CHAPTER IV 

 THE TEMPERATURE OP THE SOIL 



18. Proper Temperature Necessary for Germination. 



— Throughout the winter months, the seeds and roots of 

 plants in the earth lie dormant. Plant food, moisture and 

 air are present in the soil ; but the proper temperature is 

 lacking. Seeds can not germinate, nor plants grow unless 

 the soil absorbs enough of the heat of the sun to raise the 

 temperature of the fields somewhat above freezing. Very 

 few of the seeds or plants awaken from their winter's 

 rest at a temperature near thirty-two degrees Fahrenheit, 

 the melting point of ice. Wheat will germinate and make 

 some growth at forty-one degrees but it thrives best at 

 eighty-three. Oats may germinate at thirty-eight ; their 

 most vigorous growth, however, is made at seventy-seven 

 degrees. The soil in a cornfield should register a tempera- 

 ture of at least forty-nine degrees, while ninety-two degrees 

 is the best, or optimum temperature for the germination 

 of this seed. Cucumbers, muskmelons and squashes 

 should not be planted until the oaks are fully in leaf, when 

 the soil temperature is around eighty degrees. 



19. How Temperature of the Soil is governed. — 



Since a warm soil is so important a factor in the germina- 

 tion of seeds and the development of roots, let us consider 

 the laws that govern the temperature of the soil. These 

 laws, or principles, may be summarized in three sentences : 

 The temperature of the soil depends first upon the 

 amount of air space in it. 



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