, the inoculated soils with T, AC1, AC2, and B microbial strains improved the soil available K to 101.00, 97.67, 102.67, and 92.00 mg kg− 1, respectively. As interaction, the treated soil with P1 and AC2 strain recorded the highest content of available K (186.67 mg kg− 1) comparing with other treatments (Table 4).

3.1.7 Available Micronutrients (Fe, Mn, Zn, and Cu) in Soil

Data presented in Table 4 indicated that the available micronutrients (Fe, Mn, Zn, and Cu) which extracted by DTPA solution from the studied soil significantly increased by adding all polymers and microbial treatments either individually or in combination compared to the control treatment. The treatment of the interaction between P1 polymer and AC2 actinomycetes strain gave the highest available micronutrients contents (6.07 mg Kg− 1 for Fe, 3.99 mg kg− 1 for Mn, 1.09 mg kg− 1 for Zn, and 0.47 mg kg− 1 for Cu), while the lowest ones were recorded in the control treatment (4.33 mg kg− 1 for iron (Fe), 2.42 mg kg− 1 for manganese (Mn), 0.39 mg kg− 1 for zinc (Zn), and 0.21 mg kg− 1 for copper (Cu)).

3.2 Wheat Growth Parameters

3.2.1 Shoot Length

The Plant shoot length increased significantly with applications of polymers and biofertilizers compared to the unamended control (CK) soil (Fig. 1). Amending the sandy loam soil with P1 and P2 polymers improved the wheat shoot length from 61.17 cm plant− 1 in control to 70.57 and 69.67 cm plant− 1; by 15.37 and 13.90%, respectively. The integration between polymer P1 and Actinomycetes AC2 strain gave the best shoot length at all (75.17 cm plant− 1).

Fig. 1
figure 1

Effect of applied super absorbent polymers (SAPs) and microbial treatments on wheat shoot length. CK: control, P1: polymer1, P2: polymer2, T: Trichoderma (Trichoderma harzianum), AC1: Actynomicetes1 (Streptomyces rochei), AC2: Actinomycetes 2 (Streptomyces atrovirens), B: Bacillus (Bacillus subtilis), P1T: Polymer1 + Trichoderma (Trichoderma harzianum), P1AC1: Polymer1 + Actynomicetes1 (Streptomyces rochei), P1AC2: Polymer1 + Actinomycetes 2 (Streptomyces atrovirens), P1B: Polymer1 + Bacillus (Bacillus subtilis), P2T: Polymer 2 + Trichoderma (Trichoderma harzianum), P2AC1: Polymer 2 + Actynomicetes1 (Streptomyces rochei), P2AC2: Polymer 2 + Actinomycetes 2 (Streptomyces atrovirens) (P2AC2), P2B: Polymer 2 + Bacillus (Bacillus subtilis). Different lowercase letters denote significant differences (based on Duncan’s Multiple Range test at p < 0.05), and vertical bars show the standard errors (SE) of means

Full size image

3.2.2 Number of Tillers and Leaves

Polymers and micro-organisms application considerably affected the average of tillers and leaves number per plant in wheat compared to untreated control (CK) (Figs. 2 and 3). The number of tillers increased from 4.00 in CK treatment to 7.33 and 6.33 with P1 and P2 addition by 83% and 58%, and to 4.67, 5.33, 5.67 and 4.33 after treating soil with T, AC1, AC2 and B isolates, respectively by 17–42%. As regard to the interaction, the P1AC2 treatment showed the highest number of tillers (9.00 per plant). Regarding to leaves number and comparing with control (CK) treatment, there was about 28 and 43% increase in the average of leaves number as a result of polymers P1 and P2 application, whereas the microbes contributed to 6–29% more leaves. Also, the P1AC2 showed the best effect in enhancement of leaves number average (7.33 per plant).

Fig. 2
figure 2

Effect of applied super absorbent polymers and microbial treatments on the tillers number per plant. CK: control, P1: polymer1, P2: polymer2, T: Trichoderma (Trichoderma harzianum), AC1: Actynomicetes1 (Streptomyces rochei), AC2: Actinomycetes 2 (Streptomyces atrovirens), B: Bacillus (Bacillus subtilis), P1T: Polymer1 + Trichoderma (Trichoderma harzianum), P1AC1: Polymer1 + Actynomicetes1 (Streptomyces rochei), P1AC2: Polymer1 + Actinomycetes 2 (Streptomyces atrovirens), P1B: Polymer1 + Bacillus (Bacillus subtilis), P2T: Polymer 2 + Trichoderma (Trichoderma harzianum), P2AC1: Polymer 2 + Actynomicetes1 (Streptomyces rochei), P2AC2: Polymer 2 + Actinomycetes 2 (Streptomyces atrovirens) (P2AC2), P2B: Polymer 2 + Bacillus (Bacillus subtilis). Different lowercase letters denote significant differences (based on Duncan’s Multiple Range test at p < 0.05), and vertical bars show the standard errors (SE) of means

Full size image
Fig. 3
figure 3

Effect of applied super absorbent polymers and microbial treatments on the leaves number per plant. CK: control, P1: polymer1, P2: polymer2, T: Trichoderma (Trichoderma harzianum), AC1: Actynomicetes1 (Streptomyces rochei), AC2: Actinomycetes 2 (Streptomyces atrovirens), B: Bacillus (Bacillus subtilis), P1T: Polymer1 + Trichoderma (Trichoderma harzianum), P1AC1: Polymer1 + Actynomicetes1 (Streptomyces rochei), P1AC2: Polymer1 + Actinomycetes 2 (Streptomyces atrovirens), P1B: Polymer1 + Bacillus (Bacillus subtilis), P2T: Polymer 2 + Trichoderma (Trichoderma harzianum), P2AC1: Polymer 2 + Actynomicetes1 (Streptomyces rochei), P2AC2: Polymer 2 + Actinomycetes 2 (Streptomyces atrovirens) (P2AC2), P2B: Polymer 2 + Bacillus (Bacillus subtilis). Different lowercase letters denote significant differences (based on Duncan’s Multiple Range test at p < 0.05), and vertical bars show the standard errors (SE) of means

Full size image

3.2.3 Fresh and Dry Weight

The data in Fig. 4 showed an increase in the plant fresh and dry weight as a result of amending soil with super absorbent polymers and microorganisms and their interactions as compared to the control. As an individual effect, the application of P1 and P2 boosted the average of fresh weight by 68% and 65%, while the soil biofertilization with T, AC1, AC2 and B microbial strains elevated it by 34–45% over the control plant (16.33 g plant− 1 as an average). Based on the interaction between the applied treatments, the plant fresh weight average was maximum (42.03 g plant− 1) in P1AC2 treatment. The plant dry weight showed similar trends (Fig. 5), polymers application increased the plant dry weight by 50%, while amending soil with different microbial treatments improved the plant DW by 21–39%. The P1AC2 treatment showed the maximum plant DW (21.33 g plant− 1) and the lowest one was noticed in control (CK) plants (10.27 g plant− 1).

Fig. 4
figure 4

Effect of applied super absorbent polymers and microbial treatments on plant fresh weight. CK: control, P1: polymer1, P2: polymer2, T: Trichoderma (Trichoderma harzianum), AC1: Actynomicetes1 (Streptomyces rochei), AC2: Actinomycetes 2 (Streptomyces atrovirens), B: Bacillus (Bacillus subtilis), P1T: Polymer1 + Trichoderma (Trichoderma harzianum), P1AC1: Polymer1 + Actynomicetes1 (Streptomyces rochei), P1AC2: Polymer1 + Actinomycetes 2 (Streptomyces atrovirens), P1B: Polymer1 + Bacillus (Bacillus subtilis), P2T: Polymer 2 + Trichoderma (Trichoderma harzianum), P2AC1: Polymer 2 + Actynomicetes1 (Streptomyces rochei), P2AC2: Polymer 2 + Actinomycetes 2 (Streptomyces atrovirens) (P2AC2), P2B: Polymer 2 + Bacillus (Bacillus subtilis). Different lowercase letters denote significant differences (based on Duncan’s Multiple Range test at p < 0.05), and vertical bars show the standard errors (SE) of means

Full size image
Fig. 5
figure 5

Effect of applied super absorbent polymers and microbial treatments on plant dry weight. CK: control, P1: polymer1, P2: polymer2, T: Trichoderma (Trichoderma harzianum), AC1: Actynomicetes1 (Streptomyces rochei), AC2: Actinomycetes 2 (Streptomyces atrovirens), B: Bacillus (Bacillus subtilis), P1T: Polymer1 + Trichoderma (Trichoderma harzianum), P1AC1: Polymer1 + Actynomicetes1 (Streptomyces rochei), P1AC2: Polymer1 + Actinomycetes 2 (Streptomyces atrovirens), P1B: Polymer1 + Bacillus (Bacillus subtilis), P2T: Polymer 2 + Trichoderma (Trichoderma harzianum), P2AC1: Polymer 2 + Actynomicetes1 (Streptomyces rochei), P2AC2: Polymer 2 + Actinomycetes 2 (Streptomyces atrovirens) (P2AC2), P2B: Polymer 2 + Bacillus (Bacillus subtilis). Different lowercase letters denote significant differences (based on Duncan’s Multiple Range test at p < 0.05), and vertical bars show the standard errors (SE) of means

Full size image

3.2.4 Leaf Area Index

Results in Fig. 6 illustrated that the plant Leaf area index positively affected by adding of polymers and micro-organisms as well as their interactions. The leaf area index increased by 48% each over the unamended control soil for P1 and P2-amended soils, respectively. Adding T, AC1, AC1 and B microbes increased the leaf area index significantly from 12.97 cm2 in unamended control soil to 11.60, 16.76, 15.06 and 15.26 cm2, respectively. Polymers application with the microbial isolates together gave the highest average of leaf area index (22.57 cm2) in P2AC2 treatment.

Fig. 6
figure 6

Effect of applied super absorbent polymers and microbial treatments on plant leaf area index. CK: control, P1: polymer1, P2: polymer2, T: Trichoderma (Trichoderma harzianum), AC1: Actynomicetes1 (Streptomyces rochei), AC2: Actinomycetes 2 (Streptomyces atrovirens), B: Bacillus (Bacillus subtilis), P1T: Polymer1 + Trichoderma (Trichoderma harzianum), P1AC1: Polymer1 + Actynomicetes1 (Streptomyces rochei), P1AC2: Polymer1 + Actinomycetes 2 (Streptomyces atrovirens), P1B: Polymer1 + Bacillus (Bacillus subtilis), P2T: Polymer 2 + Trichoderma (Trichoderma harzianum), P2AC1: Polymer 2 + Actynomicetes1 (Streptomyces rochei), P2AC2: Polymer 2 + Actinomycetes 2 (Streptomyces atrovirens) (P2AC2), P2B: Polymer 2 + Bacillus (Bacillus subtilis). Different lowercase letters denote significant differences (based on Duncan’s Multiple Range test at p < 0.05), and vertical bars show the standard errors (SE) of means

Full size image

3.2.5 Weight of Thousand Grains

The weight of the thousand grains is a crucial factor that directly raises the economic yield. The data presented in Fig. 7 indicated that applying of polymers and microorganisms to the studied sandy loam soil both individually and in combination had a positive impact on the weight of 1000 grains per pot in wheat plants. The 1000 grains weight was the highest (47.51 g pot− 1) in P1AC2 treatment, while the lowest one (33.52 g pot− 1) was observed in the unamended control (CK) soil.

Fig. 7
figure 7

Effect of applied super absorbent polymers (SAPs) and microbial treatments on weight of 1000 grains in wheat plants. CK: control, P1: polymer1, P2: polymer2, T: Trichoderma (Trichoderma harzianum), AC1: Actynomicetes1 (Streptomyces rochei), AC2: Actinomycetes 2 (Streptomyces atrovirens), B: Bacillus (Bacillus subtilis), P1T: Polymer1 + Trichoderma (Trichoderma harzianum), P1AC1: Polymer1 + Actynomicetes1 (Streptomyces rochei), P1AC2: Polymer1 + Actinomycetes 2 (Streptomyces atrovirens), P1B: Polymer1 + Bacillus (Bacillus subtilis), P2T: Polymer 2 + Trichoderma (Trichoderma harzianum), P2AC1: Polymer 2 + Actynomicetes1 (Streptomyces rochei), P2AC2: Polymer 2 + Actinomycetes 2 (Streptomyces atrovirens) (P2AC2), P2B: Polymer 2 + Bacillus (Bacillus subtilis). Different lowercase letters denote significant differences (based on Duncan’s Multiple Range test at p < 0.05), and vertical bars show the standard errors (SE) of means

Full size image

3.3 Macronutrients (N, P, and K) Content in Wheat Plants

3.3.1 Nitrogen (N) Content

The wheat plants in the unamended control soil (CK) contained the lowest content of nitrogen (1.67%) (Table 5). Adding the super absorbent polymers P1 and P2 significantly improved the nitrogen content by 55% and 49%, respectively, over the control. The inoculation with T, AC1, AC2, and B microbial isolates enhanced the N content by 15–35% compared to the control plants. Based on the interaction effect, the N content reached a maximum of 3.17% in plants of P1AC2 treatment (Table 5).

Table 5 Effect of applied super absorbent polymers and microbial on plant macro- and micronutrients contents
Full size table

3.3.2 Phosphorus (P) Content

Comparing with the unamended soil (CK), polymers and micro-organisms application resulted in a significant increase in P content of wheat plants (Table 5). The maximum content of phosphorus in wheat plants (0.44%) was observed under application of P1AC2 treatment.

3.3.3 Potassium Content

The presented results in Table 5 indicated that almost all treatments increased the potassium content (%) in wheat plants. polymers applications caused an increase in phosphorus content in plant from 1.70% (unamended soil) to 2.65 and 2.80% for P1 and P2 treated soil, respectively. Amending soil with T, AC1, AC2 and B microorganisms raised P content to 1.85, 1.77, 2.32 and 2.01%, respectively. The P1 and AC2 combination also maximized potassium levels to 3.18%.

3.4 Micronutrients (Fe, Ma, Zn, and Cu) Content

A clear enhancement was noticed in the micronutrients content of wheat plants under application of polymers and microbes (Table 5). The Fe content increased significantly from 25.10 mg kg− 1 in control treatment to 36.67 and 32.00 mg kg− 1 by addition of P1 and P2 polymers, respectively and to 27.67, 26.67, 31.68 and 26.68 mg kg− 1 with applying T, AC1, AC2 and B biofertilizers only. Similarly, the application of polymers and microbes had a significant influence on the Mn content, the lowest value of Mn content (22.33 mg kg− 1) was recorded for the control treatment. Applying polymers increased the plant content of Mn to 31.00 and 28.00 mg kg− 1 with P1 and P2, respectively. Moreover, the incorporation of various microorganisms (T, AC1, AC2, and B) into the soil increased the content of Mn to 26.67, 24, 26.67 and 23.33 mg kg− 1, respectively. The Zn content in wheat plants significantly increased from 10.67 mg kg− 1 in the unamended control soil to 15.67 and 15.33 mg kg− 1 in P1 and P2-amended soils, respectively. Additionally, the different microorganisms (T, AC1, AC2, and B) addition also improved the plant content of Zn to 14.00, 13.67, 14.23 and 13.33 mg kg− 1, respectively. Also, the wheat plants content from Cu enhanced significantly from 6.33 mg kg− 1 in control treatment to 11.67 and 10.83 mg kg− 1 in the amended soils with P1 and P2 polymers, respectively. On the other hand, the biofertilization with T, AC1, AC2, and B microbes only increased the plant content of Cu significantly to 11.33, 13.00, 12.33, and 10.00 mg kg− 1, respectively.

Regarding to the effect of interaction between the applied polymers and microbes, the obtained results indicated that the plants of P1AC2 treatment recorded the highest Fe, Mn, Zn and Cu contents (43.67, 39.76, 31.33, and 15.33 mg kg− 1, respectively).

4 Discussion

The use of SAP materials and biofertilizers has been found to be effective in improving the chemical properties of the studied sandy loam soil, including pH, EC, and SOM percentage. Soil pH is a critical factor that influences the availability of nutrients for plant growth; most of the necessary nutrients are available to plants at a slightly acidic to neutral pH (6.0-7.5). A reduction in soil pH was observed after application of SAPs and biofertilizers, that may be related to the acidifying effect of the polymers’ carboxylate ions, these findings are matched with those of Ostrand et al. (2020), Ali et al. (2023) and Mahgoub (2020), who discovered that when H+ dissociates from hydrogel and other cation-cation like functional groups to the surface, negative charge is produced. This neutralizes the cation exchange sites and raises the acidity of the soil. In addition to the organic acids produced by Trichoderma sp., Bacillus sp. and Actinomycetes sp. such as fumaric, citric, and gluconic acids, which have an effective role in reducing the soil pH. Furthermore, Bacillus sp. break down complex organic compounds, releasing organic acids contributing to soil acidification and decreased pH levels. Similar explanations were obtained by Bononi et al. 2020; Saxena et al. (2020), Abdullah et al. (2021), Fu et al. (2021), Conte et al. (2022) and Singh et al. (2023).

Soil electrical conductivity (EC) has been mostly used as a measure of soil salinity. The obtained decrease in soil EC in response to SAPs and microorganisms’ application could be related to the salt ions binding in the long chain structure of the polymer, thereby reducing the pore water’s salt content (Malik et al. 2023). Additionally, the high-water holding of SAPs which is reliant on the forming of hydrogen bonds between molecules of water and hydrophilic groups which reduces the solution ionic strength and soil EC values (Zhang et al. 2021). Also, SAPs can adsorb Na+, K+, Mg+ 2 and Ca+ 2 cations due to their high CEC, thus decrease the soil EC value (Ali et al. 2023). Moreover, Actinomycetes sp., Trichoderma sp., and Bacillus sp. significantly influence soil electrical conductivity (EC) through producing organic acids that reduce the electrical conductivity of the soil by chelating metallic ions (Farhad et al. 2023). The enzymatic activities of Bacillus sp. collectively contribute to the reduction of EC in the soil (Bhatti et al. 2017; Gul et al. 2023). Moreover, Bacillus bacteria can promote the growth of plants, which can lead to increased water uptake and improved nutrient uptake, thus diluting the concentration of salts in the soil.

The percentage of soil organic matter (SOM) is an important measure of soil health and is essential to many ecological functions. It has been demonstrated that high concentrations of SOM increase crop yields and enhance soil physiochemical characteristics. The results of this study indicated that SOM content was positively influenced by amending soil with SAPs and biofertilizers. Superabsorbent polymers (SAPs) have the potential benefit of improving soil aggregate stability. The SAP structures’ hydrophilic groups enhance the adsorption and flocculation of soil particles (Ji et al. 2022 & Mamedov et al. 2017), and this gives the SAPs the benefit of helping in SOM retention in the soil by incorporating it into aggregates where it can be preserved from decomposition (Sroka and Sroka 2024), that explains the enhancement in SOC content after SAPs addition. Also, Li et al. (2019), and Kumar et al. (2020) demonstrated the positive impact of SAPs on SOM accumulation and soil fertility. Additionally, the microorganism’s application also played a vital role in improving SOM content because they enhance the populations of living soil microorganisms and the microbial communities, which are a vital part of soil organic matter and responsible for SOM accumulation. In addition to the fact of soil microbes like Bacillus bacteria and Actinomycetes can produce polysaccharides that are considered important binding agents, which can enhance soil aggregation and soil structure by soil particles adhering to form micro aggregates (Ren et al. 2022), thus increasing its capacity to protect SOM from decomposition. So, the interaction between SAPs and microbes’ application in our study confirming their effectiveness in enhancing SOM content. The biofertilizer also improves the population of beneficial microbes in soil. These findings are matched with Shukla et al. (2022) and Gul et al. (2023). Other studies highlighted the effectiveness of SAPs and microorganisms in enhancing SOM content for instance, Tahir et al. (2018), Zhang et al. (2018), and Yaseen et al. (2020).

The availability of both essential macro and micro-nutrients is a determinant of soil quality and the development of plants growing in it. The polymers’ abilities to decrease nutrient leaching and the microorganisms’ impacts on chemical properties and nutrient solubilization seemingly increased nutrient retention and availability in the treated soil. These thorough findings coincide with past studies on nutrient availability responses to polymer and microbial amendments (Ali et al., 2019). The super absorbent polymers such as Hydrogels can also be used as materials for nutrients slow release in soil (Adjuik et al. 2022). Hydrogels can increase the soil content of nutrients by acting as a nutrient mobilizer and water-holding reservoir when used in the soil (Palanivelu et al. 2022). Our findings are matched with Dahri et al. (2019), Ali et al. (2023), and Wu et al. (2023) who suggested that SAP incorporation has been found to increase levels of OM, available nitrogen, phosphorus, and potassium in the amended soil. In this study, application of P1 and P2 polymers improved the soil content of the available nutrients because of their high-water holding capacity, in addition, the first polymer (Barbary plant g3, P1), in particular, contains a reasonable content of N, P, and K (6.5%, 4.80%, and 8.2% K). Accordingly, incorporating sustainable polymers into soils can be effective approach to improve nutrients retention and availability.

The added microbes had a significant impact on enhancement of macro- and micro-nutrients in the studied soil. It has been demonstrated that Actinomycetes participate in the atmospheric nitrogen fixation process in a variety of legumes and non-legumes without nodules forming (Kontro et al. 2022). Thus, Actinomycetes have an important influence on increasing the amount and availability of nitrogen in the plant-soil system (Nosheen et al. 2021). Furthermore, Actinomycetes can affect photosynthesis process, carbon, and nitrogen metabolism. Moreover, Through the production of acidic or alkaline phosphatase enzymes, Actinomycetes can improve the mineralization of the organic phosphates and increase the P availability in soil (AbdElgawad et al. 2020). Furthermore, the chelating qualities of the flavonoids and phenolics released by the Actinomycetes may account for the observed rise in soil nutrients content following enrichment with actinomycetes. Actinomycetes enrich soil rhizosphere, they have a direct impact on plant growth through excreting plant growth-promoting substances, mineral nutrients, and enhancing the soil content of essential micro- and macro-elements. In similar with our results, AbdElgawad et al. (2020) indicated the positive effect of Actinomycetes in increasing the availability of elements like nitrogen, phosphorus, and magnesium that are necessary for biosynthesis of chlorophyll, and for the effective functioning of the photosynthetic machinery.

Certain Trichoderma strains have the ability to produce organic acids, and acidify the surrounding environment. This process allows the solubilization of P ions, micronutrients, and mineral cations, such as Fe+ 3, Mg+ 2, and Mn+ 4 which be then available for plant uptake in the soil (Kamal et al. 2018; Nosheen et al. 2021). According to Bader et al. (2020) on the effect of Trichoderma atroviride on Chinese cabbage, irrigation with this biofertilizer increased soil enzyme activity, yield by 37%, and increased the concentration of inorganic nitrogen and phosphorus content of the soil. Bacillus species can fix atmospheric N2 and provide it to plants, enhancing plant growth and yield (Radhakrishnan et al. 2017). Sun et al. (2020) indicated that by using Bacillus subtilis as a biofertilizer, the proportion of ammonia emissions was lowered by 44%, increasing the amount of residual N in the soil. Bacillus species can help dissolve inorganic phosphate, potassium, zinc, and other nutrients, making them more available for plant absorption (Prakash and Arora 2019). Bacillus bacteria can produce organic acids that help break down silicates and remove metals, allowing the potassium ions in the silicates to become soluble and available to plants. They move potassium from the inaccessible forms found in the soil (Sattar et al. 2019). Also, the biofertilizers especially Bacillus bacteria SP. have an effective role in improving the micronutrients (Fe+ 2, Mn+ 2, Zn+ 2, Cu+ 2) availability in soil through oxidoreductive systems, chelated ligands, protonation, and acidification actions that dissolve the micronutrients in the soil (Daniel et al. 2022). These mechanisms attribute the increase in the soil nutrients availability that we found in response to application of these microbes to the studied sandy loam soil.

Plant growth involves a complex process of cell division, expansion, and differentiation, leading to an increase in size and biomass. soil quality directly influences plant growth by providing water, essential nutrients, and good aeration. Application of soil amendments aid in enhancement of soil quality and hence plant growth and development. The study showed an improvement in the wheat growth parameters and the 1000-grain weight in response to the studied polymers application. This could be explained by the hydrogel’s ability to increase the amount of water available in the root zone and the efficiency of nutrient uptake. These factors boost the photosynthesis rate and the carbohydrates production which are then transported and deposited in the estuaries, increasing the weight of a thousand grains (Roy et al. 2019) or attributed to the hydrogel’s ability to retain and store water. It is used for extended periods of time before being gradually released to allow the plant to carry out all necessary functions, including photosynthesis and the production of dry matter. Additionally, the process of cell division and elongation leads to plant growth and increases the area of the flag leaf (which acts as a light intercepting area), which in turn affects the production of more dry materials and transporting them to the outfalls (grains) and thus gain in the weight of 1000 grains in wheat. These results coincide with prior findings of 15–20% greater fresh and dry weights in wheat with superabsorbent polymers (Bandak et al. 2021; Yang et al. 2022), and 10–30% increased wheat height with hydrogels and vermicompost (Kumar et al. 2022). Albalasmeh et al. (2022) observed that maize plant height improved by 26.3% in comparison with control plants in the silty clay loam soil treated with 0.5% (w/w) hydrogel polymer, while the increase was by 110.7% for plants that were cultivated in sandy soil treated with 1% (w/w) hydrogel polymer. Similar study by Benard et al. (2022) reported that the application of SAP at a rate of 0.1% increased cowpea plant height, number of mature leaves, leaf area, and dry weight/plant by 24%, 11.1%, 11.7%, and 85.9%, respectively. Another study by Yang et al. (2020) found that the maize leaf area index increased with applications of SAP hydrogels, in addition to an increase up to 26% in the 1000-grain weight compared to control. Similar findings were indicated by Kumar et al. (2019); AbdAllah et al. (2021) and Zangana et al. (2023).

Microorganisms that live in the rhizosphere can directly or indirectly promote plant development. In this study, the applied microbes through biofertilization showed growth-promoting effects. Plant growth promotion is directly influenced by increased nutrient availability and phytohormone production (Santoyo et al. 2021). It has been shown that the synthesis and excretion of certain phytohormones, such as IAA, gibberellins (GA), and cytokinins, increase the surface area of root for greater plant nutrient adsorption from the soil and growth. Indirect mechanisms that lead to better plant health and crop productivity include the bioremediation of pollutants and contaminants, abiotic stress reduction, and disease suppression by biocontrol agents (Glick and Gamalero 2021; Zhang et al. 2021). Similar results were obtained by Akbari et al. (2020) who showed that Actinomycetes (Streptomyces strains) have exhibited excellent effects, encouraged shoot elongation and increased shoot and root fresh and dry weights of Wheat. Another study by Oljira et al. (2020) indicated that Trichoderma harzianum boosted increases in critical metrics related to wheat plant growth metrics, such as shoot dry matter, leaf area, and root dry matter. By forming a favorable environment and a symbiotic relationship with plants, Trichoderma enhances the general health of plants by releasing a variety of secondary metabolites, such as growth hormones, endochitinase, and proteolytic enzymes (Kamal et al. 2018). Trichoderma can improve root proliferation, create soil organic matter by releasing hormones that promote growth, and restore the soil’s nutrition cycle (Kumar et al. 2023). According to Djebaili et al. (2021), Triticum durum plants that were inoculated with Actinomycetes microbes showed a notable increase in biomass accumulation, root and shoot growth, and N and P content. Treatment with Actinomycetes has also been shown to enhance plant development by increasing the synthesis of IAA and gibberellic acid (Sharma et al. 2023). Similar to this, it has been observed that isolates of Streptomyces, the biggest genus of Actinomycetes, stimulate the development of maize and tomatoes because they may create siderophores (Warrad et al. 2020). In matching with our results, the Actinomycetes inoculants that applied to legumes soil, produced higher plant growth, seeds yield, and mineral content (AbdElgawad et al. 2020). And in another trial, Bacillus inoculants improved the wheat growth, straw weight and grain yield significantly compared to the nontreated wheat plants (Chandra et al. 2021). From the findings of our study, it has been demonstrated that combining SAP with biofertilizers increases plant growth more than utilizing SAP alone or biofertilizers only.

The noticed enhancement in the nutrient’s availability in the studied soil in response to polymers and biofertilizers application directly and positively affect plant macro- and micro-nutrients content in the cultivated wheat. SAPs can retain a large amount of water and nutrients once incorporated into the soil, slowly releasing them to improve the microbial activity and abundance, nutrients availability in soil, plant growth, plant nutrient content, and nutrient uptake efficiency (Malik et al. 2023). SAPs provide adequate moisture in soil and thus improve the uptake of nutrients by diffusion and root interaction. These findings align with previous results of Singh et al. (2017) who found that amending soil with hydrogel significantly improved the wheat content and uptake of nitrogen, phosphorus, and potassium compared to the non-treated soil. In the wheat plant, another study by Yaseen et al. (2020) approved that exopolysaccharide-producing bacteria and SAP application greatly enhanced maize’s uptake of NPK in both normal and drought stress conditions.

Our study indicated that the synergistic combination of polymers and Trichoderma, Actinomycetes, and Bacillus microbes resulted in a higher content of plant nutrients. The rhizosphere is the area of soil surrounding the root system and the nutrients absorption by plant occurs from it, plant roots secrete a variety of exudates which act as attractants for microbes. So, the applied beneficial microbes can colonize the rhizosphere and affect the nutrients uptake by plants. These beneficial microbes promote nutrient uptake, including P, K, N, Fe, Mn, Cu, and Zn. They achieve this through processes such as solubilization of P and K, fixing N, modification of soil pH, and production of organic and inorganic acids. Additionally, these microbes can create a microenvironment by synthesizing biofilms around microbial cells, which influences the dissolution of minerals and leads to release of available forms of nutrients that can be taken up by plants. Furthermore, they can increase the uptake and accumulation of plant nutrients through the production of volatile organic compounds that induce tolerance and systemic resistance in stressed plants (Saeed et al. 2021; Santoyo et al. 2021; Etesami et al. 2023). Using those beneficial microorganisms as biofertilizers increases the amount of nutrients that plants can absorb from the soil by boosting plant metabolism, which changes the root exudates composition, affects nutrient solubility and availability, and increases interactions with other soil microbes (Daniel et al. 2022). Our results agree with AbdElgawad et al. (2021) who indicated that the Plant tissues (roots and shoots) and seeds of legumes also had higher nitrogen and carbon contents, which was a result of the actinomycetes enriching the soils and increasing their N and C content. Actinomycetes stimulate the activity of enzymes in plants that metabolize nitrogen, such as glutamate dehydrogenase, nitrate reductase, glutamine synthetase, and glutamate synthase. This increases N content and promotes the metabolism and uptake of nitrogen in plants. They also found that all actinomycetes isolates increased the concentration of Fe, Cu, Zn, Mn, Ca, K, Mg, and P elements in the seeds of the studied legumes. The abiotic and biotic soil environment, ion absorption, mineral availability, minerals content, and root growth are all impacted by organic acids that are produced in the soil by Streptomycetes spp. (genus of Actinomycetes) (Javed et al. 2021). When added as a biofertilizer, Trichoderma improves both crop uptake and soil nutrient availability for crop absorption. Similar to our results, Metwally (2020) presented that the content of nitrogen, potassium, phosphorus in Onion plants (Allium cepa) was enhanced by the presence of Tricoderma viride in the soil. Inoculation of Mustard and Tomato soils with Trichoderma harzianum Improved nitrogen content and uptake as well as increased yield by 108 and 203% (Chaube and Pandey 2022). So, these beneficial microbial inoculants can supply the crop with nitrogen, phosphorus, potassium, and other plant micronutrients, enhancing the growth of plant and raising crop production without adding chemical fertilizers to the soil. Our research indicates that applying SAP and biofertilizers collectively has been shown to enhance the nutrient content of wheat plants.

5 Conclusion

In Egypt, the national economy and food security depend to a large extent on the agricultural sector. The steady population increase in Egypt creates the need to reclaim and cultivate more new lands to meet the population’s food needs and increase agricultural production. Almost all reclaimed soils in Egypt have poor physical, chemical, and fertility properties such as coarse texture, weak structure, low water holding capacity, high salinity, low organic matter content, low content, and low availability of plant nutrients. To obtain agricultural production from these soils, different amendments and fertilizers must be applied to improve their productivity. Using biofertilizers provides an environmentally friendly tool for plant nutrition compared with chemical fertilization. Many studies approved that biofertilizer application to the reclaimed soils did not achieve the desired goal, as the arid or semi-arid climatic conditions, low moisture content, and bad characteristics of these soils negatively affect the activity and proliferation of biofertilizer microbes. As soil amendments, superabsorbent polymers (SAPs) are distinguished by their ability to increase the water retention capacity of soil compared to other amendments. Our study focused on the impacts of integrated applications of superabsorbent polymers (SAPs) and biofertilizers on sandy loam soil properties and productivity. Our result indicated that using SAPs increased the efficiency of the applied biofertilizers, and the combination of these polymers and biofertilizers could be an effective tool for improving the sandy loam soil’s characteristics and the wheat growth that grows in it. This study produces a sustainable management strategy for improving soil fertility and crop yield in wheat cropping systems, especially in sandy-textured soils that are characterized by low fertility and low water holding capacity.