Ureaform: This is a most unusual fertilizer material-it is best described as a nitrogen-bearing soft plastic material which breaks down slowly but uniformly when in contact with soil organisms and moisture. It is made by reacting urea and formaldehyde. It contains 38 per cent nitrogen, yet can be applied to grass without fear of
burning. This is because ureaform gives off nitrogen so slowly that grass can absorb it about as fast as it is released. Enormous quantities have to be applied before a burn can be produced. Ureaforms combine the best features of chemical and organic plant foods. Their one drawback is the slowness with which they begin to feed. (See recommendations under mixed fertilizers for overcoming this weakness.)
ORGANIC SOURCES OF NITROGEN
Any organic material which contains protein can be considered a source of nitrogen, but whether it will be economical to use 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 more pleasant to handle.
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 which are generally available:
Castor Pumace: 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.S 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.