Abstract: The allelopathy of Chamaecrista spp on P. notatum under different aluminum and magnesium stresses was studied. Aluminum and magnesium stresses affected the allelopathy. At three concentrations, C. rotundifolia inhibited the growth of P. notatum. The most significant inhibition effect was when the concentration of aluminum was 0.7 g/L. C. nictitans inhibited the growth of P. notatum when the concentration of aluminum was 1.1 g/L and the concentration of magnesium was 0.060 and 0.123 g/L. In general, allelopathy was stronger in the roots than in seedlings.