The amount of manure produced must be considered in planning a cropping system for a farm. If one wishes to manure one-fifth of the land every year with 10 tons per acre, there would have to be provided two tons per year for each acre of the farm. This would require about one cow or horse, or equivalent, for each six acres of land.
We like to think that the bio-extensive approach to market gardening minimizes the risk of overloading the soil with nutrients because the fallow lands make it possible to grow lots of cover crops to maintain soil structure and organic matter rather than relying on large quantities of manure and compost. However, we are now seeing the consequences of ignoring our own farm philosophy when we resorted to off-farm inputs to correct a phosphate deficiency.
Naturally there is great variation in manure according to the animals it is made by, the feeding and bedding material, and the manner in which it is kept. Different analyses naturally shows different results and the tables here given serve only as a guide or index to the various kinds. The manure heap, by the way, is no place for old tin cans, bottles, glass, and other similar waste material.