PRACTICE XXV 



EFFECT OF A LAYER OF ORGANIC MATTER ON RISE OF WATER 



Class exercise to be arranged by the instructor. 



Each student will record daily the height to which the water 

 has risen in the tubes, and note the effect of organic matter. 



Over one end of 24-inch double-thickness glass tubes \\ to 2 

 inches in diameter place a 2-ply or 3-ply disk of cheesecloth, 

 using a rubber band to hold it in place. Fill to a depth of 16 

 or 17 inches with a silt loam, compact as in Practice XI, then 

 add soil and compact until the soil stands at 17 inches in all 

 the tubes. Great care must be taken to have the compaction 

 uniform in all the tubes. 



Tube No. 1 is the check. 



To tube No. 2 add one-half-inch . layer of well-decomposed 

 organic matter, such as rotted manure or peat. 



To tube No. 3 add one-half inch of manure or peat and mix 

 with two or three inches of soil. 



To tube No. 4 add an inch layer of coarse, undecomposed 

 organic matter, such as chopped straw, coarse sawdust, or fine 

 shavings. 



To tube No. 5 add an inch of the same material as in No. 4 

 and mix as in tube No. 3. 



Complete the filling and compact somewhat further, treating 

 all alike. Support the tubes in such a manner that the soil will 

 be held in place and yet have free access to the water in tray. 

 This arrangement will help to prevent the breaking of the soil 

 columns. Note the effect of the organic matter. 



Plot curves of the daily rise of water during the first 14 days, 

 or until the water reaches the top of soil. 



What is the effect of plowing under poorly rotted manure in 

 the spring ? 



What advantage is there in disking before plowing ? 



What advantage in this respect is there in fall plowing ? 



REFERENCES. 



" Soils," Lyon and Fippin, pp. 153, 164-166, and 169. 

 "The Soil," King, pp. 173-178. 



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