What is a wicking bed?
A wicking bed is a raised garden bed with a water reservoir below the level of the soil. Water is drawn up from the reservoir to the soil above via capillary or wicking action. Moisture level in the soil is maintained at a constant rate over extended periods. This minimises the need to add water whilst evenly distributing moisture, providing better growing conditions for plants.
Benefits of using a wicking bed for growing vegetables
- Water need is reduced by as much as 90% compared to ordinary raised garden beds. This results in a significantly lower impact on the environment and less money spent on water bills;
- Increased water retention of the soil = Low watering frequency: only every 2-3 weeks. Garden beds can be left unattended for extended periods of time without any risk of damage to plants;
- Plant roots grow deeply into the soil attracted by the underground water source. This results in stronger, healthier and more productive plants;
- Soil nutrients do not leave the garden bed by being washed away during top watering. There is more food available to the plants and less need to add extra fertilisers;
- Water is added directly into the water reservoir until it reaches the overflow level. No risk of over-watering the plants;
- Reduced loss of water due to evaporation. Topsoil in a wicking garden bed remains fairly dry due to the soil below retaining the moisture, and as such topsoil evaporation is very minimal.
Possible Downsides of a wicking system
Not all plants like a moist soil. Garlic for example, will thrive in a wicking garden bed in its growing stages, but requires a fairly dry environment during last part of growth, so as to avoid mould growth.
How a wicking garden bed works
There are two main effects in a wicking garden bed:
- Capillary action. The small pores of the soil act as capillaries, allowing the water to be drawn upwards from the reservoir into the soil above.
- Reduction of excessive drainage. The down-flow of water is interrupted causing the water to reside in the soil for an extended amount of time.
Inside a Wicking Garden Bed
A Wicking garden bed is composed of three distinct ZONES (from the bottom up):
- THE WATER RESERVOIR
- THE ZONE OF SATURATION
- THE ZONE OF ROOT GROWTH
Wicking system components
- Water Inlet Pipe: Delivers water to the water reservoir.
- Slotted AGI Pipe: Connected to the Water Inlet Pipe, the Slotted AGI Pipe distributes water evenly along bottom of the garden bed.
- Water Overflow Pipe: Outlet positioned below the soil surface. Prevents the water level from raising into the Zone of Root Growth.
- Horticulture liner. Positioned at the bottom.
- Coarse aggregate, such as washed river sand or blue stone crushed rock (10mm). This medium creates the structure of the water reservoir. It has a high-water retention capacity.
- Geotextile Fabric: Positioned between the water reservoir and the soil.