EXPERIMENT STATION WORK WITH APPLES. 555 



nosotji, lowii. tho Diikotas, and ^lanitoba, droppod as lowas— 52 F. 

 The iujuiy to ajjplcs in tlic luii'scry and orcliard duiiii«r tliat jx'riod 

 was widespread and disastrous. Of 57 correspondents wlio reported 

 that the ground was destitute of snow at the time of this freeze, 43 

 stated tiiat the principal daniaoe to luirserv and orchard trees was to 

 tho root; and of 34 correspondents wlio icportcd the jjfround covered 

 witli snow, 20 reported that injury was chietly in the toj), while 

 stated expressly that there was no root injury." In Iowa youni^' a})ple 

 trees under 5 years old suffered more than older stock. The effect was 

 most severe on sandy soils not covered with vetietation. The chief 

 cause of the uiuisual winter injury was thought to be due to the lack 

 of a protectino' blanket of snow, coincident with the unusually severe 

 cold. Trees suffered more on clean soils than on exposed drj' knolls 

 with northern aspects. To obviate root killinj^the station recommends 

 as one of the essentials cover crops, preferably mammoth red clover 

 or hairy vetch. The Wisconsin Station" states that next in value to a 

 snow coverintr is a covering of litter. Oats, buckwheat, peas, vetches, 

 or mammoth clover are advised as cover crops for this })U!"pose. 

 iSIammoth clover is advised only in wet seasons. 



Professor Macoun reports that the secret of the successful culture 

 of ai)ples in the more northern regions of Canada, where the extreme 

 range of temperature sometimes varies from —40 to +104'-' F., seems 

 to lie largely in removing the snow from the roots of the trees during 

 winter, so that the ground will freeze to a depth of 4 to 5 inches, after 

 which a mulch of snow and straw is placed at the base of the tree to 

 prevent alternate freezing and thawing ])eforc tine weather comes in 

 the spring.^ 



Professor Craig ^ studied the effect of cover crops on thc^ depth of 

 freezijig and oV)tained the following comparative figures: Hare culti- 

 vated ground froze to a depth of 21 inches; under a cover crop of hairy 

 vetch it froze to a depth of 1»5 inches; under crimson clover, 15 inches; 

 under blue-grass sod, 12 inches, and under soy beans, 21 inches, the 

 latter crop affording no protection whatever. At the Delaware Station 

 ground covered with crimson clover is reported as unfrozen when 

 the temperature of the air was 14' F. In some box experiments 

 carried out by Professor Emerson'' the roots of apple seedlings were 

 much less seriously injui'od dui'ing the winter on ground covered with 

 a 4-inch straw nudcli than on bare ground. Not only did the mulch 

 protcH't the soil from so severe freezing, l)ut also from alternate freez- 

 ing and thawing. A cover crop that mats down upon the approach of 

 winter, like the hairy vetch or blue-grass sod mentioned above, affords 



"Wisconsin Sta. Bui. 77. 



''Canada Central Expt. FarniH lljtts. lS!»i>, j). K«). 



'•Nfw York Curiicll Sta. I'.nl. 1*»H. 



'^ Nehriwka Sta. Bui. 7i». 



