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K.iuliiiiiiui Fabry 



POWER MACHINERY AND CULTIVATION 



The use of power machinery has enabled us to plow and cultivate much more acre- 

 age than formerly. In this picture one man with a tractor cultivator is seen doing 

 work as fast as six men can do it with horse-drawn cultivators 



tions are becoming independent of natural supplies of nitrogen com- 

 pounds, which most of them would otherwise have to import. But by 

 the end of the first year of its participation in the Second World War, it had 

 become necessary for the authorities in the United States to restrict the use 

 of nitrogen fertilizers for all nonessential crops, lawns, and flower gardens. 

 Out of the Earth Those who live in the country usually understand 

 how our lives depend upon the soil, but city dwellers come to think of 

 the land as merely the surface, or place, upon which we live. We have 

 seen that water is necessary for all life processes, and that the carbon 

 dioxide of the air supplies material for the making of carbohydrates. All 

 the other substances present in the bodies of plants and animals come out 

 of the soil. Just as sunlight and sun-heat are the sources of our energies, 

 so earth, water and air are the sources of our bodies. The crowding of a 

 population may reduce food supplies through a shortage of soil materials. 



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