WINTER-WHEAT PEODUCTIOX AT FOET HAYS STATIOaST. 21 



and double-disked before seeding in 1916, 1918, and 1919. It has 

 received no other cultivation or treatment except seeding and 

 harvesting. Its average yield for the 7-year period from 1914 to 

 1920, inclusive, as shown in Table 8, is 20.4 bushels per acre. This 

 may be properly compared with the jdeld of 21.4 bushels on early 

 fall-plowed wheat stubble in rotation No. 401. 



Further evidence on this subject is furnished by an experiment 

 as to the frequency of plomng for winter wheat, which was started 

 in 1916. This occupies six plats continuously cropped to winter 

 wheat. Plat A is plowed each year, B is plowed one year and sown 

 in stubble the next, C is plowed one year and sown in stubble two 

 years, D is plowed one year and sown in stubble three years, E is to 

 be sown in stubble continuously, and F, originally planned for 

 another method, has been plowed each year except for the crop of 

 1917. The tniage on these plats is early plowing, which is worked 

 down inunediately and given necessary cultivation until seeding 

 time. The plats sown without plowing receive no other treatment 

 than a double-disking. In preparation for the crop of 1917 this was 

 done at the time of early plowing. Since then it has been done at 

 the time of late plowing. The yields from these plats for the 5-year 

 period from 1916 to 1920, inclusive, are given in Table 9. The land 

 was fallowed in 1915 and seeded that fall as a solid field. The plats 

 were blocked out from the field in the spring of 1916. Differences 

 in yield that year are natural differences between plats of uniform 

 treatment. For 1917 plat A was plowed and the others seeded in 

 disked stubble. All except plat A were consequently of uniform 

 treatment. For 1918 plats A, B, and F were plowed, and C, D, and E 

 were again seeded on disked stubble and again given uniform treat- 

 ment. For 1919 plats A, C, and F were plowed, and for the fourth 

 year D and E were seeded on disked stubble continued uniform. For 

 1920 plats A, B, D, and F were plowed, and uniformity between any 

 of the plats disappeared. 



In Table 9 the yields on plowed ground in the 4-year period from 

 1917 to 1920, inclusive, are printed in boldface type. Despite the 

 plat variation, as shown by differences in yield when the treatment 

 was uniform, the results are clear as to differences between plowing 

 and not plowing in the years during which the experiment had been 

 conducted, but they do not yet illuminate the question of how often 

 plowing must be resorted to or how long it may be dispensed mth. 

 The average of each plat for the 4-year period from 1917 to 1920, 

 inclusive, is given at the bottom of Table 9. In the present stage of 

 the experiment perhaps a better comparison is afforded by deter- 

 mining the average yield each year of the plowed plats and of those 

 not plowed. Such averages are shown in the right-hand columns 

 of the table. In 1917 the one plowed plat was a total failure, due to a 



