EVALUATION OF DIFFERENT SUB-IRRIGATION SYSTEMS FOR CONTAINERIZED NURSERY PRODUCTION

Overhead irrigation is commonly used in container production of ornamental trees and shrubs. From a water and nutrient management perspective, however, this system can be inefficient, resulting in a significant fertilizer leaching. Sub-irrigation with capillary mat systems reduces the amount of water needed for plant growth, as water moves upward into the growing medium by capillary action and no runoff occurs. Moreover, irrigation can be driven automatically by a substrate moisture sensor, like a tensiometer, instead of the common practice that schedules irrigation at a fixed time. Aim of this work was to compare three capillary mat systems, equipped with tensiometric probes and characterized by different water retention characteristics, with two overhead irrigation systems: water delivery control through a tensiometer or at fixed intervals. For this trial Photinia × fraseri ‘Red Robin’, grown in 3 litres containers, was used. Water consumption was recorded weekly during the trial while both shoot and root biomass were measured at the end of the experiment. Leaf and medium nutrient content were analysed at the end of the growing season. A significant reduction in plant dry weight was observed in plants irrigated through capillary mat systems, but an average of 70% reduction in water consumption was obtained with the tested sub-irrigation systems. In terms of water efficiency, expressed by the ratio plant dry weight/water delivered (g/L), the sub-irrigation systems ranged from 1.35 and 1.64, while overhead irrigation systems resulted in lower values (0.87 with tensiometric control and 0.66 with fixed interval). K, Ca and Mg levels in water extracted from the plant substrate were higher with overhead irrigation systems.