14 HINTS ON SOILS AND FERTILIZERS 
nitrogen is not as plentiful a plant food as it 
would be if it were able to be taken in by the 
plant as the other gases are assimilated by it. 
Phosphorus is a mineral element, and also 
has to be taken in through the roots of the 
plant. There is considerably more phosphorus 
removed by the ordinary farm crops annually 
than is put back into the soil, even when the 
best of care is taken to restore the plant food 
to the soil. As a result, many farms are not 
producing as large a yield as they produced 
formerly, because of the depletion of the phos¬ 
phorus supply. While this factor is not the 
only cause of lessened production, it is one of 
the outstanding reasons why many farms do 
not produce the yield now that they once en¬ 
joyed. Of course, different sections of the coun¬ 
try vary in the amount of phosphorus needed to 
maintain the soil fertility, but in the majority 
of cases it has been found that, outside of 
nitrogen, phosphorus was the most needed ele¬ 
ment. 
Potassium is not drawn on quite so heavily 
by the plants as are nitrogen and phosphorus, 
but there are many instances where this ele¬ 
ment is seriously lacking in the soil. This ele¬ 
ment is never used in its pure state (as a silver- 
white metal) but only in its combinations with 
oxygen, or oxygen and carbon, termed “potash.” 
One of the matters that is often most puz¬ 
zling to farmers, is the failure of certain crops 
to grow, despite the large amount of a certain 
kind of fertilizer placed on the land. The prob¬ 
abilities are that the farmer is not applying the 
kind of fertilizer which the soil lacks the most. 
