1919] Pendleton: A Study of Soil Types 487 



The sodium peroxide fusion method"' 3 was carried out on the two larger series 

 of soils, the Hanford and the San Joaquin. The elements sought were phosphorus, 

 calcium, and magnesium. Five gram samples, air dry, were used throughout. 

 The general method of analysis, as set forth by Hopkins, was employed, though 

 there were a number of refinements used to increase the accuracy of the results. 

 As such might be mentioned the double precipitation of the iron, aluminum, and 

 phosphorus. 



Phosphorus was determined volumetrically, according to the method of Hili- 

 bard. 56 



Total nitrogen was determined by the modified Gunuing-Kjeldahl method, 

 using ten gram samples. 



Loss on ignition was determined upon the 10 gram, air dry samples that were 

 used for the determination of the hygroscopic moisture of the samples used in 

 the chemical analysis. The soils were ignited in a muffle furnace to constant 

 weight. 



Humus was determined by the Grandeau-Hilgard method, 57 using 10 gram 

 samples, air dry. 



Potassium was determined by the J. Lawrence Smith method, using one gram 

 samples. 



Bacteriological Methods 



The only bacteriological methods employed were the determination by the tum- 

 bler or beaker method of the ammonifying, the nitrifying, and the nitrogen fixing 

 powers of the soils." 8 All cultures were run in duplicate. 



Ammonification tests were made using 50 grams of soil and 2 grams (4%) of 

 dried blood. The checks were distilled at once, and the cultures kept in the incu- 

 bator at 24°C-30°C for one week. (The incubator thermostat was unsatisfactory 

 in its action, hence the variation in the temperature.) 



The nitrifying power of the soil was tested as regards the soil's own nitrogen, 

 dried blood, cottonseed meal, and ammonium sulfate. In the Diablo clay adobe 

 and the Altamont clay loam 50 grams of soil were used, to which was added 1 

 gram (2%) of dried blood, or of cottonseed meal, or 0.1 gram (0.2%) of am- 

 monium sulfate. In the case of the San Joaquin sandy loam 50 grams of soil were 

 used, together with 1 gram (2%) of dried blood or of cottonseed meal, or 0.2 gram 

 (0.4%) of ammonium sulfate. In the series run on the Hanford fine sandy loam 

 100 grams of soil were used, to which were added 1 gram (1%) of dried blood or 

 of cottonseed meal or 0.2 gram (0.2%) of ammonium sulfate. It is to be regret- 

 ted that the several series coidd not all be run on exactly the same basis as the 

 Hanford series. But the small amount of stock soils of the samples of the earlier 

 series precluded the use of larger original samples, not to speak of the impossi- 

 bility of repeating these series. The cultures were incubated for four weeks at 

 24°C-30°C. At the end of this period the cultures were dried in the oven at about 

 90° C and the nitrate content determined by the phenoldisulfonic acid method 

 according to the modifications of Lipman and Sharp." 1 ' 



Nitrogen fixation. For this determination uniform quantities of soil were 

 used throughout — 50 grams, to which was added 1 gram of mannite. These cul- 



56 Hopkins, Soil Fertility and Permanent Agriculture, pp. 630-33; Hopkins and Pettit, 

 Soil Fertility Laboratory Manual (Boston, Ginn, 1910), pp. 42-45. 



50 Jour. Ind. Eng. Chem., vol. 5, pp. 993-1009. 



"Calif. Agr. Exp. Sta., Circ. 6 (1903), p. 21. 



58 Burgess, P. S., Soil Bacteriology Laboratory Manual, Eastern. Pa., The Chemical Pub 

 lishing Co., 1914. 



58 Univ. Calif. Publ. Agr. Sci., vol. 1 (1912), pp. 21-37. 



