An extract from my bible;
Poultry Droppings.
Droppings of all types of poultry may be used as manure.
They contain a higher percentage of nitrogen and phosphates than stable and farmyard manure, but less potash, and must be balanced by appropriate chemicals.
Weight for weight they are about four times as rich as animal manure.
One cwt. of moist droppings will dress from 24 to 40 square yards.
If dried and powdered, the quantity would have to be even more reduced, and such manure is best employed like a chemical fertilizer at 8-12 oz. per square yard.
Poultry manure should be stored under cover.
An average analysis of a moist sample is nitrogen l½%, phosphoric acid l½%. potash ½-¾%.
If thoroughly dried, this would rise to nitrogen 4%, phosphoric acid 3%, potash 1½%.
Can also be used to make liquid manure in the same way as other animal manures but should be well diluted