The 2012 ASHS Annual Conference

To investigate the feasibility of using a sensor-based automated irrigation system in pot-in-pot tree production and to determine the optimum substrate moisture contents at which the irrigation events should be triggered to turn on, a trial was conducted in a commercial nursery in Southwest Ontario, Canada, in the growing season of 2011. Acer rubrum (~2.5 cm caliper size) trees were potted in 62-litre pots with artificial growing substrates at the beginning of the season and irrigated at five different regimens (treatments). The five treatments included a control, and four automated irrigation regimens. For the control, the timing and amount of water that each tree was irrigated was determined at the grower’s discretion. This represents the current common practice in Ontario. For the automated irrigation regimens, trees were irrigated automatically whenever the substrate moisture content reached 36%, 29%, 22%, or 15%.  A soil moisture sensor was buried in the centre of each pot and the moisture content was read and sent to a computer once every 30 minutes wirelessly. These substrate moisture content readings were used to trigger irrigation events for the automated irrigation treatments.  Measurements at the middle and end of the season indicated that the caliper and height growth of the trees were not affected by the irrigation treatments; only more frequent temporary wilting events were observed for some of the trees in the 15% treatment during the growing season. Trees in the 22% treatment were not significantly different in performance (i.e. caliper and height increase, visual appearance) from trees in the control, 29%, and 36% treatments, but used 55% less water than the control. Results suggest that pot-in-pot Acer rubrum caliper trees can be irrigated using a sensor-based automated irrigation system and irrigation events can be triggered at a substrate moisture content as low as 22% to save irrigation water.