356 



FUNDAMENTALS OF FRUIT PRODUCTION 



was found that cultivation apparently increased the temperature about 

 2°.^^^ Cox states: "It is as important to cultivate as it is to practice 

 drainage," but adds that "it is impossible to determine absolutely the 

 advantage in exact degrees gained by cultivation, draining or sanding. " 

 It is evident that his statement refers to any attempt to make the 

 observed differences fit all cases. 



Cultivation is said by Petit to increase the loss from the surface of 

 the soil b}^ radiation, diminishing heat conduction from below; tamping 

 the soil is stated to lessen this danger. It should be observed that the 

 temperatures recorded are those of the surface and not of the air above. 



Table 65. — Temperatures at Surface of Cultivated and Packed Soils 



{After PetiP^^) 



(Degrees Centigrade) 



Increased surface of the loosened soil would tend to increase the loss 

 of heat by conduction and might easily raise the temperature of the air 

 immediately above it, though the surface itself be cooled. 



Significance — Particularly in Small Fruit Culture. — A saving of 

 2° or 3° may or may not be an important matter according to circum- 

 stances and consequently any one of the factors affecting temperature 

 may in itself be important. However, it is frequently the case that 

 several of them are operative at once and their combined effect is likely 

 to be considerable, particularly on nights when these differences are 

 most important. 



Cox expresses this aptly: "While there is an average difference of 3.4° . . . 

 between the minimum thermometers in the thinly vined and the heavily vined 

 sections, a difference of 2.4° . . . between the minimum thermometers on 

 peat and sanded bogs, both thinly vined, and a difference of 2.2° between the 

 surface and 5 inches, it is obvious why an average difference of 10° . . . can 

 exist between a minimum thermometer exposed at the most favorable location 

 as far as drainage and sanding and cultivating are concerned and another in a 

 most unfavorable location, an unsanded peat section with a very dense growth 

 of vegetation, and poor drainage. [The greatest difference observed by Cox 

 was 17.1°F.] It is not strange therefore that in a bog where there is a variation 

 in the conditions of sanding, draining, and cultivation, the range in minimum 

 temperatures is considerable, and that a portion of a bog is seriously injured by 

 frost while another portion completely escapes. "*« 



These inequalities are extremely localized; probably none of them is 



