2 BULLETIN 881, IT. S. DEPARTMENT OF AGRICULTURE. 
DESCRIPTION OF THE EXPERIMENTS. 
These experiments are a part of an extensive series of rotations 
conducted under irrigation at the three stations specified. The 
experiments were started with the crop season of 1912 and have been 
continued without modification. The field plats, which include one- 
fourth of an acre each, are laid out in series. The series are separated 
by 40-foot roads, and the plats in the series are separated by 5-foot 
alleys. The plats at Scottsbluff are 132 feet long by 82.5 feet wide; 
those at Belle Fourche are 264 feet long by 41.25 feet wide, and 
those at Huntley are 227 feet long by 48 feet wide. 
The present bulletin deals with the effect produced by growing 
alfalfa for one, two, or three years on plats which are later used for 
two or three years for other crops and then are reseeded to alfalfa. 
The alfalfa crops are cut for hay, and at the end of the alfalfa period 
the land is plowed soon after the last cutting, so that only the stubble 
is plowed under. The results are based on seven pairs of rotations, 
the two members of each pair differing from each other only in that 
one member includes either two years or three years of alfalfa, while 
the other does not. Each rotation occupies as many plats as there 
are years in the cycle, so that each crop is represented each year. 
The crops and sequences involved in the 14 rotations are as follows: 
Rotation 20: Potatoes, sugar beets. 
Rotation 40: Alfalfa, alfalfa, potatoes, sugar beets. 
Rotation 22: Oats, sugar beets. 
Rotation 42: Alfalfa, alfalfa, oats, sugar beets. 
Rotation 24: Potatoes, oats. 
Rotation 44: Alfalfa, alfalfa, potatoes, oats. 
Rotation 28: Wheat, oats. 
Rotation 48: Alfalfa, alfalfa, wheat, oats. 
Rotation 30: Potatoes, oats, sugar beets. 
Rotation 60: Alfalfa, alfalfa, alfalfa, potatoes, oats, sugar beets. 
Rotation 31: Potatoes, oats, sugar beets (manured). 
Rotation 61: Alfalfa, alfalfa, alfalfa, potatoes, oats, sugar beets (manured). 
Rotation 32: Corn, oats, sugar beets. 
Rotation 62: Alfalfa, alfalfa, alfalfa, corn, oats, sugar beets. 
It will be noted from the list of rotations that the comparisons 
to determine the effect of the alfalfa are made between 2-year and 
4-year rotations and between 3-year and 6-year rotations. In the 
first set of comparisons a 2-year period of alfalfa is used and in the 
second set a 3-year period. 
As these rotation experiments were started in 1912, in each case 
on land that had not previously grown alfalfa, there was no effect to 
be observed until 1913, and the crops grown that year following alfalfa 
were from plats that had been in alfalfa only one season. The first 
full effect of the alfalfa in the rotation was obtained in the 4-year 
rotations in 1914 and in the 6-year rotations in 1915, and then only 
in the case of crops which immediately succeed alfalfa in the rotation. 
