Having a productive and sustainable vegetable garden starts with understanding the soil within which you are planning to grow your plants - I always think that 80% of gardening is about the soil, and only 20% is actually about the plants!
A range of simple soil tests can provide you with important insights into your soil's composition and condition and knowing this can help you adjust your gardening practices in ways that help you create the ideal conditions for your vegetables to thrive.
The following information describes the types of soil characteristics that I strive for and the tests that I do to help me develop my garden soil to produce an ideal growing environment for the vegetable plants in my garden.
The Importance of Soil Testing
Soil composition can vary from one place to another and can also change over time. Therefore, soil testing is important because it reveals the characteristics of your garden soil at that time.
Different plants have different pH and nutrient requirements, and without knowing your soil's current state, you may inadvertently harm your plants or fail to achieve optimal yields.
Soil tests that I use provide me with the following information:
A plant's ability to absorb the nutrients they require is affected by the soil pH. If the soil pH is not within the plants limits of tolerance, it doesn’t matter how much nutrient you add to the soil, the plant simply won't be able to absorb it. So, pH affects nutrient availability to plants, not the presence of the nutrient.
Some vegetables prefer acidic soil, while others thrive in alkaline conditions. It is therefore necessary to be aware of your soil’s pH, what conditions affect it and what plants you want to grow in it.
Understanding nutrient levels helps you determine which fertilisers or amendments to use to ensure your vegetables receive the nutrients they need.
Organic matter includes all those plant based materials that ultimately break down and become a part of the soil. Within a gardening context, the most common forms of organic matter we add to a garden is compost and mulch. Ultimately, these form a part of the soil and improve its fertility, moisture retention and overall health.
Adjusting nutrients and organic matter can affect the pH, while adding compost will not only affect organic matter levels in the soil, but many nutrients and the pH as well. It is therefore important that you think about all of these soil characteristics holistically; you should not think of them in isolation.
Now, let's explore the specific types of soil tests for your vegetable garden.
Most vegetables prefer a slightly acidic to neutral pH range, somewhere between 6.0 and 7.0. While it is possible to send away soil samples to a soil testing service, I use a simple soil pH test kit. You will be able to purchase one of these from most good plant nurseries in your area.
Once you have your pH results, you can adjust your soil's pH accordingly using lime to raise it (for acidic soils) or sulfur to lower it (for alkaline soils). Ensuring that you regularly add compost to your garden will also help maintain suitable pH levels in your soil.
Soil Nutrient Testing
Nutrient testing provides insights into the levels of essential elements in your soil, such as nitrogen (N), phosphorus (P), and potassium (K), as well as secondary and micronutrients like calcium, magnesium, and iron. Low nutrient levels can lead to poor plant growth, so it's vital to understand your soil's nutrient profile.
You can conduct nutrient tests either through a professional lab or with DIY kits, but as with pH testing, I have always been very happy with the standard home gardener test kits that are readily available from many nurseries.
Based on the results, you can then customize your fertilizing strategy. For example, if your soil lacks phosphorus, you can apply a phosphorus-rich fertilizer before planting your vegetables.
Soil Texture Analysis
Many gardeners are not aware that plants must be able to use their roots to access oxygen from the soil. This enables them to produce the energy necessary for the absorption of many nutrients. It is therefore critical that the soil drains well and is well aerated. This is what soil texture is about and is determined by the proportions of sand, silt, and clay in your soil.
Organic Matter Assessment
Organic matter content is a key indicator of soil health. Higher organic matter levels improve soil structure, water retention, and nutrient availability. To assess organic matter, use the "feel and appearance" method, where you gauge organic matter content by observing the soil's texture, colour, and smell. Incorporating compost or organic amendments can increase organic matter content in your soil.
Interpreting Soil Test Results
Once you have your soil test results, interpreting them is crucial. Don’t be tempted to adjust levels by more than what is recommended on the packet/container. For example, if your test indicates that your soil potassium levels are down a bit; get some potassium rich organic fertiliser, and add as per the instructions (not more) - you can always add a little bit more later, but it is very difficult to remove it if you add too much.
Also, don’t be afraid to consult with some experts - take your results to a local nursery and ask for their advice. You can even post your questions with photos here on iCultivate.
Soil Testing FAQs
Testing your soil and then using the information you gain to adjust the various components of your soil can help you to improve the health of your plants and increase your yields at harvest time. You do need to be patient, but the work involved will produce good results in the end.
I am an educator and passionate gardener and traveler. Throughout my adult life, gardening has been my passion, therapy, drive and source of purpose. Even as a child I had an intrinsic interest in plants and a desire to understand what makes them grow.
I distinctly remember the moment this began - my family was on one of our regular road trips from Hervey Bay; Australia. We were driving past a field of sugar cane. Dad pulled the car over and we cut a couple of sugar cane stems and brought them home for a treat. To be honest, I didn’t really like the taste, but I did want to try and grow it; and that is exactly what I did. It was then that my fascination, interest and passion for gardening and understanding plants began.
Fast forward a few years and I studied biological sciences and began what would be a 36 year career as a Biology educator. From this, I don’t only love gardening, but I also love helping others learn about gardening. I am also always looking for new ways to develop my own gardening knowledge. I like to think I am truly a life-long learner.
Fundamental to my beliefs about education is that learning is often best done as a part of a community - learning from others, and helping others to learn. It is this type of community that I hope iCultivate will be for its members - a community of gardeners, keen to share their gardening knowledge and wanting to learn about new ways to garden - a community built on the love of gardening.