What is healthy soil and how can you create it for your garden?
The real secret behind being a good organic gardener lies beneath the surface of the earth. At the heart of any productive vegetable garden is well cared for and nurtured soil. Healthy soil is defined by its physical, chemical and biological properties. To be a good organic gardener, one must continually aim to improve the soil’s structure, composition and biodiversity.
If you want to learn how to improve your soil health, it’s helpful to understand a little more about the three main areas of soil fertility.
The physical properties of soil affect soil fertility by influencing how water, nutrients and roots move through it. Soil structure, texture and water repellence are three characteristics that define soil health, whereas water infiltration, waterlogging and soil erosion are all physical processes which influence soil fertility. The biggest factor influencing your soil’s physical characteristics is its mineral and organic content. Soil chemistry influences the availability of elements for plant growth as well as the presence of elements or chemical compounds that may be harm plants and soil organisms. The ability of plants to access nutrients is influenced by the presence of the nutrients in the soil, the pH of the soil, the life found to be living in the soil, and its physical characteristics.
Biodiversity in soil is important for a variety of reasons including transforming ‘parent rock’ to soils, improving the cycling of nutrients, transforming nutrients from one form to another, minimizing diseases in plants and assisting or preventing water from entering the soil. Bacteria, fungi, arthropods, earthworms, insects and nematodes all have their role to play in the biological health of soil.
So, to create healthy soil, you should focus on improving the physical, chemical and biological characteristics of the soil.
Here are 3 important steps in achieving this:
- Know your soil
By testing your soil, you can identify what it needs to become more fully balanced. Doing a soil test from your garden is quick and easy and will give you insight into the physical properties of your soil and how best to treat it into the future. Add soil and water to a clear jar, shake it until all the clumps have broken up, and allow it to settle overnight. This will allow you to see what percentage sand (large particles) silt (smaller particles) and clay (very small particles) your soil is composed of. Take note of how much organic matter is floating in the water or at the surface. If there is hardly any organic matter, more should be added over time. You can also buy cheap DIY soil tests to get a basic understanding of your soil’s chemistry, or send your soil into a local soil laboratory to get very precise results.
- Improve your soil’s physical structure:
If your soil is sandy (more than 90-100% sand) work 12-15cm of compost into the top layer of soil and mulch around your plants with leaves, wood chips, bark, hay or straw to prevent water and nutrient loss. Growing nitrogen-fixing cover crops like Lucerne, Alfalfa or Clover will also help create better soil structure and add nitrogen to the soil.If your soil is clayey (40-100% clay) work 6-10 cm of compost into the top layer of soil, and consider creating raised beds to allow roots more freedom to grow and absorb nutrients. Clayey soils pack together very tightly and can become sticky and unworkable so your beds will need to be topped up regularly with potting soil and compost to eventually become workable and productive.If your soil is silty (30-50% silt) you can improve it by adding 3cm of compost a year, avoiding compacting the surface by not walking on beds, and considering constructing raised beds if the earth tends to be compacted or difficult to work.
- Balance your soil’s pH
The pH of your soil indicates if it’s acidic or alkaline. Most plant nutrients are available to plant s when the soil’s pH is between 6.5 and 6.8. To improve your soil’s health, it’s important to balance your pH by adding amendments over one or two growing seasons. Buy a cheap pH test from your local garden center to test your soil’s pH. Once you’ve established your soil’s pH, you can adjust it slowly over time to try and reach optimum pH levels. To raise your pH you can add powdered limestone to the soil, and to lower the soil’s pH (make it more acidic) you can add ground sulphur or naturally acidic organic materials like pine needles, sawdust and oak leaves. Be careful to do so slowly and to not expect instant changes. The essence of a healthy vegetable is in the health of the soil it grew in, so take your time in creating healthy soils and it will pay off in the long run for your garden!
In our next issue, we’ll take a close look at three ways to create nutrient rich food for your soil and garden!