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might be termed fundamental differences existing between fertile, vir- 

 gin soils and unproductive, worn soils, respecting the factors that go 

 to make up what might be termed fertility, and their relative impor- 

 tance. With regard to these factors, it has been shown that, apart 

 from climatic conditions (temperatures, rainfall, sunshine, etc.), soil- 

 productiveness results from a happy assembling of the chemical 

 constituents of plant food in more or less assimilable forms, of 

 physical properties allowing soil aeration, the retention of moisture, 

 and the providing of freedom for root extension, and, lastly, the 

 presence of an abundance of these microorganisms which, living on the 

 organic matter of the soil, prepare the nourishment of farm crops. 



The work in this matter has been particularly in tracing the 

 relation of organic matter and its concomitant nitrogen, to crop- 

 producing power. Very early it was observed that virgin soils of 

 great productiveness were invariably characterized by large per- 

 centages of organic matter and nitrogen, and that, on the other hand 

 worn soils resulting from continuous grain growing or other irrational 

 systems of farming, and soils from naturally poor areas, showed 

 meagre amounts of these constituents. 



It was found, further, that in soils from humid districts, there 

 was a relationship between the organic matter and the nitrogen 

 that what affected or destroyed the former dissipated the latter; 

 while on the other hand, the methods that led to the increase of the 

 organic matter also raised the nitrogen content. Undoubtedly these 

 two constituents stand and fall together. 



Another feature of importance was that accompanying a fair 

 organic content there was usually a goodly proportion of available 

 phosphoric acid, potash and lime. 



Then again it was evident that the proportion of organic matter 

 present influenced in a marked degree the capacity of the soil for 

 holding moisture and in several other important particulars affected 

 the mechanical condition. 



It is more than probable that fertility is largely dependent 

 upon the rate of nitrification during the growing season, which, 

 though largely regulated by temperature and moisture, must be 

 materially affected by the amount of the food supply that the micro- 

 organisms find in the form of partially decomposed nitrogenous 

 organic matter. 



From all this work with soils, the Chemist concludes that the 

 percentage of organic constituents humus is directly and indi- 

 rectly a measure of the soil's fertility, and that this percentage is 

 largely influenced by the treatment the soil received. 



