IV] FERTILITY AND HUSBANDRY 43 



altered somewhat by the breeder, and the soil con- 

 ditions may be changed in some of the ways to be 

 described later on. Nothing but disappointment, 

 however, is likely to follow attempts at growing 

 plants or crops unsuited to the soil conditions. 



CHAPTER IV 



SOIL FERTILITY AND SYSTEMS OF HUSBANDRY 



We have seen that there is a close relationship 

 between the composition of the soil and the vegeta- 

 tion growing on it; an even closer connection can 

 be traced between the fertility and the system of 

 husbandry. 



Virgin land covered with its native vegetation 

 appears to alter very little and very slowly in 

 composition. Plants spring up, assimilate the soil 

 nitrates, phosphates, potassium salts, etc., and make 

 considerable quantities of nitrogenous and other 

 organic compounds : then they die and all this 

 material is added to the soil. Nitrogen-fixing bac- 

 teria also add to the stores of nitrogen compounds. 

 But, on the other hand there are losses: some of 

 the added substances are dissipated as gas by the 

 decomposition-bacteria, others are washed away in 



