Partial Flood and Drain in Gbiota Beds
Gbiota beds and Gbiota boxes are based on wicking-bed principles but are specifically designed to breed beneficial soil biology and support gut-healthy food.
Conventional wicking beds are often used as self-watering pots. Many have a base filled with inert material such as stones. The water in this lower reservoir is intended to stay relatively clean and can stand for long periods without going putrid, as long as it remains inert.
Gbiota beds are different. They are filled with organic material that feeds beneficial microbes and soil creatures. This biology-rich zone must not stay saturated for long periods, or it will favour harmful microbes and lead to anaerobic, smelly conditions.
In Gbiota boxes, drainage is controlled by a swivel tube at the very base. This allows the water to be fully drained after irrigation so the bed can return to a moist but aerated state. The goal is to keep the soil at what we call Goldilocks moisture – not too wet and not too dry.
In Gbiota beds this Goldilocks moisture is achieved using a leaky dam. The dam holds water back just long enough for it to wick evenly through the bed before the excess drains away. In newer soaker beds, the design uses zones where water can spread and wick into special areas, again followed by drainage.
This cycle of partial flooding and draining is critical. During the flood phase, stale air and gases (such as ethylene from decomposition) are pushed out of the soil. As the water drains away, fresh air is drawn in, giving the soil biology the oxygen it needs to thrive.
Hydraulic Flow – Spreading Water Evenly
To spread water along the length of a bed we rely on hydraulic flow. The base of the bed must include a layer that is largely impervious to water so it can build up and move sideways.
This base can be created by:
- A plastic liner or membrane
- A natural clay layer
- A compacted soil layer
Most Gbiota beds are long, so we use an Ag pipe (or similar perforated pipe) along the base to move water quickly along the bed. Water then flows a shorter distance sideways through the soil to irrigate the full width.
Traditionally the Ag pipe was bent up to the surface to act as a fill point. In newer designs we often add a larger vertical fill/inspection pipe so you can see the water level when filling manually.
The lowest layer around the pipe is a coarse, porous zone that helps distribute water. This can be made from:
- Wood chips or shredded branches (a micro hugelkultur layer)
- Vermicast or coarse compost
- Channels made and maintained by worms and other soil creatures
We do not want to saturate the full depth of the bed for long periods. Excess water should either drain away via an outlet or be monitored through the fill pipe so you can stop filling at the right level. The water needs to stay in the base long enough to wick upwards to the root zone (often several hours), but not long enough to become stagnant and encourage harmful biology.
Food for Soil Biology and People
To breed soil biology we must feed the bugs as well as the plants. A new Gbiota bed is usually built in layers:
- Bottom layer – porous base: Coarse material such as wood chips, shredded branches or coarse vermicast to create air-filled pores and water pathways.
- Middle layer – organic waste: Food scraps and green organic waste that break down to feed microbes, worms and other soil life.
- Manure layer: Animal manures (e.g. from chickens) to add nitrogen and accelerate decomposition.
- Top layer – growing media: Finished compost and good-quality soil for seed germination and root growth.
In practice this structure is only temporary. Once the bed is operating, worms and other creatures quickly mix everything into a biologically active, crumbly soil—essentially vermicast-rich topsoil with a strong microbial population.
As crops grow, you will need to re-feed the bed from time to time with new organic materials, manures and minerals. The exact timing and quantity depend on the type of bed, climate and crops, but the principle is the same: keep the biology well fed so it can keep feeding you.
