HOW SOILS ARE MADE AND MIXED 7 



five ounces of the second soil in the same way for at 

 least an hour. Be sure to tell about any change in color 

 that may take place during heating. Did any smoke 

 come off from either soil? Will rocks burn? Will hay, 

 or grass, or weeds bum? When each soil is cool, carefully 

 weigh again. Which one has lost the greater weight? 

 What reason can you give for this loss? 



Conclusion. — Tell which it is, rocks or plants, that 

 gives a rich soil the dark color and good earth smell. 

 Tell why it is that a new field can be worked sooner after 

 a rain than an old one. By scraping the roads we get 

 all the organic matter, or humus, worked out of them; 

 and they then bake hard and firm. If a farmer should 

 bum his cornstalks or straw instead of working them into 

 the sou again, how would it affect the supply of humus 

 in his land? Frequent cultivation aerates the soil and 

 hastens decay. Why will several crops of corn in succes- 

 sion exhaust the humus in the soil? Land that has been 

 in pasture is found to be rich in humus. Likewise the 

 addition of manure increases the amount of humus in the 

 soil. State two ways in which humus may be added to a 

 soil which lacks it. 



6. The Part Plant Life plays in making Soils. — An 

 armful of fodder, left lying in the field, or at the bottom 

 of a haystack, soon begins to decay. The dead plants 

 become covered with blue-black molds, which are them- 

 selves living plants, and which are visible to the naked 

 eye. These molds, or fungi, as they are called, absorb a 

 part of the fodder. The part which remains is acted upon 

 by tiny plants, called bacteria, which are too small to be 

 seen with the naked eye. These work upon the plant 

 remains until the whole is broken down into simple sub- 

 stances which the roots of living plants may take up again. 



