Manures and Commercial Fertilizers 115 



By studying the results on these plots for several years 

 with the same treatment annually, the farmer can come 

 very close to ascertaining the actual needs of his soil, and 

 can determine what he needs especially to buy and what 

 he need not buy. If every farmer studied his soil in this 

 way there would be an enormous saving in the purchase 

 of fertilizers, and he could buy the materials containing 

 what he needs and mix them in the proper proportions 

 better than any manufacturer can do it for him. It will 

 generally be found that phosphoric acid alone, though 

 the soil may need it, will not have its due effect unless 

 there is present naturally in the soil or is added to the 

 fertihzer a due percentage of potash, and it will also be 

 found that on a soil that is deficient in potash the potash 

 applied will not have its due effect unless a due percentage 

 of phosphoric acid is present or is added. These two 

 forms of plant food are so intimately associated in their 

 work that both must be present for the best results. It is 

 found in many soils that potash is present in sufl&cient 

 amounts, while phosphoric acid is always deficient. 



Hence, on such soils it would be purely a waste to apply 

 potash. But on many other soils, especially those of a 

 sandy nature or the black and peaty soils of reclaimed 

 swamps, it is found that both of these materials are 

 deficient and must be suppHed. 



It has been long noticed by all cultivators 

 N^e^ded Nitro- of the soil that certain kinds of plants, such 

 gen May Be as clover, COW peas, and other members of 

 Had Free of ^^iQ botanical family called leguminosae, or 

 ^""^^ pod bearers, so called because they form 



their seeds in pods of various sizes from the minute 



