EFFECT OF SOIL FACTORS ON WATER REQUIREMENT. 37 
SCHROEDER S EXPERIMENTS. 
Schroeder (1896) used the same nutrient solution previously 
employed by Hellriegel. The results of his experiments given in 
Table IV (p. 14) do not show a decrease in the water requirement 
with an increase of concentration of the nutrient solution. 
VON SEELHORST S EXPERIMENTS. 
Von Seelhorst (1899) has investigated the effect of different nutri- 
ents upon the water requirement of oats. His first experiments, the 
results of which are given in Table XXVIII, were made in zinc cans 
holding about 20 kilograms of earth. Two pots were used for each 
treatment, but the data for the individual pots are not given, so that 
it is not possible to calculate the probable error. Each fertilizer 
treatment was carried on with three different soil-moisture contents, 
so that the mean water requirement as given in the eighth column of 
the table represents the average of 6 pots in each case. It is interest- 
ing to note that the addition of potassium had no effect on the water 
requirement, phosphorus caused only a slight reduction, while a 
marked reduction accompanied the use of nitrogen, both alone and 
in combination. 
In another experiment Von Seelhorst compared the water require- 
ment of oats with the same crop following mustard. Two series of 
fertilized pots were prepared, one of which was planted to mustard, 
while the other remained fallow. The next year both series were 
planted to oats without additional fertilizer. These results, also 
given in Table XXVIII, are apparently limited to a single pot for 
each treatment. The introduction of the mustard crop increased 
the water requirement of the oat crop 67 per cent. The oats follow- 
ing fertilizer showed a slight reduction in the water requirement, due 
to the use of phosphorus, while the oats following mustard showed 
the greatest reduction with the nitrogen fertilizers. 
285 
