848 Handbook of Nature-Study 



and pulverizes the top soil by harrowing, hoeing or raking in order to 

 retain moisture for plant roots. A mulch may also be of straw, boards, 

 leaves or stones. Fallen leaves form a natural mulch in the woods. 

 There, at any time, under this covering, may be found moist earth. A 

 mulch is a soil cover which breaks the capillary connection, so that water 

 will not rise to the surface to be evaporated. To be efficient a mulch 

 must be dry. After rain the "dust blanket" on the garden bed should be 

 renewed by cultivation. 1 



Experiment 5 — Fill several vials with different soils from fields in the 

 neighborhood. If the soil in any of the vials is dry, moisten it. Take 

 a piece of blue litmus paper and press down into the soil in each vial. Does 

 the litmus paper turn red as it becomes dampened by the soil in any 

 of the vials? If so, this soil is acid. Add a little lime and mix it in 

 thoroughly with the soil m the vial that shows the acid soil. Test it again 

 with the litmus paper. Does the paper remain blue or turn red? Does 

 alfalfa and clover grow on acid soils? Why should we add lime to such 

 soils ? 



Hints for teacher on Experiment 5 — A slightly acid soil may show no 

 reaction with litmus paper. It may be well to have a prepared soil wiuh a 

 few drops of vinegar or other acid added, which will show the reaction. 

 The addition of lime will correct the acid condition. Soils for alfalfa or 



Experiment to show the proper treatment of clay soil. 



