22 DROUGHT RESISTANCE OE OLIVE IN SOUTHWESTERN STATES. 



Table V. — Analyses for potash, phosphoric acid, calcium, and organic matter in soils 

 from olive orchards at Casa Grande, Ariz., and Palm Springs, Cal., made by the Bureau 

 of Soils, U. S. Department of Agriculture, from samples collected by Mr. S. C. Mason. 



Locality. 



Casa Grande, Ariz 



Do 



Do 



Palm Springs, Cal 



Do 



Do 



Depth 

 taken. 



Inches. 

 Oto 6 

 6 to 12 



12 to 18 

 Oto 6 

 G tol2 



12 to 18 



CaO. 



Per cent. 

 1.18 

 .53 

 1.86 

 1.58 

 1.58 

 1.75 



KtO. 



Per cent. 

 0.98 

 1.00 

 1.00 

 .81 

 1.02 



PjOs 



Per cent. 

 0.03 

 .22 

 .32 

 .52 

 .38 

 .41 



Organic 

 matter. 



Per cent. 

 0.15 

 .46 

 .66 

 .19 

 .12 

 .17 



Figure 5 shows in a graphic manner the resuUs of a mechanical 

 analysis of this soil by the Bureau of Soils, as presented in Table IV. 

 This is placed for comparison below a diagram showing the results 

 of a similar analysis of the soil from the Casa Grande olive grove and 

 one from the olive orchards of Sfax. '^ The small quantity of clay 

 and silt and the large proportion of medium and fine sand distinguish 



« See "Dry-land Olive Culture in Northern Africa," by Thomas H. Kearney, Bulle- 

 tin 125, Bureau of Plant Industry, U. S. Dept. of Agriculture, 1908, pp. IS-l'J, as 

 follows : 



Mechanical analyses of soil samples from the olive orchards ofSfax. 



Locality. 



Olive orchard, Sfax 



Do 



Do 



Do 



Olive orchard, 20 miles north of 

 Sfax 



Clay, 

 0.005 to 

 mm. 



P.ct. 

 30.0 

 16.0 

 15.7 

 26.2 



29.3 



a 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 per cent). Accord- 

 ing to Trabut, a high lime content is a very favorable factor in growing olives for oil 

 production, as olives produced in limestone regions are richer in oil and the oil is of 

 better quality then where the soils are deficient in this component. It should be 

 noted that while the nitrogen and phosphoric acid content of the vSfax soils would be 

 considered low for most crops, the high yields and good quality of the oil produced at 

 Sfax are sufficient evidence that the supply of these two elements of plant food must 

 be amply vsufficient for the requirements of the olive. This can perhaps be explained 

 by Ihe fact that the roots of this tree occupy so great an area of soil (one-seventh to 

 one-tenth acre) that, while the percentage of these elements to weight of soil is every- 

 where low, the total amount available to the roots is actually rather high. 

 192 



