158 Lime Eeqiiiremefits of New Zealand Soils 



It will be noticed that with the stronger solution the end of the 

 reaction comes much sooner than with the weaker, and furthermore 

 (a point that has already been illustrated) the hme requirement 

 indicated, when using a strong solution, is greater than that shown by 

 a weak solution. Further experimental work on this point was there- 

 fore taken in hand, ten portions of soil drawn from the same sample 

 being treated simultaneously with solution of varying degrees of 

 concentration. Two series of experiments were made in this manner, 

 the results of which are shown in tabular form below in Table V, and 

 graphically in Figs. 1 and 2. 



Table V. 



Series A Initial concentration of •0295N •0268N •0246N •0227N •0211N 



solution 

 Soil from Field 21 Lime requirement indi- -196 -191 -161 -160 -157 

 S.S. cated as per cent, of soil 



•0197N •0184N •0174N •0164N -OlSSN 

 •143 134 133 131 -120 



Series B Initial concentration of •0240N •0218N •020N -OlSSN -OniN 



solution 

 Composite soil con- Lime requirement indi- -090 -050 -047 -048 -035 

 taining CaCOg cated as per cent, of soil 



•0150N •0133N •0120N •0107N •0096N 

 •027 -013 •Oil -004 



In both these series of experiments the exposure was for a period of 

 4 hours. 



A final series of experiments was made in duphcate. Six solutions 

 of varying concentration were used ; to ensure the completion of the 

 reaction, the time of exposure of the soil was 24 hours; the stoppers 

 of the bottles were placed in loosely so that the solutions were under 

 atmospheric pressure all the time. (This permitted the setthng out of 

 a small amount of Hme as CaCOg as was proved by a control bottle 

 without soil, but the amount so deposited was not sufficiently great to 

 affect the general trend of the results.) The results, which are set out 

 in Table VI, still show the same feature — that the lime requirement 

 indicated varies directly as the concentration of the solution. 



