L. J. Wild 173 



between the percentages of hygroscopic moisture and the losses on 

 ignition in the soils of Groups A, B, and C. The Southland soils 

 requiring hme have an average of 4-31 % of hygroscopic moisture and 

 an average loss on ignition of 11-61 %; while those not requiring lime 

 have only 3-03 % of hygroscopic moisture and 8-64 % loss on ignition. 

 The corresponding figures for Canterbury soils sampled and analysed 

 by the writer are 3-32 % and 8-06 % . Gray's averages for nine soils 

 are 2-87 and 6-10, while those of 25 analyses^ by Aston of Canterbury 

 soils give 2-56 % of hygroscopic moisture and 6-14 % loss on ignition; 

 while the average figures for six Southland lime-requiring soils are 

 4-18% and 11-56%. 



The sharp differences in these quantities form a clear hne of demarca- 

 tion between soils of the Southland Terrace Lands on the one hand, and 

 those of the Southland River Flats and of the Canterbury Plains on 

 the other. How far the differences in hme requirement depend upon 

 differences in the content of organic matter possessed by the various 

 soils is a matter for further consideration; meanwhile it may be 

 mentioned that the figures expressing the average percentage of 

 "soluble humus" (that is, organic matter dissolved by the approximately 

 1 % ammonia solution prehminary to mechanical analysis) have the 

 same general aspect ; they are : for Southland Terrace Lands 3-0 ; for 

 Southland River Flat soils 2-3; and for the soils of Canterbury 

 Plains 2-1. 



6. Mechanical analyses. In modern soil studies mechanical analysis 

 is deemed to play an important part. The results obtained by the 

 conventional methods of the Agricultural Education Association apphed 

 to representative soils from our three areas are shown in Table XI 

 (page 172). 



The information gleaned from a study of these mechanical analyses 

 is not particularly suggestive. If hme were needed for the amehora- 

 tion of the physical texture of the soils as conditioned by the size of 

 their ultimate particles, we should expect that the soils of the River 

 Flats, which are undoubtedly heavier than those of the Terrace Lands, 

 would prove more responsive to hming. 



The physical structure of these soils as revealed by mechanical 

 composition is conveniently brought under comparison by summing 

 into two groups the averages of the coarser fractions, namely, sand and 

 silt, on the one hand, and the averages of the finer particles, fine silt 

 and clay, on the other, as shown below : 



^ Collected from various Divisional Reports and Journals of N. Z. Dept. of Agriculture. 



1^—2 



