LAND AND OTHER AGENTS OF PRODUCTION 161 



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

 Illinois agriculture, and one may well ask, How then is it possible to 

 grow the crops now produced in this state ? In the simplest language 

 the answer to this question is: By "skimming" the soil, by working 

 the land for all that's in it, by following the example of our ancestors, 

 who brought agricultural ruin to millions of acres of once fertile farm 

 land in the original thirteen states. 



To provide nitrogen, 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 other four fields seeded to alfalfa for another five-year period, 

 and so on. If the yields are 50 bushels each of corn and oats, 2 tons 

 of clover, and 3 tons of alfalfa; if the straw and half the cornstalks are 

 used for bedding and all the 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. This is for the live-stock farmer. 



For the farmer who sells gram and hay, a 25-bushel wheat crop 

 may well be substituted for the first corn crop, clover being seeded 

 on the wheat for plowing under the next year before planting corn. 

 If the fall and spring growths of this clover aggregate i| tons, and if 

 only the grain and clover seed and the alfalfa hay are sold, all clover, 

 stalks, and straw being returned to the land, this also provides a system 

 for the permanent maintenance of nitrogen. 



These systems should be considered as only suggesting the basis 

 for solving the nitrogen problem. The important point is that the 

 landowner should know the essential facts and base his practice upon 

 them in order to provide for permanent fertility with respect to the 

 three elements, nitrogen, phosphorus, and limestone. 



45. PHYSICAL FACTORS DETERMINING THE AGRICULTURAL 

 QUALITY OF LAND 1 



BY EDWARD J. RUSSELL 



The complex that we speak of as the soil consists of four parts: 

 i. The mineral matter derived from rock material, which con- 

 stitutes the framework of the soil and is in the main unalterable, but 

 it contains some reactive decomposition products. 



'Adapted from Soil Conditions and Plant Growth (new edition), pp. 53-113. 

 (Longmans, Green, & Co., London. Used by permission of the publishers.) 



