8 
N. C. Experiment Station 
Discussion 
The composition of this typical soil shows that four of its components 
may be of influence in determining its reaction. The carbon dioxide 
produced by the oxidation of the organic matter would certainly serve 
as a solvent aiding in the loss of basic material by leaching. The silica, 
by tending to form insoluble silicates with these bases, would serve to 
oppose this action to some extent. With basic material as deficient as 
it is shown to be in this soil, however, it is probable that the acid sili¬ 
cates would increase, somewhat, the acidity of the soil. Neither car¬ 
bonic acid nor silicic acid is strong enough to increase the hydrogen- 
ion content of a soil sufficiently to render the soils toxic to plants. The 
evidence therefore points to the nitrogen and sulphur components of 
this soil as the probable sources of acidity. 
The oxidation of nitrogeneous organic matter to nitric acid might 
be expected to develop a high degree of acidity. The oxidation of sul¬ 
phur compounds with the production of sulphuric acid may share with 
nitrification the responsibility for this condition, but inasmuch as the 
content of sulphur is less than that of nitrogen, it is probable that 
acidity due to sulphuric acid is of less importance than is the acidity 
due to nitric acid. 
Aluminum is present in sufficient amount to combine with all the acid 
that is likely to be formed by nitrification, and the iron compounds if 
made soluble would be sufficient in amount to render the soil unpro¬ 
ductive for a long period. As compared with other soils of the State, 
this muck soil seems well supplied with nitrogen, phosphate and potash. 
Accurate data bearing on the response to fertilizers of crops grown on 
these plats are insufficient to warrant any definite conclusions being 
drawn, but if any great benefit or damage should follow the use of a 
fertilizer it would seem logical, on account of the comparative abund¬ 
ance of nutrient elements in the soil, to ascribe the effect of the added 
material to some influence other than that of the added plant nutrients. 
Effect of Liming on Reaction 
Many methods for the determination of the lime requirements of 
soils have been submitted to test in the hope that some way might be 
found by which to predetermine the amount of lime necessary to add 
to a soil to bring it to the optimum reaction for crop growth. Some 
of these methods have been widely accepted as of considerable value 
although the discrepancies between the several methods are such as to 
throw doubt upon the applicability of all of them. These discrepancies 
have been explained by the assumption that there are several types 
of acidity in soils and that the different methods vary in the accuracy 
with which all types are determined. 
