30 FERTILITY AND FERTIUZER HINTS 



in Europe but the short rotations of three to six years are found 

 to be profitable in the United States. 



Make up of a Rotation, — The crops used in rotations are nat- 

 urally selected according to the location, nature of the soil, avail- 

 able crops, market prices, kind of farming-, insect and plant dis- 

 eases, climate, etc. A stock farm would require different crops 

 than a tobacco farm ; a dairy farm in Wisconsin could not probably 

 use the same rotation as a dairy farm in Alabama ; two farms in 

 the same state with dift'erent soil conditions would perhaps se- 

 lect different crops for a rotation ; a farm ten miles from a 

 market would no doubt find it more practical to grow different 

 crops than one i,ooo miles away; and crops would not be chosen 

 that insects or plant diseases ruin. 



Reasons for Rotating Crops. — Some of the reasons for rotating 

 crops are : 



1. To keep down weeds. 



2. To gather nitrogen from the air. 



3. To distribute farm labor more evenly. 



4. To eradicate insect or other diseases. 



5. To furnish feed for live stock. 



6. To give the farmer a regular income. 



7. To prevent losses of fertility. 



8. To utilize plant food more evenly. 



9. To include deep and shallow rooted plants. 



10. To save fertilizer expenditure. 



11. To regulate the humus supply. 



12. To conserve moisture in dry sections. 



I. Rotation of Crops Keeps Down Weeds. — It is well known 

 that the growing of particular crops is accompanied by certain 

 weeds. Those crops that are sown broadcast, as the small grains, 

 are more apt to be weedy than cultivated crops as corn, cotton, 

 tobacco, potatoes, etc. When crops like wheat, hay, etc.. are 

 grown continuously the yields or the quality of the crops are 

 often materially reduced by weeds. Intertilled crops as corn, to- 

 bacco, cotton, potatoes, etc., when well cultivated, are known as 

 "cleaning crops." So in planning a rotation crops should be 



