VOL.
xx.
[JULY,
1898.1
No. 7.
THE JOURNAL OF THE
AMERICAN CHEMICAL SOCIETY. EVAPORATION A N D PLANT-TRANSPIR.4TION. B Y WALTER M IXWELL. Received April n, r8o8.
T
HE data which largely compose this contribution were
obtained in the course of observations bearing upon the factors which enter into a system of rational and economic irrigation, and in connection with the study of certain practical questions that relate to land irrigation on the Hawaiian Islands. These data, however, have also a more purely scientific value, and may have an interest for those who are more exclusively engaged in physiological investigations. T h e actual purpose of the observations which these data represent was to try to determine : first, the loss of moisture due to direct evaporation from the soil ; and secondly, the relative proportion that escapes by transpiration from the sugar-cane (saccharum o$cinarum) during different periods of growth, and to note the meteorological and other factors which appear to control these phenomena. The observations on soil-evaporation and plant-transpiration were made as follows : A given weight of the particular soil was put into two tubs, exactly 125 pounds into each tub. T h e tubs had perforated bottoms, over which a piece of linen cloth was laid before putting in the soil, in order to prevent the soil dropping through, or blocking up the holes. When filled thus with soil, the tubs were each set into a galvanized iron pan containing water, the water being kept up to a given mark or level,
47 0
WALTER MAXWELL.
which level was the point of contact between the soil in the tubs and the water in the pans. T h e pans were most carefully covered with moisture-proof glazed oilcloth. to prevent any evaporation from the pans except through the tubs containing the soil. When the tubs were set in place, water wasadded to each pan by means of a funnel that was inserted through the waterproof covers, and in sufficient volume to saturate the soil, whose absorptive power was 48.2 per cent. on its own weight. This was done on April I j , and on April 16 three pieces of seed-cane were planted in tub No. 2 , whilst in tub No. I no cane was planted, the latter having to record the escape of water by means of the soil, and No. 2 tub the loss by means of the soil plus the growing cane. T h e tubs were placed upon a veranda, having a south exposure and a strong light, but as they had to be protected against rainfall they were so located that no direct sunlight fell upon them. Near by the tubs, temperature readings were taken. T h e maximum and minimum thermometers gave the extremes of temperatures, and the dry-bulb and met-bulb thermometers the indications of humidity in the air.” I t has commonly been claimed that temperature and the “ relative humidity in the air” are controlling factors in evaporation. T h e writer, however, has believed not only that there is not necessarily a constant relation between temperature, atmospheric moisture, and the water given off from soil and water surfaces, but that there are other factors n-hose individual action exceeds the united influences of the factors already stated. For this reason we decided, at the time of taking the temperature and humidity readings, to determine the actual evaporation, by use of evaporators. T h e form of evaporator used was a small galvanized dish, one inch deep, and having a superficial area of 1 2 0 square inches. T h e evaporator was placed between the dry- and wet-bulb thermometers, thus having the same protection against the sun and exposure to the wind. At seven o’clock in the morning joo grams of water were weighed into the evaporator, and at the end of twenty-four hours the weight was retaken and recorded. T h e water was made up again in weight to joo grams, proceeding thus daily over the whole period of time included by the experiment. I n addition to the evaporator ‘ I
EVAPORATION AND PLANT-TRANSPIRATION.
471
described, a second one, in each item exactly identical with the former, was used. This second one was placed in a barn. T h e large doors of the barn were kept open day and night, thus providing an ample circulation of the outer air, but no violent wind disturbance or sudden movements of the air. T h e purpose in this case was to have the corresponding conditions of temperature and atmospheric humidity surrounding the former evaporator located thirty feet distant, with the exclusion of the factor of wind. T h e data furnished by the two evaporators were taken and recorded in the same way, with the corresponding thermometer readings. With this brief description of the mode of observation, the data are now given. These are numerous and occupy considerable space, but the full statement is necessary in order to observe the wide range of variations. Two statements could be made with some advantage, from the data. T h e soil-evaporation and the transpiration by the cane, however, are so bound up with the meteorological conditions that we present it as a whole : I.
44
8
5.3 02
d
a0
d
a&
$2
April 16
'' ' I
('
(' '(
17 18 19 20
21 22
'' 23
''
24
"
25
26 27 (' 28 (' 29 I' 30 May I ((
' I
"
2
74 76 75 76 76 76 75 75 74 72 75 75 76 74 75 75 72
2 t
5$
'0 'S
'0; e0
I.6
$
'0-
e,
8k .fi E!
:g
$5
s,
27.6 27.6 32.0 34.0 37,6 36.6 31.4 32.0 33.4
78 79 80 80 79 79 80 79
27.2
76 78 76 78 79 77 78 76
30.2 27.0
32.2 29.2 31.2 35.4 28.4
77
*
I..
4!.
22
d
3
3 E Cane planted. Saturated. Saturated cc. cc.
10.4 10.6 13.2 13.0 14.4 13.4 14.0 12.2
13.0 10.6 11.2 11.2
13.6 12.6 11.2 12.2
9.6
76.3 73.8 90.4 73.8 76.3 76.4 76.4 73.8 73.7 78.9 76.3 78.9 76.3 76.3 81.7 78.9 78.8
....
....
I000
Io00
800
800
Io00
Io00
500
500
200
200
500 700 700 500 700 500 500 700 500 500 500
500 700 700 500 700 500 500 700 500 500 500
472
-C
.z .
3 .*
-5
.-;=$..
.,> '5 ,. A n
d
-
5z
2 %
Saturated. cc.
34.2
;j
11.8
38.2
79 79 i9
12.6
29.2
35.4 34.4 19.2 17.2
2j.6
27.2 22.2
25.8 22.2
23.0 11.0
11.0
25.2
32.8 31.3 33.6 29.0 30.6 26.2
27.0
78 79 80 83 79 SO 80 77
7s
78 SI So 82
80 79 78 SI SO
13.2 13.4 6.8 11.0 10.0
12.6 10.6 12.2
10.8 9.0 4.2
6.0 11.0
12.6
13.2 13.0 10.6 11.6 12.0
11.6
27.2 1j.6
So
12.2
79
j0.0
SI So
9.6 12.6 12.6
82
14.0
30.2
82
14.2
34.6
83 82
14.6
81 81 79 80 79 80 80
11.0
31.6 35.2
30.2
24.0 30.0 21.0
214.8 24.0 24.6
26.2 1
81
11.4
12.0
13.2
9.2 10.6 9.h 10.0
10.8
78.9 73.7 78.9 76.4 71.5 7S.9 76.4 81.8 79.1 76.4 71.j 79.0 84.j 87.4 54.6 79.1 79.1 76.6 76.5 93.5 78.9 76.j 79.1 76.7
81.8 76.6 79.1 79.1 76.6 76.6 S7.6 79.1 76.j S1.S 81.8 79.1 S1.g 79.1
j00
j 00 j00
j00
500 500 j00
300 300
300 300
:,@O
300 jC10
9. E. N. E.
300 300
I So 22 0
I80 220 300
joo
340 3-0 S.
E.
450
E.
j 00
S.E.
joo 300
E.
300
400
S. E.
3jO 450 jjo 4jO 400
5 . E.
S. E. N . E.
400
400 400
"
The cane began to collie up and twelve stalks were up by May
21
EVAPORATION A N D PLANT-TRANSPIRATION.
473
u
Cane planted.
Sa[turated. Saturated.
June "
IO
77
28.6
I1
76 77 77 76 78 79 78 78 78 76 76 74 75 73
23.0
I2
"
13 14 1.5 16 17
"
I8
''
19
"
20
'( ( (
' I '(
21 ' I ' I '(
'I
"
22
23 24 25 26 27
"
28 29 30
July
I
"
2
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3 4
'(
5
'I
"
6 7 8 9
"
IO
"
I1
" 'I
"
', "
'( "
I2
13 14 15 16
'' 17 ' ( I8
77 75 76 76 74 80 78 77 78 80 80 78 78 77
77 77 78 79 79 78 76 76 77 78
27.6 36.6 27.2
81 80 79 82 81
29.0 31.0 28.2 30.0 26.0
80
22.2
82 81 80 79 78
16.2
12.6 9.2 6.0 13.4 5.6 13.4 13.0 13.0 31.0 25.0
23.0 30.6 32.0 31.6 23.0 27.6 23.6 25.6 27.2
25.2 27.6 29.6 26.0 27.2 21.8 28.0 26.2
82
83 83 81
81
78 82 83 81 83 85 80 81 81 85 80 83 80 79 82 81 83 82 80
SI 82 80 83
79.1 9.2 79.1 10.0 81.8 14.0 76.6 11.2 81.8 11.0 81.8 12.0 81.9 12.0 81.9 12.2 j9.2 12.2 81.9 10.6 81.9 8.2 84.7 9.2 84.6 6.0 87.5 4.2 96.7 9.6 87.6 4 ~ 4 93.5 9.6 84.7 9.0 82.0 8.0 84.7 10.0 79.3 12.0 76.7 9.0 87.5 11.2 81.9 11.2 81.9 12.6 74.3 9.8 84.7 11.2 84.7 9.6 84.7 10.2 84.6 11.2 79.1 11.0 81.9 12.0 84.7 13.0 79.2 11.0 84.6 12.0 87.7 10.2 87.5 12.0 84.7 11.8 81.9 12.0
E.
N. (L
(
O E $2 Zrn
$3
2:
-I-
:a
ern
.-5
5
E
.?
Cane planted. Saturated. Saturated.
23.0 23.0 27.6 25.4 29.0 29.0 20.6 28.0 28.8 32.2
10.6
18.2
11.0
23.0 23.6 32.6 31.0 30.2 31.6 26.2
12.0
12.6 14.0 13.0
27.2
12.2
23.0 15.0 25.4 26.6 31.2 26.2 32.2 33.0 26.0 26.0 26.0 33.4 29.6
10.8 7.6
81.9 81.9 74.1 74.0 76.6 71.7 71.7 i4.2 74.1 76.7 76.7 76.7 76.7 76.7 79. I 76.7 76.8 79.2 76.7 SI.8 76. j 71.7 71.7 71.7 79.' 84.8
2j.2
12.0
11.2
82. I
12.2
71.6 71.7 74.0 71.7 74.1 71.6 74.0 74.0 69.3 74.2
26.0 31.0 24.2 17.6
stalk of cane died.
10.0
13.0 12.0 12.0
14.0 11.2
12.2
13.2 Ij.2 12.8
14.0 12.0
11.6
11.2
13.8 12.2
13.4 12.0
12.4 13.2 13.2
13.0 12.0
15.8 14.4
E. N. E.
E.
cc.
cc.
400 400 430
700
'$00
