142 



SOME FACTORS IN PLANT COMPETITION. 



By WINIFRED E. BRENCHLEY, D.Sc. 



[Rothamsted Experimental Station.) 



(With 10 Text-figures and Plate V.) 



One of the commonplaces of agriculture and horticulture is that when 

 plants of the same or different species grow in juxtaposition a mutual 

 influence is exerted which is known as "competition." Every plant 

 needs a certain definite supply of such essentials as food, water and 

 light to enable it to reach its full development, and when other indi- 

 viduals with similar requirements are in the near neighbourhood they 

 encroach upon these supplies and a sharp struggle for existence is the 

 outcome. This fact of competition is fully recognised by every practical 

 man, and much nicety of judgment is often exercised to give a crop 

 adequate room for reasonable development in order to obtain the 

 largest yield possible from a given area of land. It is not always an 

 economic policy to give each plant the space it needs to attain its 

 maximum growth, as the individuals may benefit at the expense of the 

 total crop. Under certain circumstances, however, this policy of elimin- 

 ating competition as far as possible is markedly successful, as in the 

 case of wheat growing in the droughty districts of China^. The wheat 

 is planted in "hills" arranged in double rows spaced widely apart, the 

 hills being 24 to 26 inches from centre to centre, the rows 1() inches 

 apart, and the space between each pair of rows 30 inches. In an unusually 

 dry season a yield of 12 bushels per acre is obtained by this method, 

 whereas in a very favourable season (as 1901) as much as 116 bushels^ 

 has been reported for small areas. Without this veiy specialised method 

 of cultivation in these districts it would be impossible to obtain 

 a wheat crop at all, but in most places with larger rainfall the end 

 would not justify the means. A good many experiments have been 

 carried out on thick versus thin seeding of cereals, wide versus narrow 

 drills, etc., the results varying with locality and season. It is, however, 



' Kiiij^, F. II., Fiirnitrs <if J'\irli/ CciilHrits, pp. i';{()- :24l'. 



^ There is no evklence tu show the wciL'ht I'lr Kiislwl in this case. 



