COTTON 129 
being from 6 to 8 per cent of the former and 7 to 9 
per cent of the latter. 
Cotton Seed Meal:—Contains 7 per cent of 
nitrogen, or 140 pounds to the ton, and is the most 
important of the vegetable products used in 
commercial fertilizers. It decays very rapidly but 
lasts for a considerable length of time. It is much 
less quickly available than nitrate of soda or 
sulphate of ammonia, and more promptly available 
than tankage. 
PHOSPHORUS 
Experiments tend to show that phosphorus is the 
chief element demanded by most cotton soils. As 
is true of nitrogen, so phosphorus is necessary to 
the full and complete der lbamiens of all parts of 
the plant, but its usual use is in fruit and seed 
production. Being a mineral substance, a de- 
ficient supply in the soil can be reinforced only 
through artificial means. 
SOURCES OF PHOSPHORUS 
Phosphatic Rock:—These are mined in North 
and South Carolina, Tennessee, Georgia, and 
Florida. They must be ground finely before being 
used, and even then are slow to decay. Best 
results are obtained by treating the ground rock 
with sulphuric acid to make the phosphoric acid 
available. 
These materials make up the bulk of the phos- 
phorus supply in cotton fertilizers. ‘They contain 
from 12 to 16 per cent of available phosphoric 
acid. 
Bone Fertilizers:—Bone was early used as a 
fertilizer and is still popular today. ‘‘ Ground 
