THE SOIL 11 



dilute solutions by the absorptive surfaces of the root 

 hairs found so abundantly near the ends of the young 

 growing rootlets. Owing also to their extreme 

 solubility, they are readily leached out of the soil 

 and lost, and they are also liable to the attack of still 

 other bacteria known as denitrifying organisms which 

 set free the precious nitrogen and allow it to escape 

 back to the great storehouse of the atmosphere. 

 Losses from these two sources are often very heavy, 

 and they are continually occurring in all cultivated 

 soils that are not fully occupied by some actively 

 growing crop, excepting of course when they are 

 securely locked by the frosts of winter. The absence 

 of frost and the fact that in consequence these mani- 

 fold soil activities are progressing continuously 

 throughout the year constitutes the chief real basic 

 difference between southern and northern agricul- 

 ture. This fundamental difference must always be 

 kept clearly in mind when attempting to formulate 

 rational agricultural practices for either region, or 

 when attempting to adapt northern methods to 

 southern conditions. 



Besides this great series of organisms that we have 

 seen to be concerned in the breaking down and 

 putrefaction of organic matter and the subsequent 

 conversion of the nitrosfen it contains into the 

 available nitrates, there is another series of bacteria 

 known as nitrogen-hxing organisms Avhich have the 

 power which none of the higher plants possess of 

 seizing the free nitrogen of the air and so combining it 

 with other elements as to utilize it as food. It thus 

 becomes organic nitrogen, and when excreted by these 



