26 PRESIDENTIAL ADDRESS— SECTION B. 



Now, the superiority of these two Hooge Kraal soils can no 

 doubt be traced to the presence on the farm of certain igneous 

 rocks of basic nature. It is known, at any rate, for certain that 

 such rocks occur as local intrusions in the Malmesbury Beds in 

 that neighbourhood. This instance is cited to show the close 

 relation between geological conditions and the results obtained 

 by chemical analysis. 



But in setting up standard soil types the chemist has to go 

 further than take into consideration geological origin and chemical 

 composition. There are important physical characters — texture, 

 depth of soil, nature of subsoil, and conditions regarding under- 

 ground water-supply. In short, there are no important consider- 

 ations which will affect the welfare of the plant which may be 

 left out of view in establishing a number of types of soil for 

 purposes of comparison and contrast. 



The response of each particular type of soil to fertilizers of 

 different kinds, and its behaviour under the vicissitudes of the 

 climate of its locality, are examples of important data which it 

 must be the object of a soil survey to ascertain. It is not sug- 

 gested that the analytical chemist should work single-handed. 

 He should gather all possible information from practical farmers, 

 and his work should be carried on conjointly with that of the 

 Agricultural Colleges of the various provinces. Moreover, there 

 are biological problems in connection with soil investigations 

 which offer a most important field for research. The many-sided 

 question of plant nutrition cannot be dealt with merely from the 

 point of view of one science only, and it is only by patiently 

 combining forces in attacking the problems that present them- 

 selves that scientific men can hope to proceed onward, bearing in 

 mind that success came slowly even to men like Liebig and 

 Pasteur. 



In what I have said regarding the necessity of a systematic 

 survey of agricultural soils, with the definite object in view of 

 establishing types of soil, I have merely endeavoured to emphasize 

 what was suggested by Mr. A. D. Hall * in 1905, and his words 

 are worth quoting here: — 



" What the soil analyst can do is to characterize the type, ascertain 

 its normal structure and composition, and correlate its behaviour under 

 cultivation, its suitability for particular crops, and its response to manuring 

 in various directions. Thus an unknown soil may by analysis be allotted 

 to its known type, deviations from the type can be recognised, and conclu- 

 sions may be drawn as to the connexion of their defects. 



" Valuable as recent developments of soil analysis may have been, 

 .... the results they yield can only be truly interpreted when they 

 can be compared with a mass of data accumulated by the use of the same 

 methods on known soils. 



" One of the services, then, which the farmers in every country may 

 very properly expect from the scientific man is such a survey of the prin- 

 cipal soil types, affording the necessary datum lines by which the com- 

 parative richness and poverty of any particular soil may be gauged. In 

 an old settled country like the United Kingdom such a survey would guide 



* A. D. Hall, "Recent developments in Agricultural Science." Brit, and 

 S. Afr. Assns. for Adv. of Sc, Reports, 1905, vol. i., p. 106. 



