572 Journal of Agricultural Research voi. x. no. « 



brought about by hydrochloric and acetic acids, decidedly decreased the 

 solubility of the organic matter. 



With solutions of sodium nitrate, sodium chlorid, and sodium sulphate 

 the solubility of the organic matter is decidedly increased by the pres- 

 ence of calcium carbonate. The sodium salts, however, as shown in other 

 work, have a solvent effect upon the organic matter aside from their 

 action upon the calcium carbonate. This is particularly true of sodium 

 sulphate. 



The tables bring out one thing quite forcibly — the probable reaction 

 of the sodium salts with calcium carbonate in the presence of the soil 

 with the formation of normal sodium carbonate. In the cases where 

 the lime was added as a bicarbonate, little or no reaction was noticed 

 above the controls. In fact, the presence of calcium bicarbonate, as 

 shown by experiments not included in this paper, tends to protect the 

 organic matter rather than to bring it into solution. The action of the 

 sodium salt on the calcium bicarbonate would result in the formation of 

 sodium bicarbonate, which is much less active in the decomposition of 

 organic matter. This will be brought out later. 



The methyl-orange titration or the titration for bicarbonates (HCO3) 

 was made and for convenience calculated to calcium carbonate. This is 

 also shown in the tables. The figures represent the amount of calcium 

 carbonate that was brought into solution in the different treatments. 

 In the case of calcium bicarbonate the figures remain fairly constant 

 throughout the series. With the calcium carbonate, however, a distinct 

 increase was noticed when the sodium salts were introduced, indicating 

 to what extent the calcium carbonate had reacted with the sodium salts, 

 with the formation of sodium carbonate. 



ACTION OF CALCIUM CARBONATE UPON ORGANIC MATTER IN THE 



SOIL 



There is a belief prevalent in some sections that calcium acts as a 

 protective agent upon the organic matter of the soil. This is probably 

 due to the repeated statement of Dr. Hilgard (6, p. 283, 380-381) that 

 lime carbonate is the principal factor in the formation of humus. Lyon 

 and Fippin (7, p. 127) state that — 



The loss of humus by leaching from soils rich in lime is very much less than in 

 those soils poor in lime. 



This is probably true, but the comparisons were no doubt made be- 

 tween a fertile limestone soil and a low-lying swamp or acid peat bog, 

 and not between a limestone soil and an acid upland soil, in which the 

 presence of a real acid is questionable, or an upland soil deficient in 

 lime. It is unquestionably true that lime will precipitate many or- 

 ganic compounds, but it is yet to be shown that a given amount of 

 humus will be retained in the soil longer in the presence of lime than in 



