Agricultural Chemistry. 303 



A body which has excited a chemical action loses thereby the 

 power of exerting this action a second time. When sulphuric 

 or muiiatic acid exerts a chemical action, or decomposition, it 

 enters into a chemical combination, in which the acid has entirely 

 lost its properties. Hence we can easily see why ammoniacal 

 salts, in spite of the excess of ammonia which remains in the soil 

 in the second year, have apparently an effect so little durable. 

 This is because the excess of ammonia can exert no nutritive 

 action when the conditions of its efficacy, namely, the mineral 

 constituents, are wanting ; when they have been consumed in 

 producing the excess of produce in the previous year. 



The experiments of Kuhlmann, as well as those of Lawes, 

 supply the most convincing proofs of the truth of these deduc- 

 tions. The fields which Kuhlmann had manured, in 1844, with 

 ammoniacal salts and nitrates, yielded, in 1845, when unmanured, 

 a less produce tlian was obtained from an equal surface which 

 had not received any manure in 1844. That one which, in 1844, 

 received 500 lbs. of sulphate of ammonia, yielded in 1845, un- 

 manured, 8340 lbs. of hay. That which was not manured in 1844 

 yielded, without manure, in 1845, 8972 lbs. of hay ; that is, 

 632 lbs. more than the other. Still more striking is the following 

 fact. Kuhlmann had manured a portion of his field in 1844 

 with a mixture of 666 lbs. of sal-ammoniac, along with phos- 

 phate of lime, and had obtained an excess of produce = 12,172 lbs. 

 of hay per hectare. In the same year the portion manured with 

 500 lbs. of sulphate of ammonia (without phosphate of lime) 

 yielded an excess = 3488 lbs. of liay. The former, therefore, 

 yielded 2^ times more excess of produce than the latter. 



Meadow-plants, like all others, require for their development 

 phosphate of lime and ammonia, but also, besides these, other 

 elements of nutrition ; for example, silica and alkalies, without 

 which they cannot thrive. By the addition of phosphate of lime 

 to the ammoniacal salt the effect of the latter was augmented : there 

 were obtained in all 8684 lbs. of hay more than by the use of the 

 ammoniacal salts alone. Now, in tliis excess, whicli is equal to 

 2^ times the whoh; excess obtained by the ammoniacal salts alone, 

 there were contained 2^ times more silica, and 2^ times more 

 potash than would have been removed from the soil without the 

 use of phosphate of lime along with the ammoniacal salts ; and 

 the soil was rendered necessarily by so much the poorer in these 

 constituents. This great loss of indispensable constituents could 

 not be without influence on the subsequent crops. The field 

 which in 1844 had been manured with 500 lbs. of sulphate of 

 ammonia had no manure in 1845, and received, in 1846, 500 lbs. 

 of the same ammoniacal salt. The result was as follows : — The 

 same quantit\ of phosphate of lime and sal-ammoniac, which in 



