34 BULLETIN 1031, U. S. DEPARTMENT OF AGRICULTURE. 



and September, but grazing at that time does not seem to affect 

 tobosa-grass range, so that the latter should be used for summer 

 range and the former at other times. Should grama -grass range be 

 overgrazed this fact may be detected by the various plant species 

 that come in on the range and steps should be taken to reduce graz- 

 ing and protect the range during the growing season. 



GRAZING CAPACITY. 



The effect of drought and time of grazing upon the grazing capac- 

 ity of the range is of prime importance in working out a plan of 

 management to secure maximum maintained cattle production on 

 southwestern ranges. The summary given in the last few pages 

 shows that there is a great reduction in amount of forage produced 

 per unit of area due to drought and considerable variation due to 

 difference in the time and extent to which the grama-grass range 

 is grazed. The data show also that the reduction increases with 

 each year of drought. Should the first few years following drought 

 be favorable an increase in forage production toward the maximum 

 will undoubtedly occur. To determine approximately what these 

 changes mean in number of stock or percentage of stock, from year 

 to year throughout a cycle including a drought and the good years 

 following, is a problem that must be solved if similar conditions are 

 to be prepared for in advance and the " downs " of cattle production 

 on ranges of the Southwest be reduced or eliminated. 



By grazing capacity is meant amount of grazing that may be se- 

 cured per unit area. Usually this amount is expressed, however, in 

 acreage per head of stock on any given range for the period the range 

 is used. On most of the southern New Mexico ranges the stock are 

 grazed yearlong. Grazing capacity is therefore expressed in terms 

 of acres per head for the yearlong period, or, in other words, acreage 

 required to furnish a year's grazing for one animal, although graz- 

 ing may be lighter than average during part of the year. 



True grazing capacity obviously is the acreage of a given range 

 required to support one animal of a given class over a period of j^ears 

 without injury to the range. This ideal is difficult to attain on any 

 range and is especially so on ranges of southern New Mexico, which 

 are subject to the changes and variable factors briefly discussed in 

 preceding pages. It is hoped, however, by careful records and 

 adjustments over a period of years to approach the ideal closely 

 enough to avoid unwarranted waste of forage through nonuse and 

 certainly to avoid the serious overstocking common in the past. Im- 

 provement in grade of stock and comparatively higher prices for 

 better stock in thrifty condition will aid in approaching the ideal 

 by making it profitable to insure proper care of the stock through 



