14 
WATEK REQUIREMENT OF PLANTS. 
certain fertilizer experiments. A summary of his results is given 
under "Effect of fertilizers on the water requirement" (Table XXVII, 
p. 36). He found that white mustard grown in soil 20 per cent satu- 
rated had a water requirement nearly 30 per cent less than when 
grown in soil 60 per cent saturated. His pots were not protected 
from surface evaporation. 
SCHROEDER S EXPERIMENTS. 
Schroeder (1896) investigated the water requirement of barley when 
grown in sand moistened with nutrient solutions of different con- 
centration. The effect of different amounts of solution was also 
investigated, three series of pots being maintained, respectively, at 
80, 40, and 20 per cent of the moisture-holding capacity. His results 
are given in Table IV. The data for 1894 show a consistent reduc- 
tion in the water requirement accompanying a reduction of the 
moisture content of the soil. Schroeder placed less confidence in 
the results for 1893 on account of the imperfect prevention of direct 
evaporation by the layer of cotton employed for that purpose. 
Table IV. — Effect of different amounts of nutrient on the water requirement of barley in 
Russia, according to Schroeder (1896, pp. 194-211). 
Soil 
moisture, 
Concentra- 
Year. 
in terms 
tion of 
Dry 
Water re- 
of water- 
nutrient 
matter. 
quirement. 
holding 
solution. 
capacity. 
Per cent. 
Per cent. 
Grams. 
I 0.6 
38.93 
568 
.4 
28.22 
547 
80 
1 - 3 
20.81 
586 
.2 
15.42 
576 
I .1 
6.40 
513 
( - 6 
20.07 
505 
1894 » 
40 
x 
16.84 
9.50 
470 
536 
I .2 
7.72 
424 
f 1.2 
15.35 
338 
.8 
10.66 
399 
20 
i - 6 
6.36 
400 
.4 
5.87 
429 
I -2 
3.53 
360 
/ 70 to 100 
1.7 
8.15 
579 
40 to 70 
2.4 
6.25 
516 
5 to 40 
4.3 
3.50 
472 
1893 2 
40 to 70 
40 to 70 
1.2 
3.7 
4.33 
7.67 
414 
541 
5 to 40 
6.4 
4.54 
467 
. 70 to 100 
.85 
6.28 
329 
1 Experiments were conducted in glass pots filled with 5 kilograms of sterile sand. The soil surface 
was covered by oilcloth and a layer of cotton. The pots were taken into a shelter during the night and 
in bad weather. Growth continued from 70 to 88 days. Only one pot was used in each culture. The 
initial weight of the seed was deducted in estimating the water requirement. The nutrient solution was 
the same as that used by Hellriegel (p. 13). 
2 As in 1894, but the pots contained sand plus 150 grams of peat. The surface of the pot was covered 
with only a layer of cotton. Growth continued from 71 to 113 days. 
von seelhorst's experiments. 
Von Seelhorst (1899) has determined the effect of different percent- 
ages of soil moisture on the water requirement of oat plants which 
were harvested just before the milk stage. Pots containing about 10 
285 
