INTEODUCTOEY 3 



of colour, texture and other properties, and the differences 

 are generally intensified by cultivation. It is well known 

 that some soils are naturally much more productive than 

 others. They are called rich or poor accordingly. Some 

 of them are better adapted for the growth of certain kinds 

 of crops, and some are more difficult and expensive to work 

 than others. Careful study of the origin and properties of 

 soils is necessary in order to arrive at a clear understanding 

 of the causes which underlie these differences and the kind 

 of treatment which is most appropriate in each case. 



Manure. The expression " manure," as commonly used 

 by farmers, is generally understood to refer to the mixture 

 of animal dejecta and litter removed from the cowhouses, 

 stables and pens in which the animals are confined. From 

 time immemorial it has been customary to carry out this 

 material to the land and bury it, with the double purpose 

 of getting rid of offensive matter and of fertilising the 

 soil. Various theories have been propounded, from time 

 to time, to account for this fertilising effect of manure, 

 but very little definite knowledge was gained until the 

 science of chemistry became sufficiently advanced to in- 

 vestigate the subject. The truth was then established that 

 the manure contains plant foods. In the light of present- 

 day knowledge it is easy to see that vegetable matter, of 

 which the litter is generally composed, and also animal 

 matter derived from it, must of necessity contain sub- 

 stances required for the growth of plants. It was soon 

 recognised that these same plant foods could also be 

 obtained from other sources, and it was thought probable 

 that the substances which contain them could also be used 

 to fertilise the soil. Experience has amply justified 

 this conclusion, and such products are now also called 

 manures, or, more commonly, " artificial manures," to 

 distinguish them from the farmyard refuse to which alone 

 the name had hitherto been applied. 



B 2 



