The goal of customising soils is to create the Perfect Soil and to transform Dirt into Real Soil.
Dirt consists of sand, silt and clay and thus two of the components are inert and nutritionally worthless, they are the sand and silt components, which are really just finely ground forms of glass or silica. We actually do need the silica in the garden but in the “amorphous” not “crystalline” form.
What we really want to create is the Clay Humus Crumb, which is a fusion between the clay and humus particles in the soil. This results in very stable soil humus levels which will not easily oxidise and escape into the atmosphere as CO2 and this means the nutrient and moisture storing capacity of the soil is greatly enhanced.
Clay-Humus Crumb
Image of clay-humus crumb formation in well managed soil,
as seen under a microscope. This beautiful structure is built by microbes, which
tie humus particles to clay particles in the formation of clay-humus crumb.
Clay-humus is an architectural masterpiece of Nature.
In fact, what we want is a soil with a “Big Petrol Tank” and the scientific term for this is CEC.
CEC is short for Cation Exchange Capacity
Clay and Humus are Colloids which are large particles with a negative charge on the outside. Positively charged mineral ions which are called Cations are attracted by the negative charge on the Clay and Humus and are held in the soil instead of leaching out.
Some examples of important cations that you need for high fertility in your soil are,
Calcium Ca 2+
Magnesium Mg 2+
Potassium K +
Sodium Na +
It is absolutely critical you get some understanding of these concepts, because there is a misconception, especially in some organic circles, that all you need is organic matter or compost, and that once you have that, everything else will take care of itself. This is like thinking you can live on white bread or Kellog`s Cornflakes, in other words EMPTY CALORIES.
You need to REMINERALISE your soil !
Over millions of years the minerals have leached and eroded off the land into the sea. If you are recycling organic matter from minerally deficient soil, you will never correct the mineral deficiency, your organic matter will be minerally deficient and thus the organic equivalent of Kellog`s Cornflakes.
So I believe in using Crusher Dust and PAP7 from Paramagnetic Basalt, which is a form of volcanic rock that is loaded in minerals from the centre of the earth.
Some friends of mine in the Hokianga built an organoponic raised bed garden and only had heavy Hokianga clay soil to put into it. So we decided to try to make it more lighter and freedraining by adding one shovel of bedding scoria to every two shovels of soil. What we ended up making was a 20 metre long, one foot high Adobe Brick !
You can not lighten clay by adding sand or fine scoria, you need organic matter. So now we are going to remove 30% of the soil out of the bed and add Sawdust. Initially there will be Nitrogen Robbing but we will balance that with chemical nitrogen or chook manure.
There is no more dramatic way to shift organic matter levels in soil than by adding Sawdust. It will make any heavy soil light and fluffy, but beware of nitrogen robbing in the first few months. By far the easiest method to deal with this problem is to add Ammonium Sulphate, a few kilo to the cubic metre. The Sulphate content is important as the creation of humus needs Sulphur as well as Nitrogen. The nitrogen bound up by the sawdust will eventually be returned to the soil as the sawdust breaks down. After all it really is only the microbes breaking down the sawdust that require the nitrogen. “Microbes always feed first” and if they need nitrogen to breakdown sawdust they will be much more competitive at extracting it from the soil than your vegetable plants.
I recommend customising soil with with Crusher Dust and Organic Matter. Hopefully you will have some Clay Loam on hand, but you could experiment with drying and pulverising sticky yellow Northland Clay, if you have the time.
You will have to experiment with your materials, but roughly the proportions are 30% Soil, 30% Rock Fines, 30% Organic Matter.
A high producing, fertile vegetable garden of any type should have organic matter levels of 15%.
Many soils have levels as low as 2%
Suggested goals for organic matter levels in well managed agricultural soils:
Field crops 3-5%
Vegetables, orchards, pastures 5-8%
Gardens 10-14%
In general it is good to add Rock Dusts and Clay Powder or Clay Loam to your compost heaps and they can compromise as much as 10% of the volume of the heap.
These raised bed gardens are really banks, “Banks of Fertility”
It`s time to start depositing minerals, microbes and humus into the “Bank”, it`s essential for you future Food Security.
Soil can cure depression. Really. There’s already evidence that too much hygiene can cause autoimmune diseases like allergies, asthma, and MS. Now there’s evidence that it can cause depression and maybe other mental illnesses, too. In the case of depression, the cure is a benign bacteria that lives in soil. You inhale it if you work in the garden or walk in the woods. And ingest it if you eat lettuce or carrots grown in a home garden. (The research suggests depression may be at least partly an inflammatory disease.)
” I teach gardening for Hard Times ” Grant