feFFECf OF SOIL FACTORS OS WATEB REQUIREMENT. 
00 
SORAUER S EXPERIMENTS. 
Sorauer (1883) used water cultures in most of his water-requirement 
experiments. His results, which deal with the effect of different 
amoimts of nutrient solution on the water requirement of rye. barley, 
wheat, and oats, are given in Table XLIII. The experiments were 
of 53 days' duration, and the water requirement was found to decrease 
as the concentration of the nutrient solution increased. 
Table XLIII. — Effect of the concentration of the nutrient solution on the water require- 
ment of plants, 1 according to Soraut 
Crop. 
Rye.... 
Barlev. 
Wheat. 
Oats... 
Concentration of th lution. 
0.05 per cent. 0.25 per cent. 0.5 per cent. 
1 per cent. 
Xum- Watpr 
berof "_* 
deter - quire- 
ment. 
tions. 
Xum- Warpr Num- 
ber of N \2 ber of 
det€r - quire- derer - 
mma - ment ' mma_ 
tions. mem - tions. 
] quire- 
4 :>-4 . 
G30±24 
Mean 610 
Mean for rye 
and barley 
4 331 = 22 
_ 1 - 
I 21 ± 1 ] 
4 197±20 
0.25 per cent 
per oea 
cium ni 
Xum- to-„* — 
berof ^ er 
mina- ^ uir f 
tions. ment - 
- 
495 
5 235-25 
1 The total dry matter produced was seldom as great as 0.5 gram per pot. 
HEIXRICH S EXPERIMENTS. 
Heinrich (1894) has determined the water requirements of oat 
plants when grown in nutrient solutions of different concentration. 
The nutrient solution had the following composition: 4 H 2 KP0 4 - 
CaCh — 5 Ca(X0 3 ) 2 -f 2 MgS0 4 — 2 Fe. Five concentrations were used. 
3 grams, 1 gram, 0.5 gram, 0.25 gram, and 0.1 gram per liter. The 
iron was supplied in the form of freshly precipitated suspended iron 
phosphate. Ten jars, each containing 3 liters of solution, were used 
for each of the five concentrations. Three plants were grown in each 
jar. An equal number of jars without plants was used to determine 
the evaporation taking place directly from the culture solution. The 
plants were grown for four months, or until ripe. The transpiration 
was determined by weekly weighings. The plants in the 0.3 per cent 
solution consumed about three-fourths of the initial water supply. 
The evaporation in this case was only about 2.5 per cent of the tran- 
spiration. The results are given in Table XLTV. With the exception 
of the weakest solution, the water requirement decreased as the con- 
centration of the solution increased. 
285 
