The Low-Down on Dirt

You can choose where you live, and you can choose the house you live in. What you can’t choose (at least not for a start) is the soil beneath your feet. That’s why, for gardeners especially, it’s important to know what sort of soil you have at your disposal. Only after that, can you learn how to modify it so you can grow what you want to. In this article, we’ll take a look at how to identify the kind of soil you have in your own backyard. So … let’s get down to the nitty-gritty!

The nitty-gritty of soil

Soil all over New Zealand varies dramatically – quite often within a short distance; sometimes even within the space of your own property, depending on what earth works have been going on there over the decades. One thing all soils have in common is they exhibit three basic elements: structure, texture and colour. These three elements help you know what kind of soil you’re dealing with.

Structure

Structure is all about how soil holds together, and to find out what the structure of your soil is, try digging up a sample block of earth from the area you’re interested in (make your sample about a spade blade square, then slice off the top 10cm). Ask yourself how the block of soil is holding together. Is it tightly packed and unlikely to break into pieces easily? Does it shatter easily, and crumble into dust and little pieces, or is it somewhere in between (reasonably firm but veering towards the slightly wobbly)? If you’re not sure, drop the block onto a concrete path two or three times, and then decide. Soil that is reasonably firm with a little hint of wobble is likely to have a structure requiring the least amount of work to turn it into a garden.

Texture

Soil is made up of a lot of different ingredients, but the ones a gardener really needs to know about are sand, silt and clay. To learn about your soil texture, take a teaspoon of soil from halfway through your block, remove any stones and bits of plant material from it, mix it with just enough water to allow you to squash it against the palm of your hand. Now, use a finger to move the soil against your palm. Does your sample smear over your skin (in which case it’s likely to be clay). Does it feel slippery and soapy (in which case it’s likely to be silt). Or is it fine and gritty (in which it’s likely to be sandy)? Your answers will describe the texture of your soil. Being able to describe your soil texture is helpful when it comes to changing it to suit your gardening needs.

Colour

Humus is made of different materials that have ended up on top of the grounds and slowly broken down. These materials include leaves, twigs, seeds, and animal manure. As they break down, they often turn the soil (especially the top section) chocolaty black or brown. But not always – it depends what colour your soil was in the first place). The main clue to whether your soil has humus in it, is the change in colour between the top section (remember that 10cm slice you took off your sample), and the rest of the block. If you can notice a difference, that’s your clue you have a layer of humus going on (and that’s good news when it comes to building a garden).

Where to next?

If you’re very fortunate, your soil type will match the sort of garden you want to make. For example, if your soil shatters and crumbles easily, is sandy and gritty, and doesn’t show much colour change from upper to lower surfaces, it’s likely to be regarded as sandy. That’s perfect if you want to grow the sort of plants you might find beside a beach. But if you don’t – there’s no reason to despair. In our next article, we’ll help you name your soil type, and learn how you can change it to grow the kinds of plants you do want in your garden.