Comparing a Smartphone Irrigation Scheduling Application with Water Balance and Soil Moisture-based Irrigation Methods: Part I—Plasticulture-grown Tomato

Abstract

A new smartphone vegetable irrigation scheduling application (VegApp) was compared with current irrigation scheduling recommendations and soil moisture sensor (SMS)–based irrigation for growing tomato (Solanum lycopersicum) in southern Georgia during Spring 2016 and 2017. Plants were grown using plastic mulch and drip irrigation following standard production. The VegApp-scheduled irrigation based on crop evapotranspiration (ETc) values calculated daily from meteorological data retrieved from nearby weather stations, whereas ETc rates for current water balance (WB)–based recommendations were calculated from historic averages for the region. Water usage, soil moisture tension, fruit yield and quality, and foliar macronutrient content were measured. In 2016, plants grown using SMS-based irrigation applied the least water followed by the VegApp- and WB-grown plants. In 2017, WB-treated plants received the least water, followed by VegApp- and SMS-grown plants. Total marketable yields were similar among treatments and years. Irrigation water use efficiency (IWUE) varied between year and irrigation regime, with SMS-grown plants having a significantly greater IWUE than the other treatments in 2016. Plants irrigated using the VegApp had a greater IWUE than SMS-irrigated plants in 2017. Differences in IWUE were largely the result of variable irrigation volumes and not changes in yield. Fruit total soluble solids (TSS) were unaffected by treatment in either study year. Fruit pH was affected by irrigation treatment in 2017. Foliar nitrogen concentrations were affected by irrigation regime in 2017, with VegApp-grown plants having significantly greater concentrations of foliar N than other irrigation treatments. The results of this study suggest that the VegApp could be a reliable tool that can be used by growers to produce yields comparable to currently accepted irrigation scheduling practices and reduce water use in some seasons.