UNITED STATES DEPARTMENT OF AGRICULTURE 



BULLETIN No. 367 i 



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Contribution from the Bureau of Plant Industry 

 WM. A. TAYLOR. Chief 



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Washington, D. C. 



PROFESSIONAL PAPER 



June 23, 1916 



CARRYING CAPACITY OF GRAZING RANGES IN 

 SOUTHERN ARIZONA. 



By E. O. WooTo^j, Agriculturist, Office of Farm Management. 



CONTENTS. 



Page. 



Introduction 1 



Climatic conditions 6 



Character and distribution of forage 9 



Nature and rate of the recovery 16 



Carrying capacity 18 



The most important factor governing possible 



improvement of the range 22 



Page 



Hay-cutting operations 23 



Grazing experiments 28 



Miscellaneous notes 33 



Future investigations 36 



Summary and conclusions 36 



List of publications relating to this subject. . 40 



INTRODUCTION, 



This bulletin presents tlie results of several years' experimentation 

 and measurements leading- to the determination of the carrying 

 capacity of certain kinds of stock ranges in southern Arizona. The 

 climatic and soil conditions under which the experiments have been 

 carried on are those of the lower foothills and the sloping belt of 

 grassland 8 or 10 miles wide which surround all the mountains of 

 that region. The altitudinal variations are between 2,800 and 5,500 

 feet. All the area studied has been under control and observation 

 for 11 3^ears. Forty-nine sections which were badly run down by 

 overstocking at the beginning of the study have been under a condi- 

 tion of complete rest from stock. Approximately^ nine additional 

 sections (the most productive part of the area) have been grazed 

 according to the judgment of four men who are acquainted with the 

 region. Three of these men have been in the business of raising 

 cattle; the fourth has had a few head of horses and burros in his 

 pastures. The policy of each of the cattle raisers has been to stock 

 his area as heavily as it would bear, allowing a small margin for 

 slow improvement. The nicet}^ of adjustment of the various factors 

 involved in such a plan has depended upon each man's judgment 

 of what was the best thing to do under all circumstances. By this 

 arrangement the pastured area inside the fence has been subjected 



28465°— Bull. 367—16 1 



