52 



PRACTICE 2j 



Effect of Soil Mulches on Evaporation of Water from Soils. 



Fill all of the tubes* with the same kind of soil compacting each 

 three inches of soil added. The enlarged bases of the tube are then 

 partially filled with water and the tubes are left 

 till the surface soil becomes moist. The tubes are 

 then ready for use. The water must be replaced 

 from day to day, as it evaporates from the surface 

 by refilling the base, the exact amount of water 

 added in each case being noted. 



The loss of water is determined by the loss in 

 weight of the tubes. Weigh each day. 

 Tube 1. Check (no cultivation). 

 Tube 2. Cultivated 1 inch deep. 

 Tube 3. Cultivated 2 inches deep. 

 Tube 4. Cultivated 3 inches deep. 

 Tube 5. Cultivated 4 inches deep. 

 The cultivations should be made every other 

 day to the required depth. 



Each tube has an area of thirty-six square 

 inches and the results are to be computed in tons of water evapo- 

 rated per acre per week. 



It is very necessary that the tubes all have the same exposure to 

 heat and air currents. 



Upon what principle does a soil mulch conserve moisture? 

 What effect will cultivation have on a very wet soil? 

 If the water table were 12 inches from the surface instead of what 

 it is, what difference would there be in your results? 



Is there any argument in the experiment in favor of fall plowing? 

 What argument for cultivating as soon after a beating rain as 

 possible? 



*The tubes may be made of galvanized iron, zinc or copper. Each tube consists of 

 two parts, a straight tube 28" long and 6%" in diameter for holding the soil and an 

 enlarged base 9" in diameter and 3" high for holding the water. The former is olosed 

 by tying a piece of muslin over the end- The opening of the basal part Is olosed by a 

 flange about 3" from the end of the large tube. The small tube is for adding water as it 

 evaporates. 



