140 



METHODS OF OBSERVATION. 



The aim in this preliminary work, has been, first of all, to 

 secure a body of observations upon mixed or complex solutions, 

 such as the dissolved portions of stable manure, fertilizers and 

 soil solutions are. Since it is true that' soils are all of the time, 

 so long as they are moist and exposed to climatic conditions, 

 being treated with a mixed solution moving either capillary or 

 by gravitation, it appeared best to make the first observations 

 with solutions of a similar nature and not so concentrated, as 

 most of the solutions employed in the cases which have been 

 cited. 



In all cases the volume of the solution used has been equal to 

 .five times the water-free weight of the samples treated and gen- 

 erally 600 c. c. of solution and 120 grams of soil have been taken. 

 Most of the observations have been made with short periods of 

 contact of the solution with the soil, this being made sometimes 

 by shaking in bottles and sometimes by percolation, using the 

 arrangement described in Bulletin "B," p. 81. 



The soils have been examined for the amounts of water-solu- 

 ble salts which could be recovered from them by washing three 

 minutes in distilled water, and the amounts so recovered have 

 been added to the amounts which were added with the solution 

 to the duplicate samples of soil treated, and the absorption has 

 been taken as the difference between the amounts remaining in 

 the solution and those originally present, plus those shown to be 

 present in the soil before treatment. Only colorimetric methods 

 have been used in determining the changes which occurred in the 

 solution. 



ABSORPTION OF SALTS BY JANESVILLE LOAM. 



The first series of observations was made on the surface four 

 feet of the Janesville Loam, one sample from each of the five 

 fertilizations, thus giving five determinations for the same soil 

 type at each depth. The full set of data are given in this case, 

 so as to indicate the character of fluctuations which occurred in 

 the results obtained. 



