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FROST HEAVING: CAUSES AND EFFECTS 



Peter L.M. Veneman 

 Department of Plant and Soil Sciences 



Soil structure is generally improved by the annual cycle of 

 freezing and thawing. These processes result in better aeration, 

 increased water holding capacities, smaller clods, and smoother 

 seedbeds. Considering these beneficial effects most agronomists 

 and soil scientists will recommend fall plowing to farmers espec- 

 ially in areas where fine textured soils are predominant and if 

 soil erosion during the following winter and spring is not of 

 great concern. While freezing and thawing cycles may be advan- 

 tageous for the production of annual crops, their detrimental 

 effects on perennials such as alfalfa have been demonstrated in 

 those parts of the country where the soils are periodically frozen. 



Like alfalfa, the fruit tree has its feeder roots in the upper 

 18 inches of the soil profile, which is also the part mostly 

 affected by annual frost action. In the spring and early summer 

 of 1979 we observed that many trees throughout Massachusetts 

 experienced root injury the preceding winter especially on sites 

 with soil drainage problems. Injury initially was limited to the 

 tree roots but later in the year it resulted in the loss of some 

 branches and in the most severe cases the trees died. Some of 

 the partially damaged trees are still weak and need to be replaced. 



Most of the winter injury problems are related to the formation 

 of ice lenses in the soil profile as a result of excess soil water. 

 Since the cold season is with us once again, it seems appropriate 

 to discuss this matter in greater detail in this winter issue of 

 Fruit Notes and to indicate possible ways to prevent such damage 

 to fruit trees in the future. 



Frost heaving occurs mostly on moist to wet soils, although it 

 sometimes can be found in well drained, fine textured soils with 

 shallow water tables. Researchers (2) studying the susceptibility 

 of alfalfa to frost heaving in southern Illinois found that poorly 

 drained soils with high ground water tables exhibited the most heave 

 and greatest winter-kill of alfalfa seedlings. Well drained soils 

 had some heave but this did not result in significant injury to the 

 plants. These experiments showed that the greatest amount of heave 

 occurred when the night temperatures were a few degrees below freez- 

 ing and the day temperatures were above 32 F. 



Water in freezing soils is transformed into ice crystals. This 

 ice functions as a center for further crystallization of moisture 

 when additional water is allowed to flow towards the frozen part 

 of the soil, which can happen when the initial soil was wet or has 

 a water table close to the soil surface. As long as water can move 



