24 



In all these ashes the phosphoric acid is combined mainly 

 with potash. 



It has also been computed that an average crop of — 

 Wheat takes off about 201bs. of phosphoric acid per acre. 

 Barley „ 221bs. „ 



Oats „ 221bs. „ 



Beans ,, 36]bs. „ 



Turnips ,, 501bs. „ 



Hop flowers ,, 301bs. ,, 



These figures show how very important phosphoric acid is 

 to both plants and animals, and in the natural order of things 

 the animals get their phosphates from plants : some is soon 

 returned to the soil, and some is stored up in the animal bodies 

 to be again used up by plants when the animals die and decay. 

 It will be noticed how by our system of agriculture, which is an 

 artificial system, a large quantity of phosphoric acid, as well as 

 other essential plant constituents, are annually taken off our 

 fields never to go back, and the quantity of valuable plant food, 

 which annually goes down our drains and out to sea, is simply 

 appalling, viewed in a pecuniary sense. A portion of the 

 phosphoric acid goes back to our land in the shape of farm yard 

 manure, but if the fertility of our fields is to be kept up we 

 must also get a supply from other sources, the principle of 

 which are bones, bone ash, coprolites, apatite and guano. 



Fresh Bones, as I mentioned before, contain more 

 than 50 per cent, of phosphate of lime. They are seldom used 

 fresh, but have generally been boiled to extract the fat and the 

 gelatine. The phosphate of lime in bones, even if they are 

 used without any Chemical treatment, is valuable, as it very 

 slowly becomes soluble and in a state fit for plant food, and the 

 organic matter by decaying gives off ammonia, which also is of 

 great use to plants. Bones do good in most soils for a number 

 of years after they have been applied. 



Bone Ash is imported in large quantities from South 

 America. It contains from 60 to 70 per cent, of phosphate of 

 lime. 



Coprolites are found in many geological strata ; the best 

 come from the Greensand or Cambridgeshire, and they are also 

 found in Suffolk, Bedfordshire, Buckinghamshire, Kent, and in 

 France. Cambridgeshire coprolites contain from 50 to 60 per 

 cent, of phosphate of lime. Suffolk and French 45 to 55 per cent. 



Apaiite\;\\\\ its varieties, phosphorite, osteolite, etc., is found 

 in Spain, Norway, and in America, some of the best apatite from 

 Spain contains over 90 per cent, of phosphate of lime. 



Guanos are also a source of phosphate of lime. They may 

 be divided into two classes — Ammoniacal and phosphatic. 

 Peruvian guano belongs to the former class and should yield 

 about 12 per cent, of ammonia, as well as about 20 per cent, of 

 phosphate of lime. Good Peruvian guano is a very valuable 

 manure applied in its natural state. 



