The Absorption of Phosphorus and Iron from Nutrient Solutions

Abstract

Moderate amts. of KH2PO4 (0.5-0.7 mM) caused iron chlorosis in solns. less acid than about pH 5.5. The trouble was reduced by adding P separately after plants had absorbed Fe from non-P solutions, or by maintaining low pH. NH4NO3 reduced chlorosis because NH4 was absorbed most rapidly by 9 spp. plants so that pH''s of 2.9-3.9 were reached in unbuffered solns. These acidities were injurious to corn and cotton but not to soybeans. Reactions of different spp. and of the same sp. at different stages varied sharply, and no one soln. can be considered "best" for more than very limited conditions.