RELATION OF THE MINERALOGICAL AND CHEMICAL 
COMPOSITION TO THE FERTILIZER REQUIRE¬ 
MENTS OF NORTH CAROLINA SOILS 
By J. K. Plummer, Soil Chemist 
In the systematic study of soils little attention has been given in the 
past to the minerals which comprise the greater part of most soils. 
Since the time of Liebig, investigators have devoted their attention to¬ 
ward determining the amounts of the various elements of plant food, 
giving little thought to the way these elements were held in the soil. 
Much time has been spent in field experimentation and in a study 
of the physical properties of soils; and more recently the biological 
side has occupied the attention of many investigators. The results of 
these different methods of attack have thrown much light on the im¬ 
portant problem of producing maximum crops at the minimum cost. 
It would appear that a knowledge of the amounts of the various plant 
food constituents of the soil, from which the plant must draw its nour¬ 
ishment, and the form in which these elements are held would be of 
the highest importance to the intelligent cultivator of the soil. Taking 
this information with that afforded by carefully conducted field tests, 
much light will he thrown on the problem of soil fertility. 
This bulletin has been prepared with the end in view of supplying 
additional information to that which has already been secured as to 
the nature of the soils of North Carolina. These facts will be helpful 
in forming a more correct judgment with reference to the future man¬ 
agement and treatment in building up a rational system of agriculture 
in the State. 
In the laboratory determinations of the more important elements of 
plant food have been made on over 1,600 samples- of soil in connection 
with the soil survey of the State. Field experiments of the Division 
have been running twelve years on soils representing the important types 
of the three large provinces into which the State has been divided, 
namely, Mountain, Piedmont, and Coastal Plain. Mineralogical analy¬ 
ses have been made on the sand and silt separates on some three hundred 
soils by use of the methods described by McCaughey and Fry. 1 
The value of the mineralogical analyses cannot be overestimated, as 
they reveal the elements as they are found in the soil. These analyses 
supplement the total determinations by chemical methods. By the chem¬ 
ical analyses the total amounts of the different plant food constituents 
are obtained, but little information is gained as to the form in which 
this reserve is stored in the soil, whereas, the mineralogical analyses 
is mainly concerned in showing the chief forms of combinations in which 
the potential plant food occurs. With the mineralogical analyses an 
approximation as to the amount of each plant food constituent may be 
obtained. Their value lies in showing the form in which the plant food 
constituents are held. Experience has taught that the arbitrarily chosen 
solvents for measuring the more available portion of the stored plant 
food have given conflicting results as to the actual fertilizer deficiencies 
bulletin No. 91, Bureau of Soils, U. S. Department of Agriculture. 
