Hydrogel and Irrigation Frequency in the Production of Tomato Seedlings: Water Efficiency and Morpho-physiological Quality

Abstract

Aims: Evaluate the effects of hydrogel doses and irrigation frequencies on the morphophysiological development, vigor, and phytosanitary quality of tomato (Solanum lycopersicum L.) seedlings, seeking to identify combinations that optimize water-use efficiency and shorten greenhouse production time. Study Design: The experiment was conducted in a randomized complete block design with split-plots, using hydrogel doses [0 (control), 0.1, 0.5, 1.0 g cell-1] and irrigation frequencies (once, twice, or three times per week), with four replications. Place and Duration of Study: The study was carried out in a greenhouse at the Instituto Nacional de Innovación Agropecuaria y Forestal - INIAF, in Sipe Sipe, Cochabamba, Bolivia, during the 2023 growing season. Methodology: Morphophysiological variables such as root dry weight, plant height, leaf number, chlorophyll index (SPAD), and disease incidence were evaluated. Data were analyzed to determine the interactive effects (p £ 0.05) of hydrogel dose and irrigation frequency on seedling growth and acclimatization time. Results: Low hydrogel doses (0.1 g cell-1) combined with reduced irrigation (2-3 times per week) optimized seedling growth, resulting in a production cycle of approximately 35 days before acclimatization. Plants showed greater vigor, with root dry weight of 0.73-0.76 g, height of 10.85-11.55 cm, and chlorophyll index of 40-43 SPAD, while disease incidence remained below 5%. Conversely, the highest hydrogel dose (1.0 g cell-1) reduced chlorophyll content and seedling health. Increased irrigation frequency shortened acclimatization time (37.5-38.0 days for 2-3 irrigations per week vs. 40.25 days for the control) and decreased disease incidence (control 8.00% ± 1.41; twice weekly 5.75% ± 1.96; thrice weekly 5.25% ± 1.90). Intermediate doses (0.5-1.0 g) increased leaf number (≈ 4.15-4.22 vs. 3.58 in control), but higher doses reduced root biomass. Conclusion: The combined use of low-dose hydrogel and adjusted irrigation frequency constitutes a sustainable management strategy to enhance tomato seedling vigor, water-use efficiency, and phytosanitary quality under greenhouse conditions.