Comparing a Smartphone Irrigation Scheduling Application with Water Balance and Soil Moisture-based Irrigation Methods: Part II-Plasticulture-grown Watermelon

A new smartphone irrigation scheduling application (VegApp) was compared with current irrigation scheduling recommendations and an automated soil moisture sensor (SMS)-based irrigation system in southern Georgia during Spring 2016 and 2017. Plants were grown using plastic mulch and drip irrigation following standard production practices for watermelon (Citrullus lanatus) in Georgia. The VegApp irrigation regime was based on evapotranspiration (ETo) values calculated from real-time data collected from a nearby weather station. Current irrigation scheduling recommendations use a water balance (WB) method. The WB method uses historic averages for determining ETo rates for the season. Water applied, soil water tension at 6-, 10-, and 14-inch depths, yield, and fruit quality were evaluated. In 2016, the SMS-based irrigation plots applied the least water. In 2017, the lowest amount of water was applied to plants grown using the VegApp. Total marketable yields were not significantly affected by irrigation regime. However, 45-count fruit yields were affected by irrigation in 2017. Plants grown using SMS-based irrigation had significantly higher yields of 45-count fruit than those grown using the WB method. Irrigation water use efficiency (IWUE) was affected by irrigation treatment and year. The SMS-irrigated plants had the greatest IWUE, although it was not significantly different from plants grown using the VegApp irrigation program. Internal quality parameters including, firmness, hollow heart, and total soluble solids (TSS) were not significantly affected by irrigation scheduling during the study. The results suggest that overall water applications may be reduced and yields maintained when using VegApp compared with traditional WB methods of irrigation scheduling.