38 BOARD OF AGRICULTURE. 



strated the fact that all plants, with the exception of a compara- 

 tively limited number of species of plants growing along the 

 seashores or in the vicinity of saline springs, contain much 

 smaller quantities of soda than potassa compounds, and, as a 

 natural process of the disintegration of rocks and soil does 

 render, in all probability, soda as well as potassa accessible as 

 plant-food, there is far less reason, as a general rule, to expect 

 as soon an exhaustion of the soil on soda compounds as on 

 potassa. 



These few considerations explain to us the position, which 

 soda compounds — and chloride of sodium is not only its cheap- 

 est, but also, for obvious reasons, its most diffused form in our 

 lands under cultivation — do occupy in the vegetable economy ; 

 they have to be considered of secondary importance as plant- 

 food for the promotion of vegetable life as long as a relative 

 percentage of the various mineral substances in the ashes of 

 plants may be taken as a measurement of their importance in 

 the direct support of the promotion of their growtli. Care- 

 ful experiments by E. Wolf have left no doubt that salt 

 is liable to injure the growth of plants; he experimented 

 with seeds of two of the most important natural groups of 

 cultivated plants — the graminas and leguminosse — (barley and 

 vetch) ; he found that 0.52 percentage of salt in a soil 

 would considerably retard vegetation, and that 1.02 percentage 

 would even kill the germ ; the only saline substance among 

 our artificial fertilizers, which somewhat excelled the salt 

 (chloride of sodium), was the salmiak (chloride of ammo- 

 nium) ; finding that the nitrates, phosphates and sulphates of 

 soda and ammonia act far less injuriously, we conclude, quite 

 properly, that the chlorine — one of the constituent elements 

 of salt (and salmiak) — must be one of the causes of a fre- 

 quently-reported injurious effect in consequence of the direct 

 use of salt for fertilizing purposes. The injurious effects, of 

 late recognized in many instances, in Germany and elsewhere, 

 where the celebrated Stassfurth dungsalt has been extensively 

 used, have caused their present transformation from combina- 

 tions of chlorine into combinations with sulphuric acid or 

 into sulphates. The belief in the general efliciency of salt 

 as a fertilizer has been apparently so much shaken in Ger- 

 many that numerous factories at Stassfurth, etc., are now 



