THE FUNDAMENTALS OF 

 FRUrr PRODUCTION 



SECTION I 

 WATER RELATIONS 



The importance of moisture as a factor in the production of fruit 

 is appreciated only in part. In arid sections the lack is obvious; in 

 many regions certain lands are recognized as too moist for fruit plants. 

 In the majority of the so-called humid sections, however, there is a 

 tacit assumption that nature provides satisfactorily for the requirements 

 of fruit plants. Drought may diminish or destroy other crops, but as 

 long as trees survive there is considered to be sufficient moisture. 



The forest trees, relied on as evidence of this sufficiency, show, even 

 in a limited area, striking differences in vigor^ according to their locations. 

 One of the most important factors recognized by the forester as affecting 

 tree growth, is moisture. Certain spots even in humid regions, are 

 chronically dry, some are nearly always wet; others, favorable in some 

 seasons, are subject rather frequently to excess or deficiency of moisture. 



Much of the complacence concerning the water supply of trees is 

 based on the supposedly great range of their roots and the consequent 

 great amount of soil from which they can draw water# For this reason 

 a statement of the extent to which forest trees actually deplete the soil 

 moisture is pertinent. Zon^^^ cites data showing moisture contents 

 in June of 4.5 and 4.8 per cent, respectively at 4 and 8 inches in soil 

 through which forest tree roots were ranging, while adjacent spots within 

 the forest, exactly similar except that the roots had been excluded con- 

 tained, at the san>e depths, 13.8 and 11.0 per cent, respectively. At' 

 16 inches the root free soil had over twice as much moisture as that to 

 which the roots had access. Evidence is cited to the effect that the 

 water level is lowered under forest and that with the removal of the forest 

 the water level rises. Zon considers that the inability of many species 

 to grow under an established cover of trees, commonly called shade 

 intolerance, is in reahty due to the low supply of moisture in the soil. 

 When the roots of the top growth are excluded from an area, the intol- 

 erant species grow there with considerable vigor. 



Deficient and excessive moisture are admittedly each a hmiting 

 factor in crop production. Table 1, based on estimates by crop reporters 



1 



