80 BULLETIN" 1031, U. S. DEPARTMENT OF AGEICULTUEE. 



industry in the Southwest at present, and one of the bigo>est problems 

 of the industry to-day is to overcome these unfavorable conditions. 

 Eainfall records over a long period of years and experience of stock- 

 men during the past two or three decades indicate that droughts of 

 3 to 4 years' duration may occur in each cycle of 8 to 10 years. 



A study made in southern New Mexico, showed that on grama- 

 grass range drought alone if prolonged beyond the second year killed 

 40 per cent of the best grazing plants and reduced the quantity of for- 

 age produced approximately 50 per cent. Grazing tends to increase 

 the effect of drought to a degree varying with the time and amount 

 of use, but when limited during the main growing season — July, 

 August, and September — to from 30 to 50 per cent of the proper 

 yearly rate, it has no harmful effect. The reduction in grazing at 

 that time does not interfere with full us© of the range, since the 

 grass cures and is valuable for winter range. To restore damaged 

 grama-grass range to its former condition of productivity will prob- 

 ably require several years of judicious handling. 



In the case of tobosa grass or similar range there is less dying out 

 of the forage but the amount of feed produced varies more directly 

 with the amount of rainfall, so that the reduction in time of drought 

 is about the same as for grama grass. Tobosa grass is not easily 

 injured by grazing during the growing season and is of little value 

 for grazing after it dries up, so that it is well adapted to summer 

 grazing. 



Drought has a direct influence upon the carrying capacity of the 

 range. Data obtained thus far indicate that range with a grazing 

 capacity of 27 acres per cow per year will only carry stock at the 

 rate of 32 acres per head the first year of drought, 45 acres the sec- 

 ond, 54 acres the third, and 54 the fourth. 



Cattle raising, to be successful under such conditions, must be 

 adjusted so that the number of animals will conform to the carrying 

 capacity of the range in time of drought. In other words, there 

 should be a reduction to 85 per cent of the original number the first 

 year, to 60 per cent the second, and to 50 per cent the third. 



Since the Southwest is primarily a breeding section, and it is diffi- 

 cult to dispose of breeding cows upon short notice, the breeding herd 

 should be confined to what the range will carry in poor years or to 

 50 per cent of the carrying capacity during good years. The surplus 

 forage in good years may be utilized profitabl}^ by holding over or 

 buying young steers or heifers to be disposed of in time of drought 

 to make all range available for the breeding cows. The age, number, 

 and class of such stock to carry will depend upon the forage not 

 needed for the breeding cows and the market. 



Division of grama-grass and tobosa-grass types of range, when the 

 two occur together on a range unit, and using the former in winter 



