BY E. H. GURNEY. 5 



The above-mentioned soil conditionvS being inter- 

 dependent, the stud}' of soil fertility is a very complex 

 one, and the mistake of placing undue importance upon 

 one particular factor is easily made. 



When Liebig made the discover}" that plants required 

 mineral matter for their growth great impetus was given to 

 the study of the chemical condition of the soil, and for a 

 time, it was thought the fertility or infertility of a soil 

 could be foretold by judgment based only upon the chemical 

 analysis of the soil. But since then the influence of the 

 physical and biological factors has been more fully recognised, 

 and now, in soil investigation work consideration of all 

 these factors is inckided. But as mentioned before these 

 conditions are interdependent, therefore the recognition 

 and correction of deficiency in the chemical condition of 

 the soil is of great importance. 



From the soil, plants require, for successful growth, a 

 certain amount of food material, and the general assumption 

 is that most soils contain sufficient pi ant- food material \vith 

 the p9ssible exception of lime, potash, phosphoric acid, 

 and nitrogen, one or all of which ma}- be in some soils in 

 insufficient amount. Although investigators have at 



various times suggested that a deficiency or an excess of 

 other mineral substances in the soil may have an influence 

 upon the growth of different crops, the chemical investi- 

 gation of the soil has been to a large extent directed to the 

 determination of the above-mentioned substances, and 

 their availability to crops. 



It should be stated here that a large amount of work 

 has been done in connection with the chemistry of the 

 organic matter of the soil. 



In connection with the mineral food material mentioned 

 above, when the analyses of soils from different parts of 

 the world are examined, it is found that each substance 

 exists in very varying amounts in the different soils of the 

 same country. This is shown in the following table, which 

 gives the extreme amounts of the different substances 



