ROTATION 93 



Experiment Stations* of this region would seem to support such 

 a statement. But that does not mean that these soils are inexhaus- 

 tible or that the methods of cropping now commonly in vogue can be 

 safely continued indefinitely. By these same methods much of the 

 land of the eastern states has been reduced to a condition where ex- 

 pensive fertilizers must be used. Even in Illinois, Dr. Hopkins has 

 proved that large areas of soil require the application of phosphorus. 

 Chemical analyses of some Iowa soils show that their supply of 

 that element is by no means inexhaustible. Already, on many soils, 

 m practically every community of the corn belt, the eflfects of an 

 insufficient humus and nitrogen supply are seen in lessened crop 

 yields. If many of the present methods of handling such soils are 

 not soon radically revised, the day of the commercial fertilizer cannot 

 be long postponed. 



It is much easier and vastly more economical to maintain the pro- 

 ductivity of a fertile soil than to build up an exhausted one. By the 

 adoption of a proper rotation including leguminous crops and supple- 

 mented by barnyard manures, the time when it will be necessary to 

 use commercial fertilizers can be indefinitely postponed on the greater 

 part of the corn belt land west of Illinois. The work of the Minne- 

 sota Station has shown that by such means the expensive nitrogen 

 and the humus supplies can be maintained and even increased. 



A ROTATION FOR THE CORN BELT. Throughout the 

 greater part of this region the most profitable cereal crop that can be 

 grown on fertile soil is corn. The problem of a rotation, then, is how 

 to secure the largest area for that crop consistent with the maintenance 

 or improvement of the fertility of the soil. 



"What other crops should be rotated with corn is a problem which 

 every farmer must largely work out for himself according to his par- 

 ticular conditions, remembering that to get the best results a rational 

 rotation must be practiced; that is, the corn crop must be alternated 

 with some other suitable crops. What these other crops should be 

 and how many different ones should be included in the rotation will 

 depend upon a number of factors, among which are the kind of farm- 

 ing carried on, the kind of soil and its degree of fertility, the kinds of 

 crops which the local conditions will best produce and the extent to 

 which they may be profitably used in the system of farming followed. 

 One cardinal principle, however, must never be forgotten, and that is 



'Minnesota Bulletin No. 89. 

 -MinneBota Bulletin No. 94. 

 Iowa Bulletin No. 96. 

 Kansas Bulletin No. 147. 

 Indiana Bulletin No. 88, 



