Dec. 4,1916 
Evaporation of Moisture from the Soil 
443 
Using enough water to cover the surface with 3.14 inches, this author 
(5) found that no mulch gave a 0.72-inch loss; a 4-inch mulch, 0.21 
inch; an 8-inch mulch, 0.1 inch; and a 10-inch mulch, 0.03 inch in 14 
days—that is, the various mulches saved in 14 days 16.24, 19.75, and 
21.97 per cent of the amount applied. # 
The advantage of deep furrows as a saving in furrow irrigation is 
brought out by Fortier (5). When the same quantities of water were 
applied to tanks in furrows 3, 6, 9, and 12 inches deep, he found that the 
losses at the end of 10 days were 25, 18, 10.2, and 6 per cent of the 
total water applied. The loss was most rapid for the first 2 days, and at 
the end of 5 days 77 per cent of the total loss for 10 days had occurred. 
Widtsoe’s (19) work shows that in the two treatments, sand contain¬ 
ing 15 per cent, sandy loam containing 20 per cent, and Sanpete clay 
containing 25 per cent moisture, the average loss from the soil receiving 
surface irrigation was more than three times as great in the same length 
of time as that from a subirrigated soil. Fortier (5) shows that soil 
subirrigated 2 feet underground by pipes lost only 25 per cent as much 
water in 20 days as when irrigated by surface flooding. 
According to Stigell (17), bacterial growth retards evaporation. He 
says that this is attributed to utilization of moisture by the organisms 
in their metabolic products, and reduction of the porosity of the medium 
by the metabolic products of the organisms. Hoffman's (8) work shows 
that after the bacteria in various culture media were added to the soil, 
evaporation was increased except in the case of manure. In drawing 
his conclusions he leads one to believe that if the experiment is of long 
duration the results may be reversed, due to the accumulation of carbon 
dioxid from the organism being taken up by the soil moisture, thereby 
increasing the surface tension of the water. Gelatin was found to retard 
evaporation and for that reason could not be used as a culture media. 
EXPERIMENTAL WORK 
INITIAL QUANTITY OF SOIL MOISTURE 
To find, if possible, the specific influence of varying percentages of water 
in soils, a series of experiments was conducted at the Utah Agricultural 
Experiment Station in the years 1912 to 1916, inclusive. The pre¬ 
liminary tests show that evaporation losses increased rapidly with the 
increased wetness of the soil, or with the initial quantity. The latter 
studies were so arranged as to locate as many points of variation in the 
losses as possible. 
Preliminary Study 
Late in June, 1913, a study of the effect of initial quantity of moisture 
in the soil was begun. One hundred gm. of dry Greenville loam were 
put in small, weighed tin plates about 5 inches in diameter, and puddled 
