Growing Plants Without Soil. 
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In the last few years Hydroponics or "dirtless farming" 
has "become front page news in America. Hydroponics (from Greek 
words meaning water and labour) is a new term invented in 193& 
by men who had perfected ways of growing plants in water and 
not in soil; they labour with water, and not with dirt. Dr. 
W.F. Gericke was the pioneer of the method. After a series of 
careful experiments, dating from about ten years ago, he had 
remarkable results, producing many kinds of plants of very 
large size, and heavy crops of tomatoes, from shallow tanks of 
water. American newspapers heard of this, and Dr. Gericke had 
an embarrassing amount of publicity. Companies were promoted 
for popularizing the method by selling the necessary equipment 
to the public. The result has been some extravagant claims as 
to the simplicity and effectiveness of hydroponics. There is 
no doubt that when carefully managed the method has great 
possibilities , but it is not a short road to easy success. It 
is interesting and instructive, and something new for most people, 
and it has appealed to the popular imagination. But the method 
is not a modern discovery. Its history goes back a century, 
to the first scientific work on the nutrition of plants. 
Plants take part of their food from the air through their 
leaves, and part from the soil through their roots. From the 
air they take carbon dioxide, and with the energy from sunlight 
build this up (by combination with water) into carbohydrates: 
sugars, starch, cellulose, etc. This action on the part of 
plants was first demonstrated about the end of the 18th century, 
when modern chemistry began. It was then known that roots 
absorbed water from the soil, and with the water certain salts 
in solution, but no observations were made on the precise 
requirements of the roots until about 1840. 
The soil on which ordinary roots live is a mixture of very 
complex substances. The water in the soil gradually dissolves 
some of the simpler substances, and these are taken up by the 
roots with the water. In order to simplify the study oi this 
process, scientists devised methods of growing plants without 
soil. They used two methods. One was to use washed sand instead 
of soil; this sand contained no more soluble substances. The 
plants growing in the sand were given certain salts dissolved 
in the water used to water them. But as it is difficult to wash 
sand so thoroughly that it contains no soluble substances, a 
more sensitive method was to grow the plants with their roots 
in pure distilled water, to which weighed amounts of various 
substances were added. In this way it was possible to find what 
elements a plant needed for its growth, and in what kind of 
proportions. This method of water culture has been used by plant 
physiologists for a century past to study the nutrition oi plants, 
so that hydroponics is no new thing. Hydroponics is the appli¬ 
cation of the water culture idea to the practical purpose of 
growing plants for use. 
By means of the water culture method, it was soon estab¬ 
lished that the following elements are necessary for plant life: 
carbon, hydrogen, oxygen, nitrogen, potassium, calcium, phos¬ 
phorus, magnesium, sulphur, and iron. It was later discovered 
that other elements were also needed in smaller quantities, and 
the number of these gradually increased as methods improved. 
These elements of which only minute amounts are needed are called 
"trace elements"; different plants differ in their demands of 
them. The elements are given to the roots combined in the form 
of simple salts. Various mixtures of such salts are possible. 
