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



be found, and from one of these a column of twelve feet was 

 obtained for us by Mr. W. W. jMackie, then of the United States 

 Bureau of Soils. It was taken from a few miles northwe.st of 

 Stockton and is an excellent representative of these lands. 



The river alluvial is not especially rich in either humus or 

 organic nitrogen, though one would suppose from its alluvial 

 character that the amount of vegetable material in it would be 

 great. 



The tule or swamp lands near Stockton have to a large extent 

 been reclaimed by dykes, by pumping out the water, and by 

 protection from overflow. They contain a very large percentage 

 of decayed vegetable matter consisting of tule roots, etc., and 

 this has been quite largely humified, as shown by the tables, 

 especially in the upper four feet. Below this depth the amount 

 suddenly drops from 13 per cent in the fourth to 6.9 per cent 

 in the fifth foot, and from 1.4 per cent in the ninth to 0.36 per 

 cent in the tenth foot. No other tule soil in the state that has 

 been examined contains so high a percentage of humus and 

 organic nitrogen, probably because of extra favorable conditions 

 of warmth and moisture and excess of vegetable matter in the 

 Stockton colunni. This large amount of humus produces acid 

 soils, and liming is necessary to render them neutral and pro- 

 ductive. The 0.83 per cent of humus nitrogen in the surface 

 soil is very great, being equivalent to an average of 25,000 pounds 

 per acre. There is a still greater percentage in the second foot 

 as well as in the third; but below the latter it falls off rapidly 

 to the minimum of 0.01 per cent in the tenth foot. 



Comparison of San Joaquin Valley Soils of Different Types 



The table below gives in a concise form the relative percent- 

 ages of humus and nitrogen in the eight soil types of the San 

 Joaquin Valley, and from it we can make comparisons more 

 easily than from a .study of the soil columns themselves. The 

 types are placed in the order of highest to lowest composite 

 averages of humus in the first foot, and there is almost the same 

 succession in the combined upper three feet and the entire column 

 respectively. 



