12 HINTS ON SOILS AND FERTILIZERS 
magnesium. Such elements as carbon, hydro¬ 
gen, oxygen and nitrogen are commonly found 
as gases, but they are also found as part of 
the solid soil particles. In fact, it is very sel¬ 
dom that an element is found in the pure state, 
but most generally in combination with one 
or more other elements. For instance, the 
mineral elements are usually found in nature 
as oxides, or in combination with oxygen. 
Plants do not draw upon each of the above 
named elements in the same proportion for 
their plant food, and furthermore, hardly any 
two different kinds of plants, or crops, use the 
same proportion of plant food in maturing to a 
farm crop. For instance, an ordinary yield of 
cotton will remove in one season about 33 
pounds of nitrogen, 6 pounds of phosphorus, 
and 12 pounds of potassium from one acre, 
while a corn crop will remove from one acre, 
in one season, about 95 pounds of nitrogen, 16 
pounds of phosphorus, and 56 pounds of potas¬ 
sium. Thus, it will be seen that two different 
crops can vary considerably in the amount of 
plant food drawn from the same acreage of 
soil. 
Three other mineral elements are found in 
plants, namely, sodium, silicon and aluminum, 
but it has been proved that these elements are 
not absolutely required by the plants, and all 
the farm crops have been grown in soils de¬ 
pleted of these elements, with results just as 
satisfactory as when these elements were 
present. 
There are three elements, possibly four, that 
are used in larger quantities than are the other 
