Super Absorbent Polymer and Irrigation Regime Effects on Growth and Water Use Efficiency of Container-Grown Cherry Tomatoes

Abstract

Abstract. There is a need to develop innovative techniques to effectively use water in agriculture to meet the growing demands for food. Super absorbent polymers (SAPs), or hydrogels, can absorb and retain large amounts of water against gravitational forces and release it on demand to meet plant water requirements. Being an artificially synthesized compound, it is imperative that SAPs should not introduce toxicity to the growing medium or produce. The objectives of this study were to determine whether SAPs can improve water use efficiency (WUE) and the physiological growth of cherry tomatoes ( var. ) without causing soil toxicity. A pot-trial experiment was carried out in 2014 at the Research Greenhouse of McGill University’s Macdonald Campus (Ste-Anne-de-Bellevue, Quebec, Canada) in a completely randomized design, with three concentrations of SAP (0%, 0.1%, and 0.5%) and three irrigation intervals (daily, each alternate day, and every third day). The mean yield of the experimental cherry tomatoes was statistically significantly higher where 0.5% SAP was applied, compared to where SAP was not applied (p = 0.0056). The mean WUE was also higher where 0.5% SAP was applied when compared to where SAP was not applied (p = 0.05). To ascertain food safety, the presence of free acrylamide monomer in tomatoes was checked. The acrylamide concentrations were below the detection limit of 5 µg kg-1 in all tomato samples. To assess environmental toxicity, a Microtox toxicology analysis was also conducted on the growing medium, which revealed that the SAP used in the study was not toxic. Therefore, it can be concluded that the application of SAP could increase yield and WUE of greenhouse-grown cherry tomatoes. It also appears that SAP did not introduce toxic side-effects in the soil nor in the tomatoes, as determined by Microtox acute toxicity test and acrylamide residue analysis with LC-MS. Keywords: Acrylamide, Cherry tomatoes, Greenhouse, Microtox, Monomer, Super absorbent polymer, Toxicity, Water use efficiency, Yield.