16 



BULLETIN 1170, U. S. DEPARTMENT OF AGRICULTURE. 



cent of the vegetation has been removed by grazing. The gains 

 of the cattle per head have been between those of the steers on the 

 100-acre and the 70-acre pastures and the two small pastures. The 

 gains of the rotation steers during the past two years have been 

 produced on a basis between 4 and 5 acres per head. The quantity 

 of the vegetation remaining on a pasture at the close of the season 

 indirectly determines its grazing capacity under a system of con- 

 tinuous grazing. However, under a system of deferred and rotation 

 grazing the vegetation remaining on a pasture at the close of the 

 season has no bearing upon its grazing capacity but more nearly 

 determines the utilization of the forage. Under this system a larger 

 percentage of the vegetation can be removed annually without reduc- 

 ing the gains of the cattle to the lowest point and without the injury 

 to the vegetation attendant upon close continuous grazing. From 

 the above facts it is clear that a high percentage of foliage cover 

 removed means a lowered gain of the cattle. One reason why the 

 cattle in the rotation pasture are able to produce higher gains per 

 head on an acreage lower than the 50-acre pasture is because of the 

 advantage derived by the vegetation from the rest periods. Another 

 reason is that the cattle do not have to remain long at a time on a 

 division with a rapidly diminishing food supply. 



Table 3. — Estimated percentage of foliage cover annually removed from the 

 different experimental pastures by grazing. 





Cover removed from pastures (per cent). 



Year. 



100 acres. 



70 acres. 



50 acres. 



30 acres. 



Rotation 

 (70 acres). 



1916 



30 

 40 

 55 

 55 

 60 

 65 



50 

 65 

 75 



85 

 85 

 85 



70 

 90 



95 

 100 





1917 





1918 



100 100 



80 



1919 



100 100 ! 50 



1920 



100 1 95 90 



1921 



100 1 95 95 







Average 



51 



74 



79 



- 











1 Not all Artemisia frigida taken. 



It has been stated that " the maximum number of cattle that can 

 safely be carried on any square mile of territory is the number that 

 the land will support during a poor season." 11 



The above statement is literally true. From the results of the ex- 

 periment herein reported it might be more correct to say that " the 

 determining factor is the number of cattle that can be grazed during 

 an average season." During years of very severe drought, such as 

 sometimes occur on the Great Plains, no system of grazing can be 

 expected to furnish feed for the normal number of cattle. It would 

 not be advisable, though, to reduce the number of cattle in all seasons 

 to meet an isolated condition ; it is considered advisable, however, to 

 regulate the number of cattle to fit an average season rather than 

 to attempt to adjust the number to fit the varying seasons. Under such 

 an arrangement a season below normal will mean close grazing and 



11 Smith, Jared G. Forage conditions of the prairie region. In Yearbook, U. S. Dept. 

 Agr., 1895, pp. 309-324, figs. 70-74. 1896. 



