WINTER INJURY 



279 



plant in poor shape to endure further drying. . . . Some of the plants 

 that defer this change (to winter condition) the longest are among the 

 hardiest we have.''^*'*' 



Cultivation. — Experimental demonstrations with Wealthy apple trees, 

 on 15 widely separated farms in South Dakota, give quantitative 



Table 23. — Effect of Cultuhal Conditions 



Dakota^-s 



ON Winter Killing in South 



verification of the opinions just quoted (Table 23). Lot 1, showing the 

 lowest moisture content and the greatest injury to trees, was composed of 

 trees planted in prairie sod; Lot 2 was cultivated each 10 days till Aug. 

 10; Lot 3 was "cultivated each 10 days till July 1, followed by a cover 

 crop of fall rye or buckwheat" and Lot 4, which showed least injury, 

 was cultivated each 10 days until Aug. 10, just as Lot 2, but in addition 

 received a heavy watering just before the ground froze for the winter. 

 The investigator concluded that "summer cultivation is positivelj^ needed 

 and in very dry seasons fall watering or irrigation of some sort is not 

 only advantageous but necessary." 



Cover Crops.— Another point of interest here is the lower soil moisture 

 in the cover crop lot and the somewhat greater attendant injury, as 

 compared with the clean cultivated lot. Had a winter favorable to 

 root killing intervened, the results in these two plots might have been 

 different. However, the danger from cover crops in this region of light 

 rainfall is apparently more frequently present than the danger from their 

 absence which is discussed presently. This point doubtless has occasion- 

 ally equal application in dry situations in other regions. Comparison of 

 these results with those of Emerson, reported below, indicate that the 

 best insurance against winter injury in general in this region — and in 

 occasional sites in more humid sections — is a frost-tender cover crop 

 with a heavy late fall irrigation. To be sure, in those districts where 

 irrigation water is not available, the preventive measures against the 

 winter injuries associated with drought must of necessity be incomplete. 

 However, the recognition of the liability of a given site to this form of 

 injury may enable the grower so to shape his cultural practices early in 

 the season as to minimize the danger. 



