VALUE OF CERTAIN NUTRITIVE ELEMENTS 
321 
The water requirement of the plants grown in the magnesium-deficient 
solutions is 52 cc. less than the average water requirement of the plants 
grown in the normal solutions, but the data of one year, 191 7, show no 
perceptible difference between the water requirement of the plants 
grown in the magnesium-deficient solutions and those in the normal 
solution. Calcium-deficiency causes a slight increase in the water 
CULIUHE SOLUTIONS 
Figure 5. Curve showing the average water requirement of plants grown in 
the normal solution and in solutions with one nutrient element in each case reduced 
to one tenth normal. 
requirement of the plants when an average of three years' experiments 
is considered, but in the experiments of the first two years the water 
requirement of plants grown in the calcium-deficient solutions is less 
than that of those grown in the normal solution. The average water 
requirement of plants grown in potassium-deficient solutions is 69 cc. 
above the water requirement of the plants grown in the normal solu- 
tion. The water requirement of plants grown in phosphorus-deficient 
