SOILS 117 



cost for the purchase, delivery, and application of the lime- 

 stone and phosphate was $1.75 per acre. In the ten years, 

 then, the total cost was $17.50 per acre. Add to this the 

 original cost, $15 per acre, making $32.50, and still you have 

 pretty cheap land to produce double the average of the 

 state. Doctor Hopkins puts it -this way: "The average 

 annual investment of $1.75 resulted in an increase of 24 

 bushels of wheat (351/2 11%) per acre. Thus we may say 

 that the application of these two natural rocks, or stones, 

 brought about the production in 1913 of 864 bushels of wheat, 

 an amount sufficient to furnish a year's supply of bread for 

 more than a hundred people." 



This story of the Poorland Farm is a remarkable instance 

 of the conservation of one of our greatest resources, the soil. 

 Conservation means a saving of the resource by a wise use 

 of it. At the end of ten years of use the soil on the "Poor- 

 land Farm" is producing more wheat than the average pro- 

 duction of the state, and at the same time its fertility is 

 increasing year by year. 



Summary of facts on soil fertility. In the following para- 

 graphs the basic facts of the Illinois system of permanent 

 fertility are summarized. These should be thoroughly un- 

 derstood and become the ready knowledge of every student 

 of agriculture. 



All agricultural plants are made of ten elements, five of 

 which are always provided by nature in abundance, carbon 

 .and oxygen taken from the air, hydrogen from water, and 

 iron and sulphur from the soil. Man need not concern him- 

 self about these five elements. His fertility problem is thus 



