4 
of soils. By knowing the minerals that carry this stored plant food and 
the reaction of these minerals toward solution, certainly a more intel¬ 
ligent opinion may be rendered as to the possible requirements of soils 
for the various fertilizing materials. 
Description of Minerals Carrying Plant Food in North Carolina 
Soils. 
Potash, the felspars, orthoclase and microcline, and the micas 
(muscovite and biotite) are the minerals which supply the soils of this 
State with potash. These minerals are widely distributed and occur in 
nearly all the soils examined to a greater or less extent. However, 
there is wide variation in the amounts of these minerals found in the 
different provinces of the State. In many of the Mountain soils potash 
is derived principally from the micas, muscovite and biotite furnishing 
by far the greater part of the potash found in soils of this section of 
the State. In the Piedmont section, the micas have been replaced to 
some extent by the felspars, but in many of the soils of this region, the 
former minerals furnish much of their potash supply. Orthoclase and 
microcline are the predominant potash-bearing minerals of the Coastal 
Plain, the micas occurring only as traces in many of these soils. 
Often orthoclase fragments assume a fibrous appearance and are 
rounded in contour, as though they had been weathered to some extent. 
Microcline always shows well preserved faces and sharp edges, appa¬ 
rently having been very little affected by natural agencies, which are 
constantly operating in the soil. Biotite or black mica readily forms 
alteration products, passing over into chlorite and epidote. In this 
mineral the potash is held in the more available form than in any 
other mineral found in our soils. It contains considerable oxide of iron, 
which is very likely responsible for the readiness with which this mineral 
is decomposed. Muscovite, from its optical properties, appears to 
weather little or none, but there is evidence that this mineral does give 
up its potash with greater readiness than do the felspars. 
Results by Other Investigators With Potash Minerals. 
E. Blanck 2 gives results of comparative tests in pot experiments with 
various silicates as the source of potash. He finds that the micas fur¬ 
nish a more available supply of this constituent than do the felspars. 
D. N. Praenishnikov 3 found that in comparing the potash silicates as 
the source of potash for plants, biotite and muscovite w T ere superior to 
the felspars as carriers of potash. 
Fraps 4 reports that all the potash is extracted from biotic with 
strong HCL, about one-third from muscovite, and only a small percent¬ 
age from orthoclase and microcline. He states that practically no 
potash is removed from orthoclase and microcline by one-fifth normal 
nitric acid, less than 10 per cent, from biotite, and 15 per cent, from 
muscovite. 
These conclusions are borne out in our field experiments, which will 
be discussed more in detail in the following pages. 
2 Jour. Landw. 61, 1913, No. 1, pp 1-10. 
3 Landw. Ves. Stat. 77, 1912, pp 399-411. 
4 Tex. Station Bulletin 145. 
