EFFECTS OF DIFFERENT SYSTEMS OF GRAZTNG. 3 



but also to determine the effect of grazing upon individual species. 

 One of the first facts observed in studying the grazing of cattle is 

 that they will eat readily some species of plants and will avoid cer- 

 tain other species. This preference of cattle for some plants may 

 largely influence the determination of the best system of grazing. 

 The species that are avoided may be able to increase to the detriment 

 of those readily grazed unless the system of grazing is designed to 

 prevent such an occurrence. 



This bulletin is devoted to a study of the influence of different 

 systems and intensities of grazing upon the various species of plants 

 that make up the native vegetation near Mandan, X. Dak. This 

 phase of the experiment, however, represents only part of the results 

 obtained. The effects of different systems and intensities of graz- 

 ing upon the gains of the cattle would afford material for a study 

 as detailed as the present one. In order to afford a clear under- 

 standing of the present study it will only be necessary to summarize, 

 the cattle gains, however, since these are directly influenced by the 

 quantity of native forage available for grazing. 



E. C. Chilcott, 

 Agriculturist in Charge. 



PLAN OF THE GRAZING EXPERIMENT. 



The arrangement of the pastures used for the grazing experiment 

 near Mandan. X. Dak., is shown in Figure 1. Four pastures are oper- 

 ated under a system of continuous grazing. These are 100, 70, 50, 

 and 30 acres in size and are grazed at the rate of one steer to 10, 7, 5, 

 and 3 acres, respectively. In order to obtain different intensi- 

 ties of grazing a variation was made in the size of the pastures rather 

 than in the number of cattle carried per pasture. This is as far as 

 the plans for the experiment had been developed when it was started 

 in 1915. It was aimed to have one pasture so large that it would be 

 undergrazed and one so small that it would be overgrazed. During 

 1915 the 250 acres comprising the four pastures were fenced, and the 

 area was grazed with fifty-three 2-year-old steers for approximately 

 115 days. The cross fences which separate the various pastures 

 were constructed during the fall of 1915, and the grazing of the pas- 

 tures, according to the outlined plan, started in the spring of 1916. 

 The grazing in 1915 was preliminary to the experiment, which, at 

 the time of preparing this bulletin, had been conducted on the four 

 pastures that are grazed under the continuous system, for the six 

 seasons from 1916 to 1921, inclusive. 



The pasture designated as the " reserve " is used to carry the cattle 

 before the experiment opens in the spring and after it closes in the 

 fall. It is also used to carry four or five extra steers during the 

 grazing season. These are held in reserve for use in case of accident 

 to any of those in the regular pastures. During two or three differ- 

 ent seasons it has been necessary to make use of one or more of the 

 reserves, which made it possible to complete the season on a given 

 pasture with the regular number of cattle. The cattle from the small 

 pastures are removed to the reserve when their supply of forage has 

 become exhausted. 



TThile the original four pastures would furnish reliable informa- 

 tion regarding the number of acres required per head for a con- 



