EFFECT OF REACTION OF SOLUTION ON GERMINA- 

 TION OF SEEDS AND ON GROWTH OF SEEDLINGS 



By Robert M. Salter, Soil Chemist, and T. C. McIlvaine, Assistant Agronomist, 

 West Virginia Agricultural Experiment Station 



INTRODUCTION 



Recent investigations have emphasized the importance of the intensity 

 factor of soil acidity. The growth of plants is more logically associated 

 with hydrogen-ion concentration than with total acidity as measured by 

 a soil's capacity to neutralize or absorb bases. However, other factors 

 than the direct physiological influence of the hydrogen or hydroxyl ion 

 upon the plant itself are undoubtedly operative in producing the effects 

 attributed to soil reaction, these factors being either conditioned by the 

 reaction or associated with it. Thus, indirect efifects upon plant growth 

 would be produced by: (i) The extent to which the soil's reaction is 

 favorable for the development of soil organisms, more particularly those 

 responsible for nitrogen transformation and nitrogen accumulation; (2) 

 changes in the solubilities of soil constituents as affected by reaction, 

 this applying not only to essential elements such as calcium, magnesium, 

 potassium, and phosphorus but also to those having toxic properties, 

 such as aluminium, manganese, and ferrous iron where increases in con- 

 centration would be expected with increase in acidity; and (3) changes 

 produced in physical properties of soils attendant upon changes in 

 reaction. 



Although the mass of data on the relation of soil acidity to plant 

 growth is already large, few well-defined attempts have been made to 

 separate the individual factors concerned and study them under condi- 

 tions permitting the control or elimination of other factors. The present 

 investigation was undertaken with the aim of studying the direct physi- 

 ological influence of reaction as measured by hydrogen-ion concentration 

 upon plant growth. Solution culture was resorted to in order to control 

 or eliminate other factors as far as possible. 



EXPERIMENTAL METHODS 



In the work herein reported, wheat, corn, soybean, and alfalfa seed- 

 lings were grown in a series of solution cultures having as far as possible 

 a constant nutrient composition and osmotic concentration and varying 

 in reaction from a hydrogen-ion concentration of approximately i X 10— ' 

 to I X 10- « or 2 Ph to 8 Ph-^ 



1 In this report the Ph values of Sorensen will be used to state the reaction of the solutions, the value Pa 

 being the negative common logarithm of the actual numerical concentration of hydrogen ions. Thus a con- 

 centration of hydrogen ions of iXio— ^ would correspond to a Ph value of 5. 



Journal of Agricultural Research, Vol. XIX, No. 3 



Washington, D. C. Apr. 15, 1920 



ty Key No. W. Va.-i 



(73) 



