DS ON i Mi: I ARM. 805 



Weed seeds, too, are remarkable for their hardiness and vitality, being 



ible of germination under conditions tli.it would not suit more useful 



species of plants, and in many cases they are capable of remaining dormanl 



in the soil for long periods to germinate when mure favourable conditions 



result from .cultural <>r ol her act ion. 



Prevention and Control. 



AN hen a weed has become firmly established, it may be a very difficult — 



almost an impossible task to eradicate it, and thus methods of pre\ enl ing tlie 

 introduction, or in any case of eradicating the pest in the very early stages 

 of development, are most important considerations. 



("heap seed is often very dirty : there is no economy in buying seed that 

 can he sold cheaply because it has been hurriedly collected or taken from 

 paddocks infested with weeds. All seed, without exception, should be 



screened. 



As means of control the following suggestions are made, and farmers can 

 adapt them to their needs in accordance with the severity of the infestation 

 and the means at their disposal. 



1. Preventing the Weeds from Seeding. — Many weeds are of an annual 

 character, and the systematic removal or destruction of the flower head 

 before the seed is formed prevents the survival of the weed till next season. 

 A number of species, however, are perennials possessed of bulbous rootstocks, 

 or fleshy or woody roots that could not be effectively handled in this way; 

 but the continuous removal of the top growth during the growing season has 

 a wearing down effect on even the hardiest plant. Without leaf growth the 

 root must die, and by an aggressive policy of persistent cutting, control of 

 these types may sometimes he effected. 



Tn some very obstinate cases (as for example, Johnson grass) it is advisable 

 to worry, not only the top-growth, but the roots also, and to call in the 

 assistance of the hot sun and drying winds by continuous exposure of the 

 roots. 



2. Killing the Seedling*. — In the life of all plants, the seedling stage is the 

 most delicate, and though some species of weeds are exceedingly hard to 

 destroy even in that stage, more success can be achieved in the control if 

 they are attacked early than if they are allowed to mature. 



3. Enforced Germination. — The practice of inducing weed seeds to germ- 

 inate by cultivation before the sowing of the main crop, has proved a useful 

 means of controlling certain species of weeds that are commonly found 

 associated with particular crops. Such a weed as the wild oat can ne 

 handled in this manner as described in the Wheat .Section of this Handbook 

 (see page 248). 



-i. Grazing-off. — The depasturing of sheep on the crop of herbage that is 

 produced on the stubbles is recognised as sound practice on sheep and wheat 

 farms. It not only turns into wool and mutton the young and succulent 

 weed growth, but it prevents the undue reproduction of the weeds and is a 

 useful method of maintaining the humus content of the soil. 



5. Rotation of Crops. — Certain species of weeds are continuously associated 

 with a particular crop, mainly by reason of the fact that the cultural 

 operations in regard to that crop are such as to allow an amount of leniency 

 to the weed. A rotation of crop", besides being good practice from other 

 points of view, can be made to control these weeds if a crop is introduced 

 which, by its cultural requirements, results in conditions unfavourable to tn<> 



ffrOWtll Of the Weed. 



