168 Lime Requirements of N'etii Zealand Soils 



This statement, however, should be taken strictly in the sense in 

 which it is made. The writer does not attempt to insist that hming 

 the soils of the Canterbmy Plains, and of the Southland River Flats, 

 will not pay ; all we say is that while the benefits of hming have thrust 

 themselves under the notice of farmers in the case of the Southland 

 Terrace soils, they have not been sufiiciently obvious to those farmers 

 in Canterbury and in the other Southern area who have made the 

 experiment. Nor is it necessary for the writer to say that he fully 

 realises that a manurial dressing may be more than paying its way 

 though the fact may not be obvious merely by viewing the plots without 

 measurements. His conservative attitude is dictated by the considera- 

 tions : first, that there is as yet no positive experimental evidence 

 proving the economical importance of lime to these soils ; secondly, 

 that satisfactory results are being obtained without liming; thirdly, 

 that whereas a kind of natural selection operating among methods of 

 farming the Southland Terrace lands, brought about the evolution of 

 the practice of liming, the same processes have not achieved similar 

 results in the other areas under discussion. 



The following evidence may be brought against the writer's attitude : 

 (1) The process of nitrification demands the presence of a free base. 

 " The (nitrifying) organisms will not tolerate an acid medium ; a 

 sujB&cient excess of calcium carbonate is therefore necessary, both in 

 culture solutions and in soils^." (2) There is some physiological evidence, 

 rather uncertain it is true, that lime is required by the Canterbury soils 

 in the "depraved taste" for bones, etc., sometimes exhibited by cattle, 

 and in the weakness in bone sometimes seen in young stock fattening 

 rapidly on the very luxuriant spring growth on some of our heavier 

 lands. 



The bulk of the practical evidence suggests that soils in these areas 

 having an acidity not greater than 0-10 % stand in no immediate need 

 of hming. To translate the indications of Hutchinson and MacLennan's 

 method into practical terms, the writer proposes to use this figure as 

 a correcting^ value to be deducted from the actual indication in order 

 to get the probable practical requirement. The figure 0-10 % is selected 

 as being the present hme requirement indicated for Field 21 of this 

 College Farm which received 6 cwt. of Hme in the winter of 1915, and 

 which is now in an entirely satisfactory productive condition. 



1 Soil Conditions and Plniit Growth, Dr E. J. Russell, 2nd cd. (1915), p. 90. 

 ^ It must be remembered that the method indicates a small lime requirement even for 

 neutral soils. 



