Sensor-based Automated Irrigation Impacts Pythium aphanidermatum Infection in Petunia X hybrida 'Dreams Red'

The use of soil moisture sensors to monitor root zone volumetric water content (θ) and automate irrigation in container grown ornamental crops has been accomplished in both research and commercial settings. The ability of real time monitoring and control afforded by these systems allows for precise θ to be maintained, thereby reducing variability in root zone moisture contents. Cyclical soil moisture profiles created by traditional irrigation management subject crops to soil moisture extremes that increase incidence and severity of root infection. Observations in commercial trials have suggested a reduction in losses due to root disease when comparing sensor based automation to that of grower managed irrigation. Based on these observations, trials were conducted in a controlled setting in July and September of 2015 at the University of Georgia horticulture greenhouse complex in Athens, GA. Petunia X hybrida ‘Dreams Red’ were grown using a soil moisture senor based automated irrigation system that maintained substrate θ at 0.2, 0.3, and 0.4 m³ ·m^-3, as well as creating a cyclic soil moisture profile which underwent a 25% change in θ (0.18 to 0.43 m³ ·m^-3) between irrigation events. Once established half of the plants were inoculated with Pythium aphanidermatum and grown out for one month. Probability of root infection was lowered when θ was maintained at 0.2 m³ ·m^-3 compared to those maintained at 0.4 m³ ·m^-3 and cyclical θ. Mortality, biomass, and aesthetic quality were all unaffected by irrigation regime in both control and inoculated treatments.