On the Chemical Properties of Soils. 23 



me likely that a definite quantity of soil will remove more 

 ammonia than from a smaller amount of liquid of the same 

 strength. 



I have not, as yet, made many experiments in this direc- 

 tion. These are urgently needed, for it is clear that we cannot 

 calculate with any degree of certainty the amount of loss in 

 ammonia to which ammoniacal manures are subject in contact 

 with soil, as long as we are not fully acquainted with the 

 exact conditions under which this most interesting chemical 

 property of soils manifests itself. 



FIFTH SERIES. AMMONIA RETENTION EXPERIMENTS. 



In the preceding experiments it has been shown that all the 

 soils experimented upon possess the power of absorbing ammonia ; 

 further, that all the soils absorbed more ammonia from a more 

 concentrated than from a weaker solution ; and, lastly, 1hat in no 

 instance was the ammonia entirely removed from a solution 

 brought into intimate contact with soil. Even in the case of 

 heavy clay soils, and when very dilute ammoniacal solutions were 

 employed, ammonia invariably remained in solution. These facts 

 not only explain the different results which must be obtained in 

 experimenting upon the same kind of soil with solutions of 

 different strength, but they also prove incontestably that the com- 

 pounds which, no doubt, are produced in almost every descrip- 

 tion of soil, when ammoniacal solutions are brought into contact 

 with them, are not entirely insoluble, as has been supposed, but 

 sufficiently soluble in water to benefit the growing crops, which 

 we have no reason to suppose take up food from the soil in any 

 other than a soluble state. 



Notwithstanding the power of soils to absorb ammonia, this 

 fertilizing constituent is not fixed by the soil so completely or 

 permanently as to be of no avail to the growing plant. The 

 possibility also exists that long-continued and heavy rains may 

 wash out more or less completely the ammonia previously 

 absorbed by soils. Hence the invariable presence of ammonia 

 in spring waters. 



An important question is naturally started by these curious 

 properties of soils. It is this : Is the power of soils to retain 

 ammonia greater, and if so to what extent, than the tendency to 

 yield it again to water passed through the soil ? 



In order to facilitate the solution of this question I instituted 

 a Fifth Series of Experiments, which, under the title of " Am- 

 monia Retention Experiments," I shall now endeavour briefly to 

 describe. 



