464 THE PRINCIPLES OF SOIL MANAGEMENT 



(3) Modification in the moisture content by the 

 use of mulches, irrigation, and especially by drainage, 

 where there is an excess of water. 



(4) The attitude of the surface may be somewhat 

 changed by tillage, especially in the matter of rough or 

 smooth surface. Of course, the general slope cannot 

 be altered. 



(5) Promotion of organic decay through the addi- 

 tion of organic matter to the soil, in such a state and 

 under such conditions as will promote favorable decay 

 by which its heat may be liberated. The high tempera- 

 ture attained in hotbeds in the winter and early spring 

 exemplifies this practice. The application of manure 

 under field conditions may appreciably alter the soil 

 temperature, due perhaps to several effects. Wagner 

 observed an increase of 5 Fahr. as a result of the 

 application of twenty tons of manure per acre, and 

 during a period of several weeks there was an average 

 excess of 1 of temperature on the manured land. 

 Georgeson observed, through a period of twenty days 

 following the application of different amounts of manure 

 in the fall, temperature differences amounting to .9 

 for ten tons, 1.7 for twenty tons, 2.3 for forty tons, 

 and 3.4 for an application of eighty tons per acre. 



(6) Construction of shelters may modify the soil 

 temperature. Coldframes and greenhouses make use 

 of this principle by preventing the circulation of air and 

 by entrapping the sun's rays. Partial shade influences 

 the soil temperature, usually producing a lower average 

 and a greater uniformity. 



