77 



Crops and Weeds of Arable Land. 



A special type of plant-formation, associated with land under tillage 

 by plough, gives the case of the secondary vegetation associated with agri- 

 cultural crops. The main crops locally are confined to fields of Wheat, 

 Barley, Oats, Beans and Peas, Turnips and Swedes, Mangel and Potatoes. 

 No other crop of importance is in present cultivation. Sainfoin, Vetches, 

 Clover and Rye, as fodder crops, follow the type of Hay Pastures. Crops 

 of minor importance are grown, as Cabbage and Lucerne. Wheat is still 

 the most important crop, though potatoes are increasing. 1 



The denizens of arable land come under two distinct headings of (i) the 

 crop, as the plant intentionally cultivated, (a) the 'weeds', as intrusive vege- 

 tation, of more or less objectionable character from the standpoint of the 

 cultivator, as the accidentia of the process. The ecology of the main crop 

 is the business of the agriculturalist ; a special study involving the relation of 

 that particular plant in mass-cultivation to its climatic and edaphic condi- 

 tions ; as also its relation to preceding crops in the cultural rotation, and the 

 isolation and breeding of improved 'varieties'. The plants thus cultivated 

 may be definitely aliens of a warmer climate (Wheat, Barley, Oats, Rye), 

 or again the specialized representatives of types more or less indigenous 

 (Turnip, Brassica Rapa ; Beet, Beta maritimd) ; the former cereals with a 

 seasonal periodicity of their own, the latter root-crops of biennials vegetat- 

 ing in the first summer. 



Subsidiary forms, associated with the main crop, draining the soil of 

 food-supplies and water, are distinguished as 'weeds'; the object of the 

 cultivator being to eliminate them as far as possible, giving clean ground 

 for the main crop and making the utmost of the ecological conditions of 

 soil and climate. 



As all such arable land has at some time been taken into cultivation 

 from cleared woodland or open pasture, the indigenous vegetation may 

 persist to a certain extent ; while intrusion from similar pastures, from 

 adjacent woodland, and from residual or regressive flora of hedges, may 

 continually add to the source of weeds. In addition to this, alien seeds are 

 being continually introduced with the seeds of special crops, and other weeds 

 may be introduced from roads and waste places on the feet of men or horses 

 in the process of cultivation. The supply of weed-vegetation is thiis continuous, 

 and follows the exigencies of the agricultural situation. With the elimina- 

 tion of hedges, cultivation of fields as wider tracts of land, complete elimination 

 of all residual indigenous flora, and the preparation of clean seed, the weed- 

 problem is reduced to a minimum. 2 



The special features of such field-crops afford a study of plant-life on a 

 large and most intensive scale, as a pure association of individuals, in which 

 no other organism is considered. 3 All have been considerably modified from 

 their ancestral forms, and are so far ' domesticated ' that they do not again 

 'run wild' or re-establish themselves in competition with the indigenous flora. 



The most obvious character of arable land is the small number of plant- 



forms in cultivation. As in all human efforts at domesticating animals and 



plants, the tendency is to exploit isolated forms with special characteristics 



at the expense of the rest of creation ; and thus the cult of the horse, 



1 Orr (1916), Agriculture in Oxfordshire, p. 195, with maps and county statistics from 1866- 



Plot (1705), p. 157, records Carthamus sativus, Safflower, cultivated for scarlet dye at Aston, 

 and Caraway at Hampton. 



* Brenchley (1920), Weeds of Farmland, p. 43. 



* Percival (1910), Agricultural Botany, p. 571. 'A very large number of native wild plants, 

 which, although in Nature's great collection of living things no doubt perform some useful work, are 

 nevertheless from the farmer's special point of view, practically without any appreciable value.' 



