CHEMICAL HERBICIDES 



THIS is comparatively a new way of fighting weeds and further 

 experiment is needed for discovery of all its merits. Professor 

 Henry L. Bolley, Botanist at the State Experiment Station of 

 North Dakota, states that "the preliminary field trials at this 

 Station in 1896, were, perhaps, the first experiments of the kind 

 conducted in any country." Soon afterward the discovery was 

 made in France by M. Aime Girard that Copper sulfate would kill 

 Wild Mustard if applied when the foliage was tender. Since then, 

 in many parts of this country and Canada and in European coun- 

 tries, experimenters have been at work, trying the effects on various 

 plants of different chemicals, seeking to find the reason why the 

 treatment succeeds in some cases and not in others, and to learn how 

 it can be most economically and effectively used. Such experiment 

 has proved the worth of the following chemicals as weed-killers, or 

 herbicides : 



Common salt (Sodium chloride). This is the cheapest, handiest, 

 and safest of herbicides, but not the most useful ; for, when applied 

 in sufficiently large amounts to kill a pernicious plant such as the 

 Orange Hawkweed, it may also kill other plant-life and so permeate 

 the soil as to check all agricultural growth for a season. Its de- 

 structiveness lies in its power to absorb the moisture in the soil and 

 from the plant tissues, so that they die of thirst ; therefore, if it is 

 to be effectual, it should be applied in hot, dry weather. Small 

 areas of Quack Grass and Canada Thistle may sometimes be 

 entirely destroyed by salting freely and then allowing cattle and 

 sheep to bite down the salted herbage, repeating the operation as 

 often as new shoots appear. In places where it is needful to expel 

 all plant growth, salt may be used in the form of hot brine, the 

 solution being so strong as to show forming crystals on its surface. 



Copperas, or Green vitriol (Iron sulfate). This chemical, being 

 a by-product of the iron and steel industry, is comparatively cheap, 

 13 



