This section is from the book "Commercial Gardening Vol1", by John Weathers (the Editor). Also available from Amazon: Commercial Gardening, A Practical & Scientific Treatise For Market Gardeners.
Human excreta are rich in fertilizing substances, and their value as manures was more highly appreciated before the general adoption of the water closet and sewage systems. Even to-day the Chinese and Japanese gardeners, who achieve such marvellous results, have the highest respect for night soil as a fertilizer. On the Continent also it is valued as a manure; and under the pretty name of "poudrette" it is found mixed with gypsum, ashes, earth, peat, sawdust, etc., to mask the smell. Some market growers of flowers now use night soil for purposes of liquid manure.
Closely associated with night soil is the "native guano" obtained from the precipitated solids in sewage beds. It is mixed with various things, such as alum, charcoal, etc, and is sold in a dried state. A ton of it contains from 20 to 40 lb. of nitrogen, 60 to 120 lb. phosphate of lime, and about 50 to 100 lb. of alkalis of potash, soda, and magnesia. If too many poisonous chemicals have not been used at the sewage works, native guano is worth using as a topdressing at the rate of 1/2 ton to the acre.