IOO 



Commercial Gardening 



temperature has its effect in splitting up the soil into smaller particles. Of 

 course the temperature varies according to altitude, season, and climate, but 

 it seems to be universal that night temperatures are always lower than day 

 temperatures. 



The temperature of the soil itself, as distinct from that of the air, varies 

 according to the nature of the soil and the depth at which it is cultivated. 



All heat is derived from the sun, 

 and the gardener seeks, in tem- 

 perate climes at least, to secure 

 as much as possible for his crops. 

 Thus he likes to have his land 

 with a gentle slope between the 

 south-east and the south-west, 

 because a larger surface is thus 

 exposed to the direct rays of the 

 sun. Even on level ground, if 

 he is wise, he will always arrange 

 his rows of fruit trees and bushes, 

 Potatoes, Lettuces, Tomatoes, 

 Peas, Beans, &c., running as near 

 north and south as possible, so 

 that the sun shall shine in be- 

 tween the rows at midday to 

 warm the soil about the roots. 

 If the rows run east and west, 

 one will shade the other, with 

 the result that the soil will have 

 a lower temperature, the effect 

 of which is less feeding activity 

 of the roots. 



The annexed diagram, from 

 The Standard Cyclopcedia of 

 Modern Agriculture, shows the 

 variation of temperature in 

 clayey, sandy, and chalky soils. 

 It will be noticed in each case 

 that the temperature of the soil 

 at 4 ft. deep is always higher than that of the soil at 1 ft., and higher than 

 the air, during the first three months of the year (January, February, 

 March), and (in the case of clay and sand) during the last four months 

 of the year (September, October, November, December). During the other 

 months, April, May, June, July, August, the soil at 4 ft. deep is gener- 

 ally several degrees cooler than the air. The diagram shows the variations 

 for the three soils. 



Wind. This plays an important part in the formation of soils. It 

 sweeps over the surface, taking away the moisture from it, and in dry 



Air Temperature 



Soil Temperature at I foot deep 

 . Soil Temperature at 4 feet deep 



Fig. 84. Variation of Temperature in Clayey, Sandy, and 

 Chalky Soils 



