246 REPORT OF THE CHEMIST OF THE 
phosphoric anhydride, does not exist free as such in the plant, 
but in some combination, such, for instance, as phosphate of lime. 
The amount of potassium, calcium, phosphorus, etc., in different 
plants is not the same, and the farmer needs to become familiar 
with the wants of his different plants, just as he is with the wants 
of his different animals. 
The farmer knows that the cow and hog will not always do 
equally well upon the same kind of food, for they belong to differ- — 
ent classes, and their habits are quite different. This is just as 
true of different classes of plants, that is, plants botanically 
different, such as beets and the grains, or clover and timothy ; 
clover being a leguminous plant of the same family as 
peas, beans, etc., and timothy one of the grass family. Some 
plants like large quantities of potassium and require less of 
phosphorus to do well; others need an abundance of phosphorus 
and.less potassium, while there are others that take up a great 
deal of calcium. The clovers all require large amounts of potash 
and lime. The grains need phosphoric acid and potash, and roots 
require that there be present in the soil an abundance of available 
potash. 
The farmer, in order to succeed as well in growing field crops as 
with his animals, should become familiar with the needs of the 
plants themselves as he is with the proper kinds of foods for his 
domestic animals. He should find out in what his soil stands in 
the greatest need, and then in growing crops, knowing their 
need, he will be able to purchase just that class of fertilizers which 
furnish the required food for his crops. Of these mineral ele- 
ments there are but two to which special prominence is given in 
commercial fertilizers, for in most soils the others are present 
in sufficient quantity, although the application to the soil 
of many of the other ash ingredients may be followed by 
most beneficial results, either from their chemical or physical 
action in the soil. Phosphoric acid and potash are the two 
ash ingredients which enter into our commercial fertilizers, 
but both lime and sulphuric acid are essential ingredients of all 
super-phosphates. Potash is supplied either in the form of wood 
ashes or as potash salts, like the sulphate and muriate of potash, 
which come largely from the German mines. 
Besides these ash elements there is also required nitrogen for 
plant growth, and this is by far the most costly part of plant food. 
