Abstract
Top and root growth and nitrogen content of ryegrass and bigflower vetch in the pure and associated sand culture, fed by nitrogen-free culture solution, were measured periodically. The grass in the association was higher in nitrogen content than that in the pure stand. Especially in the later periods of growth, total nitrogen accumulation in the top parts of the grass in the associated. plots surpassed that of the grass in the pure stand, although the former had only half as many population per pot as the latter. The field experiment, in which several species of legumes are combined with the ryegrass, resulted similarly. And the grass showed the higher nitrogen percentage when the more thriving legumes were associated (significantly correlated). The facts seem to show the cooperative relation of the associated legumes as the underground nitrogen supplier to the grass.
