Mar. 3, 19*3 
Effectiveness of Mulches upon Soil Moisture 
73i 
Table II.— Loss of moisture during 33-day test 
Can No. 
Manure. 
Wood 
shavings. 
Grass. 
Hay. 
Straw. 
I... 
Cc. 
1,004.4 
980.7 
980.5 
Cc. 
825.0 
782. 6 
772.8 
Cc. 
679-5 
665. 2 
668.6 
Cc. 
674.1 
661. 1 
656.3 
Cc. 
480. 4 
439-7 
437-9 
2.. 
Average loss with manure as 100 per 
cent.. 
987 -S 
793-5 
670-4 
663.8 
452-7 
Table III .—Percentage of moisture content of mulches 
Manure. 
Shavings. 
Grass. 
Hay. 
Straw. 
144.7 
23.2 
22. 7 
20 
11. 8 
A comparison of Table III with the foregoing will show that there is 
a correlation between the moisture lost from the soil and the moisture 
contained in the mulches. The moisture content of the mulches varies 
from 144.7 per cent for the manure to 11.8 per cent for the straw, and 
the total moisture lost from the soil varies accordingly. That is to say, 
the more absorptive the mulch the more moisture is lost from the soil. 
Since the purpose of a mulch is to check the soil surface from exposure 
to the physical agencies of evaporation, the less absorptive the mulch 
the less water is brought up to the surface to be exposed and therefore 
the more moisture is held in the soil. Due to the large amount of colloid 
matter present in the manure, it is capable of absorbing water one and 
one-half times its own weight, while the dry straw absorbs only one- 
tenth of its weight. With different quantities of water distributed in 
approximately equal volumes of manure and straw, it stands to reason 
that there should be more exposed by the former than by the latter. 
The same principle can be applied to the intermediate mulches. 
However, the preceding tables do not show a reasonably close correla¬ 
tion between the moisture lost from the soil and the moisture content 
of the mulches, which tends to show that there must be some other factor 
or factors which exercise a certain degree of influence upon the effective¬ 
ness of the different mulch materials. That the effectiveness of mulch 
materials is materially influenced by their capillary system is proved 
conclusively by a similar set of mulches suspended iri wire gauze. The 
mulches, otherwise the same, were suspended about % inch above the soil 
surface, so that the direct capillary system between the soil and the 
mulches was severed. The results are shown in Table'IV. 
Table IV. —Loss of moisture through mulches in contact and mulches in suspension , 
illustrating the action of capillarity 
Shavings. 
Hay. 
Grass. 
Manure. 
Straw. 
Mulches in contact.......... . . 
Mulches in suspension. . 
Difference - - - - 
Percentage of loss due to absorption. 
Percentage of loss due to capillarity. 
Cc. 
793-5 
431- 5 
362. © 
53-6 
46.4 
Cc. 
663.8 
392.2 
. 271.6 
59- 1 
> 40.9 
Cc. 
670.4 
471- * 
* 99.2 
70-3 
29 . 7 
Cc. 
987-5 
785-a 
2Q2.3 
79- $ 
30. 5 
Cc. 
452-7 
387.8 
64.9 
83,7 
i(S. 3 
27184 — 23—-5 
