1919] Pendleton: A Study of Soil Types 473 



The calcium (as CaO) content of the soils is interesting especially 

 because of the variability. The Altamont samples show the greatest 

 variation, for the Largesl quantity of CaO is about seven limes the 

 smallest. The San Joaquin samples are second, with the Largest over 

 six times the smallest. The Diablo samples are third, with the Largest 

 over five times the smallest, while the Hanford soils show the least 

 variation, the largest being less than twice the smallest. There are 

 quite marked differences between the averages of the Diablo, Alta- 

 mont, and Hanford soils (the San Joaquin samples are intermediate), 

 but the wide variations within the types greatly minimize any sig- 

 nificance the averages might have. Hence it is not possible to state 

 that one or another type, as represented by these samples, is charac- 

 terized by high, low, or moderate amounts of calcium. 



As the analyses of the samples for calcium failed to point out any 

 striking characteristics, unless it be that of variability, so it is with 

 magnesium. Magnesium (as MgO) is variable within each of the four 

 types. The largest quantity is about three times the smallest in the 

 Diablo, San Joaquin, and Hanford types, while in the Altamont the 

 largest is twenty-seven times the smallest. Considering the Hanford 

 and San Joaquin, or the Diablo and San Joaquin, it is seen that the 

 curves do not overlap, while the Diablo and Altamont, or the Diablo 

 and Hanford curves do. The averages of the four types are distinct, 

 except between the Hanford and Diablo, which are quite close. But, 

 here again, because of the more or less wide range of values within 

 each of the types, the averages are of little significance. The lime- 

 magnesia ratio is very variable in these soils. Comparing the calcium 

 and magnesium curves for the several soils gives a good idea of the 

 relations. The Diablo curves are quite similar except for soil no. 6, 

 which shows 3% MgO and 0.5% CaO. In the Altamont soils the 

 curves are somewhat similar in direction, though the ratios differ 

 widely. In the Hanford and San Joaquin types the ratios of CaO and 

 MgO are also far from constant, yet it is readily seen from the graphs 

 that the amount of magnesium varies more or less directly with the 

 amount of calcium. 



Respecting the total phosphorus (as P 2 5 ), if the San Joacpiin and 

 Hanford samples alone be considered, there would be no doubt as to 

 the significance of the field separation, the variations within the type 

 notwithstanding. But when the other two types are considered, the 

 case is not so good in favor of the field classification. The Diablo soils 

 show considerable variation in the amount of P.O., while the three 



