Organic growers are often telling you to "feed your soil; not your plants".  Perth's sandy soils are renowned for being some of the worst in the world for growing - so building organic soil in Perth is vital.

The reason for this is that once you have created a healthy, living soil, your plants are going to thrive.  It's the micro-organisms in the soil, and their complex relationships with each other and your plants that make nutrients available for growth. 

Your crops will only ever be as nutritious as the soil they are grown in, so it’s worth spending the time (and a little bit of money) to get the healthiest produce on your table.  Whether it's vegetables, herbs or 'just' exotic plants - it all begins with the soil.

Traditionally at the start of each new growing season (autumn and spring), gardeners top up the soil to ensure that the new crop will get the best start.  For new gardeners, the choice can be overwhelming, and it's hard to choose what you THINK your soil might need.

Here are some of the common soil improvers organic gardeners use, with some pro’s and con’s of each:-

Manure (horse, cow, sheep, goat, rabbit, alpaca)

Aged manures of herbivores will greatly increase the amount of organic matter in the soil. This encourages earthworms and microbes, which help with soil structure and nutrient availability. These manures contain some nitrogen but are not overly ‘rich’. Manures from paddock animals will always contain seeds, so be aware of potential weeds. It is best to compost manures before use; to help ‘cook’ seeds, and to minimise fly problems.

Manure (poultry)

This manure packs the most ‘punch’ in regard to nutrient content, but it should be used with caution because of its strength. It provides very little organic matter but its nutrient content makes it great to use on hungry crops like corn, leafy greens and bananas. It is always best to compost poultry manure, and to use it sparingly around acid loving plants. Poultry manure used regularly will raise pH of soil. Pelletised poultry manure (eg. Multigrow) is readily available and is easy to use.

Manure (pig)

Depending on the diet of the pig, the nutrient and organic matter content of pig manure falls somewhere between herbivore and poultry manure. As always, use well composted.

Compost

Compost can be used as a soil improver, and is great for adding organic matter to the soil. Whether you make it yourself or buy a commercial product, it is one of the best ways to improve soil structure.

Compost is a fantastic way to recycle garden green waste, weeds, lawn clippings and food scraps, and prevent them going to landfill.  However, nutrient content of compost varies wildly; depending on the source of ingredients. Even if you make your own from garden waste, if it’s produced from plants grown in depleted soil there are few nutrients to recycle, and you won’t end up with a wonderfully rich batch without using additives.

For further reading on our Manure and Compost products, click here.    

Rock Dust

Imaginatively, rock dust is made from rocks, crushed to a dust! Its main benefit is that it provides minerals in a very stable, slow release form. However – again the mineral content varies hugely with the source of the rocks.  Volcanic rock dust tends to be of a high quality; containing a wide range of mineral elements that originated deep within the earth, brought to the surface by lava.  Or, find a blended product. It may be more expensive but it is the best way to ensure there is a wide range of minerals included. Usually a small application to your gardens once a year is all that’s required, or add a small handful to each batch of compost you produce.

Green Manure

Green manure is the name given to any crop which is grown specifically to chop down and dig into the soil. It is a cheap and effective method to incorporate organic matter into your garden. Green manure crops can be things like: mustard/brassicas, rye, vetch, peas, lupins etc. but any quick growing, lush plant can be used. Slash them before they go to seed or you can end up with a weed problem. For more rapid breakdown, put them through a mulcher, then dig in and leave the garden bed for as long as possible (ideally a season) before planting out. Roots and all can be left in the soil to decay. Green manure crops recycle nutrients from deeper in the soil back to the surface, when the plant decays back into the soil. Members of the brassica family are particularly useful for treating soil where root knot nematodes have been a problem.  See our fact sheet on Green Manure for more information.   GLSC sells a green manure seed in convenient packs already blended.

Seaweed Solution

A good seaweed solution acts like a tonic for your soil. It will provide a diverse range of minerals and trace elements to the soil, and stimulate soil microbes to make nutrients available to the plants. It promotes beneficial soil fungi and bacteria which all support healthy plant growth. Fresh seaweed can be very high in salt, and there are regulations prohibiting collecting it from beaches in many parts of Australia – so don’t go collecting without doing some research in your area.

Fish Emulsion

A great tonic for your garden. It usually provides a good source of nitrogen and phosphate, but little potassium. A fish hydrolysate (which still has the oil in it) is even more beneficial as an excellent source of food for soil fungi.

If you like using liquid feeds, if possible, alternate between using a fish and a seaweed solution on your garden. Different formulations will provide a range of different nutrients to the soil and this tends to promote a wider polyculture of beneficial microbes.

Blood and Bone

A great source of nitrogen and some phosphorous, but little potassium. (Add about one part of sulphate of potash to 4 parts of blood and bone for a good, general purpose organic fertiliser for all plants.) Do use a good quality blood and bone; cheaper products can contain fillers like sawdust that do little but bulk up the product.  At the Green Life Soil Co, we use pure blood & bone, with blood meal and added rock dust to provide a wide range of nutrients in our quality blend.

Worm Castings

If you are lucky enough to have access to a worm farm, castings are brilliant to use in your garden. Castings are packed with beneficial microbes and concentrated trace elements. They have the ability to retain moisture in the soil. Always use worm castings dug into the soil, not left to dry out on top. To buy in, worm castings are expensive; so it’s a great incentive to have your own worm farm. Use a small handful when you plant out seedlings to help get them off to a flying start.

For further reading on our Minerals and Fertiliser products, click here.  

Straw

Often used as a mulch on top of the soil, straw will also decompose relatively quickly (and can be put through a mulcher to aid this process) and add valuable organic material to the soil. Not particularly high in nutrients, but straw is often inexpensive and the organic material will improve both sandy and clay soil structures. Straw from nitrogen fixing plants (like peas and lucerne) are slightly higher in nitrogen than oaten, wheaten or barley straw. Be aware straw (which is the lower part of the plant after the heads have been harvested) contains less seed than hay (which includes the seed head) but there will always be some seeds remaining – so watch for weeds.

And finally…

If you have added a range of nutrients to your garden and are still concerned about the health and vigour of your plants, it is worth conducting a pH test on the soil. If your soil is either too acidic or too alkaline nutrients in the soil will be unavailable to plants, so you will need to add specific amendments to fix the problem. The good news is that adding organic material (providing it is pH neutral) will help overcome pH problems. A good garden centre will be able to offer you advice and most will do a free pH test if you take in a small sample of soil.  See our fact sheet on soil pH for more information.

We're here to help! 

As Perth's organic gardening specialists, we can offer advice on the best value way for you to improve your Perth sandy soil.  Feel free to bring in a small sample (about half a litre is enough) and we can look at the pH and the structure, and suggest ways you can build your soil health.

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