Year: 1878

Having tried some experiments some
years ago in reference to the effect upon
moisture of stirring the soil in hot, dry
time, will contribute them as bearing
upon this question MY attention was
first called to the philosophy of the appar-
ent relief of plants in drv time by the
frequent and thorough pulverization Of
the soil, in noting the effects of a mulch
OF sawdust upon newlv-set apple trees.
The writer was absent when the trees were
planted, and did not return till fifteen days
| after they were set, and finding the ground
very dry, and not bud opened. he was
alarmed at the prospect of losing them all
from long drought.


As an effort to save them, the trees were
mulched with hemlock sawdust, three
inches thick in a circle three and one-half
to four feet from the tree. When this
sawdust was placed about the trees the
ground was very dry at the top; but
twelve days after the mulch was applied,
the trees had all started into leaf, and on
examining the mulch the lower inch, as
well as the surface of the earth, was found
almost saturated with water; although,
when applied the sawdust was very dry,
as well as the surface of the ground, and
there had not been any rain in the mean
| time. Here, certainly, was an apparent
accumulation of moisture from the agency
of sawdust and how was it to be account
ed foro


The thought occurred to me that the
temperature might assist in solving the
question. And. on testing it with a ther-
mometer. placing the bulb on the earth
under the sawdust, the mercury went
down ten degrees that is, it marked ten
degrees lower than the atmosphere.
Thinking this very great difference. the
temperature was tested under the mulch
of ten different trees and found to range
from seven to ten degrees below the at
mosphere. The average was nearly eight
and half degrees. Did not the lower
temperature furnish a reasonable explain
alton of this accumulation of mosturep
1t is a well known fact that moist at
mosphere passing over a cooler surface
condenses its moisture ON that cool sur
face. A pitcher of ice-water set in the
sun, in warm day. will soon be covered
with moisture-even drops on the surface
and the atmosphere is never so dry but
what this will occur. Now the air con-
stantly circulating through this sawdust
was as constantly condensing it's moisture
in the sawdust and on the serface of the
|
furnished abundant water to the roots of
the trees, and the leaves had expanded
rapidly.


But, says one, this was only the moist
ure of the earth drawn up by the capilla-
ry attraction. Let us see if this theory be
tenahle. The experiments reported in
the Rural New Yorker appear to show
that a loose, pulverzed surface increases
the evaporation. which might be interpre-
ted that the placing OF sawdust on the sur
face would cause the evaporation from
the earth below to be more rapid-that is
that the moisture, if any, drawn up by ca
pillary attraction. would be passed off
more rapidly on account of the mulch, so
that if the surface of the earth were dry
when sawdust was placed upon it, the
mulch would not assist in retaining its
moisture coming to the surface. But as
there is a large amount of moisture under
and in the lower strata of the mulch, we
must conclude that this came mostly from
the atmosphere and but little from the
earth below. And this deposit of moisture
from the air must be very considerable.
since il would have to supply the extra
evaporation besides producing this accu-
mutation.


Having established this point of lower
temperature under the mulch. it became a
point OF interest to know whether loose
soil had lower temperature at the same
depth than a compact one, and which
differed the most from the temperature
of the atmosphere. During the same sea-
son US64) the writer compared the
temperature. by the thermometer, of a
loose. well worked garden soil, and earth
that had not been moved on the border
in the same garden He found the loose
earth, two inches below the surface, to
mark seven degrees below the compact
earth OF the border. and the earth of the
border was three degrees higher tempera-
ture than the air. and the loose soil four
degrees below the air. 1t is proper to say
the soil was clay loan. Tests were
made in several fields. and the tempera-
ture of the loose soil ranged with the
depth of its fine tith The soil well
worked six inches deep. the day after


CONTINUED on fourth pags.I