EXERCISE 72 



WHAT IS THE AMOUNT OF ORGANIC MATTER IN SOILS? 



Materials. Samples of dry soil, such as resulted from Exercise 70 ; a metal pan ; Bunsen burner 

 or a large alcohol lamp. 



Directions. The pan should be weighed before the soil is put in, and also with the soil, the 

 weights being recorded. Heat the soil to a red heat over any convenient flame, and continue until 

 all the dark material appears to be burned. Weigh again when cool. Tabulate as follows: 



Additional problem. Secure samples of soil from a swamp or peat bog, also from a sandy region and a 

 river flood plain ; determine the percentage of organic matter as above ; compare and explain differences 

 in these percentages. Does there appear to be any relation between soil fertility and amount of organic 

 matter in soils ? 



[103] 



