Soil Conservation-Some Social and Economic Aspects

Abstract

We human beings are 95 per cent car-bon, hydrogen, oxygen and nitrogen; and so are plants. Men as well as plants are only 5 per cent mineral. Luckily, for the 95 per cent there is no danger of absolute shortage. Nature has given us an unlimited supply of these elements in air and water, the most permanent of our re-sources. We can obtain all our hydrogen and part of our oxygen from water. Four-fifths of the atmosphere is nitrogen — there being no less than 20 million tons of nitrogen over every square mile. The oxygen content of the air amounts to 20 per cent by volume. Coal and petroleum, the main stored sources of carbon, are no doubt limited in supply and, therefore, call for careful husbanding; but in the carbon dioxide of the air we have an easily renewable source which we can draw upon through the synthetic processes of plant growth.