iiij FERTILITY FACTORS 27 



CHAPTER III 



WHAT IS SOIL FERTILITY AND HOW MAY IT 



BE ATTAINED? 



The relation between the soil and the plant is 

 not entirely simple, and in consequence no rigid 

 definition of soil fertility can be given. Any par- 

 ticular soil would probably prove very fertile for one 

 at least of all the thousands of plants in existence, 

 but if it were useless for ordinary agricultural and 

 horticultural purposes it would generally be called 

 barren. A fertile soil may be described as one in 

 which the conditions are favourable for the growth of 

 plants useful to man. 



Six requirements are necessary for the plant : 

 water, air, temperature, food, root room, and absence 

 of harmful factors. We must now briefly discuss 

 these in their relation to the soil. 



Water supply. The soil receives water fi'om the 

 rain and from the subsoil, but it also loses water 

 by evaporation and drainage. The actual amount 

 present in the soil at any time therefore depends 

 on several factors as it obviously represents the 

 balance of gains over losses. The amount of rain- 

 fall is important, but its distribution is even more 



