ROTATION AND CULTURAL METHODS AT EDGELEY, N. DAK. 9 



letter. The crop that is on plat C one year is on plat B the next, and 

 so on until from A it moves to the letter marking the end of the 

 rotation. The plats are 2 by 8 rods and are separated by 4- foot alleys 

 and 20-foot roadways. In the diagram the separation of rotations 

 is indicated by heavy lines. The four unnumbered blocks of four 

 plats each are the continuous and alternate cropping plats devoted 

 to the four crops designated. 



Rotations Nos. 1, 2, 71, and 72, set off by a broken line and desig- 

 nated " on hill," are duplications described in the text as being on 

 deeper soil. They do not occupy the position indicated on the dia- 

 gram, but are detached. The eight plats, also set off by a broken line 

 and designated ; ' 1913 fallow series," are also detached. They have 

 been devoted to a study of four methods of fallow. 



The circle and square designated " observatory " indicate the loca- 

 tion of the instrument yard, in which the meteorological instruments 

 are exposed. 



Rotations Nos. 1 and 3 are exactly the same 3-year rotations of 

 oats on fall-plowed wheat stubble, corn on fall-plowed oat stubble, 

 and wheat on corn ground. In rotation No. 1 the corn ground is 

 disked and in rotation No. 3 it is fall plowed in preparation for the 

 wheat. The wheat on the disked corn ground has yielded more than 

 on the fall-plowed corn ground in 11 out of 13 years, and for the 13 

 years it has averaged 2J bushels per acre more. The average yields of 

 oats from the two rotations agree within a fraction of a bushel, but the 

 corn has averaged slightly more in rotation No. 1. In 1906, when 

 the treatment was the same, the yield was about the same, indicating 

 no considerable natural advantage of rotation No. 1 over rotation 

 No. 3. 



Rotation No. 2 has the same crops, but the ground is spring plowed 

 for each of them. The yield of wheat on disked corn ground in 

 rotation No. 1 has exceeded that on spring-plowed corn ground in 

 rotation No. 2 in 10 out of 13 years, and for the 13 years it has 

 averaged 2.4 bushels more per acre. 



The same rotations have been duplicated on deeper soil since 1908. 

 In this duplication the disked corn ground has shown less advantage 

 over the plowed land than in the original plat field, but its average 

 increase for the 11-year period from 1909 to 1919, inclusive, has been 

 three-tenths of a bushel per acre. 



Rotation No. 4 is wheat on fall plowing, corn on fall plowing, and 

 oats on disked corn ground. Rotation No. 9 has the same crops in 

 the same order, but all on spring plowing. The oats on disked corn 

 ground in rotation No. 4 has yielded more than the oats on spring 

 plowing in rotation No. 9 in 10 out of 13 years. The average in- 

 crease on disked corn for the 13 years is 1.1 bushels per acre. 

 56615°— 21 2 



