29 
SUMMARY 
The field results obtained on experimental farms show that there 
is a close relation between the chemical and mineralogical composi¬ 
tion and the fertilizer requirements of the soils under experiment. 
The chemical analyses are of value in determining the total amount 
of the various elements of plant food which the soil contains, and the 
mineralogical analyses supplementing the chemical analyses, show to 
a great extent in what way these elements are combined. 
The soils of the Mountain and Piedmont sections of the State are, 
as a rule, better supplied with potash, lime, and phosphoric acid 
than are those of the Coastal Plain. 
The micas furnish to a much larger extent the potash supply in 
the former two sections than they do in the latter. In a great many of 
the Mountain soils muscovite and biotite are the main sources of 
potash, and in a majority of these soils the biotite content is well pre¬ 
served. The potash felspars are much more abundant in the soils of 
the Piedmont Plateau than they are in the Mountain section, how¬ 
ever, the micas furnish much of the potash for these soils. In the 
Coastal Plain soils, orthoclase and microcline supply most of this 
material, and it is on these latter soils that the greatest response is 
secured from the use of potash fertilizers, as shown by the field results 
thus far published. 
The phosphoric acid content of most North Carolina soils is low. 
Much of this element of plant food is found as apatite included in 
quartz and other minerals. In this form it is doubtful if the plant 
can draw its supply of phosphoric acid, certainly not for many years 
to come. The soils of the Coastal Plain carry their main supply of 
phosphoric acid in other forms than apatite, for in very few instances 
has this mineral been encountered in soils from this section. 
Lime in the Coastal Plain soils is for the most part in a less avail¬ 
able form for crops than much of that found in the sections higher 
up in the State. The former soils derive their main supply of lime 
from epidote. In the Piedmont and Mountain portions hornblende 
and the plagioclase felspars are found in larger quantities than in 
the Eastern section. The amount of the plagioclases has never been 
large, except in the soils of the Iredell series. There they are found in 
some quantity. 
In the mineralogical composition as a rule there is little difference 
between the soil and subsoil. This may be due to the depth to which 
the samples were taken. 
