30 CIRCULAR 870, U. S. DEPARTMENT OF AGRICULTURE 



years when there was a vigorous growth of soft chess with large seed 

 heads; but when yield of soft chess was low, the number of animals that 

 could be carried on dry forage was also limited by total grass production. 

 A third example is afforded by broadleaf filaree. This plant, which is 

 more dependable as a source of green forage early in the spring than any 

 of the other species, usually produced about 25 percent or more of the 

 total herbage at plant maturity. But its yield was low in 1938 because 

 of late fall rains in 1937, followed by prolonged cold rains; it composed 

 only 9 percent of the total herbage production. However, the shortage 

 of filaree in late spring was more than offset by high production of other 

 species. 



Thus it is evident that nutritive value of the forage is affected each 

 year by fluctuations in clovers, soft chess, and other valuable forage 

 species, but grazing capacity is affected mainly by variations in total 

 herbage production and total grass production. Both the kinds of land 

 on the range and the annual precipitation need to be considered in ad- 

 justing ranch stocking to meet these variations. 



SELECTING THE MOST EFFICIENT DEGREE OF 

 GRAZING 



To insure both high livestock production and good forage cover, the 

 ranch operator needs to select the degree of grazing that will give the 

 most efficient utilization of the forage over a period of years. Results 

 of the grazing-intensity experiment will aid in this selection by showing 

 how different degrees of grazing affect both cattle and herbage production. 



The experiment was planned to determine how closely annual plants 

 can be grazed without adversely affecting either forage growth or cattle 

 production. The stocking dates for each year were: 



Year: Entry date Removal date 



1936 -_ January 10 August 4 



1937 January 2 August 10 



1938 February 25 September 2 



1939 January 25 August 1 



1940 February 8 August 4 



1941 February 1 August 13 



1942 January 20 August 6 



1943 February 12 July 30 



1944 March 7 July 20 



1945 January 16 August 8 



1946 January 9 July 14 



1947 February 5 July 1 



Average January 29 August 1 



The grazing season in the experimental pastures covered the period of 

 best forage on foothill range and included only a limited period of forage 

 shortage in the most closely grazed pastures. Grazing started in the 

 winter when the plants were still growing slowly and continued through 

 the spring when the plants were growing rapidly. Since cattle could 

 not keep up with the rapid spring growth, there was adequate seed pro- 

 duction of the important forage species — at least on most sites. The 

 vegetation was not grazed to the final degree of utilization until after 

 the plants were mature and dry. Effects on vegetation of the different 

 degrees of grazing obtained should be representative of those which 

 would occur under the usual seasons of grazing. 



