Organic Nitrogen In Soil

Any organic material which contains protein can be considered a source of nitrogen for your soil, but whether it will be an economical type of fertilizer is another question.

A friend of mine once wanted to set up a factory to process garbage for use as fertilizer. In a day's time, I located thirty other waste products for him in his city which would give him a higher return for his efforts than garbage.

Many of these products could be had free and all were a more pleasant to handle way of getting more nitrogen in soil.

Organic products which are high enough in nitrogen to be worth commercial development are not too easy to find.

Here is a list of some types of fertilizer which are generally available:

Castor Putnace

This is the refuse left after castor beans are processed for oil. It cannot be used for cattle feed because it is poisonous to animals (but not to plants).

It contains about 5.5 per cent organic nitrogen. Traces of both phosphorus and potash make it a fair fertilizer, particularly on acid-loving plants.

Cottonseed Meal

Also used as a fertilizer for acid-soil plants, it contains about 6 to 7 per cent nitrogen, 2 per cent phosphorus and 2 per cent potash.

Since it can be used for cattle feed, the price is usually too high for general garden fertilizer use.

Dried Blood

Perhaps the most valuable single fertilizer available - organic or inorganic - because it contains in quickly soluble form every element needed by plants for growth.

Only the cheaper grades of dried blood (which contain about 9 per cent nitrogen) are used as fertilizers, however, since the better grades are used for industrial purposes and cattle feed and thus command high prices.

Fresh blood, sometimes available from local slaughterhouses or from poultry processing plants, can be adsorbed on peat moss, vermiculite or similar materials and used in that state.

Nothing gives foliage plants as fine a dark green color as does dried blood.

Fish Emulsions

These fertilizers are produced by soaking trash fish, offal and scraps in water to extract all the solubles. This extract is then condensed until it contains less than 50 per cent water.

Surprisingly, the condensed product does not have an offensively fishy odor. The method of extracting insures that all elements are present in soluble form and are readily available to plants.

Like dried blood, fish emulsions (they contain considerable blood) provide every element needed for growth. In my experience they are ideal for shade-loving plants like tuberous begonias, gloxinias, African violets, and so on.

Fish emulsions have a nitrogen content of about 5 per cent, but they should not be judged solely on nitrogen.

Sewerage Sludge

Perhaps this is the most widely used of all organic fertilizers for lawns. Activated sludge is a black, flocculated organic material produced by treating solids in sewerage and allowing them to settle out in special beds.

If the nitrogen content is more than 5 per cent and the analysis shows any amount of potash, the chances are that the sludge has been doctored with additional chemical nitrogen and potash.

Activated sludge is a good conditioner for other fertilizers that tend to cake in the bag, hence it is used to a far greater extent than most gardeners realize.


This is made up of packing house wastes steamed to extract the animal fats. The remaining tankage contains between 6 and 10 per cent nitrogen.

Learn More About Soil Fertilizers & Additives:

Chemical Nitrogen In Soil - understanding nitrogen in soil, and how it is used to make fertilizer products.
Fertilizer Formula - feeding rates of various fertilizer formula.
Phosphorus And Soil - phosphorus is vital to your soil of course. But bone meal is so overrated.
Fertilizer Costs - calculating the REAL cost of fertilizer.
Potassium And Soil (Potash Fertilizer) - potash is the common term for the fertilizer forms of potassium.
Mixed Fertilizers - the gardeners preference, so what do NPK values refer to?
Fertilizer Burn - how to avoid burning your plants/lawn with fertilizer.