286 NATURE STUDY AND AGRICULTURE 



Which has retained the most moisture? Why? Which 

 will keep the more moisture, a field in which the soil is 

 frequently stirred on top with a cultivator or one which is 

 left undisturbed ? Can you see why this is true ? 



Place a lump of loaf sugar so that the lower part will 

 rest in some red or black ink. Does the ink rise by capil- 

 larity to the top of the sugar ? Place another lump beside 

 this one with a layer of granulated sugar scattered over 

 the top. Does the ink rise as rapidly through the loose 

 sugar as through the lump ? Why ? 



In the same way, as long as the soil is left alone, the 

 water is constantly moving by capillarity to the surface and 

 evaporating. A layer of dry soil on top stops the capillary 

 flow of water and the moisture is conserved for the use of 

 the plants. 



Vary the soil experiments by mixing humus with clay 

 in one chimney and with sand in another, and by putting 

 lumpy soil in one and fine soil in another. 



In your study of germination of seeds you found that 

 warmth was one of the conditions that affected the germi- 

 nation. Does moisture in any way affect the temperature 

 of the soil? 



Experiment. — For this experiment you will need two 

 cans; baking powder or tomato cans. In the bottom of 

 one punch a number of holes for drainage. Fill them with 

 the same kind of soil, and water thoroughly so that some 

 water stands on the top. Set them side by side in a warm 

 place, or in bright sunshine. Insert a thermometer an 

 inch under the surface of each and take readings several 

 times during the day. Which shows the higher tempera- 

 ture at first? Later in the day? What is happening in 



