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Optimizing the Water and Air Relationship and Nutrient Concentration in a Controlled Water Table Irrigated Container Growing Medium
J.W. Buxton
Department of Horticulture
Project Description
The water and air relationship in plant growing medium is critical to the optimum growth of plants. Maintaining an optimum air/ water content for plants in containers is difficult compared to plants grown in the field.
Controlled water table irrigation (CWT) is an automatic irrigation system that is capable of maintaining optimum air and water in a container growing medium. A water table is established below the bench in a small trough. By capillarity, water is moved through a capillary mat hung vertically in the water and horizontally across a level bench. Studies showed the relationship between the distance the water table was below the bench and the amount of water in the growing medium in plug trays 4.4 cm and 2.6 cm in height and in 15 cm tall azalea pots. The water table treatments for plug trays were 0, 3, 6, 9, and 12cm and for 15cm containers 0, 1, 2 3, 4, and 5 cm below the bottom of the containers. The water content in the 3 container types decreased linearly from 0 cm to the greatest distance below the bottom of the container. The water content in the 2.6 and 4.4 cm plug was 45% and 41% greater at 0 cm than at 12 cm. In the 15 cm container the water content at 0 cm was 11% greater than at 12 cm.
The results show that controlled water table irrigation is capable of maintaining a constant amount of water and air in the growing medium for extended periods; and the amount of water and air can be adjusted by raising or lowering the water table relative to the plant growing container.
Impact
Controlled Water Table (CWT) irrigation is capable of automatically maintaining an optimum air/water ratio in pot growing medium for commercial greenhouse production. The system is easily adaptable to existing commercial greenhouses. In contrast to other pot irrigation systems, CWT, under most environmental conditions, maintains the same air/water ratio in all pots, regardless of the evapotranspiration rate. Nutrient solution does not drain from the system, thus no pollution of natural water sources. CWT irrigation potentially is capable of growing larger, better quality and a more uniform pot plant crops than other irrigation systems.