460 Journal of Agricultural Research voi. vn. No.» 
SUMMARY 
(1) The conservation of soil moisture is one of the most important 
problems of agriculture, particularly in arid regions. 
(2) One of the important factors involved in water conservation is 
evaporation. 
(3) Jn this paper a study has been made of a number of the factors 
having to do with evaporation. 
(4) Evaporation of moisture increases with the initial quantity in the 
soil. The increase is not so great with the higher percentages as with 
the lower,’ and there seems to be a number of critical points where the 
rate of loss changes rapidly. 
(5) The rate of evaporation from a moist soil is very rapidly decreased 
as the humidity of the air is increased. 
(6) Air currents greatly increase evaporation; but after about a certain 
wind velocity is reached, the rate of evaporation is only slightly increased 
by increasing the wind velocity. 
(7) For the sizes investigated, evaporation was higher from the finer 
soil particles than from the coarser when both are completely saturated. 
(8) Reducing the intensity of sunshine greatly reduces the rate of 
evaporation. 
(9) Slight changes in temperature have a marked effect on evaporation. 
(10) A thin mulch, if kept dry, is effective in reducing evaporation. 
Dry mulches, composed of fine particles, seem to be less effective than 
if composed of coarser particles. 
(11) Compacting the surface of the soil increases evaporation. 
(12) Dissolved salts in high concentrations reduce the evaporation of 
moisture from soils. 
LITERATURE CITED 
(1) Bowie, A. J., jr. 
1908. Practical Irrigation. .. 232 p., 53 fig. New York. 
(2) Buckingham, Edgar. 
1907. Studies on the movement of soil moisture. U. S. Dept. Agr. Bur. Soils 
Bui. 38, 61 p., 23 fig. 
(3) Cameron, F. K., and Galuagher, F. E. 
1908. Moisture content and physical condition of soils, U. S. Dept. Agr. Bur. 
Soils Bui. 50, 70 p., 33 fig. 
(4) Carpenter, L. G. 
1898. The loss of water from reservoirs by seepage and evaporation. Colo. Agr. 
Exp. Sta. Bui. 45 > 3 2 P*> 1 
(5) Fortier, Samuel. 
1907. Evaporation losses in irrigation and water requirements of crops. U. S. 
Dept. Agr. Office Exp. Stas. Bui. 177, 64 p. ( 19 fig. 
( 6 ) - 
1907. Evaporation losses in irrigation. In Engin. News, v. 58, no. 12, 
P- 304-307, 14 fig- 
( 7 ) 
1909. Soil mulches for checking evaporation. In U. S. Dept. Agr. Yearbook 
1908, p. 465-472, fig. 22-27. 
