46 WEEDS OF FARM LAND 



implements worked by hand and animal labour. No chemical 

 substances were recognised in agriculture, and naturally 

 enough the methods employed were conservative and farmers 

 did not foresee future improvements. In this way one finds 

 Blith 1 stating that ploughing is the only cure for weeds, 

 and that such common weeds as nettles, docks, chickweeds, 

 and hemlocks (chevils ?) are caused as much by over-rich and 

 fat soil as by anything else. Our knowledge has advanced 

 since those days, the true cause of the prevalence of weeds is 

 better understood, and many kinds of mechanical and chemical 

 methods have been devised to deal with them. 



The system under which land is farmed has much to do 

 with the particular methods adopted for the eradication of 

 weeds. Methods that are possible and effective on ploughed 

 land are impossible of application on grass-land, besides which 

 the types of weeds that occur under the two systems are quite 

 different. It will therefore be necessary to make a sharp dis- 

 tinction and to consider separately the methods of exter- 

 minating weeds on arable and grass-land. 



I. Eradication of Weeds from Arable Land. 



(a) Eradication by Methods of Cultivation Mechanical 

 Means. The primary method of removing weeds from arable 

 land is ploughing, for unless some clearance is first effected in 

 this way whatever other methods of cultivation may be carried 

 out are of little avail. In ploughing the surface vegetation 

 is bodily reversed and buried under a mass of soil which 

 prevents the leaves of the plants having access to the light 

 and air essential to them. The roots are cut off from 

 communication with the lower soil, and in this position the 

 plants are subjected to baking and consequent withering if the 

 weather be hot, or if it be wet and cold the crowns are sur- 

 rounded with so much dampness that they rot away. This 

 effectively disposes of large numbers of the annual weeds that 

 have fibrous roots, while the top growth of perennials is 

 also destroyed. 2 The act of ploughing, however, breaks 

 up the roots or the underground stems of the perennials, and 

 unless further measures are taken much harm may result. If 



1 Blith, W. (1652), " Survey of Husbandry Surveyed". 



2 The Russians advocate very deep ploughing (12 inches at least) as 

 by that means weed seeds are buried at such a depth that they cannot grow. 

 See Anzibor, S. (1912), Bull. Bur. Agric. Intelligence and Plant Diseases, III, 

 pp. 2313-4. 



