574 WEEDS : GENERAL 



The reduction of yield due to the presence of weeds may 

 reach 50 per cent. 



Ex. 270. — Select a foul piece of ground two yards square and prepare a 

 seed-bed. Divide it into two equal halves and sow about 500 grains of barley 

 or wheat in drills 8 inches vride. When the plants are well above ground 

 make both halves alike in the number of plants which are upon each. Allow 

 weeds to grow on one half and carefully pick out all weeds by hand from the 

 other. When ripe count the number of stems and weigh both grain and straw 

 on each small plot, and observe the improved yield where the weeds have 

 not been allowed to compete with the crop. 



Similar experiments should be carried out with potatoes, carrots, mangolds, 

 and turnips. 



c. In spite of hoeing and weeding, a large variety of weeds 

 are harvested with the cereals, and their seeds become mixed 

 with the grain when the crops are thrashed. The presence of 

 weed seeds in samples of all kinds reduces their market value, 

 as the purchaser naturally objects to pay for what he does not 

 require, and he often lays stress upon the slightest impurity and 

 magnifies it in order to obtain a reduction in price. The miller 

 buying cereals considers not only the actual bulk of impurity as 

 a feature to be avoided, but has to bear in mind, in the case of 

 wheat samples, the injurious effect which weed seeds frequently 

 have on the colour of the flour. The testa and pericarp of 

 many impurities are black, or nearly so, and, when ground with 

 the wheat, darken the colour of the flour obtained. Those speci- 

 ally avoided by the miller on this account are seeds of corn- 

 cockle, wild and cultivated tares, and black bindweed. 



Moreover, the contents of some seeds, such as tares, melilot 

 and crow-garlic, communicate to flour an objectionable taste or 

 an offensive odour. 



The farmer purchasing for seeding purposes has to keep in 

 view the possible danger of spreading over his field various 

 weeds which the samples may contain, and the price he is 

 prepared to pay for the latter is very low when foreign seeds 

 are present in them. 



