CHEMICAL WKED CONTROL 159 



chemicals. Weed control, as a secondary result, was noted and care- 

 ful count of the weeds occurring during the field season of 191? was 

 made. The summary (Table 1) gives the number of weeds of differ- 

 ent kinds and the treatment for each bed. 



The preceding data were gathered from an experiment which was 

 not intended for purposes of weed control and it is scarcely possible 

 that the distribution of weed seeds and root stocks was equal among 

 the beds devoted to the work. However, the very small number of 

 weeds occurring in the beds treated with zinc and copper salts sug- 

 gests that these chemicals may be efficient in destroying weeds shortly 

 after germination in this particular type of soil. 



Much work has been done in Europe on the relation of zinc and 

 copper salts to plants and soils. Baumann, in 188."), found small 

 amounts of zinc sulphate sufficient to kill a number of common mono- 

 cotyledenous and dicotyledenous species but to work no injury to 

 coniferous seedlings, even after they had been seven months in the 

 solution. He also found the chemical much more efficient in poor 

 (mineral) than in rich (organic) soils. Javallier, in 1908, found zinc 

 present in varying amounts in 45 species of plants of over half as 

 many different families, and including cryptogams and phanerogams. 

 He found it particularly abundant, however, in conifers, classing them 

 as "calamines," or zone plants. 



Experimental evidence, collected from the foregoing and other 

 sources, has led to the undertaking of a rather extensive investigation 

 of weed eradication through chemicals at the Savenac Nursery. Seeds 

 of three of the most important weeds, white clover (Trifolium repens), 

 timothy (Plileuin prafcnsc), and red-topped sorrel (Rttmcx acetosella), 

 have been sowed with the seed of western white pine {Pinus monticola) 

 in previously steam sterilized soil, and the various plots wet down with 

 different strength solutions of copper sulphate, zinc sulphate, and zinc 

 chloride. In the effort to eliminate error, due to unintentional varia- 

 tions, the installation has been in quadruplicate, making a total of 84 

 jjlots upon which to base results. 



Since, according to Beal, weed seed has strong vitality and pre- 

 sumably marked holdover tendencies, and the seed of the western white 

 pine is known to hold over one, or even two, seasons before germinat- 

 ing, results of the work may not be available for some time. The 

 planting out of stock grown under these conditions and observations 

 on their appearance for several seasons, together with determinations 

 of the effects of the chemicals on the nursery soil, will be necessary 

 even after a successful weed eradicator is found. Otherwise unfore- 

 seen and serious obstacles may appear later and overshadow any good 

 arising out of the easier method of weeding. 



