FORMATION OE HUMUS IN SOIL (OPTIONAL) 



79 



6. Allow the experiment to run for twelve clays. 



7. Arrange the results in a table. 



Table 28 — The Influence of Organic Suhstances on the EwhiUon of Carbon 



Dtoxid from SoH 





Carbon dioxid m 100 gm of soil. 



Two-day periods. 



Control 



Clover 

 2 per cent 



Barnyard 



manure 



2 per cent 



Cane-sugar 

 2 per cent. 



I 

 2 



3 



4 



5 

 6 



Mgm. 



Mgm 



Mgm 



Mgm. 



Total 











Exercise 7 



Formation of Humus in Soil (Optional) 



1, Prepare a uniform sample of soil (air-dry) by passing 

 through a sieve. 



2. Weigh out soo-gram portions and treat as follows: 



(a) Control 



(b) Add 2 per 



(c) Add 2 per 



(d) Add 2 per 



(e) Sterile, no 

 (J) Add 2 per 

 (g) Add 2 per 

 (h) Add 2 per 



cent, finely ground wheat straw. 



cent finely ground alfalfa. 



cent, finely ground dry manure 



additional treatment. 



cent, finely ground wheat straw; sterilize. 



cent, finely ground alfalfa; sterilize. 



cent, finely ground dry manure; sterilize. 



3. Pint or quart Mason jars can be used as receptacles 

 for the various soils. 



