28 Journal of Agricultural Research voi.xii, no. i 



The results from the plots to which acid phosphate has been added 

 do not show any greater H-ion concentration than the ones used as 

 controls. These plots have received rather heavy annual applications 

 of this fertilizer for the past 15 years, the total amount applied being 

 over 3,000 pounds per acre. The fine sandy loam may be some excep- 

 tion. In this case the readings are so nearly the same as from those 

 plots which have received no fertilizer that the differences are within 

 the range of experimental error. Indeed there is as much evidence in 

 indicating an increased basicity from the use of acid phosphate in the 

 clay loam and loam as from an increase in acidity in the sandy loam. 

 This is in agreement with the more recent work of Conner (5), Brooks (4), 

 and Bear and Salter (2). 



Additions of lime alone or lime in combinations with the fertilizer 

 materials have materially reduced the acidity in all plots. This is often 

 more marked in the subsoil than in the surface. With the exception of 

 the Cecil clay loam, lime has not been used in sufficient amounts to pro- 

 duce basicity. 



EFFECT OF AMMONIUM SULPHATE AND MONOCALCIUM PHOSPHATE 

 ON H-ION CONCENTRATION OF SOIL-FILM WATER 



The results heretofore reported in this paper with ammonium sulphate 

 and acid phosphate have been derived from soil suspensions. The ques- 

 tion arises. Is the film water of the soil affected in the same or different 

 manner from the free water? To secure data on this question three 

 soils were treated with the ammonium sulphate and monocalcium phos- 

 phate at optimum moisture conditions and extractions made with the 

 Morgan apparatus. The materials were applied in solution as a fine 

 spray over the soils in order to get as good distribution as possible. 

 The soils were well worked after the additions to get a uniform mass. 

 Monocalcium phosphate was substituted for acid phosphate on account 

 of its complete solubility. Table VII gives the data derived from 

 treatment with ammonium sulphate. 



The film water is shown to be more strongly acid from the treatment 

 with ammonium sulphate than that developed when the same amount 

 of salt is applied in suspension. The indications from this are that 

 methods for estimating soil reaction or lime requirement based on treat- 

 ing the soil with a neutral solution do not give the total acidity in the 

 filtered extract. 



The mechanism of this reaction has been the subject of much conten- 

 tion. The explanation which has been offered that the basic radicle has 

 been absorbed by celloidal material; and the acidity developed from 

 the combination of SO4 with 2H of the slightly ionized HjO leaves an 

 unbalanced equation. Parker {10) contends that the fine soil particles 

 catalyze the reaction (NHj2S04 + 2HOH = 2NH,OH-}-H2S04 with 

 the removal of the entire base from solution by selective adsorption 



