The effects of container geometry on water and heat regimes in soilless culture: lettuce as a case study

Abstract

Appropriate geometries and depths of containers are essential in obtaining suitable available water and temperature in the root zone of containerized grown plants. The objectives of the present study were to examine the effect of the geometry of a growth container with a given volume and irrigation frequency, on water content and temperature of the growing medium and on water uptake, yield and quality of lettuce (Lactuca sativa L.) as a model plant. Two experiments, in the spring and fall, were conducted in a greenhouse. Plants were grown in a volume of 4 L per plant of medium mixture of 0–8 mm tuff (90 %) with compost (10 %). Treatments included three container heights (10, 20 and 30 cm) and two irrigation frequencies (4–6 and 12–18 applications per day and 2 night applications for both). Lettuce head fresh weight was lower in the spring than in the fall and was not significantly affected by container geometry or irrigation frequency. However, the number of tip burn damaged leaves per plant increased significantly with container height, especially for the high irrigation frequency treatments. Container geometry had an effect on the water and temperature regimes. Water content values in tall and narrow containers were lower than those in short and wide containers that had an equal volume of growth medium per unit length. Higher medium temperatures and daily fluctuations were observed in the tall containers. The calculated evapotranspiration rate was higher in the tall containers, and a stronger effect on evapotranspiration was obtained with high irrigation frequency.