76 
WATER REQUIREMENT OF PLANTS. 
Previous to 1871 the experiments were conducted in open jars 
containing about 4 kilograms of sand. Check pots were used to 
estimate the loss by evaporation. In 1871 and during succeeding 
years the soil was covered with a board infiltrated with a wax and 
paraffin mixture, which greatly reduced the direct evaporation. The 
crops grown during the year 1867, arranged in the order of increasing 
water requirement, are barley, rye, wheat, and oats. During the 
year 1868 the water requirement of all the crops was higher than 
in 1867. In 1871 the horse bean had the lowest requirement, followed 
by barley and yellow lupine in order. The order of these crops was 
the same in 1872. The crops grown in 1872 arranged in order of 
increasing water requirement are pea, horse bean, barley, rape, red 
clover, buckwheat, and yellow lupine. The results in 1873 as com- 
pared with those of the same crops grown during 1872 shows the order 
to be exactly reversed. The differences are small in most cases, when 
the probable error is considered. 
A comparison of the results in the last column of Table LXVII 
shows the water requirement of barley and of red clover to be the 
same, wheat 9 per cent higher, rye 14 per cent higher, and oats 21 
per cent higher than barley. Of the other crops, the horse bean and 
pea have the lowest water requirement, while the remaining crops 
exceed the water requirement of barley. 
king's experiments. 
During the years 1891 to 1894 King (1892 to 1895) conducted a 
series of experiments dealing largely with the relative water require- 
ments of different crops. Correction was made for rainfall, but not 
for evaporation. King does not give the results of his duplicate 
determinations except for corn, the other results being expressed as 
mean values. The comparable results are shown in Table LXVIII. 
Table LXVIII. — Water requirement of crop plants in Wisconsin, according to King 
(1889 to 1895). 1 
1891 
1892 
1893 
1894 
Sum- 
mary. 
Relative water requirement 
compared with oats. 
Crop. 
o 
3 
4^ 
©s 
+a g 
"3 
■So 
3 
** a 
b © 
©S 
+J © 

© ^2 
"9 
a& 
3 
©^ 
©s 
+a © 
it 

© w 
3 
^ 3 
© s 
-U © 
is o> 

© IS 
3 
% 
fee 
-w © 
i 
© D 1 
Crop. 
1891 
1892 
1894 
Dent corn 2 ... 
2 
305 ±5 
2 
318±68 
4 
2 
8 
4 
2 
2 
2 
310 
390 
541 
388 
477 
481 
423 
Oats 
Barley 
Dent corn 2. 
Field pea... 
100 
80 
61 
100 
71 
60 
91 
107 
100 
2 
3390±91 
2 
2 
502 ±6 
401 ±2 
2 
2 
2 
2 
*526 
4 375 
4 477 
4 564 
4 
594 ±25 
Barley 
2 
4 398 
71 
2 4234-6 

1 In this table the writers have endeavored to eliminate errors in comparison. Consequently, they have 
omitted the determinations which were specially fertilized and have not used a weighted mean in the 
summary. The experiments in 1891 were made in 50-gallon barrels, painted and sunk level with the sur- 
face of the ground. In 1892 galvanized cans 18 by 40 inches were used in place of the barrels. In 1894 
the plants and pots were protected from rain by a'temporary cover of heavy duck. The potato cans were 
18 by 24 inches. 
2 Pride of the North variety used. 
3 For an error in King's data in connection with this value, see Table XXV (p. 35). 
4 There were two pots, but the results are given only as a mean. 
285 
