420 STATE BOARD OF AGRICULTURE 



Apparently, the point to be reached in liming soils and proper 

 amounts of liming materials to apply is still an open question. Should 

 soils be neutralized, made alkaline or held at a certain pH? Whatever 

 the answer to this question is, it is evident that more intensive research 

 should be carried on to determine more of the effects of liming soils; 

 the chemical systems set up and their effect on plant growth. The effect 

 of an excess of liming materials applied to soils may be important from a 

 practical standpoint. Evidence was given to the effect that in the presence 

 of an excess of Ca(OH)o there was a continuous reaction between soils 

 and this reagent. Provided this reaction is between Ca(OH)o and the more 

 insoluble soil acids a greater quantity of more active acids may be 

 formed in soils than previously existed there, when the added base is 

 again lost from the soils. This situation brings up a question as to 

 the advisability of adding smaller amounts of liming materials to soils 

 often, rather than a large excess at any one time; or the advisability of 

 maintaining the pH at or somewhat below, the neutral point rather 

 than making soils strongly alkaline. The possibilities of crop injury 

 due to the effects of liberating quantities of COo in soils from the use 

 of CaCOg alone and with acid fertilizers should not be overlooked. 



The proper use of various fertilizing materials on different soils con- 

 taining varying amounts of active materials involves a better under- 

 standing of the effects produced by fertilizer treatments. There is need 

 for a clearer definition of the chemical reactions involved. Changing 

 the solubility of soil bases, and varying the pH of soils, as well as the 

 formation of new compounds, undoubtedh^ exert a great influence on 

 plant growth. 



It seems reasonable to assume that the active soil materials are 

 those most concerned with crop production and fertilizer reactions. If 

 the degree of acidity of a soil correlates with crop response then the 

 proportion of active soil bases to acids assmnes great importance. The 

 magnitudes of fixation of cations of neutral salts correlates with the 

 quantity of active bases in soils, and the fixation of phosphorus de- 

 pends to some extent on these substances. Increasing the basic con- 

 tent of soils accentuates these conditions. These factors, then, play 

 an important part in the solubility and retention of fertilizers and the 

 chemical compounds formed by fertilizer salts, in addition to their ef- 

 fects on the soil reaction. 



The results presented in this publication give a better understand- 

 ing of the nature and relationships of soil components, and seem to 

 emphasize the importance of the base-acid ratio in soils. Correlations 

 of great practical value should be obtained from applications of these 

 methods to practical field problems. It is the plan to continue this 

 work along similar lines in an attempt to define fertilizer salt reactions 

 on different soils using data herein contained as a basis for operations. 



