514 



Transactions. 



hours, or sliaken by hand at intervals of about twenty minutes for four 

 hours, at the end of which time a portion of the solution is filtered, and its 

 strength again determined by titration with decinormal acid. 



II. 



In the first trials of the method made in this laboratory the results 

 shown in Table A were obtained. 



Table A. 



Soil. 



Requirement of CaO indicated. 



Percentage. 



Pounds i)er Acre. 



21* 



4 



16 



29 



Waipara Downs . . 

 Motueka 



* Numbers in all cases refer to numbers of fields on the Lincoln College farm. 



It will be noticed that the figures expressing the weight of lime required 

 per acre are higher than the average farmer would care to believe. The 

 Motueka soil is a very unpromising sample from the apple lands, and, as it 

 is known from an analysis to be devoid of calcium carbonate, the extremely 

 high figure appears not unreasonable. The question, however, presents 

 itself, Suppose we give this or any other soil a preliminary dose of carbonate 

 of lime, will the demand as indicated by the method under trial be corre- 

 spondingly lowered ? With a view to testing this, several experiments were 

 made. To 10 grams of the Motueka soil was added 0-06 gr. CaCOa (that 

 is, 0-336 per cent. CaO) ; 100 c.c. of water was poured on, and the bottle 

 left for about an hour, with occasional shaking. The bicarbonate solution 

 was then added, and the rest of the operation completed in the regular way. 

 The expected lime demand was then 042 less 0-34— that is, 0-08 per cent. ; 

 the actual requirement indicated was 0-18 per cent. However, it was con- 

 sidered that the short preliminary exposure of the soil to the lime might 

 account for this difference, and so a more comprehensive trial was arranged. 

 Two soils were taken, and determinations were made in duplicate of their 

 lime requirements, both in the natural state and after twenty-four hours' 

 treatment, with varying quantities of CaCOs in 100 c.c. of water. The 

 results thus obtained are shown in the following table. 



Table B. 



