30 BULLETIISr 1031, U. S. DEPAETMEXT OF AGRICULTURE. 



grazing and difference in soil could hardly account for more than 

 a small amount of the difference in depletion had the area not been 

 grazed, or had grazing been greatly reduced during July, August, 

 and September. The low point of the pasture 2 curve in 1918 and 

 1919 as compared with the curve for similar range protected from 

 grazing would indicate that the lack of available moisture for the 

 existing stand of vegetation was not a prime factor in depreciation 

 had the area not been heavily grazed during the growing season. 

 This view seems warranted from the further facts brought out in the 

 study of changes in the outside range when given protection during 

 the growing seasons of 1918 and 1919, and because pasture 2 itself 

 showed marked improvement under light grazing during the grow- 

 ing seasons of 1913 to 1915, inclusive. 



Table 9 and figure 7 show that the stand of good grass forage in 

 pasture 5 continued to increase up to 1918, when it reached its maxi- 

 mum for the period, but dropped 25.2 per cent in 1919 and showed 

 practically the same amount of forage per unit of area as the pro- 

 tected areas at that time. Although these results differ from those 

 on other areas under study, they appear warranted when all facts 

 are considered. Soil conditions are slightly more favorable in this 

 pasture than for the average grama -grass type, and the area received 

 a few more light showers and slightly greater total rainfall than the 

 average for the type in 1916 and 1918. In addition, the poor condi- 

 tion of the pasture in 1915 made available much opportunity for 

 improvement. These advantages, combined with reduction in graz- 

 ing during the main growing season, especially the latter, are thought 

 to account for the steady increase up to 1918. Plate II compares the 

 results of heavy j^earlong grazing with reduction of grazing during 

 the growing season. 



The drop in condition in 1919 is partly explained by the average 

 overgrazing during 1918, but was probably due more to the fact that 

 the density of the vegetation had reached a point where it was greater 

 than the available moisture would support and, consequently many 

 of the young plants died late in 1918 and early in 1919 before the 

 rainy season began. The study shows that the stand of good forage 

 grass in pasture 5 at all times during the period was less than on the 

 range totally protected against grazing. It is apparent, therefore, 

 that except for the effect of grazing the pasture would support the 

 increase in vegetation shown. The drop from 1918 to 1919 is consist- 

 ent with the depletion on the area under protection and indicated 

 that both of these areas had deteriorated to about the maximum 

 stand that available moisture of 1918 would support. The lack of 

 improvement in 1919, which was a wet year, on these two areas indi- 

 cated further that abundant moisture alone is not sufficient for 

 improvement after drought; at least one good year following drought 



