ON THE PHYSIOLOGICAL BALANCE IN NUTRIENT SOLUTIONS 
FOR PLANT CULTURES 
W. F. Gericke 
(Received for publication July ii, 192 1) 
Wheat seedlings grown for one day in a dilute solution of KNO3, the 
next day in one of MgHP04, the third day in one of CaS04, and these 
changes continued in rotation at twenty-four-hour intervals for four weeks, 
grew as large and produced approximately as much dry weight as those 
grown in complete nutrient solutions of the above-named salts and in other 
three-salt solutions that supplied the same ions. The plants grown in 
these three single-salt solutions were also much superior to those grown in 
other types of single-salt solutions that were changed likewise at twenty-four- 
hour intervals. Altogether, ten diffeient simple nutrient salts were used 
in the tests, and these were selected to give six different types of nutrient 
solutions; three or four salts being required for each type, which, with a 
trace of iron salt added, supplied the essential salt or mineral constituents 
for plant growth in aqueous solutions. All solutions, with the exception 
noted below, were of approximately the same osmotic value, this being 
approximately equal to one atmosphere osmotic pressure. Each single- 
salt solution, aside from the trace of iron it contained (this being added 
as FeS04), supplied the plants with two essential nutrients, both cation 
and anion of the salts used being of those atoms or groups of atoms con- 
sidered necessary for plant growth. It required three days to make one 
rotation to bring the plants in contact with the three nutrient solutions of 
their respective types, which supplied them with all the essential elements 
in nutrient solutions, vis.: NO3, SO4, PO4, K, Ca, Mg, and Fe. 
The salts used for the different types^ were as follows: 
Type I, KH2PO4, Ca(N03)2, MgS04; type II, K2SO4, Ca(N03)2, 
MgHP04; type III, KNO3, CaHP04 (saturated solution plus enough 
Ca(H2P04)2 to give together 0.2 atmosphere osmotic value), MgS04; type 
IV, K2SO4, CaHP04 (saturated solution plus enough Ca(H2P04)2 to give 
together 0.2 atmosphere osmotic value), Mg(N03)2; type V, KNO3, CaS04, 
MgHP04; type VI, KH2PO4, CaS04, Mg(N03)2. 
The change of the cultures from one solution to another successively 
within each of the several types at twenty-four-hour intervals covered the 
^ For the first mention of these types, see Livingston, B. E., and Tottingham, W. E. 
A new three-salt nutrient solution for plant cultures. Amer. Jour. Bot. 5: 337-346. 1918. 
Types II, III, IV, and V were modified by the author by substituting CaHP04 for 
Ca(H2P04)2 and MgHP04 for Mg(H2P04)2, the primary phosphate salts in the original 
being too acid for these tests. 
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