RANGE AND CATTLE MANAGEMENT DURING DROUGHT. 33 



Plate III, illustrate the successive stages of the effects of over- 

 grazing. 



FORAGE PRODUCTION CONCLUSIONS. 



Conclusions from the forage-production data obtained thus far 

 may have to be changed when data from observations through an- 

 other drought period are available. These tentative conclusions 

 point the way, however, toward certain essentials in determining 

 the grazing capacity of the range and are a basis for adjusting graz- 

 ing management and use preparatory to the next drought. The 

 main points indicated by the study so far are : 



(1) Grama-grass range similar to that on the Jornada Range Re- 

 serve begins to die out the second year of drought, and when a 

 drought lasts three years the stand of forage on ungrazed range may 

 be reduced as much as 40 per cent. The volume of forage produced 

 per unit of area is further reduced by decreased height growth and 

 foliage production during dry years. The vigor of the grass is 

 affected to such an extent that at least one good year following 

 drought is necessary before the range will begin to improve in 

 density. In the case of tobosa-grass range there is less dying out of 

 the grass, amounting to only 30 per cent in the third year of drought, 

 but the volume of forage produced per unit of area is affected more 

 directly by the amount of moisture received. The actual reduction 

 in the amount of forage produced at the worst of the drought, tak- 

 ing into consideration both reduction in density and reduction in 

 foliage production is about 50 per cent of the amount produced in 

 good years on both grama-grass and tobosa-grass range. 



(2) The depreciation of graipa-grass range is greater as over- 

 grazing increases and especially under too heavy grazing during the 

 main growing months — July, August, and September. If grazing on 

 it is reduced approximately one-half the year-long rate during July, 

 August, and September, and if it is not too heavy the rest of the 

 year, grazed range may be maintained in about the same condition as 

 ungrazed and run-down range may improve to approximately the 

 same condition. Apparently tobosa-grass range may be grazed heav- 

 ily during the growing season, whether or not there is drought, with- 

 out affecting it materially. 



(3) Overgrazing a range results in a decrease in the best forage 

 species on the range and their replacement by plant species of less 

 forage value. 



(4) In time of drought so great a reduction as 50 per cent of the 

 volume of forage produced in more nearly average years may be ex- 

 pected and should be prepared for. Grazing should be reduced on 

 grama-grass range during the main growing season, July, August, 



74514°— 22— Bull. 1031 3 



