A person shoveling soil

Good soil means a great harvest

Tips by Sarah the gardener

Normally most gardeners are stirred into action by the first warm day and head off to the garden centre and grab everything they want to grow, hastily clear the beds of any weeds, throw in all the plants and hope for the best.

The essence of a successful garden is having good soil

One of the most important keys to a successful growing season and a bountiful harvest is to have the best soil possible. The thing is not all soil is created equally and what is right for your neighbour may not be right for you. There is no set formula for making good soil as it is all different. You need to spend time on this, understanding your soil, you need to work out what it needs to be at its best and then do what it takes to make it at its best. 

The expression ‘you are what you eat’ applies to the soil too. If you have poor soil, then the quality of your food will be poor, however if you have nutrient rich soil then your food will be nutrient rich. It is in your best interest to really understand what is going on in the ground you will be growing your food in.

A person planting salad seedlings

What is soil?

It covers all the dry bits of the earth, and we walk all over it without giving it a second thought. As far as gardeners are concerned there are about four layers of interest. 


This is all the organic matter lying on the top like lawn clippings and fallen leaves. Gardeners can recreate this natural layer by adding it to their veggie gardens to retain moisture and suppress weeds. 


This is the bit that plants grow in – it is where their roots call home. There is loads going on in this layer. The earthworms also live there and they work hard to process organic matter, especially bringing down goodness from the mulch layer and aerating the soil by creating tunnels all through it. Microorganisms like bacteria and fungi break down organic material and convert nutrients into a plant friendly food. Fungi also help the roots to do their job of absorbing nutrients more efficiently. 

It is also made up of inorganic matter - minerals and fine particles of the rock which is based beneath it, of which there are many kinds of rock. The organic matter and the inorganic matter work together to give the soil structure, drainage and the all-important nutrients. 


This is the layer below the one where all the action happens. It is more inorganic matter and has more in common with its rock origins. It isn’t really a layer you want to incorporate into your growing zone. The main contribution this layer offers to your garden is drainage. A clay subsoil can mean a boggy topsoil, and a sandy subsoil and mean a dry garden that holds very little water. 

Water Table

This is the last layer that has any significant impact on your garden. It is the level below the surface which the water in the soil normally sits. It will increase with rain and decrease in drought, but generally it has a level that it is normally at during each season. In some gardens, this is a long way down or very near the topsoil and in winter it is often above it. This will impact things like drainage and your irrigation needs. 

And so that is what your soil is essentially made up of. All you need to do is figure out how good your soil is!



The inorganic content of your soil is generally made of a mix of three elements Sand, Silt and Clay. The ideal soil is roughly 40% sand, 40% silt and 20% Clay (+/- 10%). If one layer is larger than that, it will be harder for the plants to thrive and will need to be adjusted. 

If you have a high clay soil it can be improved by adding loads of organic material, compost, manure, and a little pumice or grit to help with drainage and a little lime to help break up the clay. 

If you have a high sand content then adding loads of organic material like compost and manures from vegetarian animals will greatly assist with the water retention of sandy soils. You can add some bought topsoil that leans towards more clay or silt to redress the balance and feed the garden often with fertilizers during the season as nutrients are easily lost. 

Loam soil is really the best kind of soil, but you have to work with what you have – or build a raised bed and fill it with a lovely loam soil.

Closeup of salad in a garden bed


These little guys are great friends in the garden and they love a healthy soil. So to check your soil quality conduct an earthworm census. Dig a hole about 20cm square and about 20cm deep and take the soil from your hole and go through it looking for worms. Count them up. If there are more than 10 you have great soil. Less than five worms then you need to add loads of organic matter. If there are no worms then your soil is in such a dreadful state that even worms won’t live there.


If you remember from science class at school, the pH scale goes from 0 – 14 with 0 being very dangerously acidic and 14 being corrosively alkaline; 7 in the middle is neutral like tap water. Most veggies like to grow in soil that is between 6.0 and 7.5. There are – like in all things – exceptions, so you also need to know about what your plants actually need. 

If the soil is too acidic, it can make the nutrients too soluble and they will float away. If the soil is too alkaline, the nutrients can be held up tightly by the soil and the plants can’t get at them. You can reduce acidic soils by adding a little lime; this is called sweetening the soil. Don’t overdo it though – less is more. Increasing alkaline soil can be done by adding sulphur – often sold as flowers of sulphur. Follow the instructions on the packet carefully.

The key thing to remember is that with the harvesting of crops and removing the plants at the end of the season you are constantly depleting your soil of goodness, so you need to be adding goodness back in all the time to keep the soil healthy. If you just grow and take and give nothing back, within a couple of years your soil will be useless for growing anything.