The Importance of Good Soil
28 Oct, 2020
When our soils are healthy and full of life, they make our lives as gardeners easier, as they help us to nurture healthy and disease-resistant plants. Poor, depleted soils are less complex, less interesting and less productive. Even a basic understanding of what kind of soil you have and how to work with it can make gardening considerably easier.
New Zealand soils are young, and as a result, there are mineral deficiencies found in most of our soils. These deficiencies can be generally addressed by using Natures Organic Fertiliser, which is full of minerals and loaded with beneficial bacteria and fungi that will help stimulate the life in your soil.
Types of soils
There are many different types of soils found in gardens around the country, and each type can be improved with a little extra care.
Clay particles are incredibly small and have a tendency to stick together. Heavier soils will regularly form a sticky, gloopy mess in winter, only to turn into an impenetrable concrete over summer.
Yet despite being frequently reviled, clay soils do have advantages. They are often nutrient-rich, but the poor structure means that your plants can't take advantage of this. By adding gypsum and organic matter (compost and sheep pellets) and by deeply aerating your garden beds, you can slowly improve the structure. And the results can be impressive; within a few years, it's possible to create a garden with lush, deep friable soil in an area that had previously only a thin layer of topsoil on top of a hard clay pan.
The problems faced by those on sandy soils are almost the exact opposite of those faced by people on clay. The large size of the soil particles means that they drain way too freely, meaning nutrients leach away and they're hard to keep moist.
Yet oddly, the solution is similar to that of clays. What you need to do is increase the amount of organic matter content in your soil by adding composts and manures, which increase the water-holding capacity of your soil dramatically and help create a structure that will resist leaching.
Gardeners that grow on volcanic soil, which is highly mineralised, are probably used to the envious looks of other gardeners as they effortlessly dig holes and grow plants! This envy is understandable: lots of people that live with clay soil love avocados, but growing them there is pointless – it's a cinch growing them in volcanic soils, as while drainage may at times be an issue, adding compost and mulching can help no end. If you're worried about your volcanic soil drying out, adding sphagnum moss or Saturaid can really help reduce any watering issues.
Growing green manure/’compost' crops to improve your soil
Another great way to protect soils, improve their structure, and add nutrients is to grow green manure crops. Green manure crops are basically cover crops that are grown at a time of year when the soil would otherwise be empty, and then dug in while they are still green. In Auckland we are lucky that it is warm enough that we can grow cover crops in our empty beds over winter and then dig them in while they are still green before planting the beds up again in spring.
Advantages of growing green manure crops
Prevents soil erosion
When exposed to the wind and the rain, bare soil will start to wash away. A green manure crop helps by improving the structure of the soil by physically holding it there with the roots, while protecting the soil with the foliage.
Bare soil is a great way to grow weeds. But green manure crops ensure that there isn't enough space for weeds to take hold of your bed. This should also help you next year as it means there should be less weed seed to germinate.
You add an array of different nutrients depending on which crops you use.
Helps beneficial microbes
Digging the organic material into the soil helps stimulate soil biology by providing many of the beneficial microbes with food. This in turn, helps the plants as a soil rich in beneficial microbes is less likely to harbour diseases and makes it easier to keep your plants well-fed.
Makes your life easier
In the long run, growing green manure crops should help you save time and money, as you won't need to weed as much, use as many weed killers or pesticides, or use as many fertilisers.
What to Grow
Bacteria attaches itself to the roots of lupins and takes nitrogen from the atmosphere, locking it into the soil. Lupins are also great at accessing phosphorus from soil minerals, which will become accessible to other plants after they have been dug in.
Sow late Summer/Autumn
Dig in October/November
Green Manure Mix – a mix of lupins, mustard and oats
The oats accumulate potassium and nitrates from deep down in the soil and then capture these nutrients in the topsoil. They are also great for the structure of the soil and when grown with mustard, very effective at suppressing weeds.
Dig in while they are flowering, before the seeds set