Impact of five insecticides on chickpea (Cicer arietinum L.) nodulation, yield and nitrogen fixing rhizospheric bacteria

Abstract

A field experiment was conducted to study the effect of five insecticides i.e. Lorsban (40% EC), Decis (25% EC), Pyrifos (40% EC), Karate (25% EC), and Ripcord (10% EC) on the survival of rhizosphere N2-fixing microorganisms, nodulation, pod damage (by pod borer), and grain yield of chickpea (Cicer arietinum L.) crop. The study revealed that Pyrifos suppressed nodulation in chickpea and specific rhizobial counts in the crop rhizosphere, indicating that this insecticide was harmful to rhizobial population in rhizosphere. All the other tested insecticides were safe as they did not affect nodulation of the crop and the specific rhizobial counts in the rhizosphere. The results also revealed that all the tested insecticides except Lorsban (40% EC) suppressed Azotobacter population in the rhizospheric soil indicating that Lorsban was harmless to Azotobacter while all other tested insecticides were harmful to the survival of this important nitrogen fixing bacterium. Pyrifos proved to be the most effective insecticide in controlling the pod borer damage and also in increasing the grain yield significantly as compared to other tested insecticides.

Keywords

• Insecticides
• nodulation
• rhizosphere
• Rhizobium
• Azotobacter
• plant infectivity test