346 



SCIENCE 



[N. S. Vol. XLVI. No. 1186 



intra-uterine gro-wth aside from its function 

 as a transfer system. 



Frederick S. Hammett, 

 Lyle G. McNeile 

 CoLLBQE or Physicians and Sdbgeons, 

 Univeesity op Southern CALiroRNiA, 

 Los Angeles, Calif. 



THE EFFECT OF DRAINAGE ON SOIL ACIDITY 



For the purpose of studying the effect of 

 drainage on soil acidity, samples of soil were 

 taken in October, 1916, from three of the ex- 

 periment fields of the Purdue Agricultural Ex- 

 periment Station. These fields are located 

 near Westport, North Vernon and Worthing- 

 ton. The soils of these fields are all heavy silt 

 loam, very low in organic matter and naturally 

 poorly drained and quite acid in reaction. All 

 of these fields have been thoroughly tile 

 drained from three to five years. A portion of 

 the Westport field is undrained and there are 

 adjacent undrained, untreated areas alongside 

 the North Vernon and the Worthington fields. 



TABLE I 

 relative acidity op drained and UNDRAINED SOILS 



Table I. shows the acidity of the soil as de- 

 termined by the potassium nitrate method. 

 Without entering into a discussion of the 

 merits of different soil acidity methods, it may 

 be said that on these soils, which are low in or- 

 ganic matter, there is no great difference in 

 the degree of acidity shown by this method 

 and the lime water and calcium salt methods. 

 These results are consistent enough to indicate 

 that drainage has a material influence on the 

 acidity of soil of this type. 



Farmers often refer to wet, poorly drained 

 land as sour. While agricultural writers have 

 placed little or no emphasis on such a correla- 



tion, it is quite probable that soils in general 

 will tend to become less acid when thoroughly 

 drained, and vice versa; they will tend to be- 

 come more acid when water-logged and poorly 

 aerated. In testing soil acidity at different 

 seasons of the year the results often vary quite 

 a little in samples from the same plots of soil. 

 These differences can not be attributed alto- 

 gether to errors in sampling. The writer be- 

 lieves that at least part of the change of acid- 

 ity is due to difference in aeration and mois- 

 ture content of the soil at different seasons. 

 Lipman and Waynick,i in an investigation of 

 the effect of climate on soil properties, report 

 that Maryland soil, which shows an acid reac- 

 tion in its original location, when transported 

 to Kansas or to California becomes neutral or 

 slightly alkaline. It is quite probable that the 

 better drainage and aeration of the soil when 

 placed under less humid conditions could ac- 

 count very largely for the changes in reaction. 



Considering SiO, an acid-forming oxide, 

 practically all soils except those very high in 

 the basic reacting elements, have a potentially 

 great capacity for developing an acid reaction. 



The writer believes that the constitution of 

 the silicates of aluminum has more to do ■with 

 injurious soil acidity than any other single 

 factor. The acidity of aluminum silicates 

 varies both with the relative proportion of 

 SiOj to ALO, and with the amount of com- 

 bined water in the silicate.^ The weathering 

 and changing of soil silicates under poorly 

 drained or well-drained conditions would un- 

 doubtedly vary the constitution of the silicates 

 and also vary the degree of soil acidity. It is 

 quite true that certain types of well-drained 

 sandy soils are acid. It is true also that a 

 number of other factors besides drainage con- 

 ditions affect soil acidity, but it is probable 

 that the most acid soils are formed in poorly 

 drained areas. S. D. Conner 



Indlana Agricultural Experiment Station, 

 Lafayette, Ind. 



1 Lipman, C. B., and Waynick, D. D., Soil Sci- 

 ence, Vol. I., No. 1, p. 5, 1916. 



2 Conner, S. D., "Acid Soils and the EfEeet of 

 Acid Phosphate and Other Fertilizers upon Them, ' ' 

 Jour. Ind. and Eng. Chem., VoL VII., No. 1, p. 35, 

 1916. 



