THE COMPETITION BETWEEN BARLEY AND CERTAIN WEEDS UNDER CONTROLLED CONDITIONS

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Abstract
Chickweed (Stellaria media) is one of the commonest annual weeds on almost all soils, and forms 20–30 % of the weed herbage on the lower greensand soils of Woburn, Beds. It occurs in all crops in this area except on very acid soils.When barley and chickweed are planted together, with abundance of water and nutrients for both, it is found that increasing the density of planting of the barley reduces the loss due to chickweed competition, but even with very close‐planted barley, the loss caused by the weed amounts to nearly two‐thirds of the total fresh weight and to four‐fifths of the grain yields. This is much greater than with the two annual weeds previously studied (spurrey and mayweed). In a sparse crop of barley, increase in chickweed growth may reduce the barley to less than 10 % of its growth without the weed, while the chickweed itself is relatively little affected by the presence of the barley.There is no evidence of any specific effect of the roots of the one plant on the other; they intertwine without any sign of attraction or repulsion between them.Comparisons are made with other annual weeds previously studied, and it is suggested that the method adopted furnishes a means of assessing the relative effectiveness of these weeds in competing with barley.