Soil Fertility and Phosphoric Acid. 
41 
and finally it is endowed as an experiment station by Sir Lawes, in 
order that the experiments which have been carried on in the same field 
and in the same way for fifty years may be continued and enlarged. 
But this was not the only effect of the book of Justus von Liebig. 
Other men experimented and the theory was developed. The founda- 
tions for our great fertilizer industry were laid, an industry which in 
this country alone markets a product selling for tens of millions of 
dollars each year — and thereby causes an increase of at least twice as 
much in the value of our agricultural products. Truly, if he who makes 
two blades of grass to grow where but one grew before is a benefactor 
to humanity, how shall we find words to express the greatness of Justus 
von Liebig and those who aided in the practical development of this 
great theory ! For we find sands once worthless, barren and generally 
good for nothing, now green with their rich spoil of lettuce or cabbage 
or potatoes, or red with the strawberry or tomato, or bearing heavy 
crops of pineapples, indeed, many of our largest and most successful 
truck growers consider a soil only as something in which to put fer- 
tilizers. 
I do not think that any one will dispute that certain elements are 
necessary to the life of plants — carbon, hydrogen, oxygen, nitrogen, sul- 
phur, phosphorus, potassium, calcium, magnesium and iron; and of 
these, carbon is furnished in the carbon dioxide of the air and hydrogen 
and oxygen as water. 
Of the seven elements which are taken from the soil, and are essential 
to the life of plants, three appear to be always present in sufficient 
quantity, namely, iron, sulphur -and magnesium, while enough of the 
other four may not be present. These four are nitrogen, phosphorus, 
potassium and calcium, and one of these, calcium, appears to be needed 
by the soil rather than by the plant, when it is needed at all.. Nitrogen, 
phosphorus and potassium, then, may not be furnished by the soil in 
sufficient quantity to produce a good crop, and the addition of the lack- 
ing elements in suitable forms will have a decided effect upon pro- 
duction. Upon this fundamental basis has been developed the fertilizer 
industry. Fertilizers are applied to the soil to supply the plant with the 
phosphoric acid, potash or nitrogen, which is needed in the soil. 
It is a matter of great importance to ascertain whether a given soil 
or class of soils is deficient in plant food, and the extent of their de- 
ficiency. It is obviously a waste to supply phosphoric acid, potash and 
nitrogen to soils which do not need them, or to apply a mixture of the 
three in unsuitable proportions. If we knew the needs of the various 
types of soils, and the requirements of different crops, we would have 
a working basis to aid the individual in his applications of plant food 
to the soil. 
