THE WEEDS OF NEW SOUTH WALES. 15 



(/) Eradication. 



Sometimes the total removal of the plant is feasible and desirable. This 

 may be done by hand-pulling 1 , forking, loosening with plough, and gathering 

 together by the harrow for burning. 



A mechanical extractor is sometimes useful. One for large weeds with 

 stems of the necessary toughness is figured at p. 814, vol. 2 (1891) of the 

 Agricultural Gazette. 



(g) Drainage. 



The drainage of land always changes the character of the vegetation upon 

 it, and is often the means of getting rid of undesirable weeds. This is the 

 best way, for example, of getting rid of such weed as Stagger Weed (Stachys 

 a-rvensis). At the same time the improved conditions permit the growth of 

 wholesome grasses. 



(/?) Rotation of crops. 



Rotation of crops is frequently advantageous for overcoming weeds not 

 easy to suppress by other means. 



(i) Smothering crops. 



Weeds are sometimes dealt with by sowing crops which smother them. 

 Change of crop is often useful, and particularly the introduction of root or 

 other crops requiring hoeing and scarifying. 



(A*) Chemical manures. 



The application of chemical manures is sometimes desirable. For example, 

 nitrate of soda stimulates the leafy growth of grasses, and a dressing of lime 

 that of clovers and other leguminous plants, and in this way weeds may be 

 smothered. 



(?) Chemical weed- exterminators. 



The use of chemical exterminators of weeds such as salt, arsenic, kerosene, 

 &c., is usually out of the question, as the labour is too great, to say nothing* 

 of the cost of materials and of the danger of sterilising the soil for a long 

 period. The method is also uncertain, and, as a rule, can only be applied to 

 special weeds, e.g., Prickly Pear. 



Sometimes a cereal crop with weeds can be sprayed by a substance which 

 is selective in its action, destroying the weeds and leaving the crop unin- 

 jured. This is a field for experiment which has been but little investigated, 

 but spraying with a 10 per cent, solution of iron sulphate for example has 

 been attended with favourable results. Copper sulphate is even more 

 favoured at the present time for this purpose. 



(m) Special treatment. 



Special weeds require special methods. For example, in Europe it is a 

 usual practice to cut the stems of such plants as Blackberry and Sweet Briar 

 with bill-hooks, and to enclose the ground containing the stumps with 

 hurdles within which sheep, goats, or other animals are folded. The stock 

 readily eat the young tender spineless shoots as they appear, and by degrees 

 the plants become exhausted and die. 



