080 STATE BOAI{l> OF AflHTCri.TURE. 



The rate of solution of the soils studied is yovenu'd (<» some extent by 

 temperature it being more rapid at l'.~) C llian at tempei-atui-es approach- 

 ing 0°C. Moreover, the moistnre content lias a mai-ke<l inflnence on 

 the rate of solubility of the soil constituents. It is probalde that bio- 

 logical activities play an important role in these plicnomena. 



T'sually the concentration of the soil solutions, at all water contents, 

 of the soils tested, were lower at the end of thirty days tliaii after ten 

 days, that it under laboratory conditions. Tliis may be due to reab- 

 sorption of the soluble material by the soil, to the ntili/alion of the salts 

 by organization and to the formation of less soluble compounds. 



The concentration of the soil solution in the soil is, variable. In several 

 soils studied it varied somt^vhat with the seasons, rainfall, different 

 depths of the soil and with plant growth. 



It is probable that the variations in the concentration of the soil solu- 

 tion, in some instances at least, have nnt been sufficiently considered in 

 biological studies where conclusions h»ve been drawn based upon the 

 results obtained from studies of the wnter extracts of soils. Moreover, 

 it does not seem possible to determine the. fertilizer needs of soils by ob- 

 taining water extracts and growing plants therein. 



The seasonable variation in the soluble salt content of soils doubtless 

 plays an important role in the results obtained from the use of fertilizers. 

 Additional information concerning the wn^nble salt content of soils will 

 be presented later. 



