Increasing Fertility 



ELEMENTS OF SOIL AND THEIR VALUE TO 

 FERTILIZERS AND SOIL BUILDING 



CROPS- 



By Cyril G. Hopkins 



Professor of Agronomy, College of Agriculture, University of Illinois 



IF he who made two bales of grass 

 grow where only one grew before is a 

 public benefactor, then he who reduces 

 the fertility of the soil so that only one 

 ear of corn grows where two have been 

 grown before is a public curse. 



Agriculture is the fundamental sup- 

 port of the American nation, and soil 

 fertility is the absolute support of agri- 

 culture. 



Without agriculture, America is 

 nothing. The forest and the earth 

 supply the timber, the stone, and the metal to build and 

 equip railroad and factory, and the fuel to operate mill and 

 locomotive, but directly or indirectly these great industries 

 are absolutely dependent on agriculture for their continued 

 existence. 



The Two Functions of the Soil— The soil has two distinct 

 functions to perform in crop production : First, the soil must 

 furnish a home for the plant, where the roots can penetrate the 

 earth upon which the plant must stand; second, the soil must 

 furnish plant food, or nourishment, for the growth, develop- 

 ment, and maturing of the plant. 



To improve the physical condition of the soil is to improve 

 the home of the plant; while to add to the soil, or to liberate 

 from the soil fertilizing materials, is to increase the available 

 supply of plant food. 



One soil may furnish an excellent home for the plant, but a 

 very insufficient supply of plant food; while another soil may 

 contain abundance of plant food, but the physical conditions 

 (such as imperfect drainage, or inadequate aeration) may be 

 such as to make an unfit lodging place for the plant. 



The Six Essential Factors in Crop Production— There are 



six essential and positive factors in crop production: (1) the seed, 

 (2) the home or lodging place, (3) moisture, (4) heat, (5) light, and 



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