PRACTICE V 



DETEKMINATION OF TOTAL MOISTURE IN THE SAME SOIL 

 UNDER DIFFERENT CONDITIONS 



Three students may work together, one taking the surface, an- 

 other the subsurface, and the third the subsoil. These results 

 may be compared. 



Collect samples of surface, subsurface, and subsoil ^ from the 

 following places: (1) sod, (2) tilled field, (3) forest. In col- 

 lecting these samples care should be taken to secure them from 

 as small an area as possible, so that the mineral composition of 

 the soil may be uniform. It is essential, also, that the topography, 

 in so far as it affects drainage, should be uniform. Expose the 

 samples to the air as little as possible while taking them. 



After taking them to the laboratory the soil should be thor- 

 oughly mixed by shaking. 



The condition of the weather at the time the samples are taken, 

 and also the amount of rainfall within the week previous, should 

 be noted. 



Make the determinations in duplicate. Weigh six soil pans 

 and use 100 g. of each soil. Weigh rapidly to avoid loss by 

 evaporation. Dry at room temperature for forty -eight hours ; 

 then place in an oven at 100° C. for at least ten hours. Cool 

 to room temperature and weigh at once. The loss in weight 

 represents » the total water content. 



Explain differences in moisture content of the soils. 



References. 



" Soils," Lyon and Fippm, pp. 144-148. 

 "The Soil," Hall, pp. 71-75. 



1 In collectiirg the subsoil for moisture determination it is sometimes well to divide 

 it into two equal parts as to depth. 



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