EFFECTS OF DIFFERENT SYSTEMS OF GRAZING. 43 



The experiment is conducted with four pastures under a system of 

 continuous grazing. These pastures vary in size from 100 to 30 

 acres. A pasture of 70 acres conducted under a system of deferred 

 and rotation grazing was added in 1918. 



The land used for the experiment is not materially different than 

 other vast areas in western North Dakota. This land, however, is 

 better than would ordinarily be used for grazing. It is well adapted 

 for experimental purposes because of its uniformity. 



Early seasonal precipitation exerts a greater influence upon the 

 production of native forage than upon other crops. 



The deferred and rotation system of grazing is designed to allow 

 different divisions of the pasture to mature a crop normally before 

 it is grazed. Under this arrangement a greater utilization of the 

 vegetation is obtained with less injury to it than in any other pasture, 

 and with the greatest total gain. 



The grazing season for this experiment is five months during the 

 summer. Winter grazing is not taken into consideration and is not 

 recommended for this section except under very unusual conditions. 



The cattle used in the experiment are 2-year-old grade steers. 

 They are weighed individually at 30-day intervals throughout the 

 season. 



The cattle have made average gains per head ranging from 294 

 pounds in the 70-acre pasture to 180 pounds in the 30-acre pasture. 

 A high gain per head does not produce the largest gain per acre. 

 A gain per head higher than the small pastures but lower than the 

 large pastures is produced on the deferred and rotation pasture. 

 The total gain per acre in the rotation pasture has been higher than 

 in any of the others since the number of cattle has been increased. 



The quantity of the foliage cover annually removed by grazing 

 varies on the average from 51 per cent in the 100-acre pasture to 

 98 per cent in the 30-acre pasture. In order to avoid injury to the 

 vegetation under a system of continuous grazing, from 15 to 25 per 

 cent of the foliage cover must remain on the pasture at the close 

 of the grazing season. A greater utilization of it may be made under 

 the system of deferred and rotation grazing. 



The most efficient system of grazing is one that will insure sufficient 

 forage during the entire season to produce the greatest total gain 

 in weight with the least number of cattle on the minimum unit of 

 land without permanent injury to the native vegetation. The re- 

 quirements of this measure of grazing efficiency are most nearly ful- 

 filled by the deferred and rotation system of grazing. 



Botanical studies in connection with the grazing experiment are 

 necessary in order to determine the effect of different systems and 

 intensities of grazing upon the native vegetation. 



The vegetation has a total basal cover of approximately 60 per 

 cent. Of the basal cover 20 per cent is made up of Bouteloua gracilis, 

 10 per cent of Stipa comata, and 30 per cent of other vegetation. 



The dominant species are Bouteloua gracilis, Stipa comata, Carex 

 filifolia, and C. heliophila. • 



As the vegetation is the " climax " type, having the highest de- 

 velopment, the grazing should be so adjusted as to maintain it with- 

 out deterioration. 



The mapped quadrats used in these experiments are of 

 value in securing a permanent record of the composition of the 



