420 SECTIONAL TRANSACTIONS.— M. 



attempt to devise a micro-chemical field method for the estimation of phosphates has 

 been made by Spurway. These by no means exhaust the list, but will serve as 

 examples. Perhaps further advances can be made along the Unes of shortening the 

 prehminary treatment, measuring the volume of precipitates and introducing micro- 

 chemical and colorimetric methods. These purely chemical extractions may or may 

 not throw light on the availability to the plant of the materials extracted. Probably 

 this will require to be standardised by means of pot trials and field experiments or 

 tests such as those of Neubauer and Mitcherhch which make use of the actual plant. 



(6) Physical Analyses. — Dr. B. A. Keen, Mr. J. R. H. Coutts (Single 

 Value Determination on South African Soils), Dr. J. P. van Zyl, 

 Dr. B. DE C. Marchand, Dr. M. S. du Toit, Prof. N. M. Comber, 

 and Dr. Sinclair. 



Dr. B. A. Keen. — An examination is made of a number of physical properties of 

 Natal soils, and an attempt made to determine which of these are likely to be most 

 useful for purposes of general classification of large numbers of soil samples. It is 

 suggested that the stickj' point, or the loss on ignition, and the Keen-Raczkowski box 

 data might well be adopted for this purpose. The moisture content of a soil in 

 equihbrium with an atmosphere of 50 per cent, relative humidity is also worth con- 

 sideration. In order to obtain an estimate of the organic matter in the soU, it is 

 necessary to determine the loss on ignition of the soil after treatment with hydrogen 

 peroxide (I,,) as well as on the original soil (lo). Then,(Io — Ij,) 4/3 gives a fair estimate 

 of the organic matter. 



Prof. N. M. Comber. — TJie Policy and Purpose of Soil Analysis. 



It is an inevitable and natural consequence of the historical origin of scientific soil 

 studies that they have aU along been pursued in close association with the industry of 

 farming. It is only in quite recent years that there have been signs of a general ten- 

 dency to segregate the scientific study of the soil. Soil studies are, therefore, very 

 largely in the position that geological studies would have been in if geology had been 

 studied almost exclusively in the interests oJ an industry, e.g. mining. The principal 

 studies in soil analysis have been directed towards recommendations for soil manage- 

 ment. It cannot be claimed, however, at any rate so far as Great Britain is concerned, 

 that these analytical studies have succeeded in doing anything like what was originally 

 hoped for and aimed at, in facihtating the business of crop husbandry. Soil analysis 

 has played but a small part in the introduction and development of the use of artificial 

 fertilisers. Indeed, if soil analysis and its consequences were ehminated from the 

 developments in the use of fertilisers during the last three-quarters of a century, it is 

 doubtful whether the position would be very much behind what it is. If we face the 

 present outcome of soil analysis with proper perspective we must admit that its most 

 important results have been to reveal the existence of, and to some extent to explain 

 the nature of, great compUcations in soil structure. It seems very desirable from 

 every point of view that this position should be faithfully admitted, and that we 

 should openly abandon the continued pursuit of this work on the main grounds of its 

 immediate utilitarian service to industry. If this is done a greater freedom and a 

 greater scope for individual initiative will result which in the long run must be to the 

 advantage of everyone concerned with the soil from whatever point of view. Anyone 

 who has been concerned with soil analysis for anj"^ number of j^ears has entertained the 

 hope that so far as their immediate utiUtarian value is concerned we might gradually 

 get away from purely arbitrary methods of analysis. There is, however, at any rate 

 in Europe, a growing tendency to increase rather than to reduce these arbitrary 

 methods ; a tendency which is finding its expression in an increasing amount of 

 co-operative work designed with a view to fixing in all their detail, international 

 methods of analysis. It seems worth while to call in question the wisdom of this 

 and to suggest that the time has not yet come, and that a great deal more investigation 

 into the constitution of the soil must be made before the time does come, when 

 international methods of soil analysis can reasonably be standardised in this kind of 

 way. 



