494 



Journal of Agricultural Research 



Vol. XV. No. 9 



The more important crops of irrigated lands of the region are alfalfa 

 (Medicago saliva), cereals, including com {Zea mays), oats [Avena saliva), 

 wheat (Triticum aestivum), and barley (Hordeum spp.), sugar beets 

 (Bela vulgaris), and Irish potatoes (Solanum luberosum). On the three 

 reclamation projects referred to above, comprising 150,000 acres, these 

 crops occupy nearly 90 per cent of the land, in the following proportions: 

 Alfalfa, 43 per cent; cereals, 31 per cent; sugar beets, 10 per cent, and 

 potatoes, 3 per cent. 



The soils are generally very productive, and, notwithstanding the 

 hazards of occasional hail storms and of the occurrence of insect pests 

 and plant diseases, abundant crops are produced. The North Platte 

 Project, which includes the Scottsbluff Station, has a light sandy soil 

 which takes water readily and is subject to wind erosion when left 

 exposed without a plant cover. The Belle Kourche soil is a heavy black 

 clay, very plastic when wet, becoming friable on drying, when large 

 shrinkage cracks are formed through which water penetrates the dry soil 

 rapidly. The soil at Huntley is not quite so heavy as that at Belle 

 Fourche, though it would be classed as a clay loam. It is very produc- 

 tive, except where the salt content is too high. 



DESCRIPTION OF THE EXPERIMENTS 



The experiments here discussed are a part of a large series of rotation 

 experiments conducted under irrigation at each of the three stations. 

 These rotation experiments were started with the crop season of 191 2 

 and have been continued without modification. The field plots include 

 X acre each. These are laid out in series which are separated by 40-foot 

 roads, and the plots in the series are separated by 5-foot alleys. The 

 plots 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 paper deals only with the effect of manure on the yields 

 and qualities of two crops, sugar beets and potatoes, at tjie three stations 

 for the 6-year period 191 2 to 191 7. The results are based on five pairs of 

 rotations, the two members of each pair differing from each other only in 

 that farm manure is applied annually, at the rate of 12 tons per acre, to 

 one crop in one rotation, and no manure is appHed to the other rotation. 

 Each rotation occupies as many plots as there are years in the cycle, so 

 that each crop is represented each year. The crops and sequences 

 involved in the 10 rotations are as follows: 



Rotation 20: Potatoes; sugar beets. 

 Rotation 21: Potatoes (manured); sugar 



beets. 

 Rotation 22: Oats; sugar beets. 

 Rotation 23 : Oats; sugar beets (manured). 

 Rotation 24: Oats; potatoes. 

 Rotation 25: Oats; potatoes (mantu^ed). 

 Rotation 30: Potatoes; oats; sugar beets. 



Rotation 31: Potatoes; oats; sugar beets 



(manured). 

 Rotation 60: Potatoes; oats; sugar beets; 



alfalfa, first year; alfalfa, second year; 



alfalfa, third year. 

 Rotation 61: Potatoes; oats; sugar beets 



(maniu-ed); alfalfa, first year; alfalfa, 



second year; alfalfa, third year. 



