Dec. 4,19x6 
Evaporation of Moisture from the Soil 
457 
Compacting the surface caused a marked increase in the loss; packing 
the second 2-inch section also increased the loss, but only about half as 
much. Compacting below 4 inches affected evaporation little if any. 
method of applying water 
An important thing to know where irrigation's practiced is the effect 
on evaporation of applying water in different ways. Fortier (5) and 
Widtsoe (19) indicate that a great saving results from applying water in 
deep furrows or by subirrigation in which the water is added some distance 
below the surface. 
In the summer of 1912 a study with soils 12 inches deep was conducted. 
Cylindrical vessels 11 inches in diameter and 13 inches deep were filled 
to within an inch of the top with Greenville loam. An equivalent of 
10 kgm. of dry soil was 
used and made up with 
moisture ranging from 
5.4 to 35.4 per cent in 
5 per cent intervals. 
Weighings were made 
on three days weekly— 
usually Monday, 
Wednesday, and Fri¬ 
day. The losses were 
made up by adding 
water through spouts 
which entered the bot¬ 
tom of the cans and 
which .were kept closed 
except while water was 
being added. Thus, the water had to move through 12 inches of soil, 
rather compact and unstirred, and evaporated from a small surface. 
Parallel to this test and used as a companion were the large galvanized- 
iron pans already described under the initial-quantity study. Here the 
soil was only about 1 % inches deep. To these shallow tanks the water was 
applied at the surface. The two trials were parallel throughout. The 
same percentages of moisture were used, weighings were made at the 
same time, they were run the same period, and the same kind of soil 
was used. A comparison of the two sets of results may be interesting, 
as they show the effect of different methods of applying water. 
Table VII gives the comparative data. In this table it may be noted 
that the losses at low percentages were somewhat more rapid from the 
shallow tanks, but that the deeper cans tended to lose more at the higher 
percentages. These had no free water exposed on top, while the wetter 
soils in shallow pans did. As already pointed out, the wet soils often 
Fig. 15—Evaporation from distilled water and from sodium-chlorid 
solutions of different concentrations. 
