Influence of hydrogel and graded levels of fertigation on growth and productivity of mulberry

Introduction

Mulberry is a robust, perennial deep-rooted foliage yielding plant, which produces high biomass and grows in tropics to temperate region throughout the year. The mulberry silkworm being monophagous insect, depends solely on mulberry for its growth and development. It has been documented that, approximately 70 per cent of silk proteins are derived directly from mulberry leaves. Silkworms must therefore be nourished with good quality mulberry leaves with sufficient quantity for obtaining sustained productivity of quality cocoons (Vijaya et al., 2009) [22] . Therefore, cultivation of mulberry with proper nutrient management is a prerequisite for obtaining maximum profit in sericulture. Mulberry is known to respond extremely well to various inputs, particularly to the soil moisture and nutrients. Insufficient water resources, erratic monsoon and long dry spell are some of the major limiting factors for the progress of mulberry sericulture. However, mulberry is being raised by the resource constrained farmers with marginal lands having shallow depth, low water holding capacity and organic matter with poor native fertility in most parts of sericulturally rich states of India. Even though with sufficient cultivable land, sericulture farmers are facing tremendous challenges for expansion and maintenance of the existing mulberry area and its productivity. Water scarcity and its implications in sericulture have become very prominent under the era of climatic change. Under such a situation, use of hydrogels to enhance water use efficiency for better productivity of mulberry can prove as suitable option for the sericulture farmers. Hydrogels are cross-linked water-absorbing polymers that absorb aqueous solutions through hydrogen bonding with water molecules. In agriculture, hydrogels -often referred as water retention granules, can swell significantly upon contact with water making them useful for improving soil water retention. Particularly in arid and semi-arid regions like much of India, these super absorbent polymers (SAPs) enhance water availability for plants by increasing the water-holding capacity of soils and substrates. The effectiveness of hydrogels varies based on their chemical properties, such as molecular weight, which affects their impact on soil properties (Neethu et al., 2018) [16] . Harshitha Mala et al. (2023) [9] reported that the highest plant growth and yield parameters in mulberry were observed in the plots treated with Zeba hydrogel @ 6 kg per acre. Apart from water, nutrient management in mulberry plays a major role in quality and productivity of foliage and the cocoons. Nutrients for plant growth and development may be provided either through soil applicants or liquid medium. Fertigation is one such technique of application of fertilizers along with irrigation water and it provides an excellent opportunity to save labour apart from maximizing the yield. Fertigation ensures adequate supply of water and nutrients with précised timing and uniform distribution to meet the crop nutrient demand. Yan et al. (2022) [23] reported that N and P fertilizer applied through fertigation increased wheat grain yield by 16 per cent over top dressed N. Fertigation allows up to 90 per cent absorption of the applied nutrients, while granular or dry fertilizer application typically result in absorption rates of 10 to 40 per cent thus saving 40-60 per cent of the applied fertilizer, which is mainly due to "better fertilizer use efficiency" and "reduction in leaching" (Kumar and Singh, 2002) [11] . Mulberry is one of the major commercial crops cultivated in eastern dry zone of Karnataka where availability of water is a major limitation. Hence, the study is planned to evaluate the combined effect of standardized dose of Zeba hydrogel @ 6 kg per acre along with varied fertigation levels on the growth and yield performance of mulberry.

Materials and Methods

The experiment was conducted during 2025 in well-established V1 mulberry garden at University of Agricultural Sciences, Gandhi Krishi Vigyan Kendra, Bengaluru. The field is located at a latitude of 12°58' N, and longitude of 77°35' East and at an altitude of 930 m above mean sea level in the Eastern Dry Zone (Zone 5) of Karnataka. The experiment was established with eight treatment combinations viz., T 1 -50% RDNK through fertigation, T 2 -50% RDNK through fertigation + Zeba hydrogel @ 6 kg ac -1 , T 3 -75% RDNK through fertigation, T 4 -75% RDNK through fertigation + Zeba hydrogel @ 6 kg ac -1 , T 5 -100% RDNK through fertigation, T 6 -100% RDNK through fertigation + Zeba hydrogel @ 6 kg ac -1 , T 7 -control (RDNK as per Package of Practice) and T 8 -control (RDF as per Package of Practice). These treatments were laid out in RCBD design with three replications. Zeba hydrogel application was carried out only once for first crop after the pruning. Fertigation (T 1 to T 6 ) application was carried out in three equal splits at weekly intervals (15 th to 29 th days after pruning) for both first and second crop (Mahesh et al., 2022) [14] , T 7 (without P for second crop) and T 8 (with P for both crops) were acted as control treatments. The fertilizers for T 7 and T 8 were applied at 20 days after pruning as per Dandin and Giridhar, (2014) [7] . FYM @ 20 t ha -1 yr -1 was applied after pruning of mulberry and irrigation was given based on soil moisture content for all the treatments. N (Urea) and K (Murate of potash) were applied through fertigation for both the crops. Phosphorus is immobile in soil, while is mainly responsible for root growth, so applied only once as basal dose for all the treatments except T 8 (Arunadevi and Selvaraj, 2013) [5] . Single point sensors were placed at 15 cm depth to ensure enough water for crop growth. Soil moisture indicator was developed by Sugarcane Breeding Institute, Coimbatore which works on principle of resistance but, the depiction will be in the form of colour (https://sugarcane.icar.gov.in/ index.php/soilmoisture-indicator/). The data on growth parameters at 30, 45 and 60 DAP and yield parameters at 60 DAP of mulberry crop were recorded in each treatment on randomly selected five plants from each net plot out of 24 plants and mean value was worked out. The experimental data collected on growth components of plant were subjected to Fisher's method of Analysis of Variance (ANOVA) as outlined by Sundararaj et al. (1972) [20] .

Results and Discussion

The results and discussion on influence of hydrogel and graded levels of fertigation on growth and productivity of mulberry are revealed as following:

The shoot length of mulberry was significantly influenced by fertigation levels and hydrogel application at all stages of observation (30, 45 and 60 DAP). Among the treatments, T 6 (100% RDNK through fertigation + Zeba hydrogel @ 6 kg ac⁻¹) recorded the maximum shoot length (116.44, 153.51 and 191.42 cm at 30, 45 and 60 DAP, respectively), followed by T 4 (75% RDNK through fertigation + Zeba hydrogel @ 6 kg ac⁻¹) and T 5 (100% RDNK through fertigation alone), which were significantly superior to their respective control treatments. The lowest shoot length was recorded in T 7 (control with RDNK) and T 8 (control with RDF). The superior performance of T 6 could be attributed to the synergistic effect of continuous nutrient supply through fertigation and improved soil moisture retention by hydrogel, which maintains an optimum moisture regime, at rhizosphere enhances nutrient uptake and promotes root proliferation and vegetative growth (Poorter and Nagel, 2000) [17] . The superiority of hydrogel-integrated treatments (T 2 , T 4 and T 6 ) over the non-hydrogel treatments (T 1 , T 3 and T 5 ) demonstrate that hydrogels improves the growth even under reduced fertilizer levels by enhancing water and nutrient use efficiency. Similar positive effects of hydrogels on shoot elongation were reported in other crops such as cucumber and chickpea (Baasiri et al., 1986; Akhter et al., 2004) [6;2] , and in mulberry by Harshita Mala et al. (2023) [9] . Drip fertigation itself has shown the enhanced vegetative growth and shoot elongation compared to conventional methods, with 100 per cent or 75 per cent recommended dose under optimized fertigation conditions yielding superior results (Mahesh et al., 2022) [14] . The poor performance of control treatments (T 7 and T 8 ) underscores the inefficiency of traditional nutrient and water delivery methods, while the combined use of fertigation and hydrogel ensured precise nutrient availability, improved moisture conservation and consequently resulted in shoot elongation.

Number of shoots per shoot

The number of shoots per plant in mulberry was significantly influenced by fertigation levels and hydrogel application at 30, 45 and 60 days after pruning. Among the treatments, T 6 (100% RDNK through fertigation + Zeba hydrogel @ 6 kg ac⁻¹) recorded the maximum number of shoots per plant (19.85, 20.73 and 22.73 at 30, 45 and 60 DAP, respectively), followed by T 4 (75% RDNK + Zeba hydrogel @ 6 kg ac⁻¹) and T 5 (100% RDNK fertigation alone). The minimum number of shoots was observed in the controls T 7 (soil application of RDNK) and T 8 (soil application of RDF as per package of practice). The superior performance of T 6 can be attributed to the synergistic interaction between fertigation and hydrogel, ensuring continuous nutrient availability and optimal soil moisture that favour shoot initiation and multiplication. Continuous and balanced nutrient supply, especially nitrogen and potassium through fertigation, promotes axillary bud differentiation and sprouting, while the hydrogel maintains a favourable moisture regime, enhances cytokinin activity and reduces plant stress, collectively resulting in enhanced shoot formation (Kaplan et al., 2021) [10] . The combined fertigation and hydrogel effect, promotes root proliferation and efficient uptake of nutrients and growth hormones, leading to better photosynthetic activity and assimilate partitioning towards developing buds. These results align with the findings of Arunadevi and Selvaraj (2013) [5] , who reported that fertigation ensures efficient use of water and fertilizers, thereby improving bud sprouting and shoot number in perennial crops. Similarly, Harshitha Mala et al. (2023) [9] reported that Zeba hydrogel @ 6 kg ac⁻¹ significantly increased shoot numbers in mulberry, with treated plants producing an average of 20.4 shoots per plant against 14.6 in control, supporting the superior performance of T 6 in the present study.

Number of leaves per shoot

The number of leaves per shoot in mulberry was significantly influenced by fertigation levels and hydrogel application at 30, 45 and 60 days after pruning. Among the treatments, T₆ (100% RDNK through fertigation + Zeba hydrogel @ 6 kg ac⁻¹) recorded the highest number of leaves per shoot (21.43, 26.45 and 32.44 at 30, 45 and 60 DAP, respectively), followed by T₄ (75% RDNK + Zeba hydrogel @ 6 kg ac⁻¹) and T₅ (100% RDNK fertigation alone). The lowest leaf numbers were observed in T₇ (RDNK control) and T₈ (RDF control), indicating the inefficiency of conventional fertilizer application compared to fertigation-based systems. The superior performance of T₆ can be attributed to the synergistic effects of continuous nutrient availability and improved soil moisture retention, which collectively enhanced leaf initiation and expansion. Fertigation ensures a steady nutrient supply, particularly nitrogen and potassium, promoting chlorophyll synthesis, protein formation and active cell division, while hydrogel maintains optimal soil moisture and turgor pressure, reducing plant stress and supporting vigorous vegetative growth. The improvement in leaf number per shoot under hydrogel-integrated fertigation treatments (T₂, T₄ and T₆) revealed the importance of combining water and nutrient management for enhanced canopy development. Efficient fertigation has been shown to promote leaf proliferation and overall vegetative growth in perennial crops (Arunadevi and Selvaraj, 2013) [5] , while Suresh et al. (2021) [21] reported that drip fertigation with 100 per cent RDF significantly increased leaf production in mulberry compared to conventional methods. Similarly, Kumar et al. (2022) [12] observed that integrating fertigation with soil amendments like hydrogels or organic mulches improved leaf expansion and total leaf number. Harshitha Mala et al. (2023) [9] also demonstrated that hydrogel application had increased shoot and leaf numbers in mulberry, reinforcing that the combined fertigation and hydrogel approach creates favourable soil, water and nutrient conditions for maximum number of leaves.

Leaf area of mulberry was significantly influenced by the interaction of fertigation levels and hydrogel application at 30, 45 and 60 DAP. The T₆ treatment (100% RDNK through fertigation + Zeba hydrogel @ 6 kg ac⁻¹) recorded the highest leaf area (93.43, 148.87 and 190.04 cm² at 30, 45 and 60 DAP, respectively), followed by T₄ (75% RDNK + Zeba hydrogel @ 6 kg ac⁻¹) and T₅ (100% RDNK fertigation alone), which were significantly superior over the fertigated treatments without hydrogel. The lowest leaf area was observed in T₇ (RDNK control) and T₈ (RDF control), reflecting the limited efficiency of conventional fertilizer application without precise nutrient and moisture management. The superior performance of T₆ can be attributed to the synergistic effects of continuous nutrient supply and improved soil moisture retention that collectively enhanced cell expansion, chlorophyll synthesis and overall leaf development. Fertigation ensures steady nitrogen and potassium availability, promoting photosynthetic activity and cell division, while hydrogel maintains turgor pressure, reduces water stress and supports sustained leaf expansion. The improvement in leaf area under hydrogel-integrated fertigation treatments (T₂, T₄ and T₆) highlights the positive interaction between water and nutrient management in promoting vegetative growth. Similar results were reported by Ajwa and Trout (2006) [1] , who found that improved water availability and nutrient uptake through hydrogels enhanced photosynthesis and leaf area. Arunadevi and Selvaraj (2007) [4] , who observed significantly higher leaf area in mulberry under drip fertigation compared to conventional fertilization. Firouzeh et al. (2007) [8] also demonstrated that soybean plants treated with 225 kg ha⁻¹ of hydrogel polymer recorded the highest leaf area index Likewise, Singh et al. (2018) [19] observed a significant increase in LAI in sugarcane when hydrogel was applied at 2.5 kg ha⁻¹ at planting. Zhang et al. (2012) [25] reported that fertigation improved maize leaf area through enhanced nutrient uptake. Collectively, these studies emphasises that integrating the fertigation with hydrogel application creates favourable soil, water and nutrient conditions, promoting leaf expansion and overall vegetative development.

Leaf yield

Leaf yield of mulberry was significantly influenced by fertigation levels and hydrogel application at 60 DAP. The maximum leaf yield was recorded in T₆ (100% RDNK through fertigation + Zeba hydrogel @ 6 kg ac⁻¹), averaging 3.73 kg plant⁻¹, 8116 kg ha⁻¹, and 40.58 t ha⁻¹ yr⁻¹, representing a 44.11% increase over control. Treatments T₄ (75% RDNK + Zeba hydrogel @ 6 kg ac⁻¹) and T₅ (100% RDNK fertigation alone) also produced significantly higher yields compared to their respective controls. The minimum yields were obtained in T₇ (RDNK control) and T₈ (RDF control), indicating the limited efficiency of conventional fertilizer application without fertigation or hydrogel. Overall, the combination of fertigation and hydrogel (T₂, T₄ and T₆) consistently enhanced leaf yield, with T₆ showing the maximum advantage. The improvement in leaf yield may be attributed to the synergistic effects of efficient nutrient delivery and improved soil moisture retention.

Continuous nutrient supply through fertigation promotes steady vegetative growth and higher biomass accumulation, while hydrogel maintains soil moisture and reduces water stress, sustaining leaf turgidity and also improves photosynthetic efficiency. Similar observations were reported by Lee et al. (1992) [13] , who recorded a 22 per cent yield increase with additional fertilizer and Naveen et al. (2019) [15] highlighted that continuous nutrient availability improves nutrient use efficiency and reduces its losses. Additionally, Arunadevi and Selvaraj (2007) [4] , Seenappa et al. (2015), Suresh et al. (2021) and Mahesh et al. (2022) [18,21&14] noted higher mulberry yields under optimized fertigation, while Singh et al. (2018) [19] and Kumar et al. (2022) [12] observed further improvements with hydrogel application. Collectively, these studies confirm that integrating fertigation with hydrogel creates favourable conditions for maximising the leaf yield in mulberry.

The quantity of water applied, water productivity and water use efficiency in mulberry were significantly influenced by fertigation levels along with the hydrogel application. The highest water productivity (611.61 kg ha cm -1 ) and lowest water requirement per kg of leaf (163.5 L kg⁻¹) were recorded in T₆ (100 % RDNK through fertigation + Zeba hydrogel @ 6 kg ac -1 ), along with the maximum water savings (21.43%) compared to conventional irrigation. Treatments T₄ (75 % RDNK + Zeba hydrogel @ 6 kg ac⁻¹) and T₅ (100 % RDNK fertigation alone) also showed improved water productivity (578.94 and 546.16 kg ha cm -1 , respectively) and considerable water savings (19.59%). In contrast, T₇ and T₈ (conventional RDNK/RDF) required the highest water application (16.89 ha-cm), exhibited the lowest water productivity (333.51-357.55 kg ha cm -1 ) and resulted in no water savings. Overall, the combination of hydrogel and fertigation (T₂, T₄ and T₆) effectively reduces water consumption while increasing yield per unit of water. The enhanced water productivity and savings observed under hydrogel-integrated fertigation treatments can be attributed to improved soil moisture retention by hydrogels, which maintain optimal moisture, reduce evapotranspiration losses and allow longer irrigation intervals without compromising crop growth. Fertigation ensures timely and precise nutrient delivery to the root zone, supporting sustained vegetative growth and efficient leaf production. The combined effect promotes deeper root growth and better synchronization of water and nutrient uptake, leading to reduced irrigation frequency and higher water productivity. These results are in confirmation with findings of Alam et al. (2020) [3] who reported that the maximum water productivity was found in alternate day irrigation with hydrogel (127.27%) which in turn has increased the leaf yield by 12.46 per cent and further it consumed 15 per cent of less water when compared to daily irrigation in mulberry. Similar results have been reported by Zhang et al. (2017) [24] in maize, Mahesh et al. (2022) [14] in mulberry and Harshitha Mala et al. (2023) [9] confirming that integrating hydrogel application with fertigation enhances water use efficiency, maximizes vegetative growth and leaf yield, and provides a sustainable strategy for mulberry cultivation under limited water conditions. It is concluded that the integration of Zeba hydrogel with fertigation significantly improved mulberry growth, and yield attributes. Growth traits such as shoot length, number of shoots, number of leaves and leaf area were maximum under 100 per cent RDNK + Zeba hydrogel @ 6 kg ac -1 , closely followed by 75 per cent RDNK + Zeba hydrogel @ 6 kg ac -1 . Leaf yield and water productivity was also highest in hydrogel-treated plots, demonstrating the synergistic role of moisture conservation and efficient nutrient availability.

References

1. Ajwa HA, Trout TJ. Polyacrylamide and water quality effects on infiltration in sandy loam soils. Soil Sci Soc Am J. 2006;70(2):643-650.
2. Akhter J, Mahmood K, Malik KA, Mardan A, Ahmad M, Iqbal MM. Effects of hydrogel amendment on water storage of sandy loam and loam soils and seedling growth of barley, wheat and chickpea. Plant Soil Environ. 2004;50(10):463469.
3. Alam M, Hussain S, Khan A. Hydrogel incorporation with alternate-day irrigation improves soil fertility and reduces nutrient leaching losses in mulberry. J Soil Water Conserv. 2020;25(2):98-105.
4. Arunadevi K, Selvaraj PK. Effect of drip fertigation on mulberry leaf growth attributes, leaf yield and leaf quality characters. Crop Res. 2007;33(1-3):237-243.
5. Arunadevi K, Selvaraj PK. Moisture distribution and fertilizer mobility under drip fertigation in mulberry. J Soil Water Conserv. 2013;12(2):123-129.
6. Baasiri M, Ryan J, Mucheik M, Harik SN. Soil application of a hydrophilic conditioner in relation to moisture, irrigation frequency and crop growth. Commun Soil Sci Plant Anal. 1986;17(6):573-589.
7. Dandin SB, Giridhar K. Handbook of Sericulture Technologies. Bangalore: Central Silk Board; 2014. p. 427.
8. Firouzeh R, Keshavarz A, Mohammadi M. Influence of hydrogel polymer and irrigation intervals on leaf area index of soybean. J Agron. 2007;6(2):300-306.
9. Harshita Mala P, Banuprakash KG, Hanumanthappa DC, Vinoda KS. Efficacy of hydrogels under sensor-based irrigation on growth and productivity of tree mulberry. Mysore J Agric Sci. 2023;57(4):135-144.
10. Kaplan M, Lenart A, Klimek K, Borowy A, Wrona D, Lipa T. Assessment of the possibilities of using cross-linked polyacrylamide (Agro Hydrogel) and preparations with biostimulation in building the quality potential of newly planted apple trees. Agronomy. 2021;11(1):125.
11. Kumar A, Singh AK. Improving nutrient and water use efficiency through fertigation. J Water Manag. 2002;10:4248.
12. Kumar R, Singh S, Patel A. Effect of fertigation and soil amendments on leaf expansion and total leaf number in tomato under integrated soil-water-nutrient management. J Plant Nutr. 2022;45(11):1785-1796.
13. Lee WC, Choi YC, Song SP, Seong MH. Effect of sub-soil drip irrigation and fertigation on mulberry yield. J Seric Entomol Sci. 1992;34(2):6-12.
14. Mahesh R, Anil P, Debashish C, Sivaprasad V. Improved mulberry productivity and resource efficiency through lowcost drip fertigation. Arch Agron Soil Sci. 2022;68(6):749763.
15. Naveen DV, Venkatachalapathi V, Vinoda KS, Bharathi VP, Naika R, Venkataravana P. Effect of graded levels of water-soluble fertilizers on growth, yield of mulberry and cocoon quality. Innov Farming. 2019;4(4):185-188.
16. Neethu TM, Dubey PK, Kaswala AR. Prospects and applications of hydrogel technology in agriculture. Int J Curr Microbiol Appl Sci. 2018;7(5):3155-3162.
17. Poorter H, Nagel O. The role of biomass allocation in the growth response of plants to different levels of light, CO₂, nutrients and water: a quantitative review. Funct Plant Biol. 2000;27(2):595-605.
18. Seenappa C, Devakumar N, Manjula N. Yield and quality of mulberry leaf and cocoon influenced by different methods, levels of irrigation and mulching during summer in eastern dry zone of Karnataka. Int J Agric Innov Res. 2015;3(5):1319-1473.
19. Singh I, Verma RR, Srivastava TK. Growth, yield, irrigation water use efficiency, juice quality and economics of sugarcane in pusa hydrogel application under different irrigation scheduling. Sugar Tech. 2018;20(1):29-35.
20. Sundararaj N, Nagaraju S, Venkataramu MN, Jagannath MK. Design and analysis of field experiments. Bangalore: Directorate of Research, UAS; 1972. p. 139.
21. Suresh K, Reddy MS, Kumar P. Optimized fertigation regimes enhance leaf number and shoot proliferation in mulberry. J Plant Nutr. 2021;44(9):1350-1360.
22. Vijaya D, Yeledhalli NA, Ravi MV, Nagangoud A, Nagalikar VP. Effect of fertilizer levels and foliar nutrition on M-5 mulberry leaf nutrient content, quality and cocoon production. Karnataka J Agric Sci. 2009;22(5):1006-1012.
23. Yan S, Zhou Y, Liu Y, Wang P. Drip fertigation effects on nutrient uptake and utilization of winter wheat. Field Crops Res. 2022;280:108415.
24. Zhang H, Liu J, Wang Y. Application of superabsorbent polymers in maize cultivation: reduction in irrigation requirements and maintenance of yield. J Soil Sci Plant Nutr. 2017;17(4):1032-1040.
25. Zhang Y, Liu Y, Wang Z. Effect of fertigation on leaf area index and nutrient uptake in maize. J Plant Nutr. 2012;35(8):1223-1235.