HO THE ESSENTIALS OF AGRICULTURE 



poor soils a liberal application (from 300 to 400 pounds per 

 acre of a high-grade complete fertilizer) is best. The same is 

 true of cotton. Potatoes and tobacco require a fertilizer high in 

 potassium. Oats and rye are similar to wheat in their fertilizer 

 requirements (Fig. 45), but the economic returns are less. 



137. Lime. Lime is not regarded as a fertilizer in the true 

 sense of the word, as it is not added for the purpose of sup- 

 plying plant food. Calcium, the important constituent of lime, 



FIG. 46. Growing corn by use of fertilizers 

 This corn, grown on the farm of Georgia State College, produced 100 bushels per acre 



is an element of plant food, but almost all soils contain 

 enough of this element in proper form for plant use. If applied 

 in large quantities, lime improves the mechanical condition of 

 soils by making stiff, heavy soils lighter and more mellow, and by 

 making sandy soils more compact. Lime also promotes favor- 

 able chemical changes by favoring the development of beneficial 

 bacteria, by preventing phosphorus from uniting with iron and 

 aluminium (in which combination it would be securely locked 

 from crops for a long time), and by helping to make the potash 

 in the soil available. It is also necessary in the changing of the 

 nitrogen of ammonia to nitrates. Lime is the most effective 

 agent with which to improve sour, or acid, soils. 



