Introduction of nitrogen‐fixing nodules through iron and zinc fertilization in the nonnodule‐forming French bean (phaseolus vulgaris L.)

Abstract

Nitrogen‐fixing symbionts associated with the french bean (Phaseolus vulgaris L.) are absent in soils in the Varanasi, India area. Greenhouse experiments were conducted to study the effects of Fe (ferrous sulfate) and Zn (zinc sulfate) on nodulation and N₂ fixation in french beans. Inorganic treatments were added to the soil. No exogenous supplement of Rhizobium was added to the soil. Iron alone at a concentration of 5 or 10 mg kg^‐1 soil or in combination with the same concentrations of Zn enhanced nodulation. At 5 mg Fe and Zn kg^‐1 soil, maximum nodulation and leghaemoglobin were noted. Enhanced in vivo N₂ fixation was also noted when either Fe or Zn (alone or in combination) were added at concentrations of 5 or 10 mg kg‐1 soil. These experiments showed that Fe could create a condition conducive to the formation of N₂‐fixing nodules in French bean. Synergistic effects of Zn in these processes could not be ruled out.

Key words:

• Nodulation
• Leghaemoglobin
• Total nitrogen
• Dry matter yield
• Symbiotic nitrogen fixation