22 PROFITABLE STOCK RAISING 



tions they occur. It also became possible to an- 

 alyze the different plants and grains and to deter- 

 mine just what elements they contain and in just 

 what proportions. It was then reasoned and widely 

 announced that by analyzing any given soil, and 

 comparing its contents with the amounts of these 

 same elements removed by each crop, it could be 

 determined exactly how many crops could be grown 

 upon any piece of land without the addition of any 

 kind of fertilizer. This theory was correct in part, 

 for it can be accurately determined exactly how 

 much nitrogen, phosphoric acid, potash and other 

 constituents of plants are contained in any class of 

 soil. The percentage of this plant food which is 

 actually available for the use of plants and is in 

 such mechanical and chemical condition as to be 

 used by them, however, cannot be determined by 

 the wisest chemist. The influence of various soil 

 bacteria, some harmful and others beneficial, is 

 knowledge which has been gained during the past 

 decade, and it is probable that our knowledge of 

 these factors is only rudimentary. 



The rotation of crops has been widely taught as 

 offering the solution of the problem of soil fertility. 

 Intelligent crop rotations are the rule in the most 

 progressive farming districts of the United States 

 today, and much larger yields are always obtained 

 than where a one-crop system is followed. Where 

 a one-crop system is necessary, as has been the 

 case in some exclusive grain-growing districts, the 

 fallowing of the land every three or four years has 

 been thought by many to be a means of restoring 

 lost fertility, because the crops secured from these 

 fallowed fields are always greater than those planted 

 preceding fallowing. Under these conditions, fal- 

 lowing is a good practice, and the rotation of crops 



