336 University of California Publications in Agricultural Sciences [Vol. 1 



salts from the soil with water. The use of the NO3 radical by 

 plants or bacteria, thereby leaving the sodium, could not have 

 occurred to any extent in this case, for the whole process re- 

 quired no longer than two hours, and was carried out in a filter. 

 The filtrate at no period in the washing process showed sufficient 

 alkalinity to account for the deflocculation. Hence the former 

 conception that residual NaoCOg causes the deflocculation seems 

 untenable, and some such hypothesis as has been advanced in 

 this paper must be adopted to explain the unfavorable physical 

 condition frequently existing in soils receiving applications of 

 NaNO.. 



With respect to fertilizer salts in general, Plall'" calls attention 

 to the deflocculation folloAving the use of neutral salts on soils, 

 but believes the effect is due to alkalinity arising from the ab- 

 sorbed base. Hessler'^^ has noted the increase in coherence of the 

 soil particles when NaCl, NaNO, and kainite have been applied 

 to soils. Hoffman,'- however, could not detect any difference in 

 the interior surface of soils due to fertilizer applications of the 

 usual magnitude. It is of interest to note that no attempt is 

 made to correlate the inferior physical condition of salt-treated 

 soils with the process of leaching the salts from them. 



How^ever, potassium and ammonium salts are effective in the 

 same direction as sodium salts when washed from the soil, al- 

 though they are generally considered flocculating agents when 

 in contact with certain colloidal particles. Hence, to be fully 

 comprehensive and expressive of the whole truth, studies on fer- 

 tilizer effects should involve not only the conditions under which 

 the salt or salts are present, but also those conditions which not 

 infrequently arise in nature, whereby the soluble salts are re- 

 moved from the soil by processes analogous to washing the soil 

 wdth water. 



The nature of the clay colloids and the cause of the relatively 

 high degree of deflocculation which they assume w^hen suspended 

 in water have long been subjects of much conjecture and much 



"■0 Loc. cit. 



'1 Cited from Exper. Sta. Eec, vol. 31, bo. 2, p. 123, 1914. 



:2 Landw. Vers. Stat., vol. 85, nos. 1-2, p. 123, 1914. 



