Making COF

The last few years I've had success using a combination of store-bought compost and manure and various mixtures of organic fertilizers. Generally speaking, organic fertilizers are not as potent or as fast acting as synthetic chemical fertilizers, so one must use a greater volume, more often. With twice the garden space as last year (up to almost 3000 sq ft now!), I'll need so much that I decided to mix my own complete organic* fertilizer (COF). The famous Steve Solomon developed a mix tailored to our slightly acid and heavier northwest soils that I used as my guide. I followed the recipe given here, on the third page of an excellent article about homemade fertilizers written by Steve.

I bought ~50 lb bags of each ingredient, all of which I was able to source at local feed stores (I had to go to two to get everything).


The components in the mix can vary, based on what's available locally (and cost!). In my mix I am using (CCW from upper right) 4 parts cottonseed meal , 1 part kelp meal, 1 part rock phosphate, 1/2 part limestone flour (calcium carbonate), and 1/2 part dolomite lime.

The finished product.

Total initial ingredient cost was about $130. The kelp meal is about $75 of this, and I could have used blood or bone meal instead and saved money, but you can read in the article I linked to and see why I chose kelp meal. This made about 25 gallons of fertilizer, enough to cover all my ~3000 sq ft @ 4-6 qts/100 sq ft. I will probably go through half of another bag of seed meal this year to have enough for side dressing the heavier feeding vegetables, but the other ingredients should be enough for the next 2 or 3 years. That boils down to ~$60 a year over the next 3 years for all the fertilizer I need, and my compost is free.

This system (compost, COF, and cover crops) is far better than simply using water soluble synthetic fertilizers; it provides all the major and minor plant nutrients, improves the soil tilth with the addition of decomposed organic matter, feeds soil biota and increases soil biological activity, controls soil erosion and nutrient leaching, and builds a solid foundation of soil health that will help the garden produce for years. $60 a year seems like a pretty good deal to me.

*the cottonseed meal in this batch is not organic and probably GM, but the kelp meal is organic. I have since found that I get organic linseed meal locally, which is what I will use in the future. The mined substances, rock phosphate (OMRI listed) and limes, are minerals so they're pretty much organic...