178 
Journal of Agricultural Research 
Vol. VII, No. 4 
LOSS OF WATER DURING THE MAXIMUM TRANSPIRATION PERIOD 
PER UNIT OF DRY MATTER HARVESTED 
MEAN DAILY TRANSPIRATION PER GRAM OF DRY MATTER HARVESTED 
It is not possible in the case of the grain crops to determine directly 
the maximum transpiration per unit of dry matter without sacrificing 
the crop in order to find the dry weight. Such calculations can, however, 
be made upon the basis of the dry weight of the crop at maturity, which 
from a practical standpoint is of more importance than the former 
determination. Computations of this kind are presented in Tables IX 
to XII for the io-day periods just considered. 
Reference to Table IX will show that during the transpiration period 
July 7 to 16, 1914, the small grains were transpiring from 12 to 16 gm. 
of water per day per gram of dry matter harvested; cowpea and lupine, 
19 gm.; and millet, sorghums, and com, 6 to 9 gm. These quantities 
are approximately proportional to the water requirement of the crops. 
Table IX .—Loss of water per unit of dry matter harvested during the maximum transpi¬ 
ration period July 7 to 16, 1914 a 
Crop. 
Dry 
matter. 
Mean daib 
tion, Jn 
Actual. 
r transpira- 
ily 7-16. 
Per gram 
of dry 
matter. 
Hourly 
transpira¬ 
tion during 
midday 
per gram 
of dry 
matter. 
Daily loss 
of water 
per ton of 
dry matter 
per acre. 
Grams. 
Kilograms. 
Grams. 
Grams. 
Acre-inches , 
Wheat, Kubanka. 
306 
4. 00 
13 - 1 
1. 3 
O. II 
Wheat, Galgalos. 
298 
4. 69 
T 5 - 7 
l. 6 
. 14 
Oat, Swedish. 
264 
4 - 34 
16. 4 
I. 6 
• z 5 
Oat, Burt.. 
251 
4-05 
16. I 
i. 6 
. 14 
Barley. 
182 
2. 20 
12. I 
1. 2 
. II 
Rye. 
195 
3- 05 
15.6 
1. 6 
. 14 
Cowpea. 
170 
3 - 17 
18.6 
i -9 
. 16 
Lupine. 
90 
1. 72 
19. I 
i -9 
• z 7 
Millet, Kursk. 
301 
2 - 39 
7 - 9 
.8 
.07 
Millet, Siberian. 
318 
2 - 57 
8. 1 
.8 
. 07 
Com, Northwestern Dent. 
304 
2- 75 
9.0 
-9 
.08 
Com, Algeria... 
417 
2. 69 
6. 5 
. 7 
. 06 
Sorghum, Minnesota Amber. 
457 
2.68 
5-9 
.6 
• 05 
Sorghum, Dakota Amber. 
427 
2. 62 
6. 1 
.6 
•os 
a Mean daily evaporation, 12.3 kgm. per square meter. 
Sudan grass during a io-day period in August immediately preceding 
the first cutting showed an average transpiration loss of from 9 to 11 gm. 
per day per gram of dry matter harvested (Table X). Amaranthus and 
alfalfa were cropped for the second time at the end of this period. 
Amaranthus showed a transpiration loss of 17 gm. per day per gram of 
dry matter produced, while the alfalfas transpired from 36 to 56 gm. per 
day per gram of dry matter harvested. The Sudan grass and alfalfa 
grown outside the screened inclosure showed a transpiration from 27 to 
30 per cent higher than the same crops inside the inclosure. This cor- 
