28 BULLETIX 10^, U. S, DEPARTMENT OF AGPJCULTUEE. 



almost or quite impracticable on account of the growth of weeds and 

 more especially the growth of volunteer wheat, which reaches nearly 

 or quite the heading stage by the time kafir is planted. In the case 

 of rotation No. 510 this seems not only to have reduced the crop of 

 kafir about one-third, but to have continued through the fallow and 

 some years reduced the yield of wheat grown on it. 



The second series of 10 rotations, numbered from 551 to 560, in- 

 clusive, was planned to study the use of manure applied directly to 

 the wheat at different rates, applied to kafir at different rates, and the 

 effect of a light dressing of straw on winter wheat. 



Except for the manure or straw that they receive, the treatment 

 of all 10 rotations is uniform. The fallow and the wheat on fallow 

 are the same as outlmed for rotations Nos. 503 to 510, inclusive. 

 After the wheat is harvested the ground is plowed in the fall, culti- 

 vated in the spring, and the kafir planted with shallow listing. 



Rotations Nos. 551, 552, and 553 receive no manure and are dupK- 

 cates run as checks on those receiving treatment. 



The winter wheat in rotation No. 554 receives a top-dressing of 

 straw late in the fall at the rate of 2 to 3 tons per acre. To hold it in 

 place, the straw is cut into the ground with a packer. 



Barnyard manure is applied as a top-dressing at the same time to 

 the wheat in rotation No. 555 at the rate of 3 tons per acre, and to the 

 wheat in rotation No. 556 at the rate of 6 tons per acre. 



In rotations Nos. 557, 558, 559, and 560 barnyard manure is used 

 preceding the kafir crop. It is spread on the plowed land in Novem- 

 ber or December at the same time the wheat is top-dressed. It is 

 used at the rates of 3 tons per acre in rotation No. 557, 6 tons in No. 

 558, 9 tons in No. 559, and 12 tons in No. 560. 



As with rotations Nos. 501 to 510, inclusive, these are arranged so 

 that the f aUow, wheat, and kafiir each occupy each year a solid block 

 of 10 plats with the rotations arranged from north to south in the 

 order in which they appear in Table 12. This table gives the yields of 

 wheat and kafir in these 10 rotations for the 7-year period from 1914 

 to 1920, inclusive. 



If it were not for the three check rotations which appear at inter- 

 vals among the manured ones, one might attempt to discuss the 

 effects of manure applied at different rates and to different crops in the 

 rotations. But with the data as they are, the only conclusion that can 

 be arrived at from a study of the yields year by year and of the aver- 

 age from the entire series of years is the general one that both barn- 

 yard manure and straw have been ineffectual in increasing the yields 

 of either wheat or kafir. To one familiar only with soils that respond 

 to manure or on wliich it is a necessity to crop production, such a 

 residt may seem almost incredible, but it is a rather usual one on the 

 Plains and the prairie soils of the dry-farming section. It is recog- 



