THE COMPETITION BETWEEN BARLEY AND CERTAIN WEEDS UNDER CONTROLLED CONDITIONS

Abstract

One of the commonest agricultural practices in Britain is the undersowing of barley and other corn crops with clover as a preparation for a clover ley after the corn crop has been reaped. The effect of the clover growing among the corn, where manuring (especially with nitrogen) is made as favourable as possible for the corn crop, is not clear. If nitrogen is deficient, it is well known that clover can furnish nitrogen for the corn, but where the supply is ample, the clover may act as a competitive crop.When barley and clover were planted together, with abundance of water and nutrients for both, it was found that the presence of even a small number of barley plants reduced the growth of the clover by over 50%, but that an increase in the density of the barley did not increase the effect. The presence of the clover reduced the barley crop by an amount which tended to get less as the density of the barley was increased. In a sparse crop of barley, increase in clover density reduced the growth of barley very little, while that of the clover was again found to be little more than half what was obtained when this plant was grown alone.There is no evidence of any specific effect of the roots of the one plant on the other. In the circumstances of these experiments it would seem that, far from the clover supplying nitrogen to the barley, it tends to steal some of that which would otherwise be available to the latter, when they are grown together.