The importance of soil health and composting

In this blog, we will explore best practices for creating a thriving garden, enriched by my personal experiences. Over the years, I’ve gathered valuable insights from various sources, including radio talks, lectures, nursery production, practical demonstrations, and workshops. We will delve into the unique challenges of South African soil and climate and how to cultivate the best environment for your garden. Join me on this journey as I share all my knowledge and experience to help you achieve a flourishing garden.

The importance of soil health

In my experience, investing in the health of your garden soil is worth every penny. Nurturing your soil yields plants that are healthier, more resilient, and better at flowering and fruiting. Neglecting your soil will result in plants failing to thrive, making them more susceptible to drought, pests, and diseases. This does not mean attempting to change your soil type but rather understanding the unique characteristics of your particular garden soil. Whether you have sandy soil, loam (lucky you), or clay soil, which could be slightly acidic or slightly alkaline, well-rotted compost is the magic ingredient. Compost balances all soil types with its dark, nutritious humic matter.

Avoid exposed bare soils

This brings us to the issue of bare, exposed soil.” Even worse is soil deliberately raked bare of any mulch or leaf litter. It cries out to me, and I hear it wailing with a chorus of unhappy plant roots accompanying this depressing sound. Think about exposed soil in nature; usually, a natural disaster has occurred, such as a fire, landslide, windstorm, or erosion. These events are damaging for soil microbes, plant growth, and root health. Naturally, nature covers her land’s soil consistently via leaf drop, decomposing plant matter, shedding bark or seeds, or even green ground-covering plants. Under these various covers, plant roots stay cool, soil remains friable, water is retained, and nutrients are recycled back to the plants. So, look to nature’s way to inspire your soil care methods.

The Root-to-Shoot balance

Plants maintain a root-to-shoot balance, which becomes evident when we prune foliage. Almost immediately, the plant responds because it has enough roots to support a certain number of shoots. By cutting back stems, you cause an imbalance, and the plant regrows to re-establish balance. This is also evident in Bonsai and root-bound plants, where restricted root growth leads to reduced top growth.

Often, a plant in newly well-prepared soil will sit for a while, making me wonder if it is happy with the choices I made on its behalf—sun/shade, morning/afternoon sun, soil depth, plant companions, planting time of year, enough water. Then I realize it is growing its roots out of sight. Once it has established and extended its root system, it will grow the shoots I am going to enjoy and celebrate! Gardening teaches one patience above all else.

Compost for healthy soil

My recipe for soil health starts with compost as the main ingredient! I compost all my gardens before planting and repeat composting seasonally, depending on how quickly the soil has absorbed the compost. In sandy soils, which are well-drained and naturally have very little humic matter, I compost as often as every three months. For clay soils, which retain more water and have a higher nutrient content, I compost only every autumn and spring. In loam soil, I apply compost once a year, just before the dry season.

I always observe the soil to see if my last application of compost and mulch has almost completely broken down before applying more. Over-composting can cause roots to anchor in the compost layer on top of the soil rather than in the actual garden soil, which is not ideal.

Planting tip

A key method in my recipe is not turning the soil too much. I apply a 5 cm thick layer of compost to the soil and plant through it. This way, it gently mixes with the planting soil rather than turning the soil vigorously. Turning the soil too much puts what should be below ‘on top,’ which is not a good idea because you’re literally turning your soil microorganisms’ worlds upside down. As we have learned more about our own gut health, we have also learned much about soil microbial health. So, dig as little as possible in your soil. Picture yourself breaking your own and your entire neighbourhood’s Wi-Fi fiber connection; the mycorrhiza in the soil have webs and threads of life connecting all.

I recommend digging only the exact-sized hole you need for your plant’s root-ball. However, if you are reworking an entire section of your garden, do what you must, as sometimes it is simply unavoidable. But realize those threads and microbial balances will take time to reestablish themselves, and you may not see your plantings thrive until they do.

What goes on top?

The next step in my recipe is to cover all the compost with a medium to fine rotted woodchip mulch to prevent it from drying out or blowing away. Rotted wood-chip is sturdier than compost and breaks down slower, providing a gradual release of nutrients into the soil. I don’t use bark nuggets because they are too big, dry, and hard, but this is a personal choice based on experience—each to our own microclimates.

In areas with heavy prevailing winds that can remove both mulch and compost, I recommended using wind-resistant products containing bits of straw or restio stems are ideal, as they tend to embed within the topsoil layers and lie over one another, preventing the wind from blowing them away easily.

Avoid using fresh or green mulch that has not yet rotted or decomposed. Instead of slowly adding nutrients, decomposing microbes will use the nitrogen in the soil/compost that should remain available to plant roots. This is because bacteria need nitrogen to do their work within the decomposition cycle. To prevent plants from suffering until the nitrogen is recycled and available again, use fresh mulch only on natural garden pathways. This also discourages weed growth or place it on your compost heap to decompose first.

The final ingredient in this fertile soil recipe is an organic-based pelleted fertilizer, applied sparingly over the top of the mulch. This ensures the supply of some additional nutrients immediately to your plants. The nutrients will trickle down to your soil roots with rain or irrigation watering. More importantly, if your mulch is not completely rotted, this will assist the decomposing microorganisms in completing this process. This preference for organic fertilizers is based on the ethos of emulating nature as closely as possible in the garden.

There are many lessons to be taught by nature and to be learned by gardeners, and with looking after roots—one lesson I learnt is “investment and patience.” Both have yielded joyous delight when that happy plant grows healthy, green foliage with an abundance of flowers and fruit!

Thank you for joining me on this journey to cultivate healthier substrates and happier plants. Share your soil adventures with us on our Facebook page! Let’s build a community where we can learn and grow together.

Cherise Viljoen
Master Horticulturist