8 CULTIVATION METHODS AND ROTATIONS FOE GREAT PLAINS. 



(7) Should corn stubble be plowed or disked without plowing as a preparation for 

 spring wheat? 



(8) Can summer tillage be profitably introduced into a rotation system? 



(9) Can any system of crop rotation be devised, involving the use of perennial 

 grasses or legumes, or biennial legumes, which will be adapted to conditions in the 

 Great Plains area? 



(10) Can green manuring be profitably substituted for summer tillage, thereby con- 

 serving both the moisture and the organic matter of the soil? 



(11) What is the best method of introducing winter wheat into a rotation? 



ANSWERS OBTAINED. 



The following tentative answers have been obtained from the 

 investigations. They are likely to be modified by future results. 

 They are, however, based upon the best evidence obtainable in the 

 present state of our knowledge: 



(1) The average yields in bushels per acre from the three methods of tillage have 

 been as follows: 



Average production per acre of wheat, oats, and barley. 



Methods of tillage. 



Wheat, 



Oats. 



Barley. 



Continuous cropping, ordinary methods 



17.4 



30.2 



21.1 



Continuous cropping, moisture conservation 



16.5 



30.5 



22.9 



Alternate cropping and summer tillage 



22.5 



44.1 



30.7 



(See Tables I, II, and III, pp. 16 and 17.) 



(2) The average results of moisture conservation methods have not proved profitable 

 as compared with ordinary methods where continuous cropping has been practiced. 

 (See paragraph 2 of Conclusions, p. 68.) 



(3) The average results of alternate cropping and summer tillage have not proved 

 profitable, as compared with continuous cropping with ordinary methods. (See 

 paragraph 1 of Conclusions, p. 67.) 



(4) Simple 3-year rotations of corn, wheat, and oats, or corn, barley, and oats have 

 proved more profitable than continuous cropping or alternate cropping with any one 

 of these four crops. (See paragraph 3 of Conclusions, p. 68.) 



(5) Corn on either fall or spring plowing, followed by either wheat or barley on disked 

 corn stubble, followed by oats on early fall plowing has given best average results. 

 (See paragraph 4 of Conclusions, p. 68.) 



(6) Fall plowing has given slightly better average results than spring plowing. 

 (See paragraph 11 of Conclusions, p. 69.) 



(7) Disking corn stubble, without plowing, has given better results than plowing 

 as a preparation for spring wheat. (See paragraph 10 of Conclusions, p. 69.) 



(8) Summer tillage has not given as good average results when used in a rotation as 

 a preparation for spring wheat or oats as has a properly cultivated corn crop. It seems 

 probable that it will be found advisable to occasionally introduce summer tillage 

 into a rotation as a preparation for winter wheat. (See paragraph 9 of Conclusions, 

 p. 68.) 



(9) The evidence so far obtained leads to the conclusion that a 5 or 6 year rotation 

 of corn, winter or spring wheat, brome-grass (three years), oats, barley, emmer, or 



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