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Journal of Agricultural Research 
Vol. XXIII, No. 9 
MULCH MATERIALS 
Any lifeless object can be used for mulching (46; 47; 48 , p. 854-859). 
Warington (42) has said that the evaporation from the soil may be con¬ 
siderably diminished by protective coverings, such as stones, earth 
mulch, farmyard manure, straw, dead leaves, or coconut fiber. Clover 
hay (17) , straw (8), hay (jo), seaweed (33), shingle edgings (13, p. 24-26) 
sawdust (13, p. 24-26) and grass {17134, p. 91-93; 39; 41) had been used 
for experimental purposes with favorable results on the yield of crops. 
It was reported by Shimm (39) that barnyard manure was more effective 
than straw or fresh manure, in that it held more moisture and secured a 
more uniform moisture content in the soil to the depth of 4 feet. Halsted 
(jo) used fresh hay, salt hay, and excelsior for mulching, but he failed to 
find any appreciable difference in the yield of peppers, egg plants, cu¬ 
cumbers, tomatoes, beets, or beans. Munson ( 32) concluded that shingle 
edgings were excellent for mulching either apple trees or strawberries, 
but that a fine dust cover could not be excelled for gooseberries. Harris 
and Turpin ( 14 ) found straw mulch to be better than 2-inch cultivation. 
depth op mulching 
Laboratory experiments on the evaporation of moisture from the soil 
under the mulches proved that the effectiveness increases with the depth 
(9, 24). Under the field conditions the same does not follow the general 
rule. Sanborn (35) and Cardon (6) recommended shallow cultivation in 
preference to deep cultivation. King (21) found the soil below a 3-inch 
cultivation to be more moist than that below 1.5-inch cultivation, 
although the third and fourth feet showed reversed results, which are 
confirmed by Chilcott and Holm (7). Shinn (39) reported a 3-inch 
barnyard manure mulch to be more effective than a 5-inch earth mulch, 
6-inch straw mulch, or 3-inch fresh manure mulch. Investigations by 
King (24) showed that shallower depths of stirring are to be preferred to 
the deeper for long-interval cultivations. That a deep mulch main¬ 
tained during a season of small rainfalls may waste more water than is 
saved on account of the fact that small rainfalls are wholly retained in 
the upper layers of the mulch and lost directly and completely to the 
air, whereas if the mulch has been thin enough to wet through, capil¬ 
larity would draw a portion of the water downward into the undistubed 
soil to render effective service when conserved by subsequent cultivation. 
The work of Burr (5, p. 53-84) showed straw mulches, deep cultivation, 
and shallow cultivation to rank in effectiveness in the order named. 
' EVAPORATION OP MOISTURE PROM DIPPERENT SOIL CLASSES 
As the soil particles diminish in size there is a large increase in the 
quantity of moisture brought to the surface (15). This is merely due to 
the surface distribution of water. Meister (30) has pointed out that the 
amount of water retained by soils depends upon the coarseness or fineness 
of the particles; the less the internal surface of the mass, the smaller will 
be the proportion of water retained. When fully saturated with water, 
sandy soils contain 30.4 per cent of water; clay, 38.5; chalk soil, 39.2; 
loam, 45.4; and garden earth, 76.8. King (18 , p. 197; 19 , p. 152 ), Lough- 
ridge and Hilgard (26, p. 80-91), and Lawes and Gilbert (25, p. no) 
have obtained somewhat similar results. 
