A Consideration of Adverse Temperatures 317 



cultural influences have already been discussed, but their 

 importance may well be restated in the present con- 

 nection. 



In some sections of the country winter injury is quite defi- 

 nitely associated with insufficient soil-moisture. The trees 

 are g^iving off moisture more or less continuously throughout 

 the dormant period. If the soil is so extremely dry when 

 winter sets in that in the slight root action which occurs, the 

 moisture that leaves the twigs and branches cannot be re- 

 placed through the roots from the moisture in the soil, injury 

 even to the extent of the death of the trees is likely to occur. 

 Thus, much of the so-called "winter injury" is in reality due 

 to a lack of soil-moisture. In regions where such soil con- 

 ditions are likely to occur, every cultural precaution possible 

 should be taken to conserve the soil-moisture. It is in this 

 connection that the growing of cover-crops which obviously 

 make demands on the soil-moisture late in the season may 

 be utterly incompatible with the welfare of the trees. On 

 the other hand, the relation of cover- and green-manure crops 

 to the humus of the soil, and in turn the relation of the 

 humus to the soil-moisture conditions, place much stress on 

 the desirability of returning to the soil adequate quantities 

 of decaying vegetable matter. 



Perhaps there has been recorded no experience which more 

 clearly shows the importance of good soil conditions in 

 relation to winter injury than the observations of Green and 

 Ballou ^ who made careful studies of the causes entering into 

 the destruction of thousands of peach trees in the Lake Erie 

 i:)each district in Ohio during the disastrous winter of 1903- 

 1904 previously mentioned. Investigations were made 

 (during the following season to determine the conditions 

 1 Ohio Bxpt. Sta, Bull. 157. 



