164 CHEMISTRY AND CROPS. 



To come nearer home, Juritz, whose method of extraction is 

 similar to that of Hilgard and Loughridge,* after about 20 

 years' experience of Cape soils, writes that the results obtained 

 by him are in good agreement with the results of cultural expe- 

 rience, t 



The method of storing acid extraction demands that the 

 operator take into account the results of cultural experience, for 

 it is only by so doing that it has been possible to determine what 

 are high precentages of plant food and what are good, bad or 

 indifferent soils. In this country we have a grand opportunity 

 for correlating chemical analysis and cultural experience, for none 

 of our lands have been so long cultivated that the principal fea- 

 tures in their history have been forgotten. Especially will it be 

 remembered what native vegetation they bore when first put 

 under the plough ; how long the first flush of production lasted, 

 and what kind of crops they have since borne. Further, since 

 the native vegetation of soils is mainly determined by soil 

 and climatic conditions, it should be easily possible to pick out 

 to-day virgin soils that are similar to those which we have cul- 

 tivated for the last 30 or 40 years. Once this has been done and 

 the typical soils analysed, it will be possible to say with much 

 certainty what our cultivated soils were like before they were 

 broken up, and what will be the future behaviour of those that 

 are about to be taken in hand. Close attention should also be 

 given to the study of the botanical, physical and geological 

 characteristics of the typical soils, and their features correlated 

 with their chemical composition would lead to the discovery of 

 the actual causes of the observed vegetative preferences. Once 

 in possession of this knowledge we should be able to recognise 

 with certainty the capabilities of soils on which native vegeta- 

 tion was either absent or not characteristic. . This would result 

 in the prevention of the enormous waste of time, energy and 

 money that obtains to-day in vain endeavours to grow particular 

 crops on soils that are naturally unsuited to bear them. 



Enough has been said to indicate that if we are to obtain 

 the fullest measure of help from chemistry in the elucidation of 

 the problems related to the fertility of South African soils, it is 

 necessary that a very comprehensive soil survey be undertaken 

 at once. It should even include a biological study of the soil for, 

 in the light of Russell and Hutchinson's recent researches on 

 partial sterilization of soil (which is a natural occurrence with us) 

 as a means of promoting nitrification, such a studv is sure to 

 furnish results of no little importance, and will no doubt explain 

 why in arid countries nitrogen as compared with phosphoric acid 

 is of secondary importance. It will have been noticed that the 

 methods of analysis described are not calculated to deal with a 

 nitrogen adequacy or inadequacy. This particular subject is 

 really of minor importance, for it is within our power, provided a 

 soil is well furnished as regards mineral plant food constituents, 

 to build up a nitrosfen store by methods of g^ood farming". 



* C. F. Juritz : "Agricultural Soils of Cape Colonv," pp. 12, 13. 

 r pp. 13, 17. 



