4 CIRCULAR 804, U. S. DEPARTMENT OF AGRICULTURE 



these three relative rates of stocking. During the last year, 1941, the 

 pastures received 2.55, 1.78, and 1.00 sheep-months of grazing use per 

 acre, respectively, and for the 6-year period stocking averaged 1.35, 

 0.94, and 0.53 sheep-months per acre under heavy, conservative, and 

 light stocking. Table 1 shows the grazing season for each year, the 

 number of yearling ewes that were grazed, and the actual grazing use 

 for each pasture each year throughout the study. 



Table 1. — Actual grazing use by yearling Rambouillet ewes in three 

 experimental pastures, by grazing season, 1936-4-1 





Num- 

 ber of 

 year- 

 ling 

 ewes 

 per 

 pas- 

 ture 



Stocking (sheep-months) 



Grazing season, 

 inclusive dates 



Small pasture 

 (332 acres) 



Middle-sized 



pasture 

 (476 acres) 



Large pasture 

 (847 acres) 





Total 



Per 

 acre 



Total 



Per 

 acre 



Total 



Per 

 acre 



June 16-Oct. 30, 1936 



Apr. 28-Nov. 24, 1937___ 

 Mar. 16-Nov. 23, 1938___ 

 Mar. 22-Nov. 20, 1939___ 

 Mar. 22-Nov. 16, 1940___ 

 Mar. 18-Nov. 17, 1941___ 



35 

 35 



42 



55 



80 



104 



159. 8 

 250. 7 

 352. 1 

 444. 6 

 631.6 

 845.6 



0.48 



.76 



1.06 



1. 34 

 1.90 



2. 55 



159.8 

 250. 3 

 350. 7 

 444. 6 

 635. 8 

 845.7 



0. 34 

 .53 



.74 



.93 



1 34 



1. 78 



159.8 

 250. 2 

 352. 

 444.6 

 632.6 

 845.9 



0. 19 

 . 30 



.42 

 . 52 

 .75 



1. 00 



Total _ 



351 



2, 684. 4 



8.09 



2, 686. 9 



5.64 



2, 685. 1 



3. 17 







Average 



58.5 



447.4 



1.35 



447.8 



.94 



447. 5 



. 53 







The sheep were quite uniform, well-bred, dry yearling Rambouillet 

 ewes from the flocks of the United States Sheep Experiment Station at 

 Dubois, Idaho. A new group was obtained each spring, grazed in the 

 pastures, then returned to Dubois at the close of the grazing season. 

 Except in 1936, when severe drought occurred, and in 1937, the grazing 

 season extended from about mid-March to late November. Weights 

 of the individual sheep on each pasture were recorded at the start, at 

 28-day intervals throughout, and at the end of each grazing season. 



A forage inventory provided the original appraisal of the range 

 vegetation and the basis for stocking the experimental pastures. 

 Permanent meter-square chart quadrats were used to study changes 

 in the range vegetation due to grazing and weather. Herbage produc- 

 tion as affected by degree of stocking was further studied by harvesting 

 the herbage from small plots that were ungrazed in 1942. Other 

 characters of the range, such as number of plants per unit area, size of 

 plants, and percentage of plants producing seedstalks, were studied by 

 various sampling techniques and the data compared for the differently 

 stocked pastures and ungrazed areas. At the end of each grazing 

 season a survey of utilization was conducted in each pasture. 



During the first 3 years of the experiment the surveys consisted of 

 reconnaissance- type estimates of utilization, but after 1938 the stubble- 

 height method (3) 2 and approved sampling techniques were employed. 



2 Italic figures in parentheses refer to Literature Cited, p. 39. 



