64 
SOIL SURVEY OF JACKSON COUNTY 
ROTATION OF CROPS* 
In discussing rotations, farm crops may be divided into three 
classes : 
1. Grain crops—generally shallow feeders, add little humus 
or organic matter to the soil, and tend to weediness. 
2. Hay crops—legumes, timothy, etc. Legumes have exten¬ 
sive root systems, tap roots, add organic matter or humus and 
also plant food (nitrogen). They also improve the physical 
condition of the soil. 
3. Cultivated crops—Corn, potatoes, etc., conserve moisture, 
favor decomposition of organic matter, and destroy weeds. 
Some are deep feeders, as corn, while root crops are shallow 
feeders. 
A good rotation should necessarily include crops belonging 
to each of these three classes. The value of such practice is 
apparent in its effect on the physical condition of the soil, on 
weediness, on organic matter supply, on plant diseases, and 
on nitrogen supply of the soil. Better yields are, therefore, 
obtained when crops are rotated than when a single cropping 
system is followed. 
Again, crop rotation permits raising livestock and means 
diversified farming. No one will deny the benefits of this type 
of farming in stabilizing farm business and making best use 
of labor and equipment the year around. 
It should not be understood, however, that crop rotation 
means maintaining the supply of plant food better than where 
a single cropping system is practiced. It is often said that 
certain crops are “hard” on the soil in the sense that they 
remove more plant food than other crops. In part that is true, 
but a more important difference is that some plants remove 
more of certain elements than others. Again a crop like corn, 
because of its root development and length of growing season, 
may utilize plant food that is less soluble. 
Potatoes require relatively more potassium; corn draws 
heavily on nitrogen; while legumes are heavy feeders on lime 
(calcium) and also require large amounts of phosphorus, po¬ 
tassium, and nitrogen (some of which may be extracted from the 
air in the soil). Again, grain crops and roots require plant 
*See Bulletins of Exp. Sta. for more information on Crop Rotation. 
