722 Journal of the Department of Agriculture. 



REPRESENTATIVE TRANSVAAL SOILS. 



The Koedoespoort Red Loam. 



By B. ])E C. Marchand, B.A., D.Sc, Chief, Divisiou of Chemistry. 



Occurrence. — This soil type has been given the above name owing 

 to its occurrence on the farm Koedoespoort No. 299, near Pretoria, 

 where it has been the subject of considerable study. The type is 

 widely distributed, being found in the Pretoria, Eustenburg, Marico, 

 Krugersdorp, Potchefstroom, Heidelberg, Middelburg, Lydenburg, 

 Barberton, and Zoutpansberg Districts. This list does not pretend to 

 exhaust the possible occurrences ; the type is probably to be found 

 in other parts. Very similar soils occur also in Swaziland, in Natal, 

 and in Rhodesia. 



Nature and Origin. — The Koedoespoort loam is a brick-red to 

 red-brown sandy clay soil, usually deep and easy to work in spite of 

 its apparent heavy texture. The sub-soil is usually a brighter red 

 than the surface soil, and is always stiffer. In some cases yellow 

 patches may be observed a short distance down, usually at from 

 18 inches depth onward. The brown varieties contain more organic 

 matter than the red, hence the difference in colour. 



The typical soil is sedentary and is derived from the diabase* 

 intrusive in the Pretoria series, but may be influenced in some cases 

 by the shales of the same series. One or two other basic igneous rocks 

 also give rise to this soil type, of which the dolerite and the diabases 

 of the Waterberg system may be mentioned. The shales of the 

 Pretoria series do not, by themselves, give rise to the Koedoespoort 

 loam. It is not possible at present to give a detailed account of the 

 distribution of this soil type. Two very similar soil types must not 

 be confused with the one under discussion, viz., (;ertain heavy red 

 soils overlying the norite, and the amygdaloidal basalt of the bush- 

 veld, since these differ from the former type in an important respect, 

 they contain considerable quantities of lime. 



* For the sake of simplicity no distinction is made between the intrusive diabase and 

 the contemporaneous amydaloidal lava. 



