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Suppression of Weeds : National Necessity. [June. 



acre but only IGJ tons when weeding after singling was omitted. 

 During the War weeds and the effort to get rid of them cost 

 British farmers millions of pounds. 



The war against weeds can be waged successfully only by 

 those who understand the ways in which these pests gain 

 access to the farm land and spread among cultivated crops. 

 Many weed seeds, such as the thistle and dandelion, are 

 carried considerable distances by the wind. Weeds are con- 

 v^eyed also by farmyard manure. They are found in screenings 

 from threshing and winnowing machines, and the sweepings 

 of barns and haylofts. They are found in manure from cattle 

 fed on inferior hay. Well-rotted farmyard manure will contain 

 fewer germinable weed seeds than fresh manure, and is there- 

 fore less liable to introduce weeds to clean fields. A potenii 

 means of conveyance is the use of poor seed. The presence 

 of 1 per cent, of dock seed in a mixture of grass and clover 

 means 10 or more dock seeds per square acre all over the field 

 on which such a sample is sown at the ordinary rate for leys. 

 Broken pieces of root also serve to spread trouble, and 

 machines, such as self-binders and travelling thrashers, are 

 often responsible for a wide distribution of weed seeds which 

 are carried on the machines and also in the mud picked up by 

 the wheels. The fruits and seeds of certain weeds such as 

 burdock, corn-buttercup, wild carrot and cleavers fasten on the 

 wool and hair of animals and the clothes of human beings 

 and are thus carried considerable distances. Birds also are 

 effective agents in distributing weed seeds. 



The most obvious means of suppressing weeds is to prevent 

 seeding. When it is recognised that mature charlock plants 

 produce from 1,000 to 4,000 seeds, a moderate sized poppy 

 10,000 to 15,000, and large plants often 50,000 seeds, the force 

 of the adage " one year's seeding is 7 years' w^eeding " becomes 

 manifest. Further, as many weeds produce seeds w^hich do 

 not all germinate at the same time the mischief is greater 

 than appears at first sight, for some may lie dormant in the 

 soil and spring up after an interval of several years. To destroy 

 weeds of this type it is advantageous to introduce into the 

 rotation root and other crops which promote a thorough 

 cleaning. Seeding of weeds in hedgerows, on roadsides, waste 

 places and round farm buildings should be prevented as far 

 as possible. Another important precaution is to avoid the use 

 of imperfectly cleaned seed. The Ministry desires to impress 

 upon farmers the great importance of ensuring that there shall 

 be no failure of crops due to the sowing of poor seed. 



