306 



FUNDAMENTALS OF FRUIT PRODUCTION 



The minimum for Jan. 30 is certainly at tiie danger point for tree roots 

 in bare ground, while under compacted snow it is 8.1°F. higher and under 

 vegetation plus compacted snow it is almost 25° higher. The fruit 

 grower cannot induce snowfall at his will but he sometimes has a choice 

 between a slope where snow will remain and one where it will melt away 

 with a little warm weather. He knows that knolls and wind swept spots 

 in general are likely to need special care and that cover crops and wind- 

 breaks tend to hold snow that might otherwise blow away. 



Different Systems of Soil Management. — A protective covering of 

 vegetation can be provided by the grower with more surety than a snow 

 covering. Table 43, arranged from data by Bouyoucos,^^ shows the 

 effect of this covering on minimum soil temperatures at 3 inches depth. 

 The superior protection afforded by cultivated, bare soil as contrasted 

 with compacted soil is worthy of note. 



Table 43. — Average Minimum Soil Temperatures in Uncultivated and Culti- 

 vated Soil and in Sod^^ 

 (Degrees Fahrenheit) 



Craig^^ in Iowa reported soil temperature at 6 inches depth on a 

 January day, after hard freezing, two degrees warmer in sod than in 

 cultivated soil. 



Depth of freezing is a fairly good indicator, though indirect, of soil 

 temperature. Gourley^^ records observations made in New Hampshire 



