266 University of California Publications in Agricultural Sciences [Vol. 1 



allcali lands. We have omitted the tule marsh lands from the 

 composite of lowlands, and the strong alkali lands and the desert 

 lands from tlie composite of uplands. 



Table 48. — Average Humus ix Soils of Different Character and Color 



The table shows the interesting and unexpected fact that in 

 their general averages the alluvial lands that border the streams 

 are but little richer in humus than the uplands, either in the 

 surface foot or at the several levels to the twelfth foot. In the 

 fourth foot the difference is 0.39 per cent, but in every other 

 level it is less than that. In the upper three feet the difference 

 is 0.60 per cent, in the upper six feet 1.45, and for the entire 

 column it is only 1.88 per cent in favor of the alluvial lands. 

 There are, of course, throughout the state instances of high 

 percentages in single soils of both the alluvial and upland classes, 

 and but for these the general averages would be much lower. 



The close agreement in humus percentages of the uplands and 

 alluvial lands, and the gradual and quite uniform diminution of 

 the same dow^nward plainly indicates that the source of the 



