The Sand Bucket Garden

For our first build, we’re going to start at the small end of the sandgarden spectrum…with the Sand Bucket Garden.

What is a Sand Bucket Garden

Sand + Bucket = Garden

The Sand Bucket Garden (SBG) that we’ll build is about 2/3 of cubic foot of fully functional organic food production space.

I’m going to use it to teach you how to sandgarden – using this tiny demonstration system – and then I’ll show you later how to parlay what you learn into a sandgarden at any scale – from a single bucket to thousands of square metres.

It’s a crash course in Sandgardening. We learn as we grow – and we grow as we learn. In effect, we limit the explanations until later sections in order to focus on applying sandgardening…in the shortest possible time.

It’s a low-cost discovery pathway to food security – for you and others. It’s a whole new way of looking at a garden – one plant at a time!

The recurring sandgardening theme of cost-effective – easy to build – simple to operate…starts here.

Why buckets?

Plastic buckets are already widely used to grow plants in a wide variety of domestic and commercial situations…so we know they work. They are a good depth for most plants.

They are used to transport and store many food products and are often available at little or no cost. The buckets themselves are fully recyclable when they are no longer serviceable – so they have a measure of sustainability about them.

Their versatility…allows for shapes…borders…circular gardens…heart-shaped gardens – options that are limited only by your imagination…etc.

They can be moved with modest effort – and that portability has several advantages. Plants can be massed together as seedlings and spaced apart as they grow. Diseased or infested plants can be isolated to reduce the risk of the problem spreading.

Renting your home needn’t stop you from food gardening if you can pick your garden up and take it with you – one plant at a time!

What size buckets?

If our SBG is going to be a true ‘miniature’ sandgarden then we need two buckets…one of 20 litres (5 US gallons) capacity – and the other of 10 litres (2.5 US gallons).

While we could get away with two 20-litre buckets, this is as good a time as any to introduce you to something called the component ratio. This is the volume relationship between the sand biofilter and the water tank…and that means that for every litre of water capacity in the tank we have two litres of sand in the biofilter…a ratio of 1:2.

We’ll talk about the reasons for this later.

What sand do I use for a sand bucket garden?

For our first build, we’re going to buy a couple of bags of filtration sand – the same stuff they use in swimming pool filters.

It is not the most cost-effective option but it will serve as a datum…a benchmark…a known quantity. It’s sand that we can buy off-the-shelf almost anywhere.

While its downside is its cost, it’s still going to be an option for some because of their specific circumstances. In coming sections, we’ll look at how we obtain more cost-effective supplies of suitable sand.

For now, however, we’ll use this sand because we can buy it in small quantities, and we know it will work without issue straight out of the bag.

How much does a SBG cost?

If I buy the sand from a swimming pool shop at (for example) $15.00…and the buckets from my local big box store for another $15.00…and a little pump and timer for another $20.00…my first SBG works out at around $50.00. These costs will vary from one location to another, but they will serve to help me illustrate how the costing of an SBG works.

If you shop around and find a cheaper source of sand…and approach your local local fast-food suppliers or bakers to see if you can purchase their surplus buckets…you can significantly reduce the SBG unit cost.

At this stage, however, our initial focus is on a two-bucket arrangement complete with its own pump, timer and plumbing.

Our first build is a functional growing system – and a demonstration unit – and a learning aid – and, regardless of any future aspirations you may have, this little unit will always serve you well.

It’s designed to get you up and going as quickly as possible and it will assist you to understand the various aspects of sandgardening as they unfold.

The bucket sandgarden may have the appearance of a toy but don’t let its size mislead you.

What you’ll need:

Two 20-litre (5-gallon) plastic buckets – UV-resistant preferred
Two ‘ebb and flow’ fittings – 19mm (3/4”)
One submersible pond pump – X litres per hour
An electromechanical timer – with 15-minute increments.
Micro-irrigation fittings and black poly pipe (provide a list that includes the overflow).
A bag of filter sand – available from swimming pool supply stores or specialist sand vendors. A 20kg bag of sand is equal to about 13.5 litres…two such bags will fill two buckets.
A couple of handfuls of gravel and a piece of shade cloth.

The Build

Locate your sandgarden where it will get sufficient sunlight – the more the better.

Position it so that the sandbed drains directly into the water tank. We use cement breeze (cinder) blocks to support our buckets but anything that you have that will achieve the same purpose will suffice.

Bore a hole in the centre of the bucket for the drain…and it must be in the bottom of the bucket so that it drains completely.

Note: I meant in the bottom – not toward the bottom. This is essential if we are to avoid having water remain in the bed at the end of the drain cycle. This will give rise to anaerobic conditions. At this stage, it’s sufficient for you to know that this is a bad thing…something to be avoided.

Position the shade cloth over the drain hole. Fix it in place with the pea gravel and then fold the shade cloth over the pea gravel.

Carefully (so as not to disturb the shade cloth and gravel) fill the bucket with sand – ensuring that the shade cloth and gravel remain in place over the drain hole. Fill the bucket to with 75 – 100mm (3 – 4”) of the top. This simple arrangement will ensure that the sand does not migrate from the sandbed to the water bucket.

Place the water pump into the water tank and attach the watering manifold to the sandbed.

Plug the pump into a power point (socket)

Note: While you may be keen to hit the button and get water flowing around the system, it’s useful to resist the urge at this stage. The dry sand in the bed has secrets to reveal but we need to wait until we reach the startup phase.

How do I Build a Sand Bucket Garden?

Take the larger bucket and put a X mm hole in the centre of its base. This is the drain for the bucket and the hole is large enough to allow it to drain completely…while still retaining the sand in place.

Place a swatch of shade cloth over the hole and then secure the swatch in place with a couple of handfuls of coarse gravel (20 – 40mm).

Fill the bucket with sand to a depth of 300mm (12”).

Position the sand bucket so it can drain into the water bucket.

Hang the pump assembly over the lip of the sand bucket.

And there you have it – an automatic sandgarden for a single plant – and a working prototype of any size sandgarden you desire.

How do I Startup my new Sand Bucket Garden?

Before you trigger the pump for the first time, ensure that the bucket contains X mm of sand.

Form a mound in the centre of the bucket…with a small ‘moat’ about 75 – 100mm (3 – 4”) deep…in which the pump assembly is suspended and the water flows. The purpose of the mound is to keep the plant crown above the water line – to avoid crown rot.

Ensure that your water bucket is filled with clean water.

Plug in the pump and switch it on. Adjust the inflow to prevent erosion of the sand mound.

A few seconds after the pump starts, water will begin flowing from the drain in the sand bucket.

Continue pumping until the water in the moat reaches to within about 50mm of the top of the mound. Switch the pump off and watch as the water continues to drain for the ensuing X minutes.

Set the timer so it switches the pump on for the minute or so that it will take to saturate the sand to the cutoff point.

Use the valve on the water pump to adjust the flow rate until it consistently reaches the marked level before the timer turns the pump off.

How often do I water the SBG?

We expose the sandgarden to eight flood cycles – of about X seconds’ duration each…separated by drain intervals of two hours. Set your timer up to reflect the following irrigation regime.

6:00am (dawn or pre-dawn) – 1st pump cycle of the day starts).
6:30am – drainage completed.
8:00am – 2nd pump cycle
10:00am – 3rd pump cycle
12:00pm – 4th pump cycle.
2:00pm – 5th pump cycle.
4:00pm – 6th pump cycle.
6:00pm – 7th pump cycle.
8:00pm – 8th pump cycle (dusk or slightly after, depending on season location).

Note: Pump remains OFF overnight.

OK, so now our sand bucket garden build is complete – and to summarise what’s happening…

Every two hours, the timer starts the pump.
The pump delivers the water to the moat in the sand bucket.
Once the water reaches a predetermined level in the moat, the timer cuts off the pump.
The water percolates down through the sand exiting the sand bucket through the drain hole in the bottom.
It will continue to drain for several minutes…and then until the next irrigation event.
This happens eight times – during daylight hours. An SBG ‘rests’ overnight – for sound biological and sustainability reasons.

Is this really a garden – or a machine?

In terms of its visible elements, one could be excused for thinking that it’s more like a machine than a garden. The definition of a machine is “a physical system using power – to apply forces and control movement – to perform an action…then that’s what it is – a simple machine.

In fact, exactly as it stands – it’s a simple but water filter.

As it recirculates the water – at timed intervals – the water becomes progressively clearer – and cleaner – with each passage through the sand.

But, since we’re going to grow a plant in it, we should now think of it as a plant production machine.

As it is, it’s a basic flood and drain hydroponics system. Indeed, we could go to our nearest hydroponics supplier – and buy a variety of similar devices (at vastly inflated prices) and choose from a bewildering array of bottled nutrients.

While the sand bucket garden will function perfectly well as a hydroponics system, we distinguish between one and the other by what we use to ‘fuel’ them.

Taking up our engine analogy again…a hydroponics bucket system utilises inorganic chemicals to produce a translucent liquid (like petrol) as fuel to feed the plants.

But an SBG runs on ‘bio-fuels’…sourced from organic sources so it’s a bio-machine

What do I feed an SBG?

For demonstration purposes, I’ll use an off-the-shelf product made from plants, seaweed and fish wastes. Its name and composition are unimportant at this stage. Suffice to say, it’s a complete organic plant food in liquid form.

Organic is Good. Right?

If knowing exactly what’s in your food…living sustainably…and having complete control over your food security – are good – then organic is good!

One of the most important benefits of sandgardening is the sense of control that it puts in the hands of the grower. You become beholden to no one in matters relating to your food.

But, unless we know how to do it, organic production in a recirculating system like a sand bucket garden can be problematic.

Let me explain.

The colour of organic nutrients is dark because it contains particulate matter – tiny particles of whatever it was made from that we refer to as solids.

Now, we’ve already said that a sand bucket garden is a simple water filter. If you pour water containing solids onto sand, they are trapped on the surface where they will eventually build up to the point where the sand will clog…and that would be bad.

Very bad!

But here’s the good news!

The combined effect of free-draining filter sand, the mound and moat – and the intermittent irrigation regime…ensures that an SBG will not clog – by design.

How does that all work?

To best understand how an SBG handles solid wastes, let’s track one through a full flood and drain sequence.

The SBG has been resting for an extended period and then the pump starts, and water (bearing the solids) is deposited into the moat.
When the water level reaches the predetermined level (50mm – 2” from the top) in the moat, the pump cuts off.
The water soaks through the sides and bottom of the moat – trapping the solids where they are exposed to the effects of sun and wind.
The water percolates down through the sand before draining from the bucket. The retreating water causes air to be drawn down deep into the sand.
The solids decompose rapidly and become plant-available nutrients.

Think of it like an engine – where the water is a piston. As that water rises in the bucket, it forces the gases that have accumulated in the sand since the previous drain cycle out of the bucket. As the water drains from the bucket, it draws in fresh air – particularly oxygen.

So, not only does a sand bucket garden not clog, but it facilitates the gaseous exchange that will benefit the plant…and the rhizosphere that powers an organic SBG.

What Rhizosphere?

As Wikipedia tells us, the rhizosphere is…

“…the narrow region of soil or substrate that is directly influenced by root secretions and associated soil microorganisms known as the root microbiome. The rhizosphere involving the soil pores contains many bacteria and other microorganisms that feed on sloughed-off plant cells, termed rhizodeposition, and the proteins and sugars released by roots, termed root exudates. This symbiosis leads to more complex interactions, influencing plant growth and competition for resources. Much of the nutrient cycling and disease suppression by antibiotics required by plants, occurs immediately adjacent to roots due to root exudates and metabolic products of symbiotic and pathogenic communities of microorganisms. The rhizosphere also provides space to produce allelochemicals to control neighbours and relatives.”

The rhizosphere has been described as the last frontier of soil science…and organic gardeners and soil scientists think of soil without a rhizosphere as just dirt – useful perhaps as an anchor for plant roots – but far less capable as a growing environment.

The rhizosphere is (what is known in business circles as) the ‘unique selling proposition’ for soil. It’s the ‘sustainable competitive advantage’ that soil has over all other media…and a big part of that advantage is that it’s not to be found in other growing media.

Except sand.

Sandgardening can replicate the rhizosphere that exists in soil…and fortunately, it’s much easier to facilitate this state than to understand its inner workings.

Sand + organics + oxygen + water + microbes + light = SOIL.

Since we’re supposed to be building an SBG here, it’s time to demonstrate how we facilitate a rhizosphere.

We add a measured quantity of the bottled plant food that I spoke of earlier, to the water tank and stir it thoroughly.
The soil microbes that inhabit the rhizosphere are naturally occurring in soil, air and water but we can accelerate their development by introducing some indigenous micro-organisms. Take a good pinch of the decomposed leaf litter that accumulates beneath healthy trees and sprinkle it lightly around the base of the moat. It contains soil microbes that are native to the area and may well contain organisms that will be helpful to plant production in the same space.
As the water in the system recirculates the water through the sand bed, the solid particles in the bottled plant food are trapped in the moat by way of mechanical filtration – where the alternate wet/dry conditions and the effect of sun and air bring about their rapid decomposition.
The soil microorganisms take the plant food particles and convert them into plant-available nutrients.

Over time, the moat will grow darker in colour. This is the decomposing plant food solids and is known as the detritus layer. Directly, below that is the rhizosphere …teaming with microbes.

In the days following startup, the microbial life expands both in species and numbers. It grows to keep pace with the plant’s requirements.

So, now that we have our little SBG up and going, it’s time to come to grips with an emerging problem.

SBG is like fine Swiss chocolate – or a macadamia nut. One is never enough!

How do I grow more?

Our first expansion option is to simply commission more buckets.

You can theoretically use as many buckets as you want…and you are only limited by your imagination as to their layout. The only requirement is that your buckets are able to drain back to the water tank. So long as you remember that you need a litre of water for every two litres of sand, you can utilise a single water tank for several sand buckets.

For example, I’ve built 4-bucket modules – where the buckets all drain into a common water tank. I use them to conduct various tests and trials. Each 4-bucket module (of 80 litres capacity shares a 40-litre water tank (note 2:1 ratio).

Since the sand buckets all share a common pump and timer, this is a much more cost-effective way to build a larger sand bucket garden.

Regardless of your future aspirations, I recommend that you build at least one SBG.

It will not only support a plant, but it will do so in conditions in which that plant will thrive.

It will function as a sand tester if you decide to upscale your sandgardening…and you want cheaper sand.

Most importantly, it will also serve as a learning aid – initially for you…and then for others as you share your efforts. This is grassroots sandgardening. What you learn from this little SBG will stand you in good stead – regardless of scale.

What if buckets don’t suit me?

For all of that, sand bucket gardens won’t suit many people who decided to go bigger – for a variety of reasons including:

a requirement for a more conventional row garden – like a garden bed.
a need for larger containers – for trees and vines.
a desire to use less plastic – in the interest of sustainability.
the desire for a less expensive (per plant) build cost.
the need for a more aesthetically pleasing garden.

So, If lots of buckets are not your thing, you’ll find what you need in the next section.

Summary

Before we begin scaling up, this is a good place to review what’s happened so far.

This section has largely been about satisfying ourselves that sandgardens are easy to build and simple to operate. First and foremost, it’s a system that demonstrates how – with the flick of a switch – anyone can garden with confidence and a high expectation of success.

We’ve built a single-plant sandgarden – a ‘bio’-machine where a little energy…and a lot of microbiology… combine to convert organic matter into plant nutrients…that grow clean fresh organic food – free of chemical fertilizers and synthetic herbicides or pesticides.

We also understand that the critical success factors for a sandgarden include:

Two impervious containers…one twice the size of the other…set up so that the larger one can drain into the smaller one – fill the top one with sand and the lower one with water.
Washed and graded quartz silica sand.
The ‘secret sauce’ – the structural arrangement of system elements that facilitates the integration of sand and organic matter. The combined effect of free-draining filter sand, the mound and moat – and the intermittent irrigation regime…ensures that an SBG will not clog – by design.

Sandgardening is organic horticulture that utilises appropriate technology to assist us in encouraging and maintaining a thriving rhizosphere. It grows the plants.

OK, it’s time to take a look at bigger sandgardens.

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