21 
(7) That potash added to phosphoric acid increased the yields 
decidedly over phosphoric acid alone, the average annual increase 
for phosphoric acid alone being 6.2 bushels per acre, and for phos¬ 
phoric acid and potash 16.5 bushels; 
(8) That potash added to nitrogen and phosphoric acid was at a 
small increase in yield and without profit; and 
(9) That the yields from the addition of lime to nitrogen, phos¬ 
phoric acid and potash were smaller than from the three fertilizer 
constituents combined. 
The most important constituent in producing increased yields and 
profits on this soil was phosphoric acid. Nitrogen and potash singly 
or combined, gave good returns when used with phosphoric acid, but 
were of little or no value when used alone or with each other. Nitro¬ 
gen added more largely to the yields than did potash. 
In table 10 will be found the average mineralogical and chemical 
composition of plats on Fields A, B, and C. 
Though the potash content in this field is much lower than those ol 
the mountain section, we find enough of this element to produce large 
crops for many years. Here the micas, also furnish much of the 
potash supply especially in the finer particles of this soil. Orthoclase 
is very abundant in the sand separates of soils of these plats and it 
is in a bad state of preservation. The faces present a fibrous looking 
appearance, resembling an ice crystal as it melts. This soil is sup¬ 
plied with an abundance of lime bearing minerals as epidote, horn¬ 
blende and the plagioclase felspars. The latter minerals are more 
abundant than in those fields of the Mountain section examined. The 
nitrogen supply here is higher than is commonly found in this type 
of soil, due to the turning under of the pea crop grown on the plats. 
Phosphoric acid is principally in the organic state, as the amount of 
apatite found was very small, not enough to anything like furnish the 
supply shown by the chemical analysis. The apatite found was 
included in quartz and microcline fragments; in this form it is of very 
little value for plant use. 
Coastal Plain Soils. 
Location of Farm and Character of Soil." 
The Edgecombe Test Farm is located near the center of Edgecombe 
County, on the main road between Tarboro and Rocky Mount, approxi¬ 
mately eight miles from either place. It is two miles south of Kings- 
boro Station. 
The main upland soil of this farm is representative of much of 
the Coastal Plain section of the State. It consists of dark gray sandy 
to fine sandy loam, eight to twelve inches deep, underlain by yellow 
sandy clay subsoil. The surface soil is light in texture, and is com¬ 
monly very deficient in organic matter. It classifies as Norfolk sandy 
to fine sandy loam. Like most of the sandy soils of the Coastal Plain, 
the sand content is mostly silica which contains no important plant 
food. The chemical analyses of the soils of this type show them to be 
7 See N. C. Dept, of Agr. Bui., Vol. 35, No. 195 for details of field results of Coastal section. 
