Enhancing wheat productivity utilizing nano- and bio-fertilizers in water-scarce Sinai, Egypt, under different irrigation systems

ABSTRACT

This study investigates the impact of different fertilizers under varying irrigation systems and crop water requirements in water-scarce Sinai, Egypt. Field experiments were conducted during the agricultural winter seasons of 2021 and 2022 to study the response of wheat growth, yield, and water productivity under drip and furrow irrigation. The results showed that under drip irrigation system, pH showed no clear trend, while total dissolved solids (TDS) decreased with depth and were reduced by bio-fertilizer and the combination treatment. On the other hand, under furrow irrigation system, maintained a slightly alkaline pH with minimal fertilizer influence. TDS levels significantly varied, and the effects of fertilizers differed. Calcium carbonate content and organic matter varied with fertilizer types and depths. Increasing the crop water requirement from 80% to 100% improved plant growth and yield, with the 80% treatment demonstrating higher water productivity. Furrow irrigation resulted in higher growth and yields, while drip irrigation exhibited greater water productivity. Nano-fertilizer treatments consistently outperformed bio-fertilizer in growth, yields, and water productivity. Specific combinations showed superior performance due to interactions between factors. Suitable irrigation methods and regimes enhance water use efficiency. Higher irrigation levels enhance wheat growth and yield, requiring careful water management to avoid stress. Drip irrigation demonstrates superior water productivity. Reducing the water input to 80% of crop water requirements improves efficiency without compromising yield. Nano-fertilizers promote growth and grain retention as an alternative to soluble fertilizers. Combining nano with bio-fertilizers further enhances wheat growth, yield, and water productivity. These findings provide valuable insights for optimizing wheat production in water-scarce regions, considering irrigation methods, crop water requirements, and nitrogen fertilization sources.

KEYWORDS:

• Nano- and bio-fertilizers
• water conservation
• irrigation systems
• wheat

Introduction

The surging Egyptian population necessitates desert soil reclamation and cultivation, demanding innovative methods in arid regions. Supplementary irrigation, a common practice, alters soil chemical composition and pH, affecting mineral saturation indexes (Hamed, Galal, Emara, & Soliman, 2019; Jacques, Šimůnek, Mallants, & van Genuchten, 2006; Jalali, 2007; Yang, Wang, Hu, & Zeng, 2017).

To optimize crop growth in calcareous soils, essential nutrition strategies are crucial. Marschner and Römheld (1994) emphasize pH’s impact on nutrient availability, affecting chemical reactions in nutrient management. The presence of CaCO₃ directly influences nutrient chemistry, impacting nitrogen, phosphorus, iron, zinc, magnesium, calcium, potassium, and copper accessibility (Taalab et al., 2019).

Considering the increasing global population and the rising food demand, agriculture faces significant pressure to enhance crop productivity while minimizing resource usage. Nanotechnology and bio-fertilizer research have garnered considerable attention due to their potential to revolutionize crop cultivation and resource management (Al-Khafaji, 2018; Duhan et al., 2017).

Wheat (Triticum aestivum L.) is a globally vital cereal crop and staple food. Irrigation system choice significantly impacts water use efficiency (Hamed, Galal, Emara, & Soliman, 2019). Drip and furrow methods, known for efficient water delivery and reduced loss, are widely adopted. Evaluating wheat responses to diverse irrigation systems and water regimes assesses their efficiency under various conditions, with drip irrigation notably superior (Jha et al., 2019; Wang, Gong, Xu, Yu, & Zhao, 2013).

Climate change, extreme weather, and land fertility depletion challenge global food production (Hossain et al., 2022). Excessive synthetic fertilizer use worsens issues, causing economic burdens and environmental pollution. Nanotechnology provides a promising solution by enhancing fertilizer performance and minimizing environmental trade-offs. Nano-fertilizers, with nanoparticles delivering essential nutrients, improve nutrient uptake, use efficiency, and reduce environmental impacts (Bhardwaj et al., 2022; El-Saadony et al., 2021; Guru, Veronica, Thatikunta, & Reddy, 2015; Tarafdar, Xiang, Wang, Dong, & Biswas, 2012). Bio-fertilizers, with beneficial microorganisms promoting nutrient availability and plant growth, contribute to sustainable agriculture (Nazir, Ayub, & Tahir, 2020; Zulfiqar, Navarro, Ashraf, Akram, & Munn´e-Bosch, 2019).

Nano-materials in agriculture demand a deep understanding of their behavior in soil and interactions with other components. Studies highlight potential benefits such as controlled nutrient release and improved water retention with nano-fertilizers. Bio-fertilizers contribute to soil fertility and crop productivity (Baruah & Dutta, 2009; Cui, Sun, Liu, Jiang, & Gu, 2010; Gilbertson et al., 2020; Manjunatha, Biradar, & Aladakatti, 2016). Both types reduce excessive chemical fertilizer use, minimize nutrient losses, and boost crop yield (Mohammed et al., 2020; Prasad, Bhattacharyya, & Nguyen, 2017; Singh et al., 2017).

Moreover, the combined effects of nano- and bio-fertilizers on wheat crops can optimize nutrient management strategies and improve water use efficiency in agriculture.

This research aims to provide valuable insights into the utilization and impact of nano- and bio-fertilizers under different irrigation systems and varying levels of crop water requirements in a water-scarce region (Sinai, Egypt). Understanding the behavior of nano-materials in the soil system and their interactions with soil components will contribute to enhancing sustainable water and agricultural practices.

Materials and methods

Agricultural operations

Two field experiments were carried out in the El Tor Pilot area, situated in the South Sinai Governorate of Egypt at coordinates 28° 18’34” N and 33° 37’ 53.3” E, during the agricultural winter seasons of 2021 and 2022 (Figure 1). Soil samples were collected at three different depths, namely 0–20 cm, 20–40 cm, and 40–60 cm, and underwent mechanical and chemical analyses. The results of the soil analyses are presented in Table 1.

Figure 1. Experimental location.

Table 1. Physicochemical analysis of experimental soil.

Soil depth	pH	TDS (ppm)	OM%	Cations (mg.kg^−1)				Anions (mg.kg^−1)				CaCO3 (%)
				Na	K	Ca^2+	Mg^2	Cl	SO4	CO3	HCO3
0–20	8.32	11,600	1.80	2268	330	400	120	3500	4050	6	1702	50.6
40–20	8.51	9340	1.25	1190	175	380	12	1838	4000	5.6	1135	55.7
40–60	8.33	9150	1.23	964	150	260	564	1488	3700	4	851	50

Experimental design

The main treatment of the experiment is irrigation systems as follows:

• Furrow Irrigation

• Drip Irrigation

The sub-main treatment of the experiment is fertilizers as follows:

• Without fertilization, zero treatment

• Nano-technology fertilization (nitrogen concentration 3000 ppm) (Nano-fertilizer)

• Biogen Fertilization (Bio-fertilizer)

• Nano-technology nitrogen fertilization + Biogen fertilization

− Three replicates were used for each treatment.

Total coefficients for statistical design

 = 2 irrigation systems × 4 fertilization treatments × 3 replicates = 24 complete experimental plots

The area of the experimental plot is = 10 × 10 = 100 m²

The total experimental area = 2400 m²

In this study, the impact of two irrigation methods, furrow and drip, was assessed on wheat cultivation with varying water regimes: 80% and 100% of crop water requirements. Four nitrogen fertilization treatments included nano-fertilizer (3000 ppm N concentration, 3.5 L ha⁻¹, applied thrice before boot stage), bio-fertilizer (“Biogenic” at 2.5 kg ha⁻¹, mixed with sand, applied after planting and 1 month later), a combined treatment of nano- and bio-fertilizers, and a control based on Ministry of Agriculture recommendations. Superphosphate fertilizer (15.5%) at 300 kg ha⁻¹ was applied pre-planting. Ammonium nitrate fertilizer (33.5%) was applied in three doses totaling 120 units, with application stopped at grain formation onset. Potassium sulfate fertilizer (48%) at 50 kg ha⁻¹ was added one-month post-planting. Experimental plots, 100 m² each with a 3-m separation between irrigation treatments, used a 1-m spacing within each replicate. Two-meter distance between the main pieces prevented the overlap of experimental factors.

The chosen wheat cultivar, Giza 171, was sown in early November of both 2021 and 2022. A seed rate of 190 kg ha⁻¹, sown at a depth of 4–5 cm with a 20 cm row spacing, optimized plant stands. Pre-sowing, superphosphate fertilizer (15.5% P₂O₅) at 110 kg P₂O₅ ha⁻¹ was applied, and 4 weeks later, potassium sulfate fertilizer (48% K₂O) at 60 kg K₂O ha⁻¹ was applied. All recommended cultural practices were followed.

Immediate irrigation took place after planting, following a pre-sowing irrigation event. The specific amount of irrigation water applied can be found in Table 2. At the final ripening stage, the plants were harvested on April 2^nd in both 2021 and 2022 seasons. Following the completion of the harvesting stage, the number of plants per square meter, biological yield (t ha⁻¹), grain yield (t ha⁻¹), and straw yield (t ha⁻¹) were determined. At harvest stage, plant samples were taken to evaluate growth and quality traits such as plant height (in cm), spike length (in cm), spike weight (in g), root length (in cm), seed index (in g), and harvest index (HI). The harvest index was calculated using the formula:

(1) $\mathit{HI}=\left(\mathit{Grain}\mathit{yield}/\mathit{Biological}\mathit{yield}\right)\ast 100$(1)

Table 2. Amount of applied water under each irrigation system.

Irrigation system	80% CWR (m^3.ha^−1)		100% CWR (m^3.ha^−1)
	1^st season	2^nd season	1^st season	2^nd season
Drip	3123	2984	3903	3730
Furrow	4674	4449	5843	5561

In addition, the quantities of irrigation water were measured using a flow-meter for each treatment, and the results are presented in Table 2. Water productivity (WP) was calculated following the equation proposed by (Ali, Hoque, Hassan, & Khair, 2007) to determine the efficient utilization of water resources.

(2) $\mathit{WP}=\frac{\mathit{Yield}\left(\mathit{kgha}-1\right)}{\mathit{Amount}\mathit{of}\mathit{applied}\mathit{water}\left(\mathit{m}3.\mathit{ha}-1\right)}$(2)

Statistical analysis

The data obtained from the experiments were subjected to statistical analysis using a split–split plot arrangement in a randomized complete block design (RCBD) with three replicates. The statistical software Genstat Twelfth Edition (Goedhart and Thissen, 2009) was employed for the analysis. To assess the significance of differences between treatment means, the least significant difference (LSD) test was conducted at a probability level of 0.05.

Results

Soil chemical properties under varied irrigation systems

Table 3 displays results of fertilization techniques on soil properties post-harvest with drip irrigation. The pH values varied with fertilizers and depths. The control group (NPK) showed pH values of 8.28, 8.42, and 8.30 at 0–20 cm, 20-40 cm, and 40–60 cm, respectively. Bio-fertilizer slightly reduced pH to 7.79, 7.89, and 8.21. Nano-fertilizer exhibited pH compared to control and the combination of nano-fertilizers and bio-fertilizers decreased pH. Drip irrigation showed no clear pH trend.

Table 3. Effect of different fertilization techniques on soil chemical properties using drip irrigation system.

Fertilizers	Depth (cm)	pH	TDS (ppm)	Cations (ppm)				Anions (ppm)				CaCO3 (%)	Organic Content (%)
				Na^+	K^+	Ca^++	Mg^++	Cl^−	SO4	CO3	HCO3
Without NPK	0–20	8.28	8700	1701	247.5	300	90	2625	3037.5	4.5	1276.5	46.1	0.62
	20–40	8.42	7005	892.5	131.25	285	9	1378.5	3000	4.2	851.25	50.0	0.68
	40–60	8.30	6862.5	723	112.5	195	423	1116	2775	3.0	638.25	50.0	0.59
Bio-fertilizers	0–20	7.79	7540	1474.2	214.5	260	78	2275	2632.5	3.9	1106.3	44.00	0.69
	20–40	7.89	7472	952	140	304	9.6	1470.4	3200	4.48	908	47.8	0.68
	40–60	8.21	8235	867.6	135	234	507.6	1339.2	3330	3.6	765.9	49.1	0.55
Nano	0–20	7.99	9860	1927.8	280.5	340	102	2975	3442.5	5.1	1446.7	46.1	0.59
	20–40	7.94	8406	1071	157.5	342	10.8	1654.2	3600	5.04	1021.5	50.2	0.53
	40–60	8.12	8692.5	915.8	142.5	247	535.8	1413.6	3515	3.8	808.5	49.0	0.51
Nano+Bio	0–20	7.75	7308	1428.84	207.9	252	75.6	2205	2551.5	3.78	1072.3	45.62	0.69
	20–40	7.82	7285.2	928.2	136.5	296.4	9.36	1433.64	3120	4.368	885.3	46.2	0.60
	40–60	8.12	8052	848.32	132	228.8	496.32	1309.44	3256	3.52	748.88	49.00	0.59

Total dissolved solids (TDS)

The control group without nano- or biofertilizer had TDS values of 8700 ppm, 7005 ppm, and 6862.5 ppm at 0–20 cm, 20–40 cm, and 40–60 cm. Bio-fertilizer reduced TDS to 7540, 7472, and 8235 ppm, while nano-fertilizer showed mixed TDS results, with higher values at 0–20 cm (9860 ppm) and similar or slightly lower values at deeper depths. The combination of nano- and bio-fertilizers resulted in decreased TDS values (7308, 7285.2, and 8052 ppm). Drip irrigation led to decreasing TDS values with depth. Bio-fertilizer and the combination generally had lower TDS compared to the control, while nano-fertilizer showed mixed effects.

CaCO₃ content

CaCO₃ content varied across depths and fertilizers. Without nano- or bio-fertilizer, CaCO₃ percentages ranged from 46.1% to 50.0%. Bio-fertilizer reduced CaCO₃ (44.00% to 49.1%), while nano-fertilizer showed slightly higher CaCO₃ (46.1% to 50.2%), especially in the 20–40 cm range. The combination treatment had mixed results, with CaCO₃ percentages ranging from 45.62% to 49.00%.

Organic content

Organic matter content percentages in the control treatment ranged from 0.62% to 0.68%. Bio-fertilizer maintained consistent organic matter content (0.55% to 0.69%), while nano-fertilizer showed slightly lower organic content (0.51% to 0.59%) in the 20–40 cm and 40–60 cm ranges. The combination treatment resulted in varying organic content levels.

Soil chemical properties under furrow irrigation

Results (Table 4) display the impact of varied fertilization on post-harvest soil properties in furrow irrigation. pH, generally alkaline (8.28–8.42) without nano- or bio-fertilizer, slightly decreased with bio-fertilizers (7.84–7.90) and nano-fertilizers (7.76–7.86). Combining both showed a slightly higher pH (7.89–7.95). Changes were minimal, suggesting the furrow irrigation system and fertilizers minimally affected pH, remaining alkaline.

Table 4. Effect of different fertilization techniques on soil chemical properties using furrow irrigation system.

Fertilizers	Depth (cm)	pH	TDS (ppm)	Cations (ppm)				Anions (ppm)				CaCO3 (%)	Organic Content (%)
				Na^+	K^+	Ca^++	Mg^++	Cl^−	SO4	CO3	HCO3
Without NPK	0–20	8.28	7540	1474.2	214.5	260	78	2275	2632.5	3.9	1106.3	44.1	0.69
	20–40	8.42	6071	773.5	113.75	247	7.8	1194.7	2600	3.64	737.75	50.0	0.69
	40–60	8.30	5947.5	626.6	97.5	169	366.6	967.2	2405	2.6	553.15	49.0	0.59
Bio-fertilizer	0–20	7.84	7192	1406.16	204.6	248	74.4	2170	2511	3.72	1055.24	41.0	0.71
	20–40	7.81	7098.4	904.4	133	288.8	9.12	1396.88	3040	4.256	862.6	45.8	0.69
	40–60	7.90	7777.5	819.4	127.5	221	479.4	1264.8	3145	3.4	723.35	45.1	0.59
Nano	0–20	7.76	9280	1814.4	264	320	96	2800	3240	4.8	1361.6	45.1	0.61
	20–40	7.86	7939	1011.5	148.75	323	10.2	1562.3	3400	4.76	964.75	49.23	0.58
	40–60	7.82	8235	867.6	135	234	507.6	1339.2	3330	3.6	765.9	48.0	0.59
Nano+Bio	0–20	7.89	6380	1247.4	181.5	220	66	1925	2227.5	3.3	936.1	44.62	0.70
	20–40	7.91	7005	892.5	131.25	285	9	1378.5	3000	4.2	851.25	45.2	0.65
	40–60	7.95	7320	771.2	120	208	451.2	1190.4	2960	3.2	680.8	48.00	0.60

Total dissolved solids (TDS)

TDS levels varied significantly. Without fertilizers, TDS ranged from 5947.5 ppm to 7540 ppm. Bio-fertilizer maintained consistent levels (7098.4 ppm to 7777.5 ppm), while nano-fertilizer showed higher levels (7939 ppm to 9280 ppm). Combining both resulted in TDS ranging from 6380 ppm to 7320 ppm. Different fertilizers and depths influenced TDS significantly in the furrow irrigation system.

CaCO₃ content

CaCO₃ content varied across depths and fertilizers. Without nano- or bio-fertilizer, CaCO₃ percentages ranged from 44.1% to 50.0%. Bio-fertilizer reduced CaCO₃ (41.00% to 45.8%), while nano-fertilizer slightly increased it (45.1% to 49.23%). The combination treatment showed mixed results (44.62% to 48.00%). Varied fertilization influenced CaCO₃ content, providing insight into furrow irrigation system effects.

Organic content

Organic content fluctuated across depths and fertilizers. The control treatment recorded organic content percentages ranged from 0.69% to 0.71%. Bio-fertilizer increased organic content (0.69% to 0.59%), while nano-fertilizer showed consistency (0.61% to 0.58%), and the combination treatment varied (0.59% to 0.70%). These findings offer insights into fertilization impact on soil properties in furrow irrigation, vital for optimizing agricultural practices and maximizing crop yield.

Crop water requirement (CWR)

The influence of different percentages of crop water requirement 80% and 100% on wheat plant characteristics and yields was investigated. Increasing the CWR had a significant positive effect on plant growth and yield in both the first and second seasons. Specifically, raising the CWR from 80% to 100% resulted in a considerable increase in spike length by 14.12% and 5.26%, spike weight by 13.79% and 17.50%, and seed index by 5.02% and 5.28% during the 1^st and 2^nd seasons, respectively (Table 5).

Table 5. Wheat plant growth and seed index as affected by crop water requirement (CWR) levels in 2021 and 2022 seasons.

CWR	Plant height (cm)		Root length (cm)		Spike length (cm)		Spike weight (g)		Seed index
	1^st season	2^nd season	1^st season	2^nd season	1^st season	2^nd season	1^st season	2^nd season	1^st season	2^nd season
80%	78.586 b	80.886 a	7.256 b	8.016 b	8.585 a	9.394 b	0.747 b	0.697 b	41.271 b	43.854 b
100%	81.338 a	80.946 a	7.519 a	8.280 a	9.797 a	9.888 a	0.850 a	0.819 a	43.342 a	46.168 a
L.S.Dat 5%	0.489	NS	0.223	0.005	NS	0.005	0.191	0.005	0.296	0.274

Furthermore, a modest but noteworthy increase was observed in biological yield (2.38% and 2.71%), grain yield (11.45% and 3.75%), straw yield (5.06% and 1.36%), and harvest index (HI) (10.89% and 1.04%) (Table 6).

Table 6. Number of plants, yields, and harvest index (HI) as affected by crop water requirement (CWR) levels in 2021 and 2022 seasons.

CWR	No. of plants/m^−2		Biological yield (t ha^−1)		Grain yield (t ha^−1)		Straw yield (t ha^−1)		HI
	1^st season	2^nd season	1^st season	2^nd season	1^st season	2^nd season	1^st season	2^nd season	1^st season	2^nd season
80%	195 a	197 a	8.770 b	8.610 b	2.673 b	2.906 b	5.217 b	5.291 b	30.48 b	33.75 b
100%	197 a	199 a	8.979 a	8.843 a	2.979 a	3.015 a	5.481 a	5.363 a	33.18 a	34.10 a
L.S.D at 5%	NS	NS	0.214	0.149	0.034	0.072	0.154	0.072	0.53	0.20

Water productivity (WP)

Conversely, intriguingly, the treatment with 80% of CWR demonstrated superior water productivity (WP) compared to the 100% treatment. Specifically, the 80% CWR treatment exhibited a notable 11.84% and 11.92% enhancement in WP for biological yield, a significant 4.55% and 11.51% increase in WP for grain yield, and a substantial 9.37% and 13.63% augmentation in WP for straw yield were demonstrated during the first and second seasons, respectively (Table 7).

Table 7. Water productivity (WP) affected by crop water requirement (CWR) levels in 2021 and 2022 seasons.

CWR	WP biological (kg.m^−3)		WP grain (kg.m^−3)		WP straw (kg.m^−3)
	1^st season	2^nd season	1^st season	2^nd season	1^st season	2^nd season
80%	2.003 a	2.085 a	0.621 a	0.707 a	1.202 a	1.284 a
100%	1.791 b	1.863 b	0.594 b	0.634 b	1.099 b	1.130 b
L.S.D at 5%	0.045	0.026	0.005	0.015	0.040	0.015

Irrigation method

Significant differences were observed among irrigation systems in terms of growth and yield traits, as well as water productivity, in both seasons, except for spike length and spike weight in the first season. The furrow irrigation system resulted in higher wheat plant growth and yields, followed by the drip irrigation system (Table 8).

Table 8. Wheat plant growth and seed index as affected by irrigation methods in 2021 and 2022 seasons.

Irrigation system	Plant height (cm)		Root length (cm)		Spike length (cm)		Spike weight (g)		Seed index
	1^st season	2^nd season	1^st season	2^nd season	1^st season	2^nd season	1^st season	2^nd season	1^st season	2^nd season
Drip	86.218 b	87.106 a	8.779 b	9.325 b	10.646 a	11.193 a	1.042 a	1.007 a	47.921 b	48.214 b
Furrow	87.585 a	85.524 b	9.203 a	9.440 a	11.065 a	11.128 b	1.107 a	0.968 b	48.999 a	49.940 a
L.S.D at 5%	0.599	0.551	0.273	0.006	NS	0.006	0.234	0.006	0.362	0.331

In terms of the harvest index, the drip irrigation system recorded values of 32.45% and 33.81% in the 1^st and 2^nd seasons, respectively, while the furrow irrigation system had values of 29.60% and 32.50% (Table 9).

Table 9. Yield and yield components of wheat as affected by irrigation methods in 2021 and 2022 seasons.

Irrigation system	No. of plants/m^−2		Biological yield (t ha^−1)		Grain yield (t ha^−1)		Straw yield (t ha^−1)		HI
	1^st season	2^nd season	1^st season	2^nd season	1^st season	2^nd season	1^st season	2^nd season	1^st season	2^nd season
Drip	208 b	210 a	10.834 b	10.795 b	3.516 b	3.650 b	6.867 b	6.690 a	32.45 a	33.81 a
Furrow	211 a	204 b	13.092 a	11.744 a	3.875 a	3.817 a	7.630 a	7.249 a	29.60 b	32.50 b
L.S.D at 5%	1	1	0.262	0.183	0.041	0.088	0.188	NS	0.63	0.24

On the contrary, the drip irrigation system exhibited the highest values of water productivity (WP) for biological yield, with an average of 2.83 kg.m⁻³ for the first and second seasons. Additionally, it showed values of 0.94 kg.m⁻³ for WP for grain yield and 1.78 kg.m⁻³ for WP for straw yield. These values represented significant increases compared to the furrow irrigation system. Specifically, there was a 24.12% increase in WP for biological yield, a 27.03% increase in WP for grain yield, and a 29.93% increase in WP for straw yield (Table 10).

Table 10. Water productivity of biological, grain, and straw as affected by irrigation methods in 2021 and 2022 seasons.

Irrigation system	WP biological (kg.m^−3)		WP grain (kg.m^−3)		WP straw (kg.m^−3)
	1^st season	2^nd season	1^st season	2^nd season	1^st season	2^nd season
Drip	2.771 a	2.895 a	0.900 a	0.980 a	1.755 a	1.797 a
Furrow	2.339 b	2.219 b	0.689 b	0.719 b	1.362 b	1.370 b
L.S.D at 5%	0.055	0.032	0.006	0.018	0.049	0.018

Nitrogen fertilization source

The data presented in Tables 11–13 revealed significant differences among nitrogen fertilization sources in the growth, yields, and water productivity of wheat plants for each season. Both the nano + bio-fertilizer treatments and nano-fertilizer treatment consistently exhibited the highest values across the studied traits compared to the bio-fertilizer treatment.

Table 11. Plant height, root length and spike length, spike weight, and seed index as affected by fertilization type in 2021 and 2022 seasons.

Fertilization	Plant height (cm)		Root length (cm)		Spike length (cm)		Spike weight (g)		Seed index
	1^st season	2^nd season	1^st season	2^nd season	1^st season	2^nd season	1^st season	2^nd season	1^st season	2^nd season
Bio	75.500 c	78.619 c	6.393 c	7.609 c	9.363 a	10.136 b	0.685 b	0.796 b	43.904 c	47.101 b
Nano	81.871 b	86.914 a	7.737 b	9.188 b	9.279 a	10.336 a	0.905 a	0.810 a	46.050 b	49.896 a
Bio+Nano	93.478 a	85.631 b	9.988 a	9.397 a	9.901 a	9.636 c	0.995 a	0.778 c	49.013 a	46.969 c
NPK	69.000 d	68.001 d	5.431 d	5.937 d	8.222 a	7.845 d	0.610 b	0.595 d	30.258 d	33.128 d
L.S.D at 5%	0.692	0.570	0.315	0.007	NS	0.007	0.270	0.007	0.418	0.380

Table 12. Number of plants/m², biological yield, grain yield, straw yield, and harvest index of wheat as affected by fertilization type in 2021 and 2022 seasons.

Fertilization	No. of plants/m^−2		Biological yield (t ha^−1)		Grain yield (t ha^−1)		Straw yield (t ha^−1)		HI
	1^st season	2^nd season	1^st season	2^nd season	1^st season	2^nd season	1^st season	2^nd season	1^st season	2^nd season
Bio	186 c	194 c	7.361 c	8.232 c	2.093 c	2.688 c	4.991 c	5.194 c	28.43 d	32.65 c
Nano	199 b	204 b	10.005 b	10.534 a	3.250 b	3.677 a	5.662 b	6.408 a	32.48 b	34.91 b
Bio+Nano	214 a	206 a	12.023 a	9.548 b	4.125 a	3.481 b	6.759 a	5.606 b	34.31 a	36.46 a
NBK	186 c	177 d	6.109 d	6.133 d	1.836 d	1.868 d	3.984 d	3.791 d	30.05 c	27.49 d
L.S.D at 5%	1	1	0.303	0.211	0.047	0.102	0.217	0.102	0.73	0.26

Table 13. Water productivity (WP) of wheat crop as affected by fertilization type in 2021 and 2022 seasons.

Fertilization	WP biological (kg m^−3)		WP grain (kg m^−3)		WP straw (kg m^−3)
	1^st season	2^nd season	1^st season	2^nd season	1^st season	2^nd season
Bio	1.579 c	1.856 c	0.446 c	0.600 c	1.072 c	1.178 c
Nano	2.124 b	2.389 a	0.699 b	0.838 a	1.213 b	1.457 a
Bio+Nano	2.569 a	2.166 b	0.889 a	0.795 b	1.460 a	1.267 b
NPK	1.315 d	1.350 d	0.396 d	0.412 d	0.855 d	0.836 d
L.S.D at 5%	0.064	0.037	0.007	0.021	0.056	0.021

The nano + bio-fertilizer treatment demonstrated remarkable enhancements in the measured parameters when compared to the control treatment. On average, it resulted in substantial increases of 30.75% in plant height, 70.60% in root length, 23.66% in spike length, 48.33% in spike weight, 51.47% in seed index, 16.02% in the number of plants at harvest, 76.31% in biological yield, 105.41% in grain yield, 58.87% in straw yield, 23.01% in harvest index (HI), 78.19% in water productivity (WP) for biological yield, 110.00% in WP for grain yield, and 60.00% in WP for straw yield compared to the control treatment.

Similarly, significant improvements were observed when comparing the nano + bio-fertilizer treatment with the bio-fertilizer treatment. The nano + bio-fertilizer treatment showed notable increases of 16.22% in plant height, 38.43% in root length, 10.85% in spike length, 20.27% in spike weight, 5.50% in seed index, 10.53% in the number of plants at harvest, 38.33% in biological yield, 59.00% in grain yield, 21.41% in straw yield, 15.88% in harvest index (HI), 37.79% in water productivity (WP) for biological yield, 61.54% in WP for grain yield, and 20.35% in WP for straw yield.

Interaction

The interplay of crop water percentage, irrigation method, and nitrogen source significantly impacted wheat growth, yields, and water productivity in both seasons. Notably, pairing 100% crop water with drip irrigation and nano-fertilizer led to superior outcomes. This combination resulted in maximum plant height (129.5 cm) (Figure 2) the highest number of harvest plants (273) (Figure 9), superior seed index (67.47 g) (Figure 3), significant straw yield (9.84 t ha⁻¹) (Figure 4), elevated harvest index (0.49) (Figure 5), and improved water productivity (WP) for biological yield (4.80 kg m³), WP for grain yield (1.83 kg m³), and WP for straw yield (3.23 kg m³) (Figure 6).

Figure 2. Combined effect of irrigation method and fertilizer type on plant height (cm).

Figure 3. Combine Effect of irrigation method and fertilizer type on seed index.

Figure 4. Combine Effect of irrigation method and fertilizer type on straw yield (t ha-1).

Figure 5. Combine Effect of irrigation method and fertilizer type on harvest index.

Figure 6. Water productivity of biological yield (t ha-1), grain and straw (kg m-3) as affected by irrigation method and fertilizer type.

Furthermore, at 100% crop water, drip irrigation, and Nano + bio-fertilizer, the highest spike length (7.7 cm) (Figure 7) and spike weight (0.7 g) (Figure 8) were achieved. In the same conditions but with furrow irrigation, and nano + bio-fertilizer, the greatest root length (14 cm) (Figure 10) and grain yield (6.06 t ha⁻¹) (Figure 11) were observed, along with the highest biological yield (17.43 t ha⁻¹) (Figure 12).

Figure 7. Combine Effect of irrigation method and fertilizer type on spike length (cm).

Figure 8. Combine Effect of irrigation method and fertilizer type on spike weight (g).

Figure 9. Combine Effect of irrigation method and fertilizer type on number of plant /m2.

Figure 10. Combine Effect of irrigation method and fertilizer type on root length (cm).

Figure 11. Combine Effect of irrigation method and fertilizer type on grain yield (t ha-1).

Figure 12. Combine Effect of irrigation method and fertilizer type on biological yield (ton ha-1).

Discussion

Soil chemical properties

Soil pH and total dissolved solids (TDS)

The drip irrigation system efficiently delivered water to plant roots, reducing TDS values with increasing depth (Elbanna, Abou El-Magd, & Abo-Habaga, 2020; Mansingh, Banik, Bag, Sunaratiya, & Das, 2023). Bio-fertilizer further decreased TDS, enhancing microbial activity and minimizing salt accumulation. Combining nano- and bio-fertilizers with drip irrigation synergistically lowered TDS, indicating enhanced nutrient availability and cycling (Lei et al., 2022).

In contrast, furrow irrigation showed TDS variations, with the control treatment displaying a wide range. Bio-fertilizer maintained consistent TDS levels, positively influencing nutrient composition. Nano-fertilizer effects on TDS were more varied, potentially due to concentration near the soil surface. Combining nano- and bio-fertilizers with furrow irrigation yielded varied but generally lower TDS values, promoting nutrient retention and cycling (Liu et al., 2019).

The pH in drip irrigation showed no clear trend across depths, attributed to calcareous soil’s buffering capacity, maintaining pH above 8. Bio-fertilizer slightly reduced pH, and nano-fertilizer variations suggested some influence on soil pH. The precision of drip irrigation minimized the overall pH impact. However, consistent pH trends were lacking in other depths, indicating a relatively stable system. These results align with (Jacques, Šimůnek, Mallants, & van Genuchten, 2006) emphasizing irrigation and fertilization’s potential impact on soil composition and pH.

In furrow irrigation, soil pH remained consistently alkaline. Fertilizer types had no significant impact on pH compared to the control. However, Yang, Wang, Hu, and Zeng (2017) found irrigation influenced soil moisture and pH (p < 0.05). Nano-bio-fertilizers showed a slightly lower pH at 20 cm depth, suggesting localized acidification. This trend was not uniform across other depths.

The pH decrease with bio-fertilizer is attributed to beneficial microorganisms enhancing soil microbial activity (Ammar et al., 2023). Some produce organic acids during metabolism, causing a slight pH decrease. pH variations with nano-fertilizer and nano+bio-fertilizer may result from specific compounds interacting with soil minerals and organic matter. These results were aligning with those of Liu et al. (2022).

The furrow irrigation system’s slightly alkaline pH may result from factors like leaching acidic compounds, carbonate in irrigation water, or natural soil composition. These align with the findings of Hu et al. (2019), where pH decreases in low rainfall, increasing water content, elevating ion concentration, and decreasing pH. Different fertilizer types minimally affect the furrow irrigation system pH. Minor pH variations could stem from localized effects, such as specific ion release or organic acids in the top 20 cm. However, inconsistent pH trends across depths suggest an overall stable pH, with variations influenced by water flow and fertilizer application.

Soil pH changes during the experiment result from factors such as initial pH, inputs of acidic or alkaline substances, and soil pH buffering capacity (pHBC) (Nelson & Su, 2010). Alkaline soils may be present due to base elements or compounds like carbonates. In the pH buffering process, CO₂ is retained as HCO₃⁻ in the solution phase, increasing with higher pH levels (Oren & Steinberger, 2008; Sparling & West, 1990).

The use of bio-fertilizer and nano+bio-fertilizer lowered soil pH. Bio-fertilizers with organic materials and microorganisms can produce acidic by-products during microbial activity, contributing to pH decrease. The combination of nano- and bio-fertilizers may enhance microbial activity, leading to a slight pH decrease (Kumar, Diksha, Sindhu, Kumar, & 2021; Li et al., 2022). Nano-fertilizers minimally impact soil pH equilibrium. However, their application may initially increase pH due to the alkaline nature of the materials used (Rajonee, Zaman, & Huq, 2017).

Calcium carbonate (CaCO₃) and organic matter content

In both drip and furrow irrigation, CaCO₃ varied with depth and fertilizer types. In the drip system, bio-fertilizer lowered CaCO₃ compared to control; nano-fertilizer slightly increased CaCO₃, especially at 20–40 cm depth. Combined treatment had mixed results. In furrow irrigation, control had varying CaCO₃ percentages, bio-fertilizer reduced CaCO₃ compared to control, and nano-fertilizer slightly increased CaCO₃, especially at 20–40 cm depth. Combined treatment had mixed results. Both irrigation systems and fertilizer types influenced soil CaCO₃ content, but changes were relatively small and inconsistent, attributed to water movement and mineral dissolution influenced by irrigation methods.

The bio-fertilizer likely boosted microbial activity, decomposing organic matter (Ammar et al., 2023). This released acids reacting with CaCO₃, reducing its content compared to the control. Conversely, nano-fertilizer impacted soil properties, affecting water retention and infiltration rates, influencing mineral movement, including CaCO₃. This explains the slightly higher CaCO₃ in the 20–40 cm depth range. These results were in agreement with Kumari et al. (2014) whom they agreed that variations in colloid and phosphorus leaching were influenced by changes in pH and ionic strength due to CaCO₃ presence.

Similarities between drip and furrow irrigation systems, in water application and soil-water dynamics, imply factors affecting CaCO₃ under drip irrigation apply to furrow irrigation. Elbanna, Abou El-Magd, and Abo-Habaga (2020) demonstrated that the accumulation of salts follows the direction of water flow. In general, the electrical conductivity (EC) and chloride concentration tended to increase as the applied water rates decreased. In drip irrigation, organic content variations across depths result from water and organic matter movement. Targeted water application near plant roots causes variations in organic matter distribution, and this finding aligns with Mursec’s (2011) study.

Bio-fertilizers boost organic matter and nutrient cycling, maintaining consistent content compared to the control. In contrast, nano-fertilizers, especially at deeper depths, may slightly decrease organic content due to nano-particle effects on soil and microbial activity, impacting decomposition. The combination treatment shows varied organic content, influenced by interactions between bio-fertilizer and nano-fertilizer, affecting decomposition and nutrient cycling differently. After irrigation, NH₄⁺ fully oxidized and nitrified as NO₂⁻ and NO₃⁻ approximately within 15 days, based on Liu, Šimůnek, Li, and He (2013).

Irrigation method and crop water requirement

Improving water use efficiency is crucial for addressing water shortages and enhancing wheat growth and yield. Varying irrigation levels, particularly from 80% to 100% of crop water requirement, impact wheat traits. Water stress in lower irrigation treatments reduces leaf area index, photosynthesis rate, and dry matter accumulation, negatively affecting plant height, spike length, weight, and overall yield components. This aligns with previous findings of Kharrou et al. (2011), Mahmoud, Hassanin, Borham, and Emara (2018), and Hamed, Galal, Emara, and Soliman (2019). Bhunia, Verma, Arif, Gochar, and Sharma (2015) and Jha et al. (2019) support these results. El-Hendawy, Hokam, and Schmidhalter (2008) noted the significant impact of different irrigation levels on grain yield.

Irrigation methods, specifically furrow and drip systems, influence wheat growth and productivity. Furrow and drip systems show superior growth and yield traits without significant differences in most studied aspects. Root water uptake is crucial, with surface drip irrigation benefiting from a shallow welting soil zone and low irrigation rates. This aids root uptake, as reported by (Gaiser et al., 2012). Slow irrigation rates in low treatments increase soil water storage, contributing to enhanced root water uptake (Jha et al., 2019). (Kang et al., 2002) found varying harvest indices under different irrigation methods, emphasizing the positive impact of drip irrigation on crop development, reproduction, and yield (Blum, 2009).

Contrarily, using 100% of CWR reduced water productivity (WP) for biological, grain, and straw yields. Reducing water input to 80% of crop requirements enhanced water efficiency without compromising yield. Drip irrigation exhibited the highest water productivity, aligning with Wang, Gong, Xu, Yu, and Zhao (2013). Improved water use efficiency can result from increased grain yield or reduced evapotranspiration. Drip irrigation stands out as the most efficient method, conserving water and minimizing deep percolation compared to surface flood irrigation (Jha et al., 2019).

Nitrogen fertilization source

Effective NPK nutrient availability in soil fosters vital plant processes, particularly nitrogen’s role in photosynthesis, hormone regulation, chlorophyll, and protein synthesis. This enhances cell division, elongation, and overall plant growth and height (AL-Samawi, 2012). This aligns with Mandal, Ali, Amin, Masum, and Mehraj (2015), emphasizing nitrogen’s significance in augmenting plant growth and improving grain percentage on spikes, positively impacting spike grain count.

The use of slow-release nano-fertilizers offers an effective alternative to soluble mineral fertilizers, enhancing nutrient absorption without leaching. Wheat growth and yields, as well as water productivity (WP), improved significantly in nano+bio-fertilizer and nano-fertilizer treatments compared to bio-fertilizer and control. Nanoparticles, ranging from 1 to 100 nm, modify physiochemical properties due to a large surface area-to-volume ratio, enhancing soil fertility (Lopez-Serrano, Olivas, Landaluze, & C´ Amara, 2014; Tapan, Biswas, & Kundu, 2010). The interaction of nanoparticles with plants influences soil fertility, increasing wheat growth and yield in nano+biofertilizer treatments (Hasan & Saad, 2020; Jakhar et al., 2022). Nano-fertilizers, with efficient nutrient use, reduce losses, causing morphological and physiological changes (Mahmoud, El-Attar, & Mahmoud, 2017). Spruogis, Jakienė, Dautartė, and Zemeckis (2018) reported an increased biological yield in barley with the use of nanoparticle fertilizers. in barley.

Biofertilizers containing non-symbiotic nitrogen-fixing bacteria enhance nitrogen availability, soil fertility, and nutrient efficiency (Mardalipour, Zahedi, & Sharghi, 2014; Hasan & Saad, 2020). Bio-fertilizers stabilize organic soil material, increasing plant lifespan and nutrient absorption, promoting growth and spike number (Ammar, 2018; Kaviani & Negahd, 2016). Bio-fertilizers stimulate growth hormones, increasing dry matter accumulation, photosynthesis, and biological yield (Mohamed, Thalooth, Elewa, & Ahmed, 2019). Foliar application of Biogen as a nano-fertilizer significantly improves wheat crop growth, seed yield, and nutrient absorption capacity (Mardalipour, Zahedi, & Sharghi, 2014). Increased yields in nano+biofertilizer and nano-fertilizer treatments contribute to higher water productivity for biological, grain, and straw compared to other treatments.

Conclusion

The drip system showed minimal pH changes, while furrow maintained a slightly alkaline pH. TDS varied across systems, with drip generally reducing TDS values, indicating improved leaching. Furrow, dependent on fertilizer type, exhibited significant TDS fluctuations, emphasizing careful selection for managing soil salinity.

Bio-fertilizers in the drip system positively influenced pH and TDS, decreasing pH due to organic acid production and reducing TDS through enhanced nutrient cycling. Furrow benefited from bio-fertilizers, maintaining consistent TDS levels and improving nutrient composition. Nano-fertilizers in furrow led to higher TDS, potentially due to increased nutrient uptake. Combining nano- and bio-fertilizers yielded positive effects, enhancing nutrient retention, leaching, and cycling for improved soil fertility and plant growth.

Water availability significantly influenced wheat growth under both systems, with no notable differences between them. The nano+bio-fertilizer treatment produced the highest growth, yield, and water productivity, followed by nano-fertilizer, bio-fertilizer, and control treatments.

In conclusion, this study underscores the need for careful irrigation system and fertilizer selection. Bio-fertilizers positively impacted soil conditions in both systems, while combining nano- and bio-fertilizers showed promise in enhancing soil fertility and crop productivity, offering insights for sustainable agriculture.

Disclosure statement

No potential conflict of interest was reported by the author(s).