6 
N. C. Experiment Station 
In the process of oxidation of organic matter, if basic material were 
liberated in amounts equivalent to the nitric acid produced, no change 
in reaction should have occurred. With a deficiency of strongly basic 
elements, however, the acidity resulting from the hydrolysis of nitrates 
of weak bases would increase to the point at which nitrification would 
be inhibited. This point may never be attained in fact as the nitrate 
nitrogen is constantly being lost by leaching or through denitrification 
in the water-logged subsoils. 
The reaction of pH 4.0 shown in Table I probably represents the 
equilibrium reaction in this soil. Obviously, the immediate effect of 
liming would be to decrease the acidity. This should result in a stimu¬ 
lation of nitrification and the nitric acid produced might quickly neu¬ 
tralize all the lime applied that was not leached from the soil as the 
bicarbonate. The soil should, thereupon, resume approximately its 
original reaction showing no residual effect of the added lime. 
A similar explanation can account for the increase in acidity follow¬ 
ing the use of acid phosphate. Fred and Hart (5) have shown that 
soluble phosphates stimulate bacterial activity in the soil. It is not 
improbable that the application of available phosphate to these soils 
accelerates nitrification with the result that the acidity is increased 
and the yield of corn is depressed. 
The toxicity to corn of compounds of iron and aluminum may not 
be entirely a chemical or physiological problem. Hoffer and Carr (7) 
have recently shown that the root-rot disease is largely confined to corn 
plants showing evidence of injury due to soluble iron or aluminum 
salts. Hopkins (9), too, has furnished data which indicate that soil 
reaction may be a factor of considerable importance in determining 
the virulence of one of the organisms associated with corn root-rot. 
The difficulty experienced in growing corn on these soils may, therefore, 
be due to the pathogenicity of soil or seed born organisms but it is 
evident, from the work of the authors last referred to, that the soil 
reaction and the generation of soluble salts of iron and aluminum are 
factors of first importance governing the susceptibility of the plants 
to disease. 
It has been stated that nitrate of soda was found very beneficial to 
corn on these soils. Jones and Shive (10), McCall and Haag (11), and 
Willis and Carrero (14), have submitted data showing that the nitrate 
fertilizers, by decreasing the acidity of the culture medium, tend to 
lessen the absorption of iron by the plant. It is highly improbable that 
these soils, already high in nitrogen, are in need of nitrogenous fer¬ 
tilizers. A better explanation of the response to applications of nitrate 
,of soda is that it is due to the precipitation of the soluble iron and 
from the nitrate. 
aluminum compounds in the soil by the unassimilated alkaline residue 
