MANUAL OF GENERAL AGRICULTURE. 



13 



8. EFFECT OF EVAPORATION ON SOIL TEMPERA- 

 TURE. 



Materials: Two tomato cans, 2 thermometers, plot- 

 ting paper. 



Fill two tomato cans with air-dry soil and saturate 

 one with water. Bury the cans side by side in a sunny 

 spot, leaving about % inch of the tops above the surface. 

 Insert a thermometer into each to a depth of about 1 inch. 

 The following day as early as possible take the first read- 

 ing and continue taking readings every hour thereafter 

 until 5 P.M. On plotting paper draw a curve of tempera- 

 ture for each can, using TIME and TEMPERATURE for 

 the co-ordinates as shown in the diagram. 



88 



8 



10 



TIME 

 11 12 



H 



