THEORIES CONCERNING SOIL FERTILITY 323 



"Lastly, it has been shown from the statistics of European countries that the 

 soils of the world are not wearing out, but that, on the contrary, after a thousand 

 years of cultivation, With the introduction of better methods, with the necessity 

 of raising larger crops, these soils are responding with an increased yield even 

 over what they produced at the beginning of the last century. 



"As a national asset the soil is safe as a means of feeding mankind for untold 

 ages to come. So far as our investigations show, the soil will not be exhausted 

 of any one or all of its mineral plant-food constituents. If the coal and iron 

 give out, as it is predicted that they will before long, the soil can be depended on 

 to furnish food, light, heat, and habitation not only for the present population, 

 but for an enormously larger population than the world has at present." 



This general outline of soil-fertility theories has been introduced 

 at this point in order that the reader may note their application 

 in the following pages; and it is hoped that the preceding and suc- 

 ceeding data are sufficient to enable him to form his own opinion. 



It is well to keep in mind a few general facts: e.g., that the total 

 corn acreage of Rhode Island and Connecticut combined averages 

 less than three townships (about one sixth of one average Illinois 

 county, of which there are 102); that the total corn acreage of 

 Maine, New Hampshire, Vermont, Massachusetts, Connecticut, 

 Rhode Island, New York, New Jersey, Pennsylvania, Delaware, 

 and Maryland, all combined, is less than the average corn acreage 

 of Georgia, whose ten-year average yield is u bushels per acre, 

 and less than one half the corn acreage of Illinois; that Illinois 

 produces the same amount of corn per annum as the aggregate 

 production of the six New England states, the six Middle 

 Atlantic states, and the six South Atlantic and Gulf states 

 eighteen in all extending from Maine to the mouth of the 

 Mississippi, although Georgia, one of these states, is larger than 

 Illinois ; that during the last ten years the average corn acreage 

 of Illinois has been increased from 7 million to 10 million acres 

 by putting under cultivation old blue-grass pastures and drained 

 swamp areas representing the richest soil of the state; that in the 

 Eastern states manure, made in part from food stuffs shipped 

 from the newer states, is worth about $2 a ton; that level 

 or gently undulating farm lands in Maryland and Virginia sell 

 for less than $5 an acre, while those of Illinois and Iowa are 

 worth $100 or $200; that, while England produces 32 bushels of 

 wheat per acre with a total production of 50 million bushels, 



