CHOPS UNDER FALL IRRIGATION AT SCOTTSBLUFF. 3 



in these experiments were grown. The total precipitation from Octo- 

 ber 1, 1910, to April 1, 1911, amounted to 1.19 inches. From Octo- 

 ber 1, 1911, to April 1, 1912, the total precipitation was 3.59 inches, 

 and from October 1, 1912, to April 1, 1913, it was 2.13 inches. The 

 average total rainfall for this 6-months period during the three 

 years was 2.3 inches, or a little less than 16 per cent of the average 

 total annual rainfall during 1911, 1912, and 1913. 



The above facts substantiate the statement previously made in 

 connection with the low precipitation of the fall and winter months. 

 Since much of this precipitation comes as small showers or as light 

 snowfalls, a large proportion of the moisture is lost by evaporation 

 from the surface soil, so that during the months from October to 

 March, inclusive, comparatively little moisture is added to the soil 

 by precipitation. This being true, soil which has given up the 

 greater part of its available moisture to a field crop remains compar- 

 atively dry during the following winter. 



The precipitation which came during the growing season of 1911, 

 1912, and 1913 could not be expected to influence greatly the results 

 obtained with fall irrigation, since it fell on all the plats in the experi- 

 ment and since irrigation water was applied uniformly to all the plats 

 during the growing season. The chief point to be considered in con- 

 nection with ihe 4 rainfall as it affected the results of these experi- 

 ments is that the fall and winter period was comparatively dry, the 

 precipitation being insufficient to increase materially the quantity of 

 moisture in the soil, particularly at depths of a foot or two below the 



surface. 



METHODS OF EXPERIMENT. 



Of the land used for these experiments one half was irrigated in 

 the fall each year, and the other half was not so irrigated. In the 

 fall irrigation, water was applied copiously to the soil, so as to sat- 

 urate the latter to as great a depth as possible. This water was 

 applied late in September or early in October each year, usually 

 between September 15 and 30. In the fall of 1910 the land to be 

 fall irrigated was plowed before irrigation, but it was found that 

 this method necessitated considerable extra labor. In order to irri- 

 gate after plowing, the land had to be leveled, and after irrigation 

 it was necessary to harrow the land in order to check evaporation. 

 If irrigation water were applied before plowing, the leveling could 

 be dispensed with. For this reason, in the fall of 1911 and again in 

 the fall of 1912 the land was irrigated before plowing. 



In the spring of each year crops were planted on the fall-irrigated 

 land, and the same crops were planted on adjacent land not so irri- 

 gated. The spring and summer treatment of the land and crops 

 was identical in both cases. Each crop was planted on the same 

 date on both the fall-irrigated land and the land not so irrigated, 



