WINTER INJURY 271 



fluctuate more with the air temperature than the heavy soil 

 because of the difference in specific heat.^ 



Hedrick - reports on the experience of Michigan and New 

 York growers with the peach. In the first case the growers, al- 

 most without exception, considered a sandy, gravelly, or stony 

 soil much more favorable to peach-growing and that peach 

 trees are more hardy in such a soil than in a heavy one. 



Bouyoucos investigated the depth and rate of freezing 

 of the following types of soil: gravel, sand, loam, clay, and 

 peat. It was found that "they all froze about the same 

 time in the upper 6 inches, but in the spring they thawed and 

 warmed up at different rates. This was attributed to their 

 different specific heats and to the downward and upward trend 

 of air temperature in the fall and spring respectively. The 

 gravel and sand thawed first, followed by clay 1 day later, 

 loam 2 days later, and peat 10 days later. After they were 

 entirely thawed out all the types of soil had almost the same 

 temperature from then on throughout the summer, autumn, 

 and winter." 



He further shows, however, that if very cold weather is 

 experienced early in the winter without any fluctuations in 

 temperature, the light soil freezes deeper than the heavy 

 ones, thus giving an advantage to higher moisture-content 

 in such a case. In New York state, however, the growers 

 would not distinguish between a heavy and a light soil so 

 far as winter injur}'- is concerned, provided the heavy soil 

 is "warm and dr}^" In both states the growers preferred 

 a gravelly subsoil in order to secure a hardy tree. 



^ There would seem to be a discrepancy between this statement 

 and the one following by Heth-ick, but this is probably explained by 

 the fact that trees growing on clay soil usually mature later and hence 

 are more subject to injury in the tops. If the injurj^ occurred in the roots 

 rather than in the tops, it would be much worse in the sandy soil. 



2 Hedrick, U. P. Trans. Mass. Hort. See. 1919. 



