ROTATION 387 



The crops of the great plains province vary extensively. Besides 

 wheat, the sorghums form a very valuable crop in the southern 

 third. To the north of this, wheat, together with some corn and 

 alfalfa, is the principal crop. No definite rotation has been worked 

 out for this area. 



The principal farm crops in the provinces west of the Rocky 

 Mountains are wheat and alfalfa, with some corn, oats, barley, rye, 

 and sugar beets. The need of soil improvement is not so evident 

 here as in humid regions, because of a much greater original sup- 

 ply of plant food. The extensive growth of alfalfa furnishes a 

 ready and effective means for building up the soil. 



QUESTIONS 



1. Define a rotation of crops. 



2. How does a scientific rotation differ from tlie above? 



3. (Jive the objects of a rotation. 



4. What are major crops ? 



5. What are minor crops? 



6. How are crops rotated in nature? 



7. What is the primary object of farming? 



8. How does rotation affect the distribution of work? 



!. Why is a one-crop system favorable to the development of insects? 



10. Can you give an instance of disease caused by continuous cropping? 



11. How does rotation prevent disease? 



12. How are weeds kept down by rotation? 



13. Give some examples of troublesome weeds in your locality that may be 



kept down by rotation. 



14. Why is it a good practice to grow crops that root at different 



depths? 



15. What part does rotation play in maintaining tilth? 



10. What are toxic substances and how does rotation affect these? 



17. (Jive the results obtained at the Iowa Station for continuous corn 



and rotation. 



18. What results were obtained at the Illinois Station? 



1!). What do the Minnesota experiments show in regard to corn? Wheat? 



Hay? 



20. Which cereal responds best to rotation? 

 '21. If corn is worth 50 cents and wheat $1.05 per bushel and hay $S per 



ton, what is the total value of the average crops in a three-year 



rotation? In a live-vear rotation? 



22. Which rotation gave the greatest acre value for the crop? (Assume 



that in a five-year rotation, three crops of hay were grown.) 



23. Give a synopsis of the Ohio results. 



24. What tilings are to be considered in planning a rotation? 



25. What importance should l>e placed on the soil in these plans? 



'2<>. What consideration should guide in the selection of crops? 



'27. What determines the succession of crops? 



'2H. What about the length of the rotation? 



2!>. Why is it difficult to get a rotation under way? 



30. Why is it advisable to divide the farm into as many fields aa there 

 are crop? in the rotation? 



