48 
Research Bulletin No. 5 
after sampling on the 28th of August, one portion of the tract 
was covered with several inches of hay. A second portion was 
not mulched until the surface became dry enough to work, when 
it was stirred to a depth of about one and one-half inches with a 
hoe. The third portion was left untreated. After putting on 
the hay, no further attention was given this mulch. The plat 
where the soil was stirred to retain a mulch was kept free of 
weeds and the surface stirred occasionally. The portion not 
worked at all soon became weedy. Tho only a few weeks of grow- 
ing season remained, a considerable growth of redroot, foxtail, 
and other grasses was produced. Just how much of the water 
lost from the plat not mulched was used by the weeds cannot be 
stated. Judging from the amount of growth, the major por- 
tion of the loss must have been from this cause. 
The table shows an average difference in the amount of water 
held until the close of the experiment of a little more than one 
per cent in favor of the hay mulch over the soil mulch, showing 
that a mulch of straw or hay is more effective in reducing surface 
evaporation than one made by stirring the soil. 
Table 19. — Effect of mulching on soil moisture, 1911. 
PER CENT MOISTURE IN THE SOIL. 
Depth 
July 31 
August 11 
Gain 
-a 
Feet 
- 
1 
9.9 
15.8 
5.9 
H 
2 
7.1 
6.9 
3 
7.2 
7.2 
1 
10.8 
15.3 
4.5 
&i 
2 
7.8 
13.5 
5.7 
3 
7.9 
7.8 
In Table 19- are given the data obtained from two samplings 
on adjacent plats of ground, one of which was covered with hay 
as a mulch and the other left bare. During the interval between 
the two samplings a total of 1.65 inches of rain fell. The plat 
left not covered retained from this about .9 inch or 55 per cent 
of the total rain, all of which was retained in the first foot of soil. 
The plat covered with a hay mulch retained 1.57 inches or 95 per 
cent of the total rainfall. More than one-half of the amount held 
penetrated into the second foot. The hay mulch would reduce 
the loss from evaporation to a minimum while the exposed sur- 
