CHAPTER XLIX 

 BIOLOGY AND AGRICULTURE 



Vocabulary 



Pulverizing, making into powder. 



Tillage, plowing, cultivating, harrowing, or hoeing the soil. 



Retain, to hold. 



Diminishing, making smaller. 



Civilization rests upon the soil. In so far as our knowledge 

 enables us to use the soil to best advantage, only so far can we 

 advance in population, wealth, and national growth. At present 

 we are far from realizing our greatest agricultural efficiency, as 

 the following tabulations show. 



China supports 3500 people per square mile. 



Japan " 2000 



Belgium " 300 



United States " 30 " 



As to crop yields we compare as follows, 



Maximum yield per acre U. S. yield per acre 

 Potatoes 500 bushels 96 bushels 



Wheat 50 " 14 " 



Corn 100 " 28 " 



Oats 100 " 32 " 



Evidently there is much to be learned before we shall obtain 

 the best results from our national resources. 



Soil Formation. Soil is formed from rock by the action of heat 

 and cold, water and ice, bacteria and protozoa, which are all 

 engaged in pulverizing its particles and adding to it organic matter 

 and nitrogen compounds. Proper tillage admits air for plant use 



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