EFFECTIVENESS OF MULCHES IN PRESERVING SOIL 
MOISTURE 1 
By F. S. Harris , 2 formerly Director and Agronomist, and H. H. Yao, Fellow in Agron¬ 
omy, Utah Agricultural Experiment Station 
INTRODUCTION 
The effective preservation of soil moisture is one of the vital problems 
which confront the dry farmer and the scientist. Any cultural method 
that has the power of conserving moisture in the soil is a great asset 
toward solving the dry-farming problem. But the question of the effec¬ 
tiveness of mulches has been much disputed. While in a majority of 
cases scientists have reported favorable results with the application of 
mulches, under different conditions the same mulches have not answered 
the purpose. Indeed, the literature pertaining to this subject presents 
such varied opinions that it inaugurates complexity into the significance 
of mulching. The need of a more thorough study of the problem led 
to the work reported in this paper. Literature on this subject is much 
scattered, and no attempt has been taken to include all in this article. 
Only those statements that are closely related to the subject matter have 
been briefly summarized. The results of the following experiments 
are tabulated from averages of thousands of measurements. 
HISTORICAL REVIEW 
OBJECT OF MULCHING 
The object of mulching is to preserve a uniform degree of moisture 
(j6) 3 and to hold more water in the soil, the effectiveness of which is 
brought about by diminishing the direct influence of the agencies of 
evaporation and by retarding the capillary rise of water to the surface 
(22, 48 ). 
EFFECTIVENESS OF MULCHING 
The pioneer on mulch work was Wilhelm ( 46 , 47), who observed that 
soils shaded by growing plants contain the least moisture, others covered 
with stones and other lifeless objects contain most, while bare soils 
stand intermediate. This has been confirmed by later workers such as 
King (20, p . J05), who stated that mulched soils contained more moisture 
to the depth of 3 feet than rolled soils, Wollny (48, p. 854-859) and 
Harris and Turpin (14), who found that the effect of mulches was notice¬ 
able several feet below the surface of the ground but that the surface 
foot showed the greatest benefit. Field investigations by Kedzie (16) 
indicate that to a depth of 16 inches cultivated plots had 3 per cent 
more moisture than naked fallow. 
1 Accepted for publication Oct. 19, 1921. 
2 Dr. F. S. Harris resigned from the directorship on Sept. 1, 1921. 
3 Reference is made by number (italic) to “Literature cited,” p. 740-742. 
Vol. XXIII, jsro.| 9 
Mar. 3, 1923H _ 
Key No. Utah-15 
Journal of Agricultural Research, 
Washington, D. C. 
acf 
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