60 



FUNDAMENTALS OF FRUIT PRODUCTION 



Table 31. — Root Distribution of a 40-yeak Old Apple Tree in a Thin Rocky 



Soil Under Sod for Many Years 



(After Jones''^) 



In Dwarfs.- — In contrast with the comparatively extensive root 

 systems of trees growing in the field are those of dwarfs occasionally 

 grown in the garden or under glass whose growth is restricted by various 

 means. Sometimes resort is made to root pruning; sometimes the roots 

 are restricted by planting in pots or tubs. Such trees develop very com- 

 pact and much branched root systems that exploit very completely the 

 soil within their range. Dwarf trees with such restricted root systems 

 are much more subject to injury from extremes of moisture than standards 

 with unrestricted root systems. Consequently their successful culture 

 necessitates much greater care in watering, fertilization, pruning, exposure 

 to light and management in general. 



The Influence of Soil Moisture Content.- — Within the ranges possible 

 for the different species, depth of rooting depends to a very important 

 extent on soil moisture and the correlated factor, aeration. Roots do 

 not grow and branch freely in a very dry soil, or in one that is approach- 

 ing a water-logged condition. The water-logged soil probably inhibits 

 root growth and activity through a lack of aeration; the dry soil through 

 a lack of the stimulating effect of the water itself. Figure 7 gives some 

 idea of the influence exerted by the percentage of soil moisture on root 

 formation and root distribution when other factors are as uniform as it is 

 possible to make them. In this case, however, the soil moisture did not 



