62 PRACTICAL CORN CULTURE 



not permanently maintain the fertility of the soil. All 

 crops require more or less phosphorus and potash as a part 

 of their plant food. Each year a drain is made on the supply 

 of phosphorus and potash. When these elements of plant 

 food are taken from the soil they must be returned in the 

 form of stable manure, commercial fertilizer or rock phos- 

 phate. No plant can put phosphorus and potash in the soil; 

 instead, they all take it out. 



For nearly fifteen years we have followed with slight 

 variation a rotation consisting of corn two years, then oats, 

 wheat and clover successively. This is the popular rotation 

 in Central Illinois and is followed to a greater or lesser 

 extent on nine-tenths of the farms in this latitude. 



Since oats are a heavy drain on the land and often an 

 unprofitable crop, we have, for the last two years, substituted 

 soy beans largely for oats. Each year we sow about 100 

 acres to soy beans. Before adopting soy beans this ground 

 was sown to oats. By following this method we are including 

 two leguminous crops in the rotation instead of one. 



The soy bean is a wonderful crop for improving the phys- 

 ical condition of the soil. An ideal seed bed for winter 

 wheat can be made on soy bean fields with very little work. 

 Remember to return the straw to the land if you wish to 

 increase the nitrogen content of the soil. (More will be said 

 of soy beans in the next chapter.) 



Alfalfa is one of the most profitable of the legume crops 

 but it is not a good crop to work in a rotation. This is due 

 to the fact that it is difficult and expensive to secure a good 

 stand and when once secured it is profitable to leave the 

 ground in alfalfa from three to five years. A good stand 

 of alfalfa will generally grow better each year for the first 

 three years. Alfalfa will grow on most of the well drained 

 soils of the Corn Belt. It will grow on thin land but it will 

 do much better on strong land. That alfalfa will build up 



