34 SOILS 



In early spring we frequently have warm rains 

 that raise the temperature of the surface soil several 

 degrees. It is after these rains that "things just 

 jump." 



Fortunately the means of controlling this factor 

 is largely in the hands of the farmer. The excess 

 water may be removed, and the soil warmed by 

 draining it. The draining of land by deep plowing, 

 ditching, tiling and other methods is considered 

 in Chapter IX. 



Influence of Exposure on Warmth of Soil. The 

 "lay of the land" with reference to the compass, and 

 the steepness of the slope, have an important in- 

 fluence on the warmth of the soil. The soil on a 

 northern slope which receives about one-third 

 less sunshine than a southern slope, depending 

 upon its steepness may average 7 to 10 cooler in 

 summer than the soil on a southern slope. The 

 soil of a gentle southern or western slope may be 

 3 to 5 warmer than the same kind of soil is on a 

 level. In the northern part of the United States the 

 sun is always more or less in the south, so that its 

 rays never strike level soil squarely. It is farthest 

 in the south when the need of greater soil warmth 

 is most likely to be felt. In early spring a slope of 

 12 to 15 feet in a hundred will catch the largest 

 number of the sun's rays, being most nearly at 

 right angles to them. Many of the rays glance off 

 from the level land because they strike it obliquely. 

 The practical conclusion is that a moderate slope 

 to the south or southwest is the best site for a crop 

 when earliness is desired; which is what hus- 

 bandmen, especially fruit growers and gardeners, 

 have known and practised for centuries. 



Dark-coloured Soils Absorb More Heat. The 

 colour of a soil is often some index to its agricul- 



