- o " 



102 



ELEMENTS OF AGRICULTURE 



or the subsoil? How does a farmer increase the amount of humus in 

 the soil? 



Have each pupil rub samples of soil and subsoil between his fingers 

 so as to become familiar with its texture. Fill one of the jars with soil 

 and one with subsoil and cover each. Label each with the name and 

 date. The samples are to be kept tightly covered for use in numbers 

 34 and 35. Similarly study and collect several different soils and sub- 

 soils. If possible, compare good and poor soils. Also compare sandy 

 soils, loams and clays. 



34. Determination of the Per Cent of Water, Organic Matter and Mineral 

 Matter in Soils. 



Materials. Soil samples collected under No. 33, porcelain cruci- 

 bles, balances. If the school does not have crucibles and laboratory 

 burners, the soil may be dried over a stove and then burned in an iron 

 shovel in a stove. 



If different members of the class take different samples, all those 

 collected may be compared. Weigh the crucible. Put ten grams 

 of the sample in it. Weigh before the water has time to evaporate 

 much. Heat this a little hotter than boiling water, but do not burn it; 

 one hour at 110 C. or five hours at 100 C. is about right. Weigh again. 

 This gives the amount of water evaporated. Now heat to dull redness. 

 After it is thoroughly burned for one hour, weigh. Compute and tab- 

 ulate results as follows: 



What change in color took place as the soil dried? Is the color of 

 the soil changed by rain? What change is there in color after the soil 

 was burned? After burning, only mineral matter remains. Compare this 



