Evaluation of irrigation threshold and duration for tomato grown in a silt loam soil

Soil moisture-based, high-frequency, low-volume (pulsed) irrigation management strategies have saved water while maintaining yields of vegetables grown in coarse textured soils. However, little is known regarding the efficacy of soil moisture-based pulsed irrigation on finer textured soils. Therefore, five tensiometer-based, automated irrigation treatments were tested for tomato (Solanum lycopersicum) grown in a Maury silt loam soil in 2009 and 2010 in Lexington, KY. Irrigation treatments consisted of paired-tensiometer systems with on/off setpoints of –30/–10, –30/–25, –45/–10, and –45/40 kPa in both 2009 and 2010 and a single-tensiometer system with setpoints of –35 kPa in 2009 and –40 kPa in 2010. In 2009, the pulsed systems (–30/–25, –45/–40, and –35 kPa) irrigated more frequently but for a shorter duration than non-pulsed systems (–30/–10 and –45/–10 kPa). Soil moisture measurements in 2009 suggested that probes set at a depth of 6 inches were more closely matched to irrigation setpoints than those at 12 inches. In both years, the –45/–40 kPa setpoint treatment used the least amount of water while maintaining total marketable yields that were not significantly different from other treatments. Yields were significantly higher in 2009 than 2010, though atypical air temperatures in 2010 may have been the cause. Leaf water potential and relative water content were measured predawn and midday throughout the growing season in 2009 and 2010. Leaf water potential was not significantly affected by the treatments in either year, though leaf relative water content was affected in 2010. In this trial, an automated, soil moisture-based irrigation system maintained yields and saved water when compared with a non-pulsed irrigation system using similar irrigation setpoints for tomato grown in a silt loam soil.