68 WEEDS OF FARM LAND 



is danger to cattle that may eat the herbage or hay afterwards. 

 The Americans apply salt solution, using 200 Ib. salt per acre, 

 dissolved at the rate of I Ib. salt in i-j- quarts of water. Two 

 sprayings a year are necessary, and it is claimed that the 

 method is effective. 1 Salt does not injure the herbage, but 

 on the contrary exercises a beneficial action as a manure, so 

 that the salt solution is free from the objection common to most 

 sprays. In Germany a 15 per cent, solution of kainit has 

 been used to eradicate nettles in springtime, and the sugges- 

 tion is made that this good effect may be due to the presence 

 of salt in the kainit. 



(2) Manures. The principles underlying the treatment of 

 grass-land and arable land by manure for the eradication of 

 weeds are essentially different. On arable land the application 

 is made directly to the weeds with a view to burning them up 

 and so destroying them, the actual beneficial action of the 

 manure on the crops being a somewhat secondary considera- 

 tion. On grass-land, however, it is impossible so to differentiate 

 between weed and crop. In this case the manures are applied 

 with the view to encouraging certain desirable species, to 

 enable them to exercise their full force of competition and so 

 gradually crowd out the undesirable plants. 



Apart from their beneficial influence on the herbage, salt 

 and lime, perhaps, exercise a more direct action upon certain 

 weeds. Nettles are less likely to recur if infested pastures 

 are treated 'with 6 cwts. per acre of salt at the time the weeds 

 are cut down in the spring. A similar dressing in early April 

 is recommended for getting rid of oxeye daisy (Chrysanthemum 

 leucanthemum). On the other hand, salt does not seem to 

 injure thistles much, as the effect of various methods of cut- 

 ting is not enhanced by an after application of salt. 2 



Lime in one of its various forms is usually most effective 

 in reducing the quantity of sorrel (Rumex acetosd] and sheep's 

 sorrel (Rumex acetosella\ though it is still doubtful whether 

 this is due to the fact that the sorrels are intolerant of the 

 lime itself or whether they are merely extremely impatient of 

 the increase of competition due to the improvement of the 

 herbage by the liming. Be that as it may, liming may be 

 regarded as the universal remedy for these weeds. The 



1 Cox, KL R. (1915), " Eradication of Ferns from Pasture Lands in the 

 Eastern United States," U.S. Dept. Agric., Farmer^ s Bulletin, No. 607, p. 12. 



2 " Destruction of Thistles" (1908), Report of Field Experiments at Harpe? 

 Adams Agric, Coll, 



