1914] Loughridge: Humus and Nitrogen in California Soil Columns 201 



lent soil underlies the hardpan, however, and when the latter is 

 broken up by dynamite good results in tree growth are usually 

 obtained. 



Columns of this land were obtained from the Butler vineyard 

 a few miles east of Fresno; from the Kearney Park west of 

 Fresno ; from Lindsay in Tulare County ; and from the place of 

 H. Mueller two miles southwest of Farmington, San Joaquin 

 County. The latter perhaps more properly belongs to the adobe 

 group, though lighter in color. 



These lands differ somewhat in their content of clay, that 

 from Farmington being of a clay nature and the other sandy 

 loams. The soil from Farmington contains good humus per- 

 centages in the three upper feet and throughout the entire 

 column of ten feet, but each of the other localities shows a 

 deficiency in the surface foot, and throughout the entire depths. 

 In the soil from east of Fresno a hardpan layer was struck in 

 the sixth foot, but was broken up and the soil below it was 

 obtained ; no humus was found below the hardpan. 



The high humus of the upper three feet of the Farmington 

 column and its high nitrogen content gives to the soil an excellent 

 nitrogen percentage of 0.12 per cent, or approximately 14,000 

 pounds of organic nitrogen per acre within the range of most 

 plant roots. Bacterial activity in this soil will do much to pro- 

 mote an abundant nitrogen supply for plants and consequent 

 high fertility. The humus of the Kearney Park soil is rich in 

 nitrogen throughout, but the small amount of humus in each foot 

 from the surface down gives but a small amount to the soil, the 

 average for each foot being 0.03 per cent, or about 1200 pounds 

 per acre. The other soil columns are also low in their nitrogen 

 content. 



Delta Plains of Kings and Kern Rivers. — There are two tracts 

 of this class of lowlands which are made of fine sediment brought 

 down from the Sierra Nevada, the Coast Range on the west con- 

 tributing little or nothing to these deltas as its streams mainly 

 discharge their sediments w^estward to the Pacific. 



The ]\Iussel Slough region bordering the Tulare Lake receives 

 its sediment from the Kings, Kaweah, and Tule rivers, and 

 covers a very large area. It is timbered with oaks, and the nature 



