Dec. 2, 1918 Effect of Farm Manure on Irrigated Field Crops 495 



With respect to any given plot the same crop recurs with each cycle 

 of the rotation. Thus in the six years since 191 2 the crops in the 2-year 

 rotations have been on the same plot three times, those in the 3-year 

 rotations have been on the same plot twice, while in the 6-year rotations 

 only one cycle has been completed. In the case of the 2 -year and 3-year 

 rotations, in which manure is applied to one of the crops, this manured 

 crop has received each year the immediate benefit of the manure and 

 in addition the benefit of any residual effect that may have remained 

 from the earlier applications. This becomes true also in the 6-year 

 rotations after the completion of the first cycle. 



One pair of the 2 -year rotations and the pair of 3 -year rotations 

 include both sugar beets and potatoes. In the 2-year rotation. No. 21, 

 the manure is applied preceding the potatoes and the beet crop that 

 follows gets only the second-year residual effect of the manure. Jn the 

 3-year rotation, the manure is applied preceding the sugar beets and 

 the potatoes receive the second-year residual effect. In the other 

 rotations the effect of the manure is noted only in respect to the crop 

 which immediately follows its application. 



The cultural operations used with these rotations are only such as 

 ordinary good farming demands. So far as the rotation pairs are con- 

 cerned, all cultural operations are the same for both members of the pair. 

 The same varieties of the two crops are used in all rotations at each 

 station each year. The same varieties are not used at the different 

 stations; nor has the same variety been used for all years at each station. 

 For the sugar beets the seed has usually been obtained from the local 

 sugar factory, and for the potatoes some good locally adapted variety 

 has been used. 



The field work of these rotation experiments has been under the 

 direction of the farm superintendent of each station, and under the 

 immediate supervision of a scientific assistant, who is charged with 

 performing or directing the cultural operations, the irrigation, the harvest- 

 ing, and taking the field notes and reporting the results each year.^ 



RESULTS OF THE EXPERIMENTS 

 IRISH POTATOES 



The effect of the manure on the yield of potatoes is shown in Table I, 

 which gives the yields in bushels per acre for the manured plots and the 

 yields from plots that have had similar treatment, except for the manuring. 



' The following is the personnel concerned with the field work of these rotation experiments: At Scotts- 

 bluff Jlr. Fritz Knorr was superintendent of the field station from 1910 to the end of 1916. Mr. James A. 

 Holdcn was in charge of the irrigated rotations at this station from 1912 to the end of 1916, when he suc- 

 ceeded Mr. Knorr as slation superintendent. Mr. David W. Jones supervised the irrigated rotations 

 during 1917. 



At BcUefourche Mr. Beyer Aune has been superintendent of the field station since 1909. He has been 

 closely in touch with the irrigated rotation work, being assisted in it at diflerent times by ^Ir. John B. 

 Wentz, Mr. N. L. Mattice, and Mr. George T. RatlifTe. 



At Huntley Mr. Dan Hansen has been superintendent of the field station since 1910. The irrigated 

 rotations were under the supervision of Mr. John M. Spain during 1912, Mr. John W. Knorr during 1914 

 and Mr. Edward G. Noble since 1915. 



88093°— 18 2 



