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How to create healthy soils for your garden


July 28, 2022


Searles Gardening Team

A healthy soil is the first essential step to growing healthy plants.

Healthy soils are full of organic matter and humus, teeming with beneficial microbial activity, earthworms and an abundance of nature’s wonderful little helpers. Plants growing in rich, healthy soil are vibrant, full of vitality and health, having few or rare problems with pest attack, diseases or nutrient deficiencies. On the other hand, plants grown in soils with little organic matter and poor microbial activity are much more likely to suffer those problems. Such plants are not as healthy and generally have less brilliant blooms; in the case of fruit and vegetables, quality and quantity is poorer.

So the key to growing healthy plants is first to build up a healthy garden soil!

Very simply, with compost (a good, mature compost), animal manures, organic fertilisers and more compost. Then mulch the garden well and continue to do so. Nature does this. Take a look at some soil in a forest or bushland and observe that the soft, crumbly topsoil is full of organic matter. All the leaves and plant material fall onto the soil, forming a layer of natural mulch. This natural mulch is constantly breaking down into rich humus as more and more organic matter falls on top, constantly replenishing the soil and forming part of a natural cycle.

Humus is the end product of broken down (decayed) organic matter. Humus is an essential component of healthy soils that has many great benefits. Below is detailed just some of the great benefits of humus and why it is so important to be constantly building humus levels in our garden soils.

  • Humus dramatically improves soil structure
  • Humus has exceptionally high water-holding capacity
  • Humus supplies a very rich source of plant nutrients
  • Humus has an incredibly high nutrient storage capacity
  • Humus has excellent insulating properties against both heat and cold
  • Humus helps to buffer soil pH to an optimum range
  • Humus allows more oxygen to enter the soil, increasing root growth
  • Humus increases water penetration into the soil
  • Humus increases plant root ability to grow deep into the soil, developing a stronger and more rigid root and plant structure

Overall, the development of humus in the soil will greatly increase gardening success, reduce watering needs to a minimum, grow much more healthy, vibrant and lush plants that are less stressed than plants grown in soils lacking organic matter and humus.

All we need to do is add plenty of compost, animal manures, organic fertilisers and mulch. Then let Nature do the work of building humus from these. Good matured compost will already contain humus.

Every few months or after a crop of plants has finished, add some more compost and mulch again. Mulches that break down are excellent. As they break down, they are also feeding the soil. By constantly adding a little at a time, you are helping to create a natural cycle within the garden. Your garden will use much less water and the soil will hold more moisture. The end result will be improved plant growth and health, with all the organic matter and humus in the soil.

The major importance of soil pH* is in relation to nutrient availability. The optimum range of soil pH is generally accepted to be between 6 - 7 for most plants. As pH increases above 7.5 or below 5.5, certain nutrients begin to lock up in the soil, becoming less available to the plant. Sometimes there is a lot of concern over soil pH, but it is an easy problem to overcome.

As we add compost and organic matter to the soil, this builds up humus. Humus has the amazing ability of storing nutrients readily available to the plant, as the plant needs them. Interestingly enough, as the soil builds more and more humus, the pH tends to naturally balance itself. This is a natural phenomenon. Even if organic matter has a high or low pH to start with, once it has been in the soil for a some time, it usually tends to balance itself. Keep on adding compost, organic fertilisers, animal manures and mulch and let Nature do her wonders.

If the pH of your soil is causing immediate problems, there are numerous products available which will help to correct the problem. Normally, if the pH is acidic, Dolomite or Lime is added to raise the pH. On the other hand, if the soil pH is alkaline (above 7), then applications of sulphur powder will quickly lower the pH. Full details of quantities to use and how to apply are detailed on the bags and packaging. If you have a specific problem with a plant or plants, ask your local garden centre or nursery for the best advice suited to your area and specific problem.

Healthy plants very rarely have problems from garden pests and garden diseases. When plants are stressed in some way, such as lack of water or nutrients, they become much more susceptible to pests and diseases. But healthy, well-mulched soils with plenty of humus hold much more water, supply an abundance of nutrients as the plant requires them, allow plenty of oxygen to circulate around plant roots and contain healthy populations of beneficial micro-organisms and earthworms.

The end result - healthier plants, healthy growth, more flowers, better fruit and vegies and - very importantly - fewer pests and diseases.

Worldwide scientific research has shown time after time that compost can be very effective at preventing and suppressing plant diseases. Good, mature composts have been shown to contain qualities which help to suppress plant diseases in the soil, thus protecting them. Research trials indicate that plants growing in soils which have added compost suffered up to 60 - 70% less disease than the same plants grown in soils with no added compost.

Well, we have found the best results from digging Searles Premium Compost and 5 IN 1 Organic Fertiliser into the top 5- 10 cm of soil or garden bed before planting. Not only does the compost provide an abundance of nutrients essential for healthy plant growth but it also greatly improves the structure of the soil with the ability to absorb water easily, hold more moisture for longer periods of time and allow essential aeration for good root growth and development. All this plus the addition of essential organic matter and humus to the soil already mentioned.

If you are starting a new garden, add plenty of Searles Premium Compost or 5 IN 1, about a 5 - 10 cm, thick layer over the soil and work down about 10cm with a fork or hoe. Remember not to work the soil too much if it is very wet; not only is this hard work, but it also may damage the soil structure. Also, if the soil is very dry, moisten it a little first. Moist soil is just right.

If you are growing annuals or vegies, add some Searles Premium Compost or 5 IN 1 after each crop. There is no set amount to add; the more you add, the better the end result will be.

After each application, or season, you may notice that the soil is constantly improving and becoming easier to work.

Weeds will be much easier to pull out as compost-rich soil tends not to set hard.

Also plant growth and plant health will constantly improve after each crop and you will need to add less compost each time for the same or better results. This is the beauty of compost. Compost is an excellent soil conditioner as well as fertiliser.

With established gardens, it is very difficult to dig compost into the soil close to plants without the risk of damaging their roots, but this is easy to overcome. We have found great success in topdressing compost on to the garden bed using a no-dig method.

Moisten the garden bed first if it is very dry. Then spread Searles Premium Organic Compost or 5 IN 1 over the surface approximately 1 - 2 inches deep. Then cover the entire garden with a good, thick mulch using a material that will allow water to penetrate and which will eventually decompose itself, thus also adding organic matter to the soil.

Searles mulches are terrific for this purpose. Sometimes, the soil may be very compacted and hard, and is not easy to wet. In this case, it would be beneficial to gently fork into the soil, not turning it but just gently loosening a little by rocking the fork back and forth. This avoids possible plant root damage from too vigorous digging. It also helps crack the soil open, allowing both water and air to penetrate. Then apply the compost and mulch as mentioned above. You may be able to chip the compost into the top few centimetres of soil away from plants, being careful not to damage any roots.

Now let Nature do the work. Earthworms are usually prevalent in most soils, even though they may not be seen. They have an amazing habit of just turning up when the conditions are right. And moist soil with plenty of compost and mulch provides excellent conditions for earthworms. These are wonderful helpers who do most of the work for us. They consume the organic matter and compost, carrying it down deeper in to the soil and depositing it as excreta in the form of worm castings (vermicast). Thus they enrich, condition and renew the soil, and create minute tunnels for air and water to penetrate deep down to plant roots.

By adding compost to our garden beds we are actually feeding the soil and allowing Nature to do the work. Through feeding, the soil becomes rich and healthy. Healthy soils grow nutritous and healthy plants full of vitamins and minerals. Try not to think so much of feeding the plant but instead think more in terms of feeding the soil and letting the soil feed the plants.

* The acidity or alkalinity of soil is measured on a ‘pH scale’ of 1 - 14, with acid soils at the lower end of the scale (less than 7) and alkaline soils at the higher end (greater than 7). A soil pH of 7 is considered neautral, neither acidic or alkaline.