148 FOREST PROTECTION 



F. DAMAGE TO THE SOIL. 



Conclusive experiments prove that soluble sulphuric salts of cop- 

 per (like blue vitriol) fail to cause any damage to the plants, 

 whether applied in the form of dust or in the form of watery 

 solution. Very concentrated solutions, however, cause cor- 

 rosion; also dust falling on leaves wet with dew. 



Although the roots of plants are unable to refuse entrance to dam- 

 aging liquids, it has been found that soluble salts of copper, 

 when entering the soil, form at once an insoluble chemical 

 combination with the bases of the soil. It is possible, how- 

 ever, that poor quartz-sand, in the immediate proximity of 

 the smelters, can be affected by soluble salts of copper. 



Insoluble salts of copper are, obviously, harmless in the soil. 



Absolute proof for or against soil-poisoning can be obtained only 

 by planting seeds and seedlings into soil supposed to be poi- 

 soned, after removal to a point far from the smelters. Plant- 

 ing experiments made by Reuss have failed to prove any posion- 

 ing of the soil, even under extreme conditions. 



The sulphuric acid contained in the soil is by no means propor- 

 tioned to the damage appearing in the trees. On the other 

 hand, trees stocking on sulphuric soil (e. g. gypsum soil) show 

 invariably a high percentage of sulphuric acid within the leaves. 

 It seems as if sulphuric acid obtained through the roots is 

 innocuous, whilst sulphuric acid inhaled through the leaves 

 is noxious. 



If by condensation of the gases at the smelters the atmosphere 

 is purified, the soil in the proximity of the smelters is as ready 

 to produce as ever. In other words, there is no such thing 

 as irreparable damage caused by smelterfumes. 



Experiments with plants watered with a solution of SOj prove 

 conclusively that no damage results from such watering. On 

 the contrary! After Freytag, plants watered with a solu- 

 tion of SO a have shown better yields than those which were 

 not watered with SO 2 . 



In other words, sulphuric acid has a chance to become a blessing 

 to agriculture, especially where the soil contains insoluble 

 phosphates; and there is, decidedly, no such thing as the "poi- 

 soning of the soil" through SO 2 or SO 8 , applied in gaseous 

 form or liquid form, as salt or acid. 



G. DAMAGE TO FARM CROPS AND FRUIT TREES. 



Within the vegetation economically used, farm crops suffer less 

 from fumes than trees. In the case of farm crops potatoes 

 seem to be least sensitive, cereals follow next, whilst legumi- 

 nous plants are more sensitive. 



