CHAPTER VIII 

 GETTING ACQUAINTED WITH PLANT FOOD 



The elements usually deficient in the soil are nitrogen, 

 phosphorus and potassium. All others are found in quan- 

 tities sufficient for the needs of the plant. In some soils 

 lime has proved of value when added, largely because of 

 its influence in sweetening the soil, and sometimes be- 

 cause it may be needed as food substance. 



Our early faith in chemical analysis. When chem- 

 istry was directed toward agriculture some sixty years 

 ago, and when a great deal of attention was devoted to 

 analyses of soils and plants, it was believed that much 

 light was thrown on the many problems concerned with 

 soil fertility. And such was the case. The soil and plant 

 analyst gave the world much information that served both 

 as a guide and as a help in solving some of the mysteries 

 of soils and plants. 



We had a great deal of faith in the analyses of those 

 early days. For was it not reasonable to suppose that 

 when you analyzed the plant, ascertaining its many con- 

 stituents and substances, and then when you analyzed 

 the soil, you should be able to judge, and to know within 

 reason, just what element was required for any soil for the 

 maximum yield of the crop? 



The plant, therefore, was analyzed, a careful study 

 of the elements composing it was given, a comparison of 

 these chemical studies with plants of the samo kind, 

 though grown in other soils, was made ; in short, it was 

 carefully determined just how much of each and of every 

 kind of elements essential to plants was withdrawn from 



