Study on proper irrigation procedures for ornamentals using Hydrogel

Soilless substrates exhibit low water retention capacity, necessitating frequent and precisely timed irrigation events, a critical limiting factor in greenhouse production systems, as well as during the postproduction transition of plants to retail environments. The ability of hydrogels to absorb water and release it slowly, while improving water retention, positions them among the most effective soil amendments for addressing this problem.

Hydrogels can be classified as synthetic or bio-based, with the latter emerging as a promising product due to their reduced long-term environmental impact. AquaSteady (AS; Pratt Institute, Brooklyn, NY, USA) is a novel, bio-based hydrogel derived from alginate extracted from kelp ( Macrocystis pyrifera ) and is available in various forms. This study evaluated the impact of spiral form AS hydrogel on irrigation interval length and growth in two ornamental plants, calibrachoa ( Calibrachoa × hybrida ‘Rainbow Bermuda Blue’) and verbena ( Verbena × hybrida ‘Empress Flair White’). A spiral AS hydrogel was applied at 3 g per container (5 mg·g ⁻¹ based on 600 g substrate). Experiments were conducted from Sep 2025 to Jan 2026 at the Fabian Garcia Research Center in Las Cruces, NM, USA. For each cultivar, there were two treatments: one with AS and one without AS. There were 112 replicates of calibrachoa, 56 per treatment. There were 48 replicates of verbena, 24 per treatment. Four irrigation events were applied throughout the experimental period. Parameters evaluated included irrigation interval, water use efficiency (WUE), chlorophyll content, aboveground and belowground biomass, and stomatal conductance. Plant types were evaluated independently due to inherent differences between species. The results show that pots with AS extended the final irrigation interval by 2 d in calibrachoa (and 1 d in verbena), indicating potential to reduce irrigation frequency in practice; actual applied water was equal (16 L per container) in this study. WUE did not differ for calibrachoa (AS 0.98 vs control 0.97 g·L ⁻¹ ) and was statistically similar for verbena (AS 0.85 vs control 0.91 g·L ⁻¹ ). No significant differences in aboveground dry biomass, root dry biomass (for calibrachoa), stomatal conductance, or chlorophyll content were detected between AS-treated and control plants.

However, verbena root dry biomass was lower in AS than control (2.2 vs 2.7 g; P = 0.045) without affecting shoot biomass or visual quality. These findings demonstrate that the use of AS hydrogel in greenhouse production systems is an effective strategy to retain substrate water availability and reduce irrigation frequency, without negatively impacting plant health.

Paudel, Miraj & Joukhadar, Israel & Sotomayor-Ramírez, David & Kehlet, Cindie & Idowu, Omololu. (2026). Greenhouse Case Study: Irrigation Protocol for Ornamental Plants with AquaSteady Hydrogel. HortTechnology. 36. 835-847. 10.21273/horttech05918-26.

Source: ResearchGate