318 



thai each double l>o\, holding aboul I cubic foot, contained the same amount 

 of organic ma1 ter. The contents of I he boxes were as follows: 



TABLE I. 



Box 1 contained 2 lbs. hen manure + 50 gr. CaCOa. 



Box 2 contained 3.2 lbs. sheep manure. 



Box 3 contained 2.4 lbs. hog manure. 



Box 4 contained 3.0 lbs. horse manure. 



Box 5 contained 6.6 lbs. steer manure + 50 gr. CaCOg. 



Box 6 contained 6.0 lbs. cow manure + 50 gr. CaCOa. 



Box 7 contained 4.0 lbs. horse manure + 101 gr. CaO, MgO. ' 



Box 8 contained 4.0 lbs. horse manure + 171 gr. CaO. 



Box 9 contained 4.0 lbs. horse manure + 179 CaC0 3) MgCO s . 



Box 10 contained 4.0 lbs. horse manure + 175 gr. CaC0 3 . 



Box 11 contained no treatment. 

 On May 30, 1914, the manure, limestone and soil were well mixed and the 

 boxes were placed in the ground out of doors in order to approximate field 

 conditions. At the same time samples of the mixed soil were taken for humus 

 determinations. Other samples were taken on the following dates: Novem- 

 ber 25, 1914; February 16, 1915, after winter freeze; April 13, 1915, after a 

 period of quite warm weather; June 1, 1915, October 15 and November 22, 

 1915. 



Humus Determination. 



Effort was made to follow the course of changes brought about by bacteria 

 and the weathering agencies, etc., by determining the amount of humus 

 present at the various periods. The term humus, as used by American soil 

 investigators, does not refer to the total organic matter present in a soil, 

 but only to that which is soluble in 4 per cent NH. t OH, the calcium and mag- 

 nesium having been removed. The Official Method as modified by Smith was 

 used in all the determinations. The following tables give averages for the 

 different periods: 



