Fertilizers for Cereals and Grasses 229 



The necessity of adding more plant-food than is required 

 by a definite increase in crop. 



It may be asked, why add more of the constituents 

 than is necessary to provide for a definite increase in 

 crop? Assuming that the average yield of the land is 

 twenty bushels of wheat to the acre, and the aim is to 

 secure thirty bushels, why not add the constituents in 

 the amounts and proportions necessary to provide for 

 this extra increased yield, rather than any excess of these 

 amounts? The answer is, that in order that such a 

 result may be accomplished, the conditions would need 

 to be absolutely perfect, so that the plant would have at 

 its command the amount of food needed each day. If a 

 period in the growth of the plant should be so wet or so 

 dry as to prevent the plants from acquiring the food 

 necessary for their continuous growth, there would be no 

 opportunity for them to gather food faster, when the 

 better conditions followed the unfavorable conditions, and 

 thus to overcome the ill effects of the period of partial 

 starvation. In other words, if there were only sufficient 

 food to supply the plant under normal conditions of sea- 

 son, the plant, after a period of time during which there 

 was no growth, could not grow faster than it did before, 

 hence it could not catch up in its growth and make a 

 full crop. Furthermore, the plan of applying only that 

 needed for the increase must necessarily assume that the 

 plant-food is in the best forms, and that the physical con- 

 ditions of soil are so perfect as to cause it to absorb and 

 retain all the food applied, and in such a manner as to 

 permit it to be readily obtained by the plant. A further 

 advantage is to enable the clover plant in the rotation 

 to fully exercise its power of acquiring nitrogen from the 



