EXERCISE 14 



Object. To study the effect of plowing under undecayed 

 organic matter on the rise of soil moisture. 



Explanation Moisture moves from a wetter to a drier 

 portion of the soil by means of capillarity. In order that 

 capillary movement of moisture may take place the soil 

 particles must be in close contact. If the soil particles are 

 not in close contact, capillary movement of moisture cannot 

 take place. When large amounts of barnyard manure or 

 rank growths of green plant material are plowed under in the 

 soil, the soil particles are held apart by this layer of material 

 and the capillary rise of water cannot take place in the 

 surface soil. If a crop is planted on a soil in this condition, 

 it will be unable to secure moisture from the lower soil in its 

 early stages of growth, and if the season is dry, will suffer 

 greatly for water. It is, therefore, undesirable to plow under 

 barnyard manure, straw, or green manure just before plant- 

 ing a crop. If manure is to be used just before planting, it 

 should be applied lightly as a top dressing. 



Equipment. 1. Three glass tubes, rack, and pan, like 

 those used in Ex. 8. 



2. Cheesecloth. 



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