SECTIONAL TRANSACTIONS.— M. 419 



Mr. A. Stead. — Chemical analysis is used for three main purposes, namely : — 



1. For ascertaining manurial needs. 



2. For assisting in checking soil types in survey work. 



3. For investigating the constitution of the soil. 



Much of the adverse criticism levelled at soil analysis is probably due to a wrong 

 perspective. While it is fully understandable that chemical analysis may be very 

 misleading when applied for the purpose of determining the manurial needs of long 

 and intensively cultivated soils, so far as this country is concerned, there is not the 

 least doubt that poor and good virgin soils are reliably indicated as the result of 

 chemical analysis. 



The value of chemical analysis in determining soil types is undoubted and need 

 not be stressed ; neither need its indispensableness in investigating the soil as sod. 

 The trouble about chemical analysis of the soil, however, is its laboriousness and 

 expense. Reasonably accurate and very quick methods of analysis are badly needed 

 to enable the chemical investigation of the soil to be very much extended. We have 

 devoted much attention to such methods with gratifying results, as will be detailed 

 by Dr. v. Zyl of my stafi. I would, however, refer especially to the need of a fairly 

 accurate micro method for the direct determination of base-exchange sodium. This 

 would put one in a favourable position to ascertain by laboratory experiment what 

 change the physical condition of the soil is likely to undergo as the result of con- 

 tinuous irrigation with the particular water or waters that are available to irrigate 

 it. The inability always to prophesy what will be the result of irrigating arid and 

 semi-arid soils is one of the principal handicaps confronting the soU survey investigator. 



Dr. W. 6. Ogg. — The Value of Rapid Methods in the Chemical Examination 

 of Soils. 



There are certain lines of soU investigation which call for very numerous chemical 

 analyses, and in view of the lengthy and laborious nature of some of these analyses 

 it may be useful to consider the possibility of developing more rapid methods. The 

 need for sometliing of the kind is particularly apparent in surve}' and advisory work. 



In soU survey work, chemical analyses are useful in establishing the type to which 

 a soil belongs, in throwing light on its properties and in checking the boundaries 

 established by field workers between types. A soU type which may be incapable of 

 further sub-division on field characters, may show a considerable range in chemical 

 properties, and it is usually necessary to carry out a large number of analyses in order 

 to determine what is normal for the type and how it may vary. In many cases, at 

 any rate for a beginning, a large number of approximate tests would be more useful 

 than a small number carried out mth extreme accuracy. 



The same is true in advisory work. To carry out analyses by the present oflScial 

 methods requires a considerable amount of time and the accuracy of the residts 

 obtained is rather out of proportion to our ability to interpret and apply them. It 

 would be sufficient in many cases to be able to determine whether the amount of the 

 constituent in question was very low, low, medium, high or extremely high. 



It is, of course, very important to recognise the limits of accuracy of such methods 

 and not to push their interpretations too far. 



There are already in use several tests which can be carried out rapidly and which 

 have proved of considerable value. For example, in studying questions of soil 

 acidity, such tests as those suggested by Truog and Comber, and the determination of 

 hydrogen ion concentration provide useful data, and recently a rapid electrometric 

 method for measuring ' Lime Requirements ' has been pubfished by Hardy & Lewis. 



An extensive field to field pH survey has been carried out in the South-East of 

 Scotland. The admittedly inadequate information obtained from the pH figures has 

 been supplemented by other tests, such as the determination of exchangeable calcium, 

 carried out on a limited number of samples from the various areas surveyed. The 

 results obtained give interesting information on the intensity and distribution of acidity 

 in the districts studied and indicate the places most in need of lime. The rapidity 

 with which pH measurements can be carried out has made this investigation possible 

 on a much larger scale than would otherwase have been the case. Attempts have also 

 been made to devise rapid tests for phosphate, potash and nitrogen. Purely qualitative 

 tests are described by T. B. Wood in his ' Course of Practical Work in Agricultural 

 Chemistry ' ; rapid quantitative tests are given in Hilgard's ' Soils ' ; and an 



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