190 University of California Ptiblications in Agricultural Sciences [Vol. 1 



Mes.\. L.^xds 

 SAX JOAQUIX COUNTY 



AC.^MPO 



Humus- 

 Soil Xitrogen in 



' ^ V 



Humus Humus Soil 



Red loam 60 7.02 .04 



Red loam 18 7.80 .01 



Red loam 10 



Red loam 10 



Red loam 10 



Red loam 07 



1.15 

 .19 



.88 

 .29 



Range of most annual plant roots. 



iu the first foot but in each succeeding level down to the tenth 

 foot. The entire amount in each column is but little more than 

 the average of the tirst foot for the state at large. The darker 

 clay soil from the region of Aeampo has more humus in tlie 

 surface foot and but very little in the lower depths. 



The humus of the Sheridan and Aeampo soils is rich in 

 nitrogen, but the quantity of humus itself is so small that the 

 amount given to the soil is very little, and below the second foot 

 was inappreciable. 



The other soil is peculiar in having a humus that contains 

 very little nitrogen in its third and fourth foot. As a consequence 

 the soil itself is very poor in nitrogen. 



All of these soils need good green-manuring with some 

 nitrogen-rich legumes for several successive years to improve 

 their texture and their productiveness. 



Comparison hxj Classes. — The average percentages of humus 

 in composite columns of soils of the same class gives an indication 

 of what to expect in lands of these four classes. 



