12 BULLETIN 790, U. S. DEPARTMENT OF AGEICULTUEE. 



3^oung grass to maintain them tliroug-li the necessary period of 

 recuperation. 



By the time 25 per cent or more of the heads of the earlier forage ' 

 grasses begin to show or are conspicuous in the sheath sufficient leaf- 

 age has been produced to afford a good bit of forage. It is then 

 unnecessary for the animals to travel great distances for the supply 

 of food needed, and the damage from grazing is not nearly so great 

 as during the earlier period. This stage of development comes nor- 

 mally from 10 days to two weeks after growth begins. 



Grazing when the soil is saturated or very wet results in packing* 

 the soil by trampling, so tliat it hardens when it dries. In this con- 

 dition it does not absorb later rainfall as readily as when mellow, 

 as it ordinarily is if not trampled. As a consequence, the moisture 

 available for the plants is reduced and erosion is more active than 

 on unpacked soil. The greatest danger from trampling and packing 

 is over, normally, so far as the spring period is involved, by the time 

 the main forage plants have been growing about two weeks. 



Two weeks, then, after growth of the earlier forage grasses begins _ 

 may be set as the earliest date at which stock should be allowed on the 

 range. Where overgrazing or premature grazing has been practiced 

 until the range has deteriorated the opening of the season may have to 

 be delayed longer, or it may be necessary to apply deferred grazing 

 on the overgrazed area to allow the range to recuj)erate. 



The beginning of growth for a given exposure is later by about 

 7 to 10 days for each 1,000-foot increase in altitude, and there is 

 considerable variation in the time at which growth begins on differ- 

 ent exposures of the same altitude. Further, tlie time at which 

 growth begins varies somewhat in different j^'ears, perhaps as much 

 as two weeks. On the other hand, the opening date of the grazing 

 period for any one year must be decided in advance, but may be 

 changed in years following. These various factors must be kept 

 in mind and harmonized as far as practicable in deciding this open- 

 ing date. In doing so the following suggestions may be helpful : 



1. On sirring ranges and on summer ranges decide upon the area 

 which should be used during approximately the first third of the 

 period. 



2. Allov' grazing to begin when the early forage grasses at about 

 the center of altitude on this area are in the head. 



3. Inspect this range for a number of years to determine the aver- 

 age date at which the early forage grasses at this central altitude 

 are in the head, and eventually use this date as the beginning of the 

 grazing period. 



The choice of one-third of the range and of the central altitude 

 of this third may not fit an individual case; but it Avill serve as a 



