

CHAPTER XX 

 MIXTURES FOR CROPS 



Composition of Plant not a Guide. It has 

 been pointed out that a chemical analysis of a 

 soil is not a dependable guide in the selection of a 

 fertilizer. Years ago the theory was advanced 

 that the analysis of the crops desired should be a 

 guide, but it has proved nearly worthless. This 

 theory does not take into account the soil's supply 

 of plant-food. Moreover, a certain crop may de- 

 mand a large supply of an element at a time of 

 the year when the soil's supply is inactive. The 

 need of nitrogen for grass in the early spring, 

 before nitrification in the soil is active, is an illus- 

 tration. Let the causes be what they may, the fer- 

 tilizer formulas that call for plant-food in a ferti- 

 lizer in the same proportions that it is found in 

 plants are disappointing in their results. The 

 analysis of the plant is not a dependable index. 



The Multiplication of Formulas. Fertilizer 

 manufacturers have made all possible combina- 

 P [209] 



