Scientists analyzing the connections between soil fertility and the
nutritional value of crops have repeatedly remarked that the best
crops are grown with compost and fertilizer. Not fertilizer alone
and not compost alone. The best place for gardeners to see these
data is Werner Schupan's book (listed in the bibliography).
But say the word "fertilizer" to an organic gardener and you'll
usually raise their hackles. Actually there is no direct linkage of
the words "fertilizer" and "chemical." A fertilizer is any
concentrated plant nutrient source that rapidly becomes available in
the soil. In my opinion, chemicals are the poorest fertilizers;
organic fertilizers are far superior.
The very first fertilizer sold widely in the industrial world was
guano. It is the naturally sun-dried droppings of nesting sea birds
that accumulates in thick layers on rocky islands off the coast of
South America. Guano is a potent nutrient source similar to dried
chicken manure, containing large quantities of nitrogen, fair
amounts of phosphorus, and smaller quantities of potassium. Guano is
more potent than any other manure because sea birds eat ocean fish,
a very high protein and highly mineralized food. Other potent
organic fertilizers include seed meals; pure, dried chicken manure;
slaughterhouse wastes; dried kelp and other seaweeds; and fish meal.