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AMERICAN AGRICULTURIST. 
[September. 
Soil Temperatures. 
The temperature of the soil is an important 
element in the growth and maturity of crops. It 
is to the roots what the temperature of the air is to 
the foliage, and influences the whole life of the 
plant. Hence the study of its governing laws and 
principles is an exceedingly important one. A 
series of investigations have been instituted at 
“Houghton Farm,” for the purpose of acquiring a 
better knowledge in this field. One season has al¬ 
ready been devoted to the work, which is still 
being carried on with the intention of obtaining a 
large amount of data and repeated experience, 
before attempting to deduce laws. Many interest¬ 
ing facts have been noted, however, and it is the 
purpose of this article to give a brief review of ob¬ 
servations, which have been discussed at greater 
length in a published report. 
So far as agricultural operations are concerned, 
the sun is the principal source" of heat in the soil, 
although ehemieal changes produce an appreciable 
effect. The amount of heat absorbed from the 
sun does not determine the temperature of the 
soil : other natural causes, such as radiation from 
the surface, the amount of moisture in the soil and 
air, and the color, and chemical and mechanical 
condition of the soil itself, all have a modifying* 
influence. 
The soil, in which observations were made, was a 
gravel containing some clay with a clayey subsoil, 
without a crop, and undisturbed during the season. 
The manner of taking the temperature was as fol¬ 
lows: Accurate thermometers were fastened in the 
hollow extremities of light wooden rods, and these 
were inserted to different depths in the soil, in 
closely titting zinc tubes, from which they could 
be easily withdrawn for reading. The thermometer 
bulbs were enclosed in cisterns of oil, to prevent 
the too rapid effect of the air temperature on the 
reading of the mercury. The zinc tubes were kept 
idled with water, which surrounded the thermo¬ 
meter, and prevented conduction of heat from 
above. The temperature of the surface soil was 
taken by means of a thermometer, with its naked 
bulb in the loose soil. Thermometers were placed 
at the following depths : surface, three inches, 
six inches, nine inches, one foot, three feet, five 
feet, and eight feet. These were read hourly from 
7 A. M. to 9 P. M., from May 1st to October 31st. 
and an accurate record kept of their readings. 
The temperature and relative humidity of the air 
was also recorded every hour. 
The temperature of the soil, following the 
changes in the air, is constantly fluctuating, and 
hourly, daily, and monthly variations were observ¬ 
ed. The first are confined to the upper layers of 
the soil, with which most of our crops have to deal. 
These changes are often sudden and violent, and 
may be produced by a variety of causes.—For in¬ 
stance, a sudden shifting of the wind from south 
to north, and the .clearing up of - a cloudy sky just 
at sunset, caused a fall of 24 degrees F. in one 
hour ; a thunder storm caused a fall of 16° F., and 
a sudden clouding over of the sky, obscuring the 
sun, a fall of 17° F. in one hour, in the surface 
soil. These changes lose their abruptness as we 
go below the surface, until at a depth of one foot, 
there is rarely a variation of more than one or two 
degrees in an hour. In the same layers of soil, 
which are subject to hourly variations, there is 
also a wide range of temperature in every twenty- 
four hours, caused by excessive absorption of heat 
by day, and radiation in the night. This range is 
greatly reduced if the sun be obscured during the 
day, if it be rainy, or if the ground be filled with 
moisture. The surface soil is subject to these 
changes in much the same degree as the air, and 
the daily range is often 40° to 50° F. during the 
hot summer mont hs, while it may be as little as 5° 
F., rarely less. Lower down the change is less, 
but is plainly felt to a depth of one foot or more. 
On an ordinary summer’s day, the maximum 
temperature at the surface comes about midday, 
and the minimum a little after midnight. These 
extremes are a little later at the successive depths 
below the surface, until at one foot they are re¬ 
tarded some eight or ten hours, and we have the 
curious feature at evening of the one foot thermom¬ 
eter rising, while that at the surface is failing, 
and again in the morning their movements are re¬ 
versed. Both the daily range and hourly variations 
of temperature are checked by the presence of 
moisture in the soil, and in the six months’ ob¬ 
servations the extremes occurred during drouths. 
Beginning in the spring, there is a constant rise 
in the temperature of the soil, easily observed at 
a depth of eight feet. Storms or cold cloudy 
weather will check this advance, but only tempora¬ 
rily, and their influence is rarely felt below one 
foot. After the summer heat is passed, begins the 
decline, and so steadily does this increase and de¬ 
crease occur, that if it were graphically depicted, 
we should have a broad easy curve rising from May 
to July and August, and then falling in the same 
mauner. It is noticeable, that this change of the 
average daily temperature is greatest during the 
Spring and Autumn months, when there is most 
THERMOMETERS IN THE SOIL. 
moisture in the soil. Of course, this is largeiy ex¬ 
plained by the fact, that the soil is passing from 
one extreme of temperature to another by rapid 
transitions, but the influence of the constantly 
varying amounts of watery vapor in the soil, pro¬ 
duced by evaporation, must not be overlooked. 
These changes extend to a depth of eight feet 
and probably lower, but no temporary decrease 
in temperature at the surface was observed to 
penetrate below three feet, and rarely to this dis¬ 
tance. From three feet down there was a constant 
and unbroken rise from May 22d to September 1st, 
and the eight-foot thermometer did not begin to 
fall until September 23d. 
The mean temperature at the different depths 
observed for the six months, from May to October 
inclusive, were as follows : surface, 66.4°; 3 inches, 
65.3° ; 5 inches, 65.3°; 9 inches, 65.3°; 1 foot, 
64.2° ; 3 feet, 62.8° ; 5 feet. 58.6° ; 8 feet, 55.8. 
That is, at a depth of eight feet the mean tem¬ 
perature for six months was only 10.6° lower than 
at the surface. During the month of October, the 
average temperature at eight feet was higher by 
3.8°; at a depth of five feet by 4.1°; at three feet, 
4.5°; at one foot, 2.2°; than the average at the sur¬ 
face. From this it appears, that during the Fall 
months, when the temperature of the upper layers 
of the soil is falling, there is a zone of subsoil be¬ 
ginning at a depth of one foot or lower, as the cool¬ 
ing off at the surface progresses, and extending to 
an indefinite depth, which is from two to four de¬ 
grees higher in temperature than the soil above. 
If we consider that this excess is being constantly 
radiated upward, we shall see that this warm zone, 
or the stored-up heat which it contains, must have 
an appreciative effect in elevating the temperature 
of the surface soil, and prolonging the season. In 
the same way, the heat absorbed from the sun each 
day, by its radiation during the night, averts frost, 
and maintains a more nearly even temperature. 
The moisture in the soil is an important factor in 
this problem, but its study is very complicated. 
A Late Sowing of Turnips. 
Turnips may be divided into three classes, ac¬ 
cording to the length of time they require to ma- 
mature: 1st. The Ruta Baga Turnips.—These 
require a long season ; they must be sown early,, 
and are the best keepers, lasting well into spring. 
These are sown in May and June. 2. Intermediate 
Turnips, which may be sown in July and August,, 
aud make a good crop. With proper land, and 
well cultivated, they often yield largely and pay 
well. The leading varieties of this class are : the 
Yellowstone, the Yellow Aberdeen, and the Cow 
Horn, which last is intermediate between this class 
and the next. Either of these may be sown in 
August, and yield a profitable crop. The Aberdeen 
is a popular market sort, and remains in good con¬ 
dition until the end of winter. Lastly, the Late or 
Autumn-sown Turnips, of which the Red-top Strap- 
leaf is the most popular. These may be sown 
during the first half of the present month. It 
is not giving any kind of turnips the best cul¬ 
ture to sow the seed broadcast, but with a “catch 
crop,” on stubble or upon other crops, to occupy 
the ground when they come off, it is the most 
available method. Those who grow sweet-corn, at 
the last hoeing, often sow turnip seed broadcast, 
and after the corn-stalks are cut off, get a valuable- 
crop of turnips. The most profitable method, one 
that is most likely to yield a good crop, is to plow 
and thoroughly prepare land that has been devoted 
to some well manured crop. The use of the har¬ 
row and roller after the plow will bring the soil 
into good condition. If the land has been well 
manured for the previous crop, three hundred 
pounds of superphosphate to the acre will be likely 
to give a paying yield of turnips. Drill the seed 
in rows w'ide enough to allow the cultivator to run 
between, say twenty-four or thirty inches. Three 
or four pounds of seed to the acre will be needed. 
When the plants are well up, use a sharp hoe, with 
a blade six inches wide, cutting out all the plants 
but a few, which arc to be left in bunches at this 
distance. In a few days, go over and remove by 
hand all but the strongest plant in each bunch, 
taking care to leave that one well set in the 
soil; if disturbed by pulling up the others, press 
the earth firmly around it. Use the cultivator be¬ 
tween the rows as often as necessary, and in a 
favorable season a profitable crop may be harvested. 
A Convenient Bailed Box. 
The common box with a bail, or handle, is a use¬ 
ful farm appliance; it auswers the purpose of a 
basket, is much more durable, and.a great deal 
cheaper. Some of our readers may not be familiar 
with this box, and we accordingly describe one for 
their benefit. Instead of a fiat bail, we would 
suggest, for heavy work, a green hickory or other 
tough stick, to be chamfered off where it is 
nailed to the sides of the box, the portion for 
the hand being, of course, left round. It will be 
found useful to have these boxes of a definite size, 
to hold a half bushel or a bushel. A legal bushel 
is two thousand one hundred and fifty (and a frac¬ 
tion) cubic inches. A box may be made of this 
capacity of any desired shape. Ends a foot square, 
and side pieces and the bottom eighteen and a half 
inches long, will make a bushel box. If desired 
narrower, make the ends eight inches high aud 
fourteen inches wide, with the sides and bottom 
two feet long. Such a box holds a verv little 
more than an even bushel. It is inexpensive. 
