Friday, 11 April 2014

Complete Organic Fertiliser

My last post, Grow Your Own Nutrition, was all about how I'm intending to remineralise my soil for the best results in my garden and allotment, and how it's really all about feeding the soil, not the plants - if you missed it please do take a look. The best way to remineralise a soil is to send off a soil sample to a lab, find out exactly what it's got and calculate exactly what it needs, and my new favourite book The Intelligent Gardener can help to do that. But The Intelligent Gardener offers a simpler one-size-fits-all solution too, and because I've got a lot else going on this spring and I could really do with another read-through of the book before I jump in too deep, I've decided to use this recommended 'Complete Organic Fertiliser' (COF) for my plot this year. Steve Solomon, the author, stresses that COF has its limitations and can cause its own imbalances if used year on year, but promises much better results - better growth, better plant health, better flavour and far more nutritious food - than with the conventional organic way of feeding soil just with compost and manure.

There's a version of the COF recipe online here in Solomon's own words, so it can't hurt to share the recipe I've settled on with you here. In the book, Solomon recommends a few other optional additions, but I'm keeping it simple this year and sticking to the main ingredients below:

4 parts seedmeal
Seedmeal is what's left over when oils are pressed, and added to soil it provides a natural, highly-effective, slow-release source of nitrogen as the soil organisms feed on it.

1/3 part lime, 1/3 part dolomite lime, 1/3 part gypsum
The lime provides calcium - probably the most important soil mineral - while the dolomite and gypsum provide more calcium plus doses of magnesium and sulphur, respectively.

1 part bonemeal
This provides phosphorus. There are other things you could use, such as hard or soft rock phosphate - arguably better as it doesn't contain the sodium that bonemeal does - but bonemeal is more sustainable and more easily available, and soil needs a little sodium anyway.

1 part seaweed meal
Seaweed meal is rich in trace elements and also provides plant hormones which boost plants' natural defences.

This mix is to be applied once a year, at a rate of 4-6 litres per 100 square feet, along with a modest amount of compost or manure. If the thought of adding lime to soil every year challenges you, or you're wondering why there's no potassium in the mix (actually, there's just a little in the seedmeal), do go back and read my previous post!

Bonemeal and lime were easy to find in a garden centre, and I ordered the seaweed meal, dolomite and gypsum from The Organic Gardening Catalogue. The seedmeal presented a bit more of a challenge: it's apparently sold as animal feed in the US and Tasmania, where Solomon lives, but here in the UK I struggled to find it anywhere - but I eventually found a friendly local farmer growing rapeseed for oil who was happy to sell me a couple of big bagfuls. It came as quite large pellets, which wouldn't mix well with the powdered ingredients, so I've been stomping on it in a washing up bowl to smash the pellets up.


They don't break down completely - it'd take ages! - but it's a big improvement. I found using a stick blender worked really well too - until the thing overheated. Now I have to buy a new stick blender... Doh!

I've been making COF in small 7 litre batches using 1 litre as 1 part - partly because I have only ordinary-sized buckets to mix it in, partly because I'm using it bit-by-bit anyway as each bed gets prepared for planting, and partly to reduce any effects of the stuff not mixing together evenly: if I find a pile of seedmeal pellets at the bottom of the bucket it's easy enough to remedy on a small area.

It's dusty stuff, and I've had to be careful to mix it (and spread it) when winds are low to stop all the gypsum and dolomite blowing away!

Solomon recommends digging it into the soil, but it can also just be raked into the surface for no dig plots like (most of) mine.

I've spread it over much of the plot already and I intend to use it everywhere. It's too early to see the results, but you can be sure I'll keep you posted!

1 comment:

Roger Distill said...

Fascinating science! I look forward to seeing the growing results.

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