Dec. 37,1915 
Petrography of Some North Carolina Soils 
577 
interesting. These ham-shaped, isotropic particles are the remains of 
some form of life that flourished here during the submergence of this 
land. 
In the Orangeburg series occurs a higher content of minerals other 
than quartz than is found in either the Norfolk or the Portsmouth series, 
but still the amount is small. The soils of the Orangeburg series re¬ 
semble the Norfolk in many respects, and the same general minerals are 
encountered. 
The low content of other minerals than quartz in the soils of the 
Atlantic Coastal Plain is in close agreement with the total chemical 
analyses of the three plant-food constituents—phosphoric acid, potash, 
and lime. Many chemical analyses of the soils of this province show the 
above-named elements of plant growth to be exceedingly low. Not only 
do there appear to be close relationships existing between the total chem¬ 
ical analyses and their mineralogical complexity here, but in the soils 
of the entire State. This would suggest that since the petrographic 
methods have reached so high a state of development they may be used 
with a fair degree of accuracy for estimating the amounts of the mineral 
plant-food constituents carried by a soil. On account of the ease of 
manipulation and the time saved in their use, they lend themselves 
readily for such purpose; especially is this true in scanning soils for the 
farmer. The information gained is usually not commensurate with the 
time and expense involved in making “bulk analyses” of soils for 
farmers. As a rule, it is not necessary that he know the exact number 
of pounds of plant food contained in his soil; an approximation will 
usually suffice. A very close estimate as to the quantity of the elements 
present may be easily secured with the microscopic methods; even 
more, the way these elements are held is revealed. If more data were 
at hand showing the availability of the various mineral elements of plant 
growth furnished by the different soil-forming minerals, more definite 
information could be obtained as to the fertilizer requirements of the 
land with the microscope than by “bulk analyses.” 
In a former publication 1 the writer submitted data from which there 
appeared to be some relationships existing with certain crops between 
the mineralogical and chemical composition of the soils of this State and 
their requirements for the inorganic elements found in the usual ferti¬ 
lizer mixture—namely, phosphoric acid, potash, and lime. Additional 
evidence will be submitted along this line, using the cotton plant as the 
indicator for measuring the relative densities of the soil solution. 
In Table II will be found the average results of seven years' fertilizer 
treatments with cotton at the Iredell Substation, located upon typical 
Cecil clay loam. 
1 Plummer, J. K. Relation of the mineralogical and chemical composition to the fertilizer requirements 
of North Carolina soils. N. C. Agr. Exp. Sta. Tech. Bui. 9, 39 p. 1914. 
