How to Make a Complete Organic Fertilizer

Recipe for a complete organic fertilizer

I've been using this recipe, which to the best of my knowledge was created by Steve Solomon (founder of Territorial Seed Company), for six years now with good results. One word of caution: Instead of buying the components in small boxes, buy bulk bags (40-50 lbs.) at a farm supply or feed store. As long as you keep them dry, they will last for many years.

All measurements are in terms of volume, not weight.

4 parts seed meal
1 part dolomite lime
½ part bone meal -or- 1 part soft rock phosphate
½ part kelp meal

Seed meal

This component provides nitrogen, with smaller amounts of phosphorus and potassium. I like to use cottonseed meal, which is cheap (~$13US for a 40 pound bag) and easily available. In some states, though, it is not allowed in a certified organic operation (not something a home grower needs to be concerned about). Other options are alfalfa meal, or rape/canola meal. Cottonseed meal has a NPK value of around 6-2-1.

In spring I like to substitute blood meal in place of some seed meal, since blood meal is somewhat faster acting. Try using three parts seed meal and one part blood meal.

Lime

Seed meals tend to be acidic, so lime is included to balance that out. Dolomite limestone is roughly half Magnesium Carbonate and half Calcium Carbonate. Calcitic limestone is pure Calcium Carbonate. Plants usually need more calcium than magnesium; so, if you want to be really tricky, use 1/3 part dolomite lime and 2/3 part calcitic lime.

If your soil is alkaline, you might experiment with reducing or eliminating the lime in this mix.

Bone Meal and Rock Phosphate

These ingredients make up the bulk of the phosphorus component. Less bone meal (NPK ~ 0-10-0) is required since it releases its phosphorus more readily. The advantage of using rock phosphate (NPK ~ 0-3-0) is that it continues to contribute phosphorus to your soil over many years.

I like to use bone meal. Not only is it easier to find, but also it is already being produced as a byproduct of the beef industry. Rock phosphate is mined. Twenty pounds of bone meal will run about $5US.

Kelp Meal

Kelp meal (NPK ~ 0-0-10) contributes potassium, and also many micronutrients. This tends to be more expensive than the other components: I recently paid $35US for a 50 pound bag.

Another possible potassium source is Jersey Greensand. It has the same advantages and liabilities as rock phosphate (it's very slow release). In addition, it does not supply micronutrients.

How Much Do I Use?

I often get e-mails that say "Great recipe! But how much do I spread in my garden bed?". There is no single answer that fits all situations, because different plants have different nutritional requirements. It also makes more sense in many cases to fertilize plant by plant, instead of broadcasting it into the entire bed. If you want to know how much I use for the various vegetables, check out my FAQ on Maritime Vegetable Culture. This recipe will also work for ornamental plants, and even for lawns; but I haven't developed guidelines for those uses.