NEED OF COMMERCIAL FERTILIZERS 



of soil in every field." This is true in a way, it 

 may be, but if all the field has had the same treat- 

 ment in the past, the probability is that the fer- 

 tilizer which is best for one part of the field will 

 be quite good for the other parts. The likeness in 

 characteristics that permits the land to be cropped 

 as one field gives some assurance of likeness hi 

 plant-food needs, even where the proportion of 

 clay and sand varies and the color is not the same. 

 There may be wide variation in the productive 

 power of the fields of a farm, due to the treat- 

 ments they have received. The land that grows 

 heavy clover in a close rotation, or receives all 

 the stable manure, may need neither nitrogen nor 

 potash, while another field, hard-run by timothy 

 and corn, may need a complete fertilizer. When 

 a careful fertilizer test on land of only average 

 productive power has been made, the owner has 

 some definite knowledge of his soil that enables 

 him to give more intelligent treatment to all his 

 fields than was possible before the test had been 

 made. He observes the appearance and yield 

 of plants where the plant-food requirement was 

 fully met, and makes allowance in other fields for 

 gains or losses in the soil due to different treat- 

 ment. It is out of the question to become dis- 



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