730 
Journal of Agricultural Research 
Vol. XXIII, No. 9 
that the 4-year average moisture content was higher in the spring-plowed 
plots; but the first 2 feet of the fall-plowed plots contained a higher 
percentage of moisture. 
MULCH VERSUS NO MULCH 
In order to demonstrate the effectiveness of mulching in preserving 
moisture in the soil, an experiment was carried out by using sand im¬ 
mersed in water. The sand was of uniform physical structure, passed 
through a 100-mesh sieve. It was placed to the depth of 3 inches in 
a round can, 6 inches in diameter. The bottom was perforated, so that 
when the can was immersed in water, the soil could be completely satu¬ 
rated through its capillary system. The experiment consisted of free 
water surface, bare sand, and a i-inch straw mulch. Each set was per¬ 
formed in triplicate to eliminate experimental error. The experiment 
extended from April 5 to May 7, and during these 33 days the loss of 
moisture is recorded in Table I. 
Taking the moisture lost from the bare sand as 1,000 per cent, then 
that which is lost from the soil under the i-inch straw mulch amounts 
to 40 per cent. In fact, between the free water surface and bare sand 
there is only a difference of 8 per cent in favor of the latter. Thus it is 
to be concluded from this experiment that a i-inch straw mulch, other¬ 
wise under identical conditions, is capable of preserving 60 per cent 
more moisture in the soil than without mulching. 
Table I .—Loss of moisture during the 33-day test 
Can No. 
Free water 
surface. 
Bare sand. 
Straw 
mulch. 
Cc. 
1 , 425-3 
h 323 - 7 
I, 404. 2 
Cc. 
I, 160. 5 
I, 144-3 
I, 102 
Cc. 
480. 4 
439-7 
437-9 
Average loss.. 
i, 384. 4 
1. 13 S- 6 
45 2 * 7 
EFFECTIVENESS OF DIFFERENT MULCH MATERIALS 
With the effectiveness of mulching ascertained, the question of the 
relative effectiveness of mulch materials naturally arises. Almost any 
lifeless material can be used for mulching, but the relative effectiveness 
of the different mulch materials varies according to their physical and 
chemical properties. For the purpose of comparison, five kinds of mulch 
materials were used—fresh manure, wood shavings, grass, hay, and straw— 
all maintained uniformly at the depth of 1 inch. 
It is seen from Table II that so far as the conservation of moisture is 
concerned, straw is by far the most effective, and then come hay, grass, 
wood shavings, and manure, in the order of their effectiveness. The 
difference between the first and the last is 54.1 percent; hence the im¬ 
portance in choosing the proper type of mulch material. Such a pro¬ 
found difference demands an elucidation. It was observed that the 
straw was the most loose and open, whereas the manure mulch formed 
a uniform and compact covering. When the experiment was over, 
the mulches were removed and ' their moisture content determined 
(Table III). 
