98 WEEDS OF THE FARM AND GARDEN 



We may note that carbolic acid was found destructive to 

 pigweed, smartweed, and pigeon grass. The amount of 

 material used would make it so expensive that its use 

 cannot be recommended to kill quack grass or other 

 weeds mentioned in the above list. 



An experiment was made at the Iowa station with the 

 Canada thistle, using the carbolic acid at the rate of one 

 part of acid to four parts of water, the solution being thor- 

 oughly agitated in order to make a good mixture. At 

 first an ordinary garden sprinkler was used, but this 

 method was found to be expensive and not effective, the 

 tops alone being killed. In another experiment a small 

 mechanic's oil can was used and the acid was placed in 

 direct contact with the root, the effect penetrating from 

 eight to ten inches below the surface of the ground, but 

 below this point the roots sprouted out again in many 

 instances. This method was not considered entirely ef- 

 fective for the destruction of Canada thistle. 



Sulphuric Acid. This has also been recommended as 

 an herbicide. Professor Jones used it at the rate of one part 

 to forty parts of water, applying at the rate of forty gal- 

 lons to the square rod. It did not kill the weeds, espe- 

 cially the roots, presumably because it formed an insolu- 

 ble compound. Where the fluid came in contact with the 

 plants they were killed, but they soon recovered, produc- 

 ing new shoots. 



Slaked Lime. Slaked lime has been recommended for 

 the extermination of certain classes of weeds, the lime 

 being spread broadcast over the weeds; however, this 

 has not proven a very effective remedy. In an experi- 

 ment with lime at the rate of 484 barrels per acre, it was 

 not effective with quack grass or morning glory, milk- 

 weed, foxtail, or other weedy grasses. While it did, to 

 some extent, decrease the number of quack grass plants 

 coming out, it did not eradicate them. The same may be 

 said of morning glory and milkweed. 



