. Cyclopedia of farm crops : a popular survey of crops and crop-making methods in the United States and Canada. Agriculture -- Canada; Agriculture -- United States; Farm produce -- Canada; Farm produce -- United States. Chemicals useful as herbicides. Any soluble chemical, even including the various commercial fertilizers, if used in sufficient amount, will kill plants. Some act directly and quickly as poisons, e. g., arsenic and carbolic acid; others, such as salt, have little or no direct poisonous effect but kill the plants primarily by drawing the water from the tender foliage, or by holdi
. Cyclopedia of farm crops : a popular survey of crops and crop-making methods in the United States and Canada. Agriculture -- Canada; Agriculture -- United States; Farm produce -- Canada; Farm produce -- United States. Chemicals useful as herbicides. Any soluble chemical, even including the various commercial fertilizers, if used in sufficient amount, will kill plants. Some act directly and quickly as poisons, e. g., arsenic and carbolic acid; others, such as salt, have little or no direct poisonous effect but kill the plants primarily by drawing the water from the tender foliage, or by holding the moisture of the soil so that it cannot be absorbed by the roots. It is important in this connection to note that in either case the herbicide is most effective on young plants that are in active growth. Effectiveness in one or the other of these ways, together with cheapness and convenience of application, are the things to determine choice among the various compounds available. Without attempting to list all of these, we include those whose worth has been best estab- lished by trial. Salt (sodium chlorid) is probably more commonly used than any other compound, chiefly because of cheapness and handiness. Its action depends almost wholly on the withdrawal and retention of moisture from the plant, therefore it should be applied dry or in strong solution; and it is most effective in hot, dry weather. Salt can be used in any weed- killing operation, but it is most valuable on road- ways and like surfaces and for certain lawn weeds. Blue vitriol (copper sulfate).âThis is more pow- erful in herbicidal action than salt, but its cost prohibits its general use. For most purposes it is best used in solution, 2 to 10 per cent being effec- tive. It is often used on gravel walks and similar surfaces, but salt will generally be found cheaper ss*^^ Fig. 157. Heads of orange hawk- '^ -i^i â ^i^^ -^^i" -^, ^ ;. 156. The orange hawkweed, or paint-brush (Hieracium aur(intiaru
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