PREVENTION AND ERADICATION OF WEEDS 53 



to keep it in check. Consequently half of the field was fallowed 

 in 1914 for a season and the other half in 1915, and the 

 following years far less of the pest was in evidence. 



When all other means of eradication fail, whether they be 

 methods of cultivation or " chemical " means, obstinate weeds 

 will sometimes disappear if the land be laid down to grass for 

 a term of years. Thi-; was fully recognised in the eighteenth 

 century, and is still practised when necessary at the present day. 



Anderson 1 (1779) noticed that couch-grass and knotgrass 

 only occur while the land is under cultivation, or at most for a 

 year or two after it is laid down to grass, " after which they 

 usually disappear and are no longer seen till the land has been 

 again in tillage for some time. And it is in this way alone 

 that the farmers, in some of the worst cultivated parts of Scot- 

 land, know how to get rid of these destructive weeds." 



Adam 2 (1789) claimed that to extirpate coltsfoot (Tussilago 

 farfard^j thoroughly the land must be long laid down to grass, 

 though he admitted that it was once almost destroyed by two 

 successive crops of vetches, and that it may be killed by allow- 

 ing the land to lie for a sufficient time under clover and ryegrass. 



Most excellent results have been obtained by an adaptation 

 of this method in recent years in dealing with wild onion 

 (Allium vineale]. This is only troublesome on heavy soil, 

 but is sometimes so abundant as to ruin the crops, and no 

 ordinary method is effective in reducing it. The plant spreads 

 in three ways, by means of seeds, by bulbils formed in the 

 flowering head, and by "offsets" from the subterranean bulb. 

 Experiments were carried out at the Woburn Experimental 

 Station 3 and also on fields at Woburu and Chelsing in which 

 the pest was very abundant. Many chemical treatments were 

 tried, with little or no success in most cases, and various 

 mechanical treatments, such as cutting off the flowering heads, 

 pulling up plants by hand, deep-ploughing the land, and 

 burning the soil, were equally unsuccessful. Experiments 

 in. which the soil was lightened by mechanical addition were 

 more promising, indicating that if the land could be opened 

 up and more effective drainage provided the weed might 

 eventually be got under. It was therefore decided to sow 

 plots down with " Elliott's mixture," a mixture of grass 



1 Anderson, J. (1779) (3rd edition). " Essays on Agriculture," II, p. 38. 



''Adam, J. (1789), "Practical Essays on Agriculture On Weeds," pp. 

 173-198. 



Voelcker, J. A. (1911), "Eradication of Wild Onion," Jour. Roy. Ag. 

 Soc., 72, pp. 404-409. 



