96 THE LAND AND ITS PROBLEMS 



manure properly, and millions of pounds worth of its 

 fertilizing properties are lost every year. 



Again, our farmers only apply about one-half the 

 amount of farm-yard manure that it is customary to 

 apply per acre on the Continent. One often sees applica- 

 tions of manure (which has lost half its value owing to 

 bad handling) so thinly scattered on the land that the 

 results therefrom are practically negligible ; this is 

 clearly uneconomic. 



ARTIFICIAL MANURES 



About one hundred years ago the use of artificial 

 manures began to be understood, again not including 

 lime which has been used for centuries. The value of 

 animal superphosphates (i.e. from bones) was discovered 

 by Liebeg ; and Lawes and Gilbert of Rohamsted first 

 discovered how to treat and make available as plant 

 food the mineral phosphates, which are found in deposits 

 in different parts of the world. Much more recently 

 basic slag, a by-product of the iron furnace, was found 

 to be a valuable manure giving phosphate and lime. 

 Then a great importation of nitrate of soda from Chili 

 developed. But as the import of this was stopped by the 

 war our farmers had perforce to use sulphate of ammonia 

 (a by-product of the gasworks) as their main nitrogenous 

 manure. 



All these artificials gradually came into use as supple- 

 mentary to farm-yard manure for certain crops — roots 

 and potatoes particularly ; but even to-day the amount 

 of artificials used per acre is far below that used generally 

 on arable land on the Continent. And even more serious, 

 a large proportion of the artificials used by farmers 

 are bought as " ready mixed " manures, whereas the 

 chemicals should be bought separately and mixed at 



