Green Man Char feature tip – Horticultural Charcoal for Aquaponics
Learn how to make your own Aquaponics system with Horticultural Charcoal.
In an Aquaponics system, water from an aquaculture system is fed to a hydroponic system where the by-products are broken down by bacteria into Nitrates and Nitrites, which are utilized by the plants as nutrients, and the water is then recirculation back to the aquaculture system.
Let Charmaster Laird show you how it is done – your fish and your plants will thank you.
Application rates will vary depending on soil types, vegetation and environment. For a general application guide:
- 1-5 litres / m2 for gardens.
- For mixing with potting medium or composts, mix biochar at approximately 1-10% of volume.
- For large scale applications in horticulture rates of minimum 5t/ha equivalent strategically targeted to root growth zones. Repeat applications on a multi-year period will slowly build the biochar content of the soil.
- For large scale agricultural applications, a minimum rate of 35 kg/ha is recommended on a multi-year application regime. Alternatively, one off or multi-larger scale applications in the tonnes/ha are recommended.
Applications can be repeated annually, mixed into the root zone with your favourite fertiliser to fuel plant growth. For existing crops, it can also be applied as a top dressing.
Biochar and your Compost
Put simply, a biochar+compost blend generally works better than either biochar or compost alone. Here’s an easy way to combine them.
Anything from 10% to 25% biochar works well (more biochar tends to gives better structure, aeration and drainage), and for best results, the biochar should be spread throughout the compost. An easy way to do it and avoid hard work mixing manually with a shovel etc is to keep a bag of biochar and a scoop on hand next to the compost bin and add a dose of it each time you toss your kitchen scraps, lawn clippings, compostable wastes etc. into the bin.
The biochar you add should be well moistened, otherwise the worms will bypass it. As a guide, add 30 to 50 litres of biochar over th
e course of filling a typical backyard compost bin.
Garden Beds – how best to add Char
Adding char (horticultural char or biochar) to garden beds will help retain nutrients and assist drainage.
As a guide, add about 10 to 15 litres of char per square metre of garden bed (around ½ pound for every square foot). To apply, simply till the garden bed area, then spread the char evenly over the top and till it in completely to a depth of 200 mm (8 inches). Then water and fertilize thoroughly.
Turning Biochar into Superchar
Here’s a quick-brew recipe suggestion for a nutrient loaded biochar that should be rocket fuel for your plants. You will need:
- Liquid fish emulsion = 350 mL
- Seaweed concentrate = 350 mL
- Water soluble trace elements mix = 60 mL
- Wood vinegar = 40 mL
- Water = 8 litres
- Biochar = 10 litres
Add everything but the biochar to the water and mix / dissolve thoroughly.
Pour the liquid mixture over the biochar, stir in thoroughly and allow to soak for 3 days
You now have “Superchar”! Mix into the garden bed soil at no more than 30% (1/3rd).
Or to make your own complete “Supersoil”, simply add the Superchar to 10 litres of fine sand and 10 litres of your own garden soil, and plant directly into the mix.
Note: don’t use Superchar when growing carrots or parsnips – it’s too rich for them and it may cause root forking.
Biochar and your Terrariums
Adding a layer of horticultural char to your terrarium soil helps to absorb toxins and odours, improve drainage and yield healthier happier plants.
When building the soil bed for a terrarium, after first placing a 25mm (1 inch) layer of gravel or pebbles at the very bottom of the container, add a layer of horticultural char of similar depth immediately on top of the gravel. Then add a layer of coir or sphagnum moss (this acts as a separator to stop potting mix settling into the char) and then at least 100 mm (4 inches) of good quality potting mix.
Biochar and your Vegie garden soil
If you’re starting out on a new vegetable garden in unconditioned ground with poor soil, or simply want a starter mix for a raised bed, here’s a good recipe to get things going:
- Fresh compost = 3 wheelbarrow loads (around 230 litres)
- Spent mushroom compost = 75 litres
- Cow manure = 50 litres
- Chicken manure = 50 litres
- Biochar = 40 litres
Mix everything together well, cover with mulch and let it age 2 weeks before planting. Suits a garden bed around 3 square metres.
Charcoal briquettes are not biochar
Do not use commercial cooking charcoal briquettes in the garden as a biochar substitute – Some cooking charcoals and briquettes include fuel volatiles and chemical additives to improve burn characteristics and these additives will not be good for the soil.
Note that our Green Man Cooking Charcoal is a natural, pure charcoal with no additives of any sort.