PETROGRAPHY OF SOME NORTH CAROLINA SOILS AND 
ITS RELATION TO THEIR FERTILIZER REQUIREMENTS 
By J. K. Plummer, 
Soil Chemist , Division of Agronomy , North Carolina Agricultural Experiment Station 
INTRODUCTION 
In connection with the detail study of the soils of North Carolina, the 
writer has had occasion to make many mineralogical analyses of the 
existing soil types as defined by the United States Bureau of Soils. These 
examinations have included all types of any prominence thus far en¬ 
countered in the survey and give some rather interesting data as to the 
formation and character of these soils which may be of more than local 
interest. 
The available data showing the mineral composition of soils are 
meager. The scope of those found is so broad that definite conclusions 
can hardly be drawn as to the relationships which exist between the 
mineral component and the character of soils. The behavior of the 
various sod-forming minerals toward the forces of weathering will have 
to be known before the soil investigator will be able to solve many of the 
complex problems confronting him. 
The methods used in these analyses are essentially those compiled 
by McCaughey and Frye. 1 Unfortunately, one serious criticism may be 
made regarding these methods—i. e., the defiance of members of the day 
group against identification. It is quite possible that this group plays 
the most important r 61 e in the various soil phenomena of all the sepa¬ 
rates which compose the soil. Yet it would seem that since the clay 
owes its origin to the coarser particles, some definite knowledge of 
the composition of the latter would be imperative. 
SOILS OF NORTH CAROLINA 
The soils of North Carolina are quite heterogenous and furnish well- 
defined examples for a discussion of the petrography of soils. The 
State is divided into three provinces, determined largely by the physio¬ 
graphic provinces used in any study of physical geography. There are 
the old Appalachian, locally known as the Mountain section, Piedmont 
Plateau, and Atlantic Coastal Plain. As will be shown later, wide varia¬ 
tions in the mineralogical composition of the soils of these provinces are 
encountered. 
Practically all of the soils of the mountains are of residual origin and 
are derived from igneous and metamorphic rocks, mainly gneiss, schists, 
1 McCaughey, W. J., and Fry, W. H. The microscopic determination of soil-forming minerals. U. S. 
Dept. Agr. Bur. Soils Bui. 91, 100 p., 12 fig., 12 tab. 1913. Bibliography, p. 99-100. 
(569) 
Journal of Agricultural Research, 
Dept, of Agriculture, Washington, D. C. 
bp 
Vol. V, No. 13 
Dec. 27, 1915 
N. C.—2 
