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MISCELLANEOUS PUBLICATION 1271, U.S. DEPARTMENT OF AGRICULTURE 



season-long at the same rate. However, improve- 

 ment in range condition would be more rapid 

 under complete deferment for 1 or 2 years. At 

 Antelope Range, rest-rotation grazing resulted 

 in good improvement in range condition, but 

 sheep production was lower than with season- 

 long grazing. At Manhattan, Kans., an earlier 

 study showed an advantage in vegetation re- 

 sponse to deferred-rotation grazing, but a later 

 study showed no advantage in vegetation by de- 

 ferred-rotation grazing and a disadvantage in 

 livestock performance (2, 11). 



In the northern part of the West, early plant 

 growth is generally dependent upon winter- 

 spring precipitation and periods of warm 

 weather. Many workers recognize that grazing or 

 clipping during the early part of seasonal growth 

 is detrimental to subsequent plant vigor (for ex- 

 ample, h 16). On ranges grazed seasonally, sev- 

 eral studies have shown an advantage to spring 

 deferment, but this must be balanced against the 

 detrimental effects of concentrating livestock dur- 

 ing this critical period of plant growth. At 

 Squaw-Butte, nonuse during the growing season 

 for 4 years did not overcome the detrimental ef- 

 fects of 2 consecutive years of concentrating the 

 stock during the growing season. In the areas 

 with short growing seasons, an important ques- 

 tion, often not considered, is: how many of the 

 desirable plants are actually grazed during the 

 critical period of growth under a moderate stock- 

 ing rate in a continuous system? At Burgess 

 Junction, Wyo., Festuca idahoensis was not util- 

 ized until mid-August on the season-long unit, 

 whereas it was moderately utilized as early as 

 late July in the rotation units. It appears that 

 any deferment period on ranges grazed only for 

 part of a year should be brief, and that it should 

 coincide with a critical period of growth. It 

 should be recognized that the dates of this critical 

 period vary from year to year depending on 

 phenological development. 



Another important consideration on ranges 

 grazed seasonally is : Are range managers trying 

 to maintain the right species? Undoubtedly, wo 

 must have species that will maintain the soil re- 

 source. However, from the evidence presented in 

 this paper, Festuca idahoensis. Carex geyeri. 

 Agropyron spicatum. and possibly others, are 

 poorly adapted to grazing by livestock in some 



areas. Species that are not well adapted climat- 

 ically also should not be considered important in 

 many instances. For example, although Bouteloua 

 gracilis is quite resistant to grazing, its produc- 

 tion is low in some high altitudes in the South- 

 west. 



At Woodward, a number of studies have shown 

 no advantage to rotation grazing over continuous 

 grazing in livestock performance. An early study 

 showed an improvement in floristic composition 

 due to grazing. The Woodward station is located 

 in a broad regional ecotone with considerable 

 fluctuations in floristic composition due to weath- 

 er conditions. There is a reduction in percentage 

 of tall grasses in the floristic composition in a 

 series of dry years regardless of grazing treat- 

 ment. Similarly, during a series of wet years, the 

 tall grasses increase rapidly under any grazing 

 treatment other than heavy stocking. This wide 

 fluctuation in floristic composition due to weather 

 conditions is common to some other parts of the 

 West. With this situation, a classification of range 

 condition at any point in time must allow for 

 previous weather conditions. 



Of the studies reviewed, the deferred-rotation 

 system at Sonora, Tex., has shown the most strik- 

 ing results. At that location, a range unit is 

 grazed with a combination of livestock for 12 

 months and deferred for -i months. This infre- 

 quency of livestock movement means that the 

 livestock must adjust to new forage conditions 

 only once a year. Livestock are in a given unit 

 for a complete cycle of plant growth. The major 

 species, Hilaria belangeri, is quite resistant to 

 heavy grazing. Another point is that there may 

 be some growth of at. least some of the plant 

 species at anytime of the year 'when there is suf- 

 ficient moisture. Therefore, a 4-month deferment 

 during each third of the year every 4 years has 

 resulted in a substantial improvement in carry- 

 ing capacity ^ 



Most studies have shown that livestock produc- 

 tion per animal is the same or lower for a rota- 

 tion system compared to continuous grazing. Gen- 

 erally, there must be an improvement in range 

 condition, and subsequently in carrying capacity, 

 to justify a rotation scheme using livestock per- 

 formance as a criterion. Animal performance per 

 unit area is more important than performance of 

 individual animals. In some instances, it may take 



