12 
WATER REQUIREMENT OF PLANTS. 
was continued for 57 days. The results of the experiments are shown 
in Table I. The water-requirement ratio is based on the water added 
to each pot instead of on the water actually used. 
Table I.— 
Effect of different cmwunts of water on the water requirement of buckwheat, 
according to II enhov (1865, p. 162). 
Pot No. 
Water added. 
Dry 
weight 
(grams). 
Water 
require- 
ment. 
Relative. 
Liters. 
1 
2 
3 
4 
5 
1 
i 
i 
I 
25.0 
12.5 
6.25 
3.12 
1.56 
6.20 
13.94 
6.28 
1.93 
.39 
4,030 
900 
995 
1,616 
4,000 
Water was not added daily, but pot No. 1 was kept nearly satu- 
rated. The table shows that the water requirement was very high, 
owing probably to the fact that the experiment 
was conducted in porous pots. Since no account 
is taken of evaporation or of the initial and final 
moisture content of the soil, the results are far 
from conclusive. 
fittbogen's experiments. 
Fittbogen (1873) conducted a series of careful 
experiments on the influence of soil-moisture con- 
tent on the water requirement of the oat plant. 
He used glass jars of the form shown in figure 1. 
Each jar contained 3 to 4 kilograms of soil, which 
rested on a 4-centimeter layer of gravel. The jar 
was closed with a zinc cover (a) having two 
tubulures. The center tubulure carried a cork (b) 
fig. i.— Glass jax employed bored with a 6-millimeter hole, through which the 
meafuring g t e he water re* stems of the three oat plants passed. The other 
quirement of plants. tu bulure was kept closed with a cork stopper (c) 
except when water was being applied. Fittbogen thus had a nearly 
closed system, and the evaporation loss must have been small. 
Five series of experiments were made with different soil-moisture 
contents, as shown in Table II. 
Table II. — Effect of different soil-moisture contents on the water requirement of oats, 
according to Fittbogen (1873, p. 359). 
Production. 
Water content, in terms of moisture-holding 
capacity. 
10 to 20 
per cent. 
20 to 30 30 to 40 
per cent, per cent. 
40 to 60 
per cent. 
60 to 80 
per cent. 
"Drv matter i Mean weight, grams : 
Dry matter. .j Water requirement , 
Train /Mean weight, grams . 
UTdU1 \ Water requirement 2 . 
1.6 
405±14 
0.6 
1,022±96 
7.8 j 
414±10 
4.1 
790±12 
12.8 
444±7 
6.1 
934±25 
12.2 
457±9 
5.3 
1,050±16 
13.7 
534±14 
6.0 
1,213±59 
1 4 pots used in each determination; 3 plants per pot. 
285 
2 Computed from Fittbogen's data. 
