Dirt is a gardener’s most important commodity, writes TINO CARNEVALE
All the dirt on how gardeners can get the best out of their soil
Itruly love dirt and I have spent most of my life covered in it in some way or another. It is easy to just write off soil as boring background and not give it the respect that it deserves but it is a living, breathing thing and as such you can do things that help it or you can do things that harm it.
As a gardener your soil is your most important commodity, it is the medium that supports and sustains your plants. It helps to anchor them, protects roots from sunlight and temperature variations but most notably it allows the plant to access the oxygen, water and nutrient that it holds.
Our soils are generally made up of differing proportions of sand silt, clay and organic material. This is referred to as the soils’ texture and how those particles are arranged is known as the soils’ structure. The soil texture is determined by the parent rock, weathering, and past and existing vegetation. The parent rock is what has eroded down over time to create
In the immortal words of Young and Scott, Dirty Deeds can be done dirt cheap.
the soil and in Tasmania we have three main parent rock types — dolerite, basalt and sandstone.
Dolerite is that rock which rises up in columns and makes up the mountains that dot our state. It forms that chocolatey coloured soil that all in all is pretty good. Basalt is that distinctive red soil from the North-West Coast which inspires the old saying that it’s so fertile even the power poles start sprouting leaves.
Then there is soil from sandstone which if I was being kind I would describe as light and well drained, and if I was not, completely gutless. The best way to check your soils’ texture is feel it in your hands and look at it closely, examining the aggregates that make up the soil.
If you are still unsure you can perform a ball and ribbon test, in fact the first time I was on television I demonstrated it. It is simply grabbing a handful of soil, moistening it with a small amount of water and rolling it into what can only be described as a mud poo. With that as a
national TV debut it is surprising I am still on the show. If the soil is unable to stick together then it has a high quantity of sand,. If it forms a solid roll and when bent in the middle doesn’t break apart then your soil is heavy clay, and if it forms but breaks when bent then luckily you have a loam.
Loam is the soil that plebs like me with heavy clay only dream of. It is a soil with the perfect balance of sand silt and clay so it holds on to good amounts of water and nutrients but is light and drains well. The remedy for the rest of us that don’t possess a delicious loam, is compost. It gives a sandy soil a bit of bulk allowing it to hold onto more water and in clay soils it gets in between the particles, keeping them apart and allowing the soil to drain.
If your soil is sandy, chances are you are having to throw either lots of water at it to keep your plants happy or loads of organic matter, or both. Because it drains so freely, anything added to a sandy soil will eventually leech away.
Something you can try to improve this is to dig a trench and add a good amount of charcoal or biochar as this will absorb nutrient that would otherwise have leeched away, holding it and making it available to your plants. Mixing up some clay into a slurry in your watering can and watering it over your soil will help hold onto more water and nutrient.
If you’re dealing with a heavy clay soil, sadly adding sand has very little effect unless it is an unreasonable amount. I find the simplest way to improve drainage is by trench composting. A great additive to clay is Gypsum, it works to improve all soils but is best for breaking clay particles apart. The thing is for it to be effective long term it needs to be coupled with the addition of composted organic matter to then keep them apart.
Improving your soil does not have to be costly. In the immortal words of Young and Scott, Dirty Deeds can be done dirt cheap. Many people use the no-dig method which is very effective at building a good soil, although it can be expensive depending on how you go about collecting materials.
For me though, part of the joy of gardening is incorporating compost into the soil with my trusty fork and driving my hands into the dirt. It doesn’t matter how you choose to do it, doing it at all is the main point.