The competition between barley and certain weeds under controlled conditions

Abstract

The nature of the competition between the serious weeds Spergula arvensis and Matricaria inodora has been studied where the available root space, water, light, and N supply are limited and controlled. When grown alone under these conditions, barley or either of the weeds give a yield which reaches a maximum with definite density of plants per volume of soil. If excess of N fertilizer is added, a limit is reached with either weed when extra N only raises the % of N in the plants grown. When barley and weeds are grown together, an increase in the density of barley diminishes the injurious effect of the weeds and the wt. of both weeds decreases as the number of barley plants increases. The increase in the numbers of either weed does not much affect the yield of barley till the number of weed plants exceeds that of barley plants, but the presence of a strong well-grown crop of barley largely reduces the production of both weeds, especially of Spergula. There is no evidence that there is any special relationship between barley and either of the weeds. The effect seems to be only one of competition for root space or for N when there is not an excess of the latter.