1914] Loughridge : Humus and Nitrogen in California Soil Columns 269 



Table 50., — Percentage of Humus and Humic Phosphoric Acid in Several 



OF THE Soil Columns 



It will be seen from this table that the highest amounts 

 of phosphoric acid in organic combinations occur in the upper 

 two feet of each column with the exception of the Russian River 

 and the Santa Clara, each of which have high percentages in 

 their lowest depths, although the amount of humus is much 

 lower than in the upper part. 



The general average is 0.05 per cent for each of the two upper 

 feet of the seven columns, 0.03 per cent for each of the succeed- 

 ing eight feet, and 0.02 per cent for each of the two lowest feet 

 of the five columns whose depth reaches twelve feet respectively. 



If we estimate the percentages into pounds per acre, we find 

 that the amount of this humic phosphoric acid for the column 

 is approximately as follows: 



