Comparative evaluation of irrigation schedules and hydrogel formulations for enhancing growth and nutrient uptake of wheat

Introduction

Wheat is the second most important staple cereal after rice in India, underpinning both national food security and rural livelihoods across the region. Wheat occupied an area of 31.83 million hectares with a production of 113.29 million tonnes and a productivity of 3559 kg/ha (MoA & FW, 2023-24). Wheat productivity is tightly coupled to the timing and adequacy of irrigation, since the crop is largely grown on residual soil moisture supplemented by a limited number of irrigations during the winter (Rabi) season. Annual per capita water availability in India fell from over 5,000 m³ in the 1950s to below 1,450 m³ today, pushing large parts of the country below the international water-stress benchmark of 1,700 m³ per capita (Rajanna et al., 2022) [16] . India faces critical groundwater depletion driven heavily by agriculture, which consumes 80% to 90% of the country's available freshwater (Roy et al., 2019) [17] . Erratic and declining rainfall, groundwater depletion, and rising pump-irrigation costs have intensified the need for management strategies that either improve water-use efficiency or reduce the number of irrigations needed to sustain yield. Against this backdrop, soil-applied superabsorbent hydrogels have attracted growing agronomic interest as a low-cost, field-deployable technology to buffer soil moisture availability during critical crop-growth stages (Agbna et al., 2025) [2] .

Hydrogels are three-dimensional, cross-linked hydrophilic polymer networks capable of absorbing and retaining water at many times their own dry weight, and of releasing this water gradually to the surrounding rhizosphere as the soil dries (Saini et al., 2023) [18] . Beyond their function as water reservoirs, hydrogels modify soil physical structure by reducing bulk density and increasing porosity, particularly in coarse-textured soils, and can improve aggregate stability and soil aeration through repeated swelling-shrinkage cycles (Wang et al., 2026) [23] . In addition to improving soil moisture retention, hydrogels can reduce nutrient leaching by 20-30%, thereby promoting nutrient conservation and potentially enhancing soil fertility (Kebede et al., 2022) [11] Despite this accumulating evidence, most published trials have evaluated a single hydrogel product against an untreated control, leaving open the question of how different commercially available hydrogel formulations differing in polymer chemistry, particle scale and recommended application rate compare with one another when tested side by side under a common irrigation gradient. Therefore, the present study was undertaken to evaluate the effect of three irrigation schedules and four hydrogel formulations, together with an untreated control, on growth parameters of wheat cv. HD-2967 and nutrient uptake in grain and straw

Materials and Methods

Experimental site and climate

The experiment was conducted during the winter (rabi) season of 2020-21 at the college farm of Bihar Agricultural University, Sabour, Bhagalpur, Bihar, India, located in the middle Gangetic plain (Agro-climatic Zone IIIA of southern East Bihar) at 25°50′ N latitude, 87°19′ E longitude and 52.73 m altitude above mean sea level. The site experiences a sub-tropical climate with hot, dry summers, moderate rainfall and cold winters; during the 2020-21 crop season, weekly minimum and maximum temperatures ranged from 7.7 to 19.9°C (29 January-4 February) and 24.8 to 36.1°C (9-15 April), respectively. Total rainfall received during the crop period was only 0.40 mm, against a normal of 56.0 mm, so that crop water supply was almost entirely determined by the imposed irrigation treatments. The experimental soil was sandy loam in texture, neutral in P H , and contained 0.50% organic carbon, 179.38 kg available nitrogen/ha (Subbiah and Asija, 1956) [20] , 23.52 kg available P 2 O 5 /ha (Olsen et al., 1954) [14] , and 193.00 kg available K 2 0 /ha (Jackson, 1973) [10] .

Treatment details

The field trial was laid out in a split-plot design replicated thrice. Three irrigation schedules were assigned to main plots: I 1 , one irrigation at the crown root initiation (CRI) stage; I 2 , two irrigations at CRI and the boot leaf stage; and I 3 , three irrigations at CRI, late jointing and the milking stage. Four hydrogel treatments: T 1 , Eco Sarovar hydrogel (7.5 kg ha⁻¹); T 2 , Vedic hydrogel (7.5 kg ha⁻¹); T 3 , Vaaridhar G1 hydrogel (2.5 kg ha⁻¹); T 4 , Nano hydrogel (20 kg ha⁻¹); and T 5 , an untreated control (no hydrogel), formed the sub-plot factor, giving 15 main-plot × subplot treatment combinations. Wheat variety HD-2967 was used as the test cultivar, and the recommended fertilizer dose of 150:60:40 kg N: P₂O₅: K₂O ha⁻¹ was applied through urea, diammonium phosphate and muriate of potash.

Growth parameters

Plant height (cm) was recorded on five randomly selected, tagged plants per plot at 30, 60 and 90 days after sowing (DAS) and at harvest, measured from the base to the tip of the plant using a meter scale, and averaged per plot. The number of tillers m⁻² was counted at three randomly selected locations per plot at the same growth stages and averaged. Leaf area index (LAI) was measured directly at 30, 60 and 90 DAS using a ceptometer (AccuPAR LP-80, Decagon Devices Inc., Pullman, WA, USA) at three randomly selected locations per plot. Total dry matter accumulation (g m⁻²) was determined destructively from a 25-cm row-length sample cut from the third row of each plot at 30, 60 and 90 DAS and at harvest; samples were sun-dried and then oven-dried at 60 ± 5 °C to constant weight. Crop growth rate (CGR, g m⁻² day⁻¹) was calculated for the intervals 0-30, 30-60, 60-90 DAS and 90 DAS-harvest using the classical formula of Watson (1947) [24] :

where W₁ and W₂ are dry matter accumulation (g m⁻²) at times t₁ and t₂, respectively.

Plant sample analysis and nutrient uptake

At harvest, grain and straw samples from each plot were ovendried for 48 h at 60 ± 5°C, ground in a Willey mill and passed through a 30-mesh sieve for chemical analysis. Nitrogen content was determined following digestion with concentrated H₂SO₄ and H₂O₂ in the presence of a catalyst mixture, using the modified Kjeldahl method (Piper, 1966) [15] . Phosphorus content was estimated after di-acid digestion by the vanadomolybdatephosphoric yellow colour method (Jackson, 1973) [10] , read spectrophotometrically. Potassium content was determined on the same di-acid digest using a flame photometer (Jackson, 1973) [10] . Nutrient uptake (kg ha⁻¹) in grain and straw was calculated using the formula below, and total uptake was obtained by summing grain and straw uptake.

Nutrient uptake (kg ha⁻¹) =

Nutrient concentration (%) 100 × Yield (kg ha⁻¹)

Statistical analysis and data visualization

All data were subjected to analysis of variance appropriate to the split-plot design, with irrigation levels as the main-plot factor and hydrogel treatments as the sub-plot factor, replicated thrice. Treatment means were compared using the critical difference (CD) at P = 0.05; where the F-test was non-significant, treatment effects were reported as non-significant (NS) as described by Gomez and Gomez (1984) [7] . In addition to the standard analysis of variance, treatment-mean data for all recorded traits were used to construct a series of complementary visualizations including temporal growth-trajectory line plots, stacked bar charts for grain/straw nutrient partitioning, a percentage-increase-overcontrol summary chart, and standardized (z-score) heat map to facilitate multi-trait comparison among the five hydrogel treatments. All these figures were generated in Python using Matplotlib (Hunter, 2007) [9] and NumPy (Harris et al., 2020) [8] at a resolution of 300 dpi.

Results

Growth parameters

Plant sample analysis and nutrient uptake

Nitrogen, phosphorus and potassium uptake in grain, straw and total are summarized in Table 6. Nutrient uptake for all three elements increased consistently with increasing irrigation frequency. Nitrogen, phosphorus and potassium uptake by wheat was higher with three irrigations (I 3 ), but it was statistically at par with I 2 for all three nutrients. Nano hydrogel recorded 32.95, 31.88 and 25.29% higher N, P and K uptake over the control and was statistically comparable with Vedic hydrogel for straw nitrogen uptake. Irrigation × hydrogel interactions were nonsignificant for nitrogen, phosphorus and potassium uptake in both grain and straw.

Multi-trait visualization of treatment performance

The percentage-increase-over-control summary for hydrogels (Figure 7) and the corresponding percentage-increase-oversingle-irrigation summary for irrigation schedules (Figure 8) quantify the relative efficacy of each treatment level across all measured traits simultaneously. Nano hydrogel delivered the largest relative gain for every trait among hydrogel treatments, followed by Vedic and Eco Sarovar, which performed similarly to one another, while Vaaridhar G1 provided only a modest improvement over the control; among irrigation schedules, three irrigations (I 3 ) produced the largest relative gain over a single irrigation for every trait, with two irrigations (I 2 ) delivering roughly half of that gain, reflecting a diminishing-returns pattern as irrigation frequency increased.

The standardized (z-score) heat maps (Figures 9 and10) provide an integrated, multi-trait view of treatment performance for each factor separately. Nano hydrogel (T 4 ) and three irrigations (I 3 ) schedule independently maximized all agronomic and nutrient uptake traits. Notably, T 4 elicited the highest comparative efficacy across all parameters (z-scores ranging from +1.00 for LAI to +1.40 for tillers m⁻²), whereas the control (T 5 ) uniformly suppressed trait development (z = -1.28 to -1.46). Furthermore, trait performance scaled positively with water availability, the I 3 regime secured peak standardized scores (z = +0.59 to +1.10), while the moisture-restricted single-irrigation (I 1 ) regime resulted in pronounced, systemic deficits across all measured indices (z = -0.85 to -1.15).

Discussion

Growth parameters

Plant height and Number of tillers m⁻² at 90 DAS and at harvest was significantly improved by three irrigations at CRI, late jointing and the milking stage likely reflect better utilization of applied water across three critical growth stages, consistent with Buttar et al. (2018) [4] , Kumar et al. (2019) [12] , Tripathi et al.

(2023) [21] , and Gupta et al. The highest LAI at 60 and 90 DAS recorded under three irrigations, statistically at par with two irrigations at 90 DAS and significantly superior to one irrigation, consistent with Singh et al. (2017) [19] , Gupta et al. (2025) and Tripathi et al. (2023) [21] . Dry matter accumulation increased with three irrigations and statistically at par with two irrigations most plausibly reflecting sufficient water supply across three critical growth stages under I 3 , in line with Kumar et al. (2019) [12] , Tripathi et al. (2023) [21] and.Gupta et al. (2025). Two and three irrigations produced statistically comparable CGR at 60-90 DAS, while three irrigations were superior during 90 DAS-harvest, consistent with Singh et al. (2017) [19] , Kumar et al. (2019) [12] and Gupta et al.

Nano hydrogel (20 kg ha⁻¹) recorded significantly greater plant height at 90 DAS and at harvest than the control, plausibly reflecting greater moisture availability within the root zone of hydrogel-treated plots, consistent with Roy et al. (2019) [17] , Tripathi et al. (2023) [21] and Gupta et al. (2025). The number of tillers m⁻² at 60, 90 DAS and at harvest was higher with nano hydrogel, supported by the findings of Dar and Ram (2017) [5] , Gupta et al. (2025) and Tripathi et al. (2023) [21] . Significantly higher LAI at 90 DAS was recorded with nano hydrogel than the control, in agreement with El-Karamany et al. (2015) [6] , Singh et al. (2017) [19] , Tripathi et al. (2023) [21] and Gupta et al. Total dry matter accumulation was significantly superior with Nano hydrogel, plausibly reflecting more available root-zone moisture and more efficient utilization of applied water for photosynthesis and nutrient uptake, consistent with Kumar et al. (2019) [12] and Tripathi et al. (2023) [21] . Nano hydrogel recorded significantly higher CGR at 30-60, 60-90 and 90 DAS-harvest, in agreement with Singh et al. (2017) [19] and Kumar et al. (2019) [12] .

Nutrient uptake

Nutrient uptake (N, P and K) by the crop was significantly increased with three irrigations, which was statistically comparable with two irrigations, most likely because additional irrigation events promote greater mass-flow and diffusion of nutrients to the root surface. Similar results were reported by Tyagi et al. (2015) [22] , Singh et al. (2017) [19] and Kumar et al.

(2024) [13] . Nano hydrogel recorded significantly higher N, P, and K uptake by plant than all other treatments and the control, plausibly reflecting prolonged moisture availability and reduced leaching losses of water and nutrients, consistent with Singh et al. (2017) [19] , Bisen et al. (2018) [3] and Abd-Eladl (2018) [1] . This pattern is also consistent with the broader agronomic literature on hydrogelmediated controlled nutrient release, in which sustained soil moisture and reduced nutrient leaching are repeatedly identified as the principal mechanisms underlying improved crop nutrient status under hydrogel amendment (Wang et al., 2026) [23] .

Conclusion

Under the sandy-loam, sub-tropical field conditions of the middle Gangetic plain, both irrigation scheduling and hydrogel amendment significantly influenced the plant growth, dry matter accumulation, crop growth rate and nutrient uptake of wheat cv. HD-2967, with three irrigations at CRI, late jointing and milking stage generally statistically at par with two irrigations for most traits at later growth stages. Among the hydrogel formulations evaluated, Nano hydrogel (20 kg ha⁻¹) was consistently and significantly superior to Eco Sarovar, Vedic and Vaaridhar G1 hydrogels as well as to the untreated control across nearly every trait measured, a pattern corroborated by complementary multitrait visualizations (percentage-increase and standardized heatmap analyses). The absence of a significant irrigation × hydrogel interaction for any trait indicates that the benefit of hydrogel amendment, and of Nano hydrogel in particular, was additive across irrigation regimes. These findings support the integration of nanocomposite hydrogel amendment into wheat production packages in water-limited environments as a practical means of improving crop growth and nutrient-use efficiency, while underscoring the need for further multi-location and multi-season trials, together with a formal economic (cost:benefit) evaluation, before broad-scale recommendation.

References

1. Abd-Eladl M. Integrated management of wheat under dry land conditions. J Soil Sci Agric Eng. 2018;9(12):781-791. doi:10.21608/jssae.2018.36537.
2. Agbna GHD, Zaidi SJ. Hydrogel performance in boosting plant resilience to water stress: a review. Gels. 2025;11(4):276. doi:10.3390/gels11040276.
3. Bisen N, Singh SP, Singh RK, Prasad SK. Productivity and water use efficiency of bread wheat (Triticum aestivum L.) as influenced by irrigation schedule, mulching and hydrogel in eastern Indo-Gangetic plains of India. Bangladesh J Bot. 2018;47(4):921-926. doi:10.3329/bjb.v47i4.47387.
4. Buttar PS, Kingra PK, Singh SP. Effect of sowing dates, irrigation and mulching on growth and yield of wheat. Agric Res J. 2018;55(2):243-250. doi:10.5958/2395-146X.2018.00046.7.
5. Dar SB, Ram H. Productivity of wheat (Triticum aestivum L.) in relation to hydrogel as by different irrigation regimes and nutrient levels. Int J Chem Stud. 2017;5(5):609-613.
6. El-Karamany MF, Waly A, Shabaan AM, Bakry BA, Elewa TAA. Utilization of hydrogel for reducing water irrigation under sandy soil condition. 1 -Preliminary study on the effect of hydrogel on yield and yield components of sunflower and wheat under newly reclaimed sandy soil. Res J Pharm Biol Chem Sci. 2015;7(4):1056-1063.
7. Gomez KA, Gomez AA. Statistical procedures for agricultural research. 2nd ed. New York: John Wiley & Sons; 1984.
8. Harris CR, Millman KJ, van der Walt SJ, Gommers R, Virtanen P, Cournapeau D, et al. Array programming with NumPy. Nature. 2020;585(7825):357-362. doi:10.1038/s41586-020-2649-2.
9. Hunter JD. Matplotlib: a 2D graphics environment. Comput Sci Eng. 2007;9(3):90-95. doi:10.1109/MCSE.2007.55.
10. Jackson ML. Soil chemical analysis. New Delhi: Prentice Hall India Pvt Ltd; 1973. p.183-192.
11. Kebede B, Tsunekawa A, Haregeweyn N, Tsubo M, Mulualem T, Mamedov AI, et al. Effect of polyacrylamide integrated with other soil amendments on runoff and soil loss: case study from northwest Ethiopia. Int Soil Water Conserv Res. 2022;10(3):487-496. doi:10.1016/j.iswcr.2021.12.001.
12. Kumar S, Sharma PK, Yadav MR, Sexena R, Gupta KC, Kumar R, et al. Effect of irrigation levels and moisture conserving polymers on growth, productivity and profitability of wheat. Indian J Agric Sci. 2019;89(3):509514. doi:10.56093/ijas.v89i3.87597.
13. Kumar S, Singh AK, Kumar A, Kumar R, Kumar D, Kumar B. Impact of vermi-compost and hydrogel (Pusa) on soil dynamics, nutrient uptake and water productivity of wheat crop. Int J Environ Clim Change. 2024;14(2):1024-1039. doi:10.9734/ijecc/2024/v14i24014.
14. Olsen SR, Cole CV, Watanabe FS, Dean LA. Estimation of available phosphorus in soil by extraction with sodium bicarbonate. Washington (DC): United States Department of Agriculture; 1954. Circular 937.
15. Piper CS. Soil and plant analysis. New York: Academic Press; 1966.
16. Rajanna GA, Manna S, Singh A, Babu S, Singh VK, Dass A, et al. Biopolymeric superabsorbent hydrogels enhance crop and water productivity of soybean-wheat system in IndoGangetic plains of India. Sci Rep. 2022;12(1):11955. doi:10.1038/s41598-022-16049-x.
17. Roy T, Kumar S, Chand L, Kadam DM, Bihari B, Shrimali SS, et al. Impact of Pusa hydrogel application on yield and productivity of rainfed wheat in North West Himalayan region. Curr Sci. 2019;116(7):1246-1251. doi:10.18520/cs/v116/i7/1246-1251.
18. Saini AK, Malve SH. Impact of hydrogel on agriculture: a review. Ecol Environ Conserv. 2023;29(Suppl):S36-S47. doi:10.53550/EEC.2023.v29i01s.007.
19. Singh SP, Singh RK, Kumar S. Response of irrigation schedule, mulching and hydrogel on various growth analysis attributes and nutrient uptake of wheat (Triticum aestivum L.). J Pharmacogn Phytochem. 2017;6(5):2569-2573.
20. Subbiah BV, Asija GL. A rapid procedure for the estimation of available nitrogen in soil. Curr Sci. 1956;25:259-260. doi:10.5555/19571900070.
21. Tripathi A, Gupta S, Singh AK, Mishra H, Tripathi S. Effect of irrigation scheduling and hydrogel level on growth and yield of wheat (Triticum aestivum L.). Pharma Innov J. 2023;12(6):4934-4937.
22. Tyagi V, Singh RK, Nagargade M. Effect of hydrogel, NPK and irrigation levels on yield, nutrient uptake and water use efficiency of wheat (Triticum aestivum L.). Res Crops. 2015;16(4):653. doi:10.5958/2348-7542.2015.00091.1.
23. Wang L, Hu J, Wang L, Xue X, Guo P, Dong Y, et al. Hydrogels for agricultural applications: from soil amendment to crop enhancement. Gels. 2026;12(5):413. doi:10.3390/gels12050413.
24. Watson DJ. Comparative physiological studies on the growth of field crops: I. Variation in net assimilation rate and leaf area between species and varieties, and within and between years. Ann Bot. 1947;11(41):41-76.