Impact of irrigation management of greenhouse tomato: yield, nutrition, and salinity of peat substrate

Irrigation dynamics and the response of greenhouse tomato (Lycopersicon esculentum Mill. 'Caruso') to different irrigation management treatments (nutrient solution EC and irrigation matric potential setpoints) were examined in plants grown in peat-based substrate during either the spring or fall of 1989. Two nutrient solutions with differing electrical conductivity (EC of 1.5 and 3.0 dS m −1 ) were automatically applied to plants until saturation at one of two substrate matric potential (SMP) setpoints (−6.5 or −4.5 kPa). Yield measurements indicated no significant effects due to different SMP setpoints but spring total yield and average marketable fruit weight were higher for low-EC solution treatments. Blossom-end rot was slightly higher in the fall under the highest EC treatment. Foliar mineral concentration analysis of spring-grown plants indicated increases in nitrogen, potassium, zinc, and manganese, and a decrease in calcium in plants receiving high-EC solution. The EC of peat substrates was also found to be higher than applied solutions indicating an overall accumulation of salts within the peat under different irrigation regimes, even with periodic overwatering. This study indicates that increasing nutrient solution EC from 1.5 to 3.0 dS m −1 can negatively affect the production and nutritional status of tomato plants more than changing irrigation setpoints from −4.5 to −6.5 kPa. Key words: Electrical conductivity, fruit quality, peat, tensiometers, matric potential