Division of Microbiology, Indian Agricultural Research Institute, New Delhi, India The effect of different doses ( × = the normal dose, 2 × and 5 × ) of MCPB and Disyston was tested in the presence or absence of farmyard manure (FYM) on legume-Rhizobium symbiosis, using pea as a test crop. The studies were extended to see the effect of pesticides on soil microflora. The recommended dose of MCPB and Disyston inhibited nodulation of pea crop during the initial stages (4th week). Normalcy was restored at later stages of plant growth. An application of MCPB with and without FYM did not affect the grain yield significantly. Disyston applied at different doses increased the grain yield and addition of FYM along with Disyston further increased the grain yield appreciably. The rhizosphere microflora (the three major groups, viz., bacteria, fungi, and actinomycetes) responded differently to MCPB and Disyston application. MCPB proved inhibitory to bacterial population, while Disyston showed a stimulatory effect. No significant change in fungal and actinomycete population was noticed with application of both pesticides. Application of FYM, along with MCPB and Disyston, significantly increased the population of both fungi and actinomycety at different stages of plant growth. Azotobacter population was stimulated by MCPB, and it was further increased when FYM was incorporated along with the herbicide. Es wurde die Wirkung verschiedener Dosierungen von MCPB (× = normale Dosis, 2 × und 5 ×) und Disyston, mit und ohne Stalldunggabe, auf die Leguminosen-Rhizobium-Symbiose sowie auf Bodenmikroorganismen geprüft. Die empfohlene Dosis von MCPB und Disyston hemmte die Knöllchenbildung an Erbse bis zur vierten Woche, nicht jedoch in späteren Wachstumsabschnitten. Die Stalldunggabe erhöhte den Ertrag nicht. Disyston hingegen erhöhte den Ertrag in allen Dosierungen, besonders in Kombination mit Stalldung. MCPB inhibierte die Bakterienpopulation der Rhizosphäre, Disyston erhöhte sie. Bei Pilzen und Aktinomyzeten bewirkten die beiden Substanzen keine Unterschiede, in Verbindung mit Stalldung erhöhten sie jedoch deren Keimzahlen in allen geprüften Entwicklungsabschnitten der Pflanze. Die Azotobacter-Keimzahlen wurden durch MCPB erhöht, insbesondere in Verbindung mit Stalldung.