32 RANGE INVESTIGATIONS IN ARIZONA. 



the annual grasses Bouteloua aristidoides and Aristida americana^ 

 which without doubt produce as many pounds of growth upon the 

 inclosure as all other grasses combined. It is ver}' doubtful if these 

 are eaten except under enforced conditions after the seed begins to 

 ripen. Their period of usefulness as stock feed is therefore ver}^ 

 short. Fifty per cent more should be deducted from the total avail- 

 able for stock feed for plants of this kind which are of little or no 

 value when dr}- and therefore are not capable of complete consump- 

 tion. The two species of lotus enumerated in the record of plot 

 measurements and Pectocarya are from their habits of growth not 

 grazed to any extent, by cattle especially, until they begin to fruit, 

 on account of their lying flat on the ground until this time. Their 

 period of usefulness is therefore very short. When this deduction is 

 made, and it is believed that all of these deductions are conservative, 

 we have left 176 pounds of dry feed per acre to be utilized under 

 necessarily wasteful pasture practices, where green feed is present for 

 about five months, and the season of grass production in July to Sep- 

 tember is often closely followed by a few light showers of rain, which 

 greatly decrease the value of the cured forage. This remainder of 176 

 pounds is increased somewhat l)y the Ijrowse plants, which have not 

 entered into our calculation. 



If we consider 18 pounds per day of well-cured hay sufficient for the 

 maintenance of a mature idle animal without adding anything to its 

 Aveight, it will require 37 acres to support such an animal one year. 

 This calculation considers the native feed equivalent to well-cured hay 

 and allows nothing for increase in weight. Neither does it allow any- 

 thing for labor performed bj^ the animal in gathering its food and walk- 

 ino-a distance of 5 to 10 miles for water. When additional allowances 

 are made for these factors, the number of acres required to pasture one 

 animal is very materially increased and approaches very closely the 

 50-acre estimate given upon a previous page. 



CARRYING CAPACITY. 



Before any rational adjustment for the proper control of public 

 grazing lands to meet the evident pressing demands for a change in 

 this direction can be made, nuich should be definitely known regard- 

 ing the amount of stock that these lands will carry profitably year 

 after year. This must form the basis of all equitable allotments. To 

 secure such information is a most diflicult task in a region where the 

 seasons, the altitude, the slope, and the rainfall are so variable. It 

 can be determined very easily in the Great Plains region, where con- 

 ditions are uniform and reasonably constant, and indeed it is very 

 definitely known there; but here the case is very dift'erent. There is 

 in the Territory comparatively little native pasture land under fence, 

 and that- which is fenced is usually the better land, representing a 



