1914] Loughridge: Humus and Nitrogen in California Soil Columns 223 



the surface foot being 0.16 per cent, or approximately 6-100 

 pounds per acre. This extreme richness in humus and nitrogen, 

 as well as in potash and phosphoric acid, is responsible for the 

 high productiveness and the national reputation the valley 

 enjoys as a vegetable-seed producing region. 



Santa Maria Valley. — The soil is chiefly a sandy loam of a 

 brownish color and very deep. A column was taken by Mr. F. 

 E. Johnson near the sugar-beet fields five miles west of the town 

 of Santa Maria. 



Lompoc Valley. — Three chief classes of soils occupy the 

 valley — adobe near the hills, sandy alluvium near Santa Inez 

 River, and an intermediate type of clay loam between them. 

 The Burpee seed-farm is situated on the clay loam lands, and a 

 column of soil was taken there to a depth of twelve feet, at 

 which point water was reached. 



Santa Maria Valley soil has a fair amount of humus in the 

 upper three feet and low percentages through the rest of the 

 column, and this humus has high percentages of nitrogen. The 

 smaller amounts in the second and third foot may be due to 

 withdrawal by plant roots. The general average of organic 

 nitrogen in the upper three feet of soil is good, but for the entire 

 column the percentage is low, because of the low amount of 

 humus. 



In strong contrast to the sandy loam soil of Santa Maria 

 Valley is the heavier clay of the Lompoc Valley through which 

 flows Santa Inez River. The upper seven feet of the Burpee 

 soil each contains more than 1 per cent of humus, and this, 

 though not especially rich in nitrogen, gives to the soil itself 

 fairly high percentages, the average in the upper three feet 

 being 0.09 per cent, or about 10,000 pounds per acre. 



Summary of Results in Coast Range Region 

 The soils of the valleys of the Coast Range are remarkably 

 high in their humus content when compared with the other soils 

 of the arid region. The general average of the state is 1.25 per 

 cent in the surface soil, while that for these coast valleys is 1.94 

 per cent. But especially does this difference appear when we note 

 the many soils in which more than 1 per cent of humus is found 



