Complete Organic Fertiliser

Complete Organic Fertiliser is the term used by Steve Solomon for a fertiliser that he recommends to people for use in their food gardens.  Steve, who used to be a seed farmer in the United States, migrated to Northern Tasmania a number of decades ago and continued food gardening here.  Over time he began to realise that the organic way of only using compost, mulch, blood and bone and lime or dolomite and nothing else left his soil deficient of certain minerals.

Ready to use COF mix

Steve Solomon's thinking in regard to soil fertility

His thinking was straightforward, but not accepted wisdom at the time or even now: if your soil and the soils in your region in general are lacking in certain minerals (and most Australian soils do be cause they are old soils), then you can compost and mulch until the cows come home, but you will never add the minerals that are lacking to your soil, simply because they are not there in the first place.  They won't be in any of the plant material that comes from your garden.  They won't be in any mulches or manures you buy and that come from your region, if all soils in your region are lacking in this mineral.  In this situation the only way you can add the element is in the form of fertilisers that come from elsewhere and that contain the element.

Steve began to experiment with what he called Complete Organic Fertiliser (COF), a mix of elements, some in the form of pulverised seeds, others pulverised rock, in order to provide his vegetables and fruit trees with all the minerals they need and to optimise the nutritional value in them.

Steve's Complete Organic Fertiliser

Steve's recipe evolved over the years as his knowledge of soils and fertilisers increased.  When he presented a workshop to our group he gave permission for his recipe to be used here.

Here is Steve Solomon's recipe for COF as it was per June 2012:

Combine the following ingredients:

• 4 litres of canola seed meal
• 1 litre of soft rock phosphate or guano (not as potent, costs more0
• 1 litre of kelp meal
• 1/2 litre of agricultural lime
• 1/2 litre of agricultural gypsum
• 1/3 cup of potassium sulphate
• 1 teaspoon of laundry borax
• 1 1/2 (1.5) teaspoons of zinc sulphate
• 1 1/2 (1.5) teaspoons of manganese sulphate
• 1 1/2 (1.5) teaspoons of copper sulphate

If your soil is very coarse sand without a clay-subsoil: use dolomite lime instead of agricultural lime.
If your citrus or other plants show signs of iron deficiency: add 1 tablespoon of iron sulphate.
If your soil is heavy clay and has never been limed: double quantities of lime and gypsum for 2 years.

You can read more about Steve Solomon's COF and the science behind it in Growing Vegetables South of Australia (see the 'We Recommend' page on this blog) and The Intelligent Gardener (see Steve Solomon book review).

A simplified COF recipe

The mix I make and use is less perfect than Steve's recipe, but it is easier to achieve and it has worked well in my garden over a long period of time:

• 3 scoops of seed meal, 
• 1 scoop of kelp meal, 
• 1 scoop of good quality blood and bone, 
• 1 scoop of rock phosphate, 
• 1/3 scoop of sulphate of potash, 
• ½ scoop of gypsum,
• ½ scoop of agricultural lime

How to use COF

Many gardeners apply COF directly to soils, rake it in and then water it in. Others feel that COF directly applied to soils is too disruptive to soil organisms and apply it to their compost heap instead.  When the compost is ready the COF has been converted into more readily accessible elements and is less disruptive to organisms living in your soil.

Where to buy COF ingredients

One way of getting COF is to buy all the ingredients yourself and combine them in the ratio described above.  Many of us have done so. 

Ingredients can be bought from agricultural supply businesses and hardware stores, but will require a bit of shopping around because not every supplier will have all ingredients and quality and prices will vary a lot. 

Ready to use COF mix

Buying larger quantities can lower the price per kilogram significantly.  Purchase of larger quantities of ingredients will obviously cost more and you may wonder whether you will ever use it all, but those of us who have bought big bags at low prices per kilogram see this as a long-term investment that will make their produce more nutritious for quite a few years.

In Southern Tasmania ingredients are available from agricultural suppliers such as Hollander Imports (they had all ingredients at the time this post went live) , Roberts (has most ingredients) and hardware stores (have some ingredients mostly in smaller quantities).  In some cases you can buy ingredients directly from producers, eg. kelp meal from Marrawah Kelp Pty Ltd .

What about ready-made COF?

Making your own COF may involve transportation of bags that are not light, and storage and mixing of ingredients in the right quantities.  It is easy to see why some of us prefer to spend a bit more per kilogram and buy premixed ready-to-use COF in quantities of just a few kilos. 

For an indication of where you might be able to buy ready-made COF please see COF Suppliers on this blog.

It's all about soil fertility

Soil fertility is the key to a food gardener's success.  The use of organic fertilisers in addition to compost will improve your soil, make your food more nutritious and make you healthier.

Happy food gardening!