158 AGRICULTURAL ECONOMICS 



dasheens grown in Florida, and that the growers were confident of 

 making a commercial success of the venture. 



The cranberry has long been used as a reclaimer of bog lands, 

 nearly or quite useless for other crops 18,000 acres in Massachusetts, 

 New Jersey, and Wisconsin. Rice is doubtless the largest user of wet 

 lands in the United States. In Arkansas alone it has aided in bringing 

 100,000 acres of river-bottom lands into profitable use within the last 

 few years. EDITOR. 



C. Fertility as a Limiting Factor in Agricultural Production 



44. CHEMICAL CONTENT AS A MEASURE OF PRODUCTIVE 



POWER 1 



BY CYRIL G. HOPKINS 



In brief, there are ten elementary substances that bear the same 

 relation to the making of crops as brick and mortar bear to a wall 

 of masonry. If any one of these ten elements is entirely lacking, it 

 is impossible to produce a grain of corn or wheat, a spear of grass, or 

 a leaf of clover. 



Two elements, carbon and oxygen, are taken into the plant from 

 the air through the leaves; hydrogen is secured from water absorbed 

 by the roots; and iron and sulphur are also supplied by nature in 

 abundance. But the other five elements require careful considera- 

 tion if lands are to be kept fertile. These are potassium, magnesium, 

 calcium, phosphorus, and nitrogen; and every landowner ought to 

 be as well acquainted with these five elements as he is with his five 

 nearest neighbors. 



Instead of making this acquaintance and gaining a knowledge of 

 important facts and principles, the average farmer in the older states, 

 with failing fertility, has made the acquaintance of the fertilizer agent ; 

 and instead of purchasing what he needs for the permanent improve- 

 ment of his soil, he buys what the agent wants to sell, with the common 

 result that the seller is enriched while the soil is merely stimulated to 

 greater poverty. 



Potassium. A careful study of the facts shows that potassium is 

 one of the abundant elements in nature; that the average crust of the 

 earth contains i\ per cent of this dement; and that normal soils bear 

 some relation in composition to the average of the earth's crust. If 

 normal soil );ad the same percentage, then the plowed soil of an acre 



From Circular No. 167, Agricultural Experiment Station, University of 

 Illinois, pp. 3-9. 



