CORN 63 



organic matter also renders available the potassium which 

 in normal soils is usually in sufficient abundance to supply 

 standard yields. This method of supplying plant-food to the 

 soil in connection with good systems of crop rotation not 

 only increases the annual yields of each crop in the rotation, 

 but leaves the soil permanently richer in plant-food after 

 the single applications, as stated above, and after four or five 

 crops of the rotation have been produced. 



Plan of soil treatment, the corn series. The following is 

 the general plan of soil treatment for ten plots in each of a 

 series of five at the University of Illinois. The figures show 

 the yields of corn in one season: 



Corn yield 



Plot No. Soil treatment bushels 



1 None 60 



2 Legume (catch crops and crop residues) 60 



3 Manure 75 



4 Legume, lime 65 



5 Manure, lime 80 



6 Legume, lime, phosphorus 87 



7 Manure, lime, phosphorus 90 



8 Legume, lime, phosphorus, potassium 90 



9 Manure, lime, phosphorus, potassium 93 



*10 Legume (manure, lime, phosphorus, potassium, 



X5) 96 



VII. PLOWING FOR CORN 



Time of plowing 1 . The time of plowing for corn will 

 usually be determined by the convenience of the farmer. It 

 is a pretty well established fact that the differences in yield 



*Five times the amounts used in (9) were applied. 



