120 



UNIVERSITY OF CALIFORNIA EXPERIMENT STATION. 



Nos. 2430, 2432. MECHANICAL COMPOSITION OF HILLTOP ADOBE : BERKELEY. 



The soil mass is of rather extreme physical composition, in the great 

 predominance of very fine materials, amounting in the subsoil to over 

 80 per cent; and such land must always be difficult to handle in culti- 

 vation, and be uncertain on account of its dependence upon favorable 

 rainfall. Unless very deeply cultivated it will crack open in summer, 

 tearing the roots and drying the soil into a mass of rocky hardness. As 

 it is not intrinsically very rich, it would be desirable to utilize it for 

 suitable timber growth, provided sufficient root-penetration can be 

 secured. The lack of this is probably one cause of the low growth of the 

 English oak. 



CHEMICAL ANALYSIS OF ADOBE SOIL OF BERKELEY HILLS, No. 2430. 



Per cent. 



Insoluble matter ..72.19) 7R ^ n 



Soluble silica 6.5lf 78</u 



Potash (K 2 O) 33 



Soda(Na 2 0) - -- .29 



Lime(CaO) - .76 



Magnesia (MgO) 76 



Br. ox. of manganese (Mn 3 O 4 ) _ ._ .08 



Peroxidof iron(Fe 2 3 ) .- 6.02 



Alumina (ALO,) 4.58 



Phosphoric acid (Po0 5 ) ._ 07 



Sulfuric acid (S0 3 ) .02 



Water and organic matter. ._ 8.93 



Total - - 99.72 



Humus. .- - 1.85 



Nitrogen, per cent in humus 8.70 



Nitrogen, per cent in soil 16 



Hygroscopic moisture (absorbed at 15 C)__ . 9.09 



In its chemical composition this soil, as might be expected, does not 

 differ widely from that of the lower slopes and the yellow ridge soil 

 of the University grounds (No. 4, in Report of 1884). It is poor in 

 potash for a California soil; and for so heavy a material the lime con- 

 tent, although relatively high from a general point of view, is too low 

 to insure ready tillage. The content of phosphoric acid is an average 

 one, its humus content is good for the arid region, and the nitrogen per- 

 centage of the humus sufficiently high. The fact that in years of abund- 

 ant rainfall this land bears a very heavy growth of grasses and certain 

 classes of weeds, shows that if improved in texture it might be highly 

 productive for a time. 



