DISTRIBUTION OF WEEDS 15 



The. danger of weed transport in manure is probably less 

 nowadays than it used to be, as with the improvement in 

 threshing tackle a much cleaner separation of grain, straw and 

 rubbish is effected, and the practice of burning the rubbish 

 (containing most of the weed seeds) is becoming more widely 

 spread. Also there is comparatively little transport of manure 

 from one country district to another, but where stable manure 

 is brought from towns much care should be exercised, as 

 the litter and feeding stuffs are more likely to be contamin- 

 ated with weed seeds than in the case of manure produced on 

 farms. 



(c) Distribution by Means of Farm Implements. With the 

 increase in the use of farm machinery of late years the danger 

 of weed infestation from this source has become more acute. 

 Almost every implement that is used in farm operations may 

 serve as a carrier of seeds or growing parts of weeds, but as 

 hand implements and the smaller horse machines are usually 

 the property of the farm, weed distribution by this means is 

 localised. With the advent of peripatetic tractors, threshing 

 machines, reapers and binders, etc., the area of distribution 

 was at once widened, and now care is necessary to prevent 

 trouble arising. Farm implements spread weeds in various 

 ways, the most obvious being by means of the clods of earth 

 that are carried about on the wheels and on the horses' hoofs. 

 The soil is full of weed seeds and in many cases broken pieces 

 of weed are also present which are capable of striking root 

 elsewhere. If machinery passes from farm to farm over a wide 

 area, from badly-tilled farms to well-cultivated ones, the 

 efforts of careful farmers to reduce their weed population may 

 be greatly hindered if they do not take care that the incoming 

 machines are well cleaned before they are allowed to pass on 

 to the land. Threshing machines introduce another problem, 

 as weed seeds collect within them, only to pass out when 

 further threshing is carried out. Such weeds as wild oats 

 (Avena fatua) are particularly troublesome in this way, as not 

 only are they bad weeds on the land, but the hairy fruits with 

 their bent and twisted awns collect in balls and rapidly choke 

 up the machine (Fig. 4). Here again scrupulous care in 

 cleaning before use is necessary if weed distribution is to be 

 avoided. 



(d) Carriage by Moisture or in Mud. Though to some ex- 

 tent mud carriage is dealt with under the preceding heading 

 other aspects must be considered here. Traffic of every kind 



