Abstract
Some legumes were examined on residual effect on nitrogen content of succeeding gramineous crops in pot culture using nitrogen-poor soil. The tested legumes were pea (Pisum sativum L.), broad bean (Vicia faba L.), alfalfa (Medicago sativa L.) and red clover (Trifolium pratense L.). After these legumes, corn and wheat were cultured successively. The results are summarized as follows. 1. Nitrogen content of tops was highest in broad bean and in red clover, medium in alfalfa and lowest in pea. Nitrogen contents of underground parts of alfalfa and red clover were higher than those of broad bean and pea (Table 1). 2. Nitrogen content of tops of the succeeding first crop, corn, was not proportional to the nitrogen contents of underground part of the preceding legumes. The corn following red clover produced the highest nitrogen yield, that following alfalfa or broad bean medium and that following pea the lowest (Fig. 1). 3. Nitrogen contents of tops of the succeeding second crop, corn, and of the third crop, wheat, were lower than that of the first corn. The nitrogen contents of these crops varied with the species of the preceding legumes. The nitrogen content after alfalfa was the highest, whereas that after red clover or pea was the lowest (Figs. 2 and 3). It is found from these results that legumes increase nitrogen contents of succeeding corn and wheat and that this increase varies with the species of the legumes. It is suggested that this variation is due not only to nitrogen content of legume residues after harvest but also to decay rate of the residues.
