THE USE OF IRON IN NUTRIENT SOLUTION 
FOR PLANTS. 
G. E. CORSON AND A. L. BAKKE. 
Nutrient solutions have been made use of to a considerable 
extent in endeavoring to determine the specific role of certain 
nutrients as well as questions of nutrition in general. It is 
known that iron, although used in small quantities, is essential 
for chlorophyll production. The present work is a study for 
the purpose of ascertaining the value of different amounts of 
iron to an otherwise balanced solution. This feature has sug- 
gested itself in that the majority of such Solutions do not con- 
tain definite amounts of iron, but are simply designated by a 
‘ ‘ trace. ? ’ This amount will naturally vary with different work- 
ers. The relative value of iron in the ferrous and in the ferric 
condition was tested out. The present study does not present 
any evidence as to the respective merits' of various solutions 
that have been previously used. This has been done by Totting- 
ham 1 and Shive 2 and so is not within, the province of this in- 
vestigation. Tottingham and Shive have introduced a measure- 
ment that is based on total atmospheric pressure. The concen- 
tration of each salt is measured according to its molecular weight. 
Gram molecular concentrations are used. Shive ’s solution con- 
taining three salts 3 is an improvement over Tottingham ’s. It is 
natural then that Shive ’s solution should lie the more popular 
of the two. This solution consists of the following compounds : 
potassium phosphate (KH 2 P0 4 |§ 0.0180 m; calcium nitrate 
(Ca.(N0 3 ) 2 0.0052 m ; magnesium sulphate (Mg S0 4 ) 0.0150 m; 
iron phosphate (Fe P0 4 ) 0.0044 grams per liter. The pressure 
in atmospheres of this solution is 1.75. This medium has proven 
to be 27 per cent better than the old solution of Knop which 
has been looked upon as more or less of a standard. 
In the present study, wheat and Canada field pea plants were 
used. The wheat was germinated in clean quartz sand. When 
Nottingham, W. E., A quantitative chemical and physiological study of 
nutrient solutions for plant cultures: Physiol* Res., 1 , 133-245, 1914. 
2 Shive, J. W., A study of physiological balance in nutrient media: Physiol. 
Res., 1, 327-397, 1916. 
3 , A three salt nutrient solution for plants: Amer. Jour. 
Bot., 2, 157-160, 1915. 
