312 Soda- Salts in Agriculture. 



ducing on the one hand soda, which became fixed in the soil ; 

 and on the other, chloride of ammonia, which passed into solu- 

 tion. 



This analytical result throws light on the function of salt in 

 agriculture. It is well known that salt is most beneficially 

 applied to light land, after a good dressing with farmyard-manure, 

 alone or in conjunction with Peruvian guano, and that its appli- 

 cation under these circumstances is particulai'ly useful to wheat 

 and grain crops in general. Practical experiments on a large 

 scale have shown, indeed, that by salt alone a large increase of 

 grain was produced on land in good heart — that is, that had 

 been previously well manured. In this case the application of 

 salt evidently has the effect of liberating ammonia and rendering 

 it available for the immediate use of our cereal crops, which we 

 know from experience are much benefited by it. 



On land out of condition, salt must not be expected to produce 

 such a favourable effect, and as this manure no doubt is some- 

 times put upon land exhausted by previous cropping, in which, 

 therefore, it does not find ammoniacal compounds upon which 

 it can act, one reason becomes evident why salt is inefficacious 

 as a manure in some cases, whilst in others its beneficial effects 

 are unmistakcable. 



Peruvian guano and salt is a favourite dressing with many 

 farmers, and justly so. It has been supposed by agricultural 

 writers that the benefits resulting from this mixture are due to 

 the property of salt to fix ammonia ; I have shown, however, 

 elsewhere, that good Peruvian guano does not contain any 

 appreciable quantity of free ammonia, and, moreover, that salt 

 does not fix ammonia. 



Whilst theory has erred in ascribing to salt a power which it 

 does not possess, the practice of mixing guano with salt is one 

 which can be confidently recommended. So far from fixing 

 ammonia, salt rather tends to liberate and disseminate through 

 the soil the ammonia contained in the Peruvian guano applied to 

 the land, which then becomes fixed by the soil. 



It is worthy of notice that the soil employed in Experiment 

 No. G, received a liberal dressing of Peruvian guano in the pre- 

 ceding year, and retained, as shown by analysis, an appreciable, 

 though small amount of ammonia in a loose state of combina- 

 tion. On the addition of a solution of salt, a portion of the 

 ammonia entered into union with an equivalent proportion of 

 chlorine of the chloride of sodium and passed into solution, whilst 

 the soda of the decomposed chloride of sodium became fixed in 

 the soil. The admixture of salt to Peruvian guano thus increases 

 the efficacy of the latter, and on this account proves economical 

 in practice, especially on light land. 



