The Magic of Organic Matter

Now we come to one of my favorite topics – organic matter!

In organic gardening, you learn to feed the soil and let the soil feed the plants. The best way of doing this is taking advantage of organic matter. Often we remove decaying organic matter from our gardens in an effort to keep them neat and tidy, but in reality it is how nature feeds her plants and we should find ways to incorporate it into our soil.

As I have said in a previous article, typical unimproved garden soil will contain about 90% mineral residue and only about 10% decayed organic matter. This small quantity of organic matter is home to a community of insects, microorganisms, earthworms and other soil dwelling creatures.  The more organic matter, the more food for the beneficial organisms that aerate the soil, release nutrients and create even more organic matter with their waste and decomposition. Apart from this, organic matter offers a host of other benefits! 

Partly decomposed organic matter

Some of these include: 

  • Acting as one of the major reservoirs of soil nutrients, as water and nutrients cling to the surface area of the particles.
  • Fresh organic matter and compost absorb water like a sponge, holding up to 3 times their own weight in water;
  • Prevents erosion by allowing better water infiltration.
  • Improves the soil structure by helping soil particles to clump together.
  • Improves tilth and permeability, making it easier to work, better aerated, and absorb water more readily.
  • Contains acids that can make plant roots more permeable, improving their uptake of water and nutrients, and can dissolve minerals within the soil, making them water soluble and unlocking goodness for your plants.

One of the first questions is the definition of organic matter and humus.  In the study of soil, humus refers to a very specific type of organic matter that has reached a point of chemical and biological stability, where it won’t break down any further and may remain the same providing conditions do not radically change. Humus is very important in its ability to create healthy soil, therefore helping to control plant diseases by allowing valuable soil organisms to feed and reproduce. The more beneficial microorganisms your soil can support, the less bad organisms will survive. The good guys feed on harmful microbes like nematodes and certain soil born diseases. Often described as the life-force of the soil, humus is only a part of the organic component of soil. The rest is made up of from other sources.


Sources of organic matter

There are many sources of organic matter.  Here are some suggestions:

  • Compost
  • Animal manure
  • Mulched material 
  • Straw
  • Paper and cardboard
  • Vegetable kitchen scraps
  • Grass clippings 
  • Garden waste – from weeding, pruning, mowing. 

Black Gold – rich compost ready to go!

Let’s look at some of these more closely:


Compost is an earthy-smelling material that is the product of decayed organic nitrogen and carbon.  Not all composts are alike and differ depending on what materials and processes were used to make the compost.  Compost at its best looks like rich soil and should be dark and crumbly.  If you haven’t made it yourself, it may be a good idea to test the pH of the compost before using. Compost can be added to your garden beds at anytime, either turned into the soil or used as mulch.

Animal manure

Animal manure is organic matter with the added bonus of soil nutrients. Do not use fresh manure as it will burn your plants and may contain potential for disease and weeds.  It should be aged for several months and can be added to your compost heap to break down further. Avoid manures of carnivores such as cats and dogs.  Cow and sheep manures are highly nutritious and add plenty of structure to your soil.  Horse manure doesn’t hold many nutrients but helps to add organic matter and improve soil structure. Poultry manure is very strong, particularly in nitrogen and needs to be composted well before use. Worms love to help with this!

In my garden I use the second cut of lucerne, unfortunately called ‘offal’, for my mulch as it is reasonably priced and I use a LOT of mulch! Any type of straw can be used, depending on what you need. Meadow hay is cheap but doesn’t add much goodness and often contains weed seeds. Pea straw is great for adding nutrients and is easy to spread. The first cut of lucerne is the cream of straw, adding lots of goodness to your soil, but it is also the most expensive, so is mostly used sparingly in ‘no-dig’ gardens.

Straw mulch keeps roots cool, suppresses weeds and keeps moisture in. Watch out for bugs though – you may need to pull the mulch back until seedlings have established.

Bark chips from mulched prunings from the garden.

Mulched material, straw and paper products

These materials can be either added to your compost heap or added directly as mulch around your plants.  I put all suitable scrap paper through a shredder to use as bedding for the chickens, and then add it to the compost when I clean out their house. It makes a very clean and comfy nest! Other paper products should be soaked in water before adding to the compost bin, and large pieces of cardboard and newspapers can be soaked and used directly as mulch under straw or bark chips. (I will share my method for the ‘no-weed’ garden in a future post.)

Green manure/cover crops

A lush crop of oats and woolly pod vetch.

A green manure or cover crop is often grown when the soil needs enriching and replenishing after a hungry veggie crop or around fruit trees. It is simply annual leafy plants grown with the intention of turning into the soil at a certain time of growth to add fresh organic matter and nitrogen.

This can really only be done in the veggie garden or in a new garden bed, as digging in the crop could harm existing plants. However, if you use the ‘no-weed’ garden method of mulching, the green crop can be planted around established perennial shrubs and trees and when grown will be smothered and start to break down immediately.

A variety of plants can be grown, offering different advantages. For example, alfalfa is grown for its deep roots, helping to breakup and loosen compacted soil.  Legumes like clover, vetch and peas collect and store nitrogen and release it into the soil through their roots. If allowed to flower, clover is especially attractive to pollinators and beneficial insects.

Green manures also help to prevent erosion and water runoff in ground that would otherwise be bare.

For great advice on choosing green manure crops and organic seed collections, visit-


Other organic matter

A balanced compost mix

Other organic matter that hasn’t broken down yet, such as vegetable kitchen scraps and garden waste from weeding, pruning and mowing should all be composted before adding to the soil.  One of the reasons is that the breaking down process is biological and living, involving bacteria, fungi and other soil organisms.  These creatures need food to do their work and will initially take it from the soil, which will in turn take it from your plants.  Once it is decomposed, it will be black gold for your garden!

Find out more about composting in my next post.

Until then, cheers and happy gardening,

3 thoughts on “The Magic of Organic Matter

  1. Lisa says:

    On the article about parsley you wrote about the Hamburg Parsley and not finding it in Australia. I think Eden Seeds sell the seeds to this one.

    • Amanda says:

      Hello Lisa,
      Thanks so much for sourcing this – I’ll definitely give the Hamburg Parsley a try! Cheers, Amanda

  2. ana says:

    Hi Amanda, I just wanted to confirm our tentative booking for the 31st of July at about 12.30pm-2.30pm
    workshop with Amanda Reynolds from Green Platypus. Propagation of plants. Includes seeds, all materials, handouts. Cost $7

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