32 COMMON WEEDS 



small percentage of dead or weak seeds will, if sown, 

 cover the ground far from completely, and this is 

 offering a premium on the spread of weeds, which 

 tend to grow more strongly in the absence of a heavy 

 cultivated crop. The presence of but i per cent of 

 Dock seed in a mixture of grass and clover seed means 

 no less than ten or more Dock plants per square yard 'all over 

 the field whenever such a sample is sown at the ordi- 

 nary rate for leys. 1 



(e) Rotation of Crops. In the management of a farm 

 rotations are of very great value for several reasons, 

 only one of which need be mentioned here. The 

 change of crops due to rotations affords an oppor- 

 tunity of cleaning the land. When an area is sown 

 with wheat in autumn and the crop is not harvested 

 until the following August it is obvious that little can be 

 done in the way of suppressing weeds, except in the case 

 of Thistles, Docks, and one or two other large weeds 

 which may be removed by hand, or Charlock, which can 

 be destroyed by spraying. In certain cases, however, 

 corn crops are hoed when young, while harrowing in 

 spring to destroy annuals is extremely useful. After 

 the end of May little can be done, and the crop and 

 land must be left untouched until the harvest, by 

 which time many weeds will have shed their seeds. 

 When, however, wheat land is ploughed up, left to 

 mellow during winter, well cultivated in spring, and 

 then used for taking a root crop, an opportunity 

 occurs for suppressing weeds. During spring and 

 summer especially, when the previous year's seeds 

 germinate, hand and horse hoeing are employed to 

 keep the weeds well in hand, and seeding is almost 

 entirely prevented. The rotation of crops commonly 

 followed, by which a root crop is taken once in four 



1 Leaflet No. 112, Board of Agriculture and Fisheries. 



