56 THE POPULAR SCIENCE MONTHLY 



soil of all important elements of fertility, and on normal soils always 

 results ultimately in land ruin, unless some system of restoration is 

 practised. Clover takes large amounts of calcium and phosphorus from 

 the soil, and does not increase the nitrogen content if only the roots and 

 stubble are left, because they contain no more nitrogen than the clover 

 itself will take from soils of normal productive power. 



To increase or maintain the nitrogen and organic matter of the soil 

 is the greatest practical problem in American agriculture. In an hour's 

 time one can spread enough limestone or phosphate on an acre of land 

 to provide for large crops of wheat, corn, oats and clover, for ten or 

 twenty years, while to supply the nitrogen for the same length of time 

 would require from 20 to 40 tons of clover, or from 80 to 160 tons of 

 farm manure., to be added to the same acre of land, even though one of 

 the four crops harvested secured its nitrogen from the air. 



Certainly we are making no such additions to the soil in average 

 corn-belt agriculture, and one may well ask, How then is it possible to 

 grow the crops now produced in this country? In the simplest lan- 

 guage the answer to this question is : By " skinning " the soil — by work- 

 ing the land for all that's in it — by following the example of our an- 

 cestors, who brought agricultural ruin to millions of acres of once fertile 

 farm land in the original thirteen states. 



To provide nitrogen in the Illinois system of permanent agriculture 

 requires the use of common sense and positive knowledge, the same as 

 in providing limestone and phosphorus. 



For the live-stock farmer I would suggest a five-field system — a four- 

 year rotation of- corn, corn, oats and clover, grown upon four fields for 

 five years, while the fifth field is kept in alfalfa. At the end of the fifth 

 year the alfalfa field is brought into the rotation and one of the four 

 fields seeded to alfalfa for another five-year period, and so on. 



If the crop yields are 50 bushels each of corn and oats, 2 tons of 

 clover and 3 tons of alfalfa; if the straw and half the corn stalks are 

 used for bedding and all other produce for feed, and if 60 per cent, of 

 the nitrogen in the manure is used for the production of crops, then a 

 system is provided which will permanently maintain the supply of 

 nitrogen. 



For the farmer who sells grain, a 25-bushel wheat crop may well be 

 substituted for the first corn crop, clover being seeded on the wheat for 

 plowing under next year before planting com. If the fall and spring 

 growths of this clover aggregate 1^ tons, and if only the grain and 

 clover seed and the alfalfa hay are sold, all clover, stalks and straw being 

 turned to the land, this also provides a system for the permanent main- 

 tenance of nitrogen. 



If the crop yields are all increased by 50 per cent., or even by 100 per 

 cent., these systems still provide for the nitrogen supply, unless with 

 the larger yields on richer land a somewhat greater amount is likely to 



