862 Journal of Agricultural Research voi.xx.No. n 



mean the total calcium hydroxid used to bring the reaction to that point. 

 In interpreting the results of these electrometric measurements the fol- 

 lowing factors must be considered: (i) Kind of soil with reference to the 

 amount of sand, clay, and organic matter; (2) influence of climatic condi- 

 tions; (3) amount of calcium present, particularly in the carbonate form. 

 The amount of sand, silt, clay, or organic matter present in a soil may 

 have a greater influence on the initial reaction than the amount of cal- 

 cium present. Pratt loamy fine sand from Reno County has the lowest 

 calcium content of the soils placed in group I, Table I, but it has the 

 highest alkalinity as shown in Table II. Benton loam No. 1043 and 

 Crawford clay No. 1227 are both high in calcium and both have a high 

 initial alkaline reaction. The clay soils and the silty clay soils as a rule 

 require more calcium hydroxid to change to a certain hydrogen-ion con- 

 centration than the sandy soils. 



Soils placed in group III, Table II, are distinctly acid in reaction. As 

 the initial acidity increases, the amounts of calcium hydroxid needed to 

 change the reaction to neutral (indicated by P H 7) also increases, but not 

 uniformly. This is due to factors mentioned in the preceding paragraph. 

 The influence of clay is shown by the figures in Table III. 



Subsoils as a rule contain a larger amount of calcium than the surface 

 soils, particularly calcium in the carbonate form. These same subsoils 

 usually contain a larger amount of clay but a smaller amount of organic 

 matter. The calcium was determined in a number of the subsoils cor- 

 responding to the surface soils mentioned in Tables I and II. The elec- 

 trometric measurements were also made. The results are found in 

 Table III. The figures for the surface soils are repeated from Tables I 

 and II for the sake of comparison. The results in Table III are arranged 

 within the groups with reference to the decreasing amounts of calcium in 

 the surface soils. The results show that, with few exceptions, the sub- 

 soils have a higher calcium content than the surface soil and that in the 

 majority of cases the subsoil requires a larger amount of calcium hydroxid 

 to change it to the same reaction as the surface soil. 



The soils in which the calcium content is less in the subsoil than in 

 the surface soil are: 1297, Oswego silt loam; 1271, Bates loam; 1273, 

 Bates very fine sandy loam; and 1277, Bates shale loam. In the first 

 one of these soils the titration figure is larger for the subsoil than for the 

 surface soil. This would be expected from the larger clay content and 

 the smaller amount of calcium. The last two have sandy subsoils; and 

 while no mechanical analyses were made, observations recorded at the 

 time of taking the samples show that the subsoils have less clay than 

 the surface soils. Both these soils were acid, and the subsoil is more 

 acid than the surface soil. Yet the lesser amount of clay in the subsoil 

 was of more influence in determining the amount of calcium hydroxid 

 needed to bring to neutral reaction than the initial acidity. 



