458 



THE PRINCIPLES OF SOIL MANAGEMENT 



ture. Its effect due to color is reduced by the higher 

 water-content which such a soil normally retains. 

 (See page 101.) Red soils absorb more heat than yellow 

 or gray ones, and yellow soils absorb more heat than 

 gray ones. 



327. Slope of the soil. A smooth surface absorbs 

 more heat than a rough or rigid surface. The effect 

 of the direction and angle of slope on the amount of 

 heat received from the sun is shown by the following 

 diagram. 



Fig. 125. Diagram illustrating the influence 

 ot the slope of the land surface upon the 

 amount of sunshine received. 



On the 21st of June, on the 42d parallel, the sun- 

 beam which falls on a given level area would be dis- 

 tributed over almost 6 per cent less area when the slope is 

 toward the sun at an angle of 20, while on a slope of 20 

 away from the sun the same amount of sunshine would 

 fall upon 16 per cent greater area. The area which 



