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Wicking beds have become increasingly popular in recent years due to their water-saving capabilities and ability to grow a wide range of plants in small spaces. These beds are particularly useful in urban environments where space is limited, and water conservation is crucial.
At UrbanVeg.com.au we have installed many
beds of various shapes and sizes, and long ago realised that to ensure optimal performance and longevity, it is essential to incorporate an air gap in your wicking bed.
In this article, we will explore what an air gap is and why it is necessary in sub irrigate (SIP) planters.
Wicking Bed Air Gaps
This is a small space between the water reservoir and the growing medium in a wicking bed for around 80-90 percent of the growing area. This means that only 10-20 percent of the area is actually wicking with the rest subject to an aerated space that allows for the exchange of air between the soil and the water, creating a more oxygen-rich environment for plant roots. The air gap is breached by the growing medium in a number of areas in order to allow wicking over part of the bed, but it is surprising how little wicking area is required.
Why is an Air Gap Necessary in a Wicking Bed?
An air gap is essential in a wicking bed for several reasons. First, it helps prevent the soil from becoming waterlogged, which can lead to root rot and other plant diseases. When the soil is constantly saturated with water, it becomes anaerobic, meaning that there is little to no oxygen present. This lack of oxygen can be detrimental to plant growth and can even kill the plants.
Second, an air gap allows for better drainage and water distribution throughout the growing medium. As water is drawn up from the reservoir through capillary action, it is distributed evenly throughout the soil. However, if there is no air gap, the water will saturate the soil in the lower layers of the bed and may not reach the upper layers. This can lead to uneven water distribution and can also contribute to anaerobic conditions in the lower layers of the soil.
Finally, an air gap allows for the proper functioning of the wicking bed. The capillary action that draws water up from the reservoir relies on the presence of air in the soil. Without an air gap, the capillary action can become disrupted, and the wicking bed may not function as intended.
How to Create an Air Gap in Your Wicking Bed
There are a number of ways to achieve a good air gap. By far the easiest is by using a plastic wicking cell such as those we use at UrbanVeg.com.au. These cells allow water underneath to stay clean and free of roots whilst providing "feet" to fill with a permeable material for wicking over an appropriate percentage of the growing area. It is vitally important the the water exit drain is placed at a height slightly lower than the bottom of the main growing medium. This ensures the water cannot saturate the potting mix, but still flows up through the medium in the feet of the wicking cells.
Alternatively, a good DIY approach is to use 100mm (4") slotted drainage pipe laid flat over a proportion of the floor of the reservoir, and set the drain height to be just below the top of the pipe. This way a small air gap is achieved in the top of the pipe.
Benefits of Incorporating an Air Gap in Your Wicking Bed
Incorporating an air gap in your wicking bed offers several benefits. First, it helps prevent root rot and other plant diseases by ensuring that the soil is well-drained and oxygenated. This leads to healthier plant growth and can help prevent the loss of plants due to waterlogging.
Second, an air gap allows for more efficient water distribution throughout the growing medium. By ensuring that water is distributed evenly throughout the soil, you can ensure that all of your plants receive the water they need to grow and thrive.
Finally, incorporating an air gap ensures that your wicking bed functions as intended. By allowing for proper capillary action, you can ensure that the water is drawn up from the reservoir and distributed evenly throughout the soil. This leads to more efficient water use and can help save water in the long run.
Lower Maintenance Wicking Beds
Another benefit of incorporating an air gap in your wicking bed is that it can help reduce the amount of maintenance required. Without an air gap, the soil can become waterlogged, which can lead to plant stress and the need for more frequent watering.
By ensuring that the soil is well-drained and oxygenated, you can reduce the frequency of watering and overall maintenance needed for your wicking bed.
Furthermore, incorporating an air gap in your wicking bed can also help extend the lifespan of your bed. When the soil is constantly saturated with water, it can cause the soil to compact and become dense, making it difficult for roots to grow and plants to thrive.
By creating an air gap, you can prevent soil compaction and ensure that the soil remains loose and aerated, providing an optimal environment for plant growth. We wrote an in-depth article on soil mixes for wicking planters last year, which is well worth a read.
In conclusion, incorporating an air gap in your wicking bed is essential for ensuring optimal plant growth and reducing maintenance requirements.
An air gap helps prevent soil waterlogging, ensures even water distribution throughout the growing medium, and ensures that the wicking bed functions as intended. By following the simple steps outlined above and using the resources provided in our other articles, you can create a healthy and thriving wicking bed that will provide a sustainable source of fresh produce for years to come.
