Effects of a Nonionic Surfactant on Plant Growth and Physiology

Abstract

With a continuous declining trend in the availability of groundwater or public surface water to greenhouse and container nurseries, nursery growers and researchers are searching for effective ways to reduce water use and maintain optimal plant growth at the same time. In this project, we studied the effect of a low concentration of surfactant Tween 20 (polysorbate 20) on plant growth and physiology of two nursery crops. In laboratory soil columns, the initial wetting of a commercial substrate Fafard 3B was accelerated and the moisture retention of the substrate treated with 100 mg·L-1 Tween 20 solution increased 40.5% compared to that of water treatment at initial wetting. In an outdoor container study, growth of New Guinea impatiens (Impatiens hawkerii 'Celebrate Salmon') in the treatment of 100 mg·L-1 Tween 20 at the 60% of full crop evapotranspiration (ET) irrigation level was increased 11% compared to the control (0 mg·L-1 Tween 20 at 100% of ET) after three months. Growth of impatiens in treatment combinations of 50, 75, 100, or 125 mg·L-1 Tween 20 at the 20% or 40% irrigation level was similar to that in the control throughout the experiment. Under a 3 × 6 complete factorial design plus a control, irrigation levels of 20%, 40%, 60% of the full crop ET requirements were used in combination with Tween 20 concentrations of 0, 25, 50, 75, 100, and 125 mg·L-1. The control was tap watered to container capacity with 30% leachate. Plants mostly grew equally at the 40% or 60% irrigation levels when combined with 100 mg·L-1 or higher concentrations of Tween 20. When Tween 20 concentration increased from 0 to 100 mg·L-1 at the 60% of ET irrigation level, the transpiration rate and stomatal conductance decreased 43% and 47%, respectively, and water use efficiency was increased 47%. In hydroponic studies containing 0 (control) to 125 mg·L-1 Tween 20 modified Hoagland solutions, fresh and dry weight of peace lily (Spathiphyllum floribundum ‘Viscount’) and impatiens increased 17% to 33%, and 7% to 18% respectively, in the solutions with 50 to 125 mg·L-1 Tween 20 compared with the control. Water use efficiency of peace lily and impatiens in 100 ppm Tween 20 solution was increased 166% and 221% compared to control, respectively. In a greenhouse study, peace lily grew equally with at 60% of ET compared to 100% irrigation when the reduced water regime included Tween 20 at 75 mg·L-1 or higher concentrations. Cost estimation indicated the minimal increase in cost from Tween 20 was offset by decreased water costs based on current municipal water costs.