18 



DRY-LAND OLIVE CULTURE IN NORTHERN AFRICA. 



first 8 inches of the soil had been thoroughly moistened the next 16 

 to 24 inches were very dry and powdery. 



As to texture, this soil when dry has the appearance of a sandy 

 loam, with rather coarse particles. An average of the results of 

 mechanical analyses by the chemist of the Tunisian government of 

 82 samples collected in every part of the Sfax region gives 80 per 

 cent of " coarse sand " and 20 per cent of " fine material." Yet 

 an apparently typical sample collected by the writer in an olive 

 orchard about 5 miles from Sfax was found by the Bureau of 

 Soils of the United States Department of Agriculture to contain 

 a great deal of silt and clay, amounting together in the surface foot 

 to 45 per cent of the whole and in the third foot to 23 per cent. The 

 remaining 55 and 77 per cent, respectively, consisted mainly of " fine 

 sand " and " very fine sand." The real state of the case appears to 

 be that in the natural condition of the soil these fine particles are 

 held together by lime or some other cementing material, so as to 

 form particles that resemble grains of coarse sand. These become 

 separated when the soil is shaken for a long time in water. 6 



Table III shows the results of mechanical analyses made by the 

 Bureau of Soils of the United States Department of Agriculture of 

 soil samples from the Sfax olive orchards. 



Table III. — Mechanical analyses of soil samples from the olive orchards of Sfax. 



Locality. 



Depth 

 taken. 



Fine 

 gravel, 

 2tol 

 mm. 



Coarse 

 sand, 



1 to 0.5 

 mm. 



Me- 

 dium 

 sand, 

 0.5 to 

 0.25 

 mm. 



Fine 

 sand, 

 0.25 to 

 0.1 mm. 



Very 

 fine 



sand, 



0.1 to 

 0.05 



mm. 



Silt, 

 0.05 to 

 0.005 

 mm. 



Clay, 

 0.005 to 

 mm. 





Inches. 



P. ct. 



P. ct. 



P. ct. 



P. ct. 



P. ct. 



P. ct. 



P. ct. 



Olive orchard, Sfax 



Oto 12 



0.2 



4.3 



7.1 



24.1 



20.9 



14.1 



30.0 



Do 



13 to 24 



.4 



7.7 



9.7 



33.9 



24.0 



9.1 



16.0 



Do 



25 to 36 



.5 



7.9 



10.3 



34.3 



24.6 



7,1 



15.7 



Do 



Oto 12 



.2 



4.6 



6.8 



26.4 



22.5 



13.4 



26.2 



Olive orchard, 20 miles north 



















of Sfax 



(*) 



.3 



2.7 



3.3 



14.9 



27.0 



22.9 



29.3 



* Adhering to olive truncheons, probably about 12 inches. 



Chemical analyses of a large number of samples of the Sfax olive 

 soils by the chemist of the Tunisian government show them to be very 

 rich in lime (calcium carbonate), of which there is an average of 

 from 5 to 10 per cent. The potash content is also good, the average 

 being 0.1 to 0.2 per cent. On the other hand, they are rather poor in 

 nitrogen (0.03 to 0.05 per cent) and in phosphoric acid (0.04 to 0.05 



a Bertaincliand, 1. c. 



6 In the French method of mechanical analysis of soils, much less water is 

 used and the digestion is much more rapid than in the method followed by the 

 Bureau of Soils; consequently by the former method the aggregates of fine 

 particles are less likely to be broken up through the solution of the cementing 

 material. 

 125 



