To meet the global food demand, agricultural production must increase by 70% by 2050.1 This demand has triggered the need for sustainable strategies to increase agricultural production and overcome the adverse effects of climate change. Researchers have developed innovative materials that enhance productivity while minimizing environmental impacts to promote sustainable agricultural practices. This article examines the use of advanced hydrogels to achieve sustainability in agriculture.
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Global Agricultural Challenges
Desertification is a process in which fertile lands degrade into deserts due to natural causes, such as drought, or human activities associated with deforestation and improper agricultural practices.2
Rapid climate change has resulted in low annual rainfall, temperature variations, and increased drought frequency, collectively contributing to decreased agricultural production. Many regions worldwide face desertification and global warming, significantly impacting crop yields.
Hydrological drought, characterized by an abnormal reduction in water supply in rivers, lakes, streams, reservoirs, and groundwater, has seriously impacted crop yields. To tackle this problem, scientists have developed many strategies, including low-pressure micro-sprinklers and drip irrigation systems. These techniques require a high operational budget, so they are mostly implemented on high-value crops.
Hydrogels in Agriculture
Hydrogels are three-dimensional polymer networks that are hydrophilic and retain a large amount of water without dissolving.3 They are also known as superabsorbent polymers because they can absorb almost 400 times more water compared to their dry weight. Furthermore, hydrogels can slowly release encapsulated active ingredients from their polymer matrix in response to mechanical stress. This unique characteristic of gradually releasing absorbed water could facilitate a reduction in irrigation frequency, a promising solution during water scarcity or drought.
Hydrogels can be sourced naturally (e.g., biopolymers), synthetically (e.g., superabsorbent polymers), or as a hybrid (e.g., nanocomposite hydrogels) of both.4
Natural hydrogels based on chitosan, starch, guar gum, lignin, alginate, and gelatin are obtained from plants, animals, fungi, and bacteria. Compared to synthetic hydrogels, bio-polymeric hydrogels are more eco-friendly and offer superior biodegradability and biocompatibility. Therefore, natural hydrogels are considered a potential tool for agricultural applications.
Composite hydrogels, prepared using starch grafted polyvinyl alcohol (PVA) and poly(acrylic acid-co-acrylamide) (AA-co-AM) hydrogel with nano-cellulose (NC), have exhibited pH-sensitive swelling behavior and significant swelling ability in saline medium, making them a promising candidate for agricultural use.2
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Scientists have combined fertilizers with hydrogels to develop slow-release fertilizer hydrogels, which have the potential to enhance plant nutrition and reduce the negative impact of conventional fertilizers.5 They also designed PVA and Polyvinyl Pyrrolidone (PVP) hydrogels for pest control and fertilization.6
Multiple studies have exhibited the hydrogel’s capacity to improve soil quality, promote seed germination, and facilitate plant growth in arid and semi-arid areas. Typically, hydrophilic hydrogels are applied during planting or coated onto the seeds. In agricultural practices, hydrogels are applied as nutrient carriers and soil conditioners.
Mechanism of Action of Hydrogels Releasing Water and Nutrients in Soil
Polymeric networks in hydrogels differ and have been classified as homo-polymeric hydrogels (cross-linking one type of polymer) and co-polymeric hydrogels (cross-linking two different types of polymer). The cross-linking density and the number of hydrophilic groups influence the water-holding capacity of hydrogels.
Water is considered a solvent because of its innate polarity and ability to form hydrogen bonds. Furthermore, an increased water temperature enhances molecular motion, increasing its solubility.
Although water molecules tend to dissolve the hydrogel by cleaving the strong covalent bonds that are cross-linked, it only enables the cleavage of hydrogen bonds. The alteration in hydrogen bonding promotes the restriction of water molecules within the pores of the hydrogel's network structure, a process known as swelling.7 Osmotically active mobile polar molecules promote swelling.
When water is exposed to land, it gets trapped within the soil granules. When soil is moist, the hydrogel uses osmosis to absorb water molecules within its network. However, when the soil is dry, it quickly releases water into the environment from its internal polymer network. Therefore, as required, water is released from a hydrogel network and returned to the soil.
In hydrogel-fertilizer formulations, nutrients are released gradually in the soil. This results in reduced fertilizer leaching, higher crop yield, and lower fertilizer requirements. It has been estimated that fertilizers loaded into hydrogel are released into the environment via a diffusion mechanism at a rate half that of conventional fertilizer treatments. The diffusion mechanism initiates a deswelling process, in which water molecules from the hydrogel are diffused and carry fertilizer through the porous network into the surrounding environment.
Conclusions
Hydrogels are gaining popularity in agricultural practices due to the global water shortage crisis, the increased frequency of droughts, soil degradation, and the need for higher agricultural production through sustainable strategies.2 Hydrogel application promotes sustainable agriculture by promoting efficient use of water resources by lowering water loss from evaporation and runoff.
Coating hydrogel formulations in plant roots provides the plant with access to water, thereby protecting it from drought or insufficient water resources. This approach enhances crop resilience to drought and maintains crop yields even in unfavorable conditions. Furthermore, an increase in the soil water-holding capacity stabilizes soil surfaces and decreases erosion. Therefore, the application of hydrogels combats soil deterioration and safeguards arable land.
Hydrogel engineering facilitates the controlled release of nutrients, providing a steady supply of essential elements for plant growth. Therefore, increasing hydrogel formulations in agriculture could improve the microclimate for plant growth and serve as a protective barrier against biotic and abiotic stresses.
References and Further Reading
- van Dijk M. et al. A meta-analysis of projected global food demand and population at risk of hunger for the period 2010–2050. Nat Food. 2021; 2, 494–501. https://doi.org/10.1038/s43016-021-00322-9
- Tariq Z, et al. Significance of biopolymer-based hydrogels and their applications in agriculture: a review in perspective of synthesis and their degree of swelling for water holding. RSC Adv. 2023;13(35):24731-24754. doi: 10.1039/d3ra03472k.
- Ahmad Z, et al. Versatility of Hydrogels: From Synthetic Strategies, Classification, and Properties to Biomedical Applications. Gels. 2022;8(3):167. doi: 10.3390/gels8030167.
- Zhao L, et al. Natural Polymer-Based Hydrogels: From Polymer to Biomedical Applications. Pharmaceutics. 2023;15(10):2514. doi: 10.3390/pharmaceutics15102514..
- Rodrigo L, Munaweera I. Employing sustainable agriculture practices using eco-friendly and advanced hydrogels. RSC Adv. 2025;15(26):21212-21228. doi: 10.1039/d5ra03035h.
- Malka E, Margel S. Engineering of PVA/PVP Hydrogels for Agricultural Applications. Gels. 2023;9(11):895. doi: 10.3390/gels9110895.
- Ali K, et al. Progress and Innovations in Hydrogels for Sustainable Agriculture. Agronomy. 2024; 14(12):2815. https://doi.org/10.3390/agronomy14122815
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