110 NATURAL MANURES. VI. 



have not sufficiently commended themselves to the practical 

 farmer to be adopted to any extent on the large scale. 



It is with the improvements in the chemical state of the soil 

 that this chapter has mainly to deal. 



These are effected by the application of Manures. The 

 word manure has apparently a connection with the Latin 

 manus a hand and was probably used because of an old 

 belief that the main function of a manure was, by its fermen- 

 tation in the soil, to aid in the work of pulverisation usually 

 brought about by hand labour, i.e., tillage. 



It is no longer used in this sense, but is now the name given 

 to any material which is intended, by its application to the 

 soil, to restore those constituents which have been removed by 

 cropping and thus to render it possible for the soil to supply 

 another crop with a sufficiency of plant food. 



The constituents of a soil which are most liable to be 

 deficient in amount, and which it is therefore advisable to 

 replenish by manuring, are combined nitrogen, phosphates, 

 and potash compounds. 



Manures, therefore, are usually valued according to their 

 richness in these three constituents, though in the case of 

 many so-called natural manures, e.g., farm-yard manure, 

 many other constituents which may serve as useful items of 

 plant food are also present. 



These natural manures, from a chemical standpoint, are 

 exceedingly complex, and might, perhaps, with propriety have 

 been left until the simpler chemical manures had been 

 discussed; but, on account of their extensive use and their 

 great importance in farming practice, they will be described 

 first. 



Farm-yard Manure. This has long been the most popular 

 manure used on the farm. It would seem that, inasmuch as 

 it contains the remains of the vegetable substances used as 

 food and litter on the farm, it should be a most suitable means 

 of restoring to the land the ingredients removed from it in the 

 crops. A little thought, however, will show that it cannot 

 restore completely such losses. Some of the crops are sold; 



