Comparing water availability of injected polymers and tension reservoirs in growing media used in hanging baskets

Improving irrigation efficiency of post harvest potted plants is important to municipal maintenance services, longevity of hanging baskets once delivered to consumers and obviously water savings. Adding hydrophilic polymers as late as possible, prior to outdoor use is one possible strategy, but the efficiency of such strategy has not been tested so far. Alternatively, water tension reservoir can store and release water into the substrate at a specific potential, therefore releasing liquid when the plant demand is low, which offers the advantage of delaying irrigation further. An experiment was carried out to try to compare the effects of polymers and tension reservoir on water availability in post harvest potted plants. Petunia × hybrida cuttings were planted into 8-L plastic hanging baskets (30 cm diameter) filled with a peat/perlite/vermiculite (75, 12.5, 12.5% v/v/v) substrate. In one of the treatments, a 2.3 L reservoir was placed in the center of the hanging basket at the time of planting and left empty. When the marketable stage was reached (after eight weeks of greenhouse production), a hydrophilic polymer Aquamend® was injected at 3 g L-1, giving 24 g of hydrophilic polymer by container, distributed evenly at 12 locations within the hanging baskets. Following the application of the polymer, the containers remained in the greenhouse for two weeks and were irrigated as needed with water. Then, the reservoir was filled up with water and the irrigation was stopped to allow permanent wilting. The test confirmed the effectiveness of post-production injection on time to wilting, baskets with at least 3 g L-1 of polymers resisting 1.0 day longer (4.0 against 3.0 days) than the control before wilting, and showed a slightly higher efficiency for the tension reservoir (4.5 against 3.0 days for the control).