I III. CHEMISTRY OP THE BOIL. 6 I 



section u. 



The Chemistry of the Soil/ 



Introductory. 



The essential difference between the new methods of farming and the old is 

 that the old rule-of-thumb methods are being superseded by those which are 

 based on a study of the conditions under which crops grow, and of the 

 relationship of the growing plant to soil and air and water. These new 

 methods have become necessary because of the changed conditions under 

 which farming is carried on. The number of people who have to be supplied 

 with food is continually and rapidly increasing, competition is getting 

 keener, the available land of good quality is diminishing, and poorer land or 

 land in a less favourable climate has to be opened up, and the need has arisen 

 of utilising to the utmost the resources of the soil. This is only possible by 

 the application of principles which science has discovered. This does not 

 mean that the farmer must necessarily be a scientific man, but it is becom- 

 ing every day more and more necessary that he should understand something 

 of the principles on which farming depends. 



Agriculture is an art, and it is an art that was practised centuries before 

 the sciences were born with which it has become associated in modern times. 



Man raised corn and made bread and wine thousands of years before he 

 knew anything of the constituents of grain and grape, or the nature of fer- 

 mentation, and a man can to-day be a thoroughly successful farmer without 

 knowing anything about botany or pathology, or entomology or chemistry. 



Nevertheless, the farmer of to-day, working under modern conditions, 

 cannot afford to neglect the teachings of science as far as they affect his own 

 art, and that farmer will be the successful one who is able to understand 

 what science has to tell him, and to utilise the weapons which she puts into 

 his hands. And agriculture is indebted to science not only for the knowledge 

 of useful facts and principles, but in a still higher degree for the scientific 

 method of work, the spirit of inquiry, the patient, accurate, and systematic 

 attention to the minutest details. Without this, the farmer becomes a mere 

 sowing and reaping machine, incapable of progress, and at the mercy of 

 adverse seasons and crop diseases. 



The following notes are written with the object of affording some infor- 

 mation (avoiding technicalities as far as possible) of the nature and func- 

 tions of this all-important material — the soil — which, though it is no more 

 than a fine dust-film on the surface of the globe, and is infinitely small com- 

 pared with the mass of the earth, is nevertheless the substance on whose 

 support all the teeming life of the earth depends. 



The point of view from which our study of the soil will proceed will be 

 that of the conditions which make for soil fertility. By a fertile soil is 

 meant one that is most favourable for producing crops, and if we know the 

 factors on which this depends we shall bo aide to maintain the fertility of a 

 good soil, to restore it to impoverished soils, and to increase it in barren ones. 



* F. B. Guthrie. 



