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The effect of leaf extracts of Parthenium hysterophorous L. (Astaraceae), Trianthema portulacastrum L. (Aizoaceae), and Synedrella nodiflora L. (Astaraceae) were studied on root nodule formation of Rhizobium sp, phosphate soubilizing bacterial population in rhizospheric region of Phaseolus aureus plant as well as the seed germinability, seed viability, field emergence capacity, and TTC stainability of the bioassay plant Phaseolus aureus. Zone of inhibition by leaf extracts containing putative allelochemicals of above selected plants were also studied on isolated Rhizobium sp and phosphate solubilizing bacteria. Percentage seed germination, seed viability and field emergence capacity were significantly reduced along with enhancement of T50 (Time required for 50% germination) values of the test species by leaf extracts of donor plants. Leaf extracts also adversely affected the root nodulation and population of Rhizobium sp and phosphate solubilizing bacteria in soil. The results of this investigation are suggestive of possible using of the leaf extracts from said plants as potential agents for formulation of new herbicides and also proper management of Parthenium hysterophorous, Trianthema portulacastrum, and Synedrella nodiflora as well as other exotic weeds having harmful allelopathic effects.