Efficacy of Arbuscular Mycorrhizal Fungi and Bacterial Inoculants in Enhancing Yield of Phaseolus mungo L. and Vigna radiata (L.) R. Wilczek under Central Indian Conditions

The pulse production, stagnating around 22–24 million tonnes in India, is short of present domestic requirement by around 8 million tonnes, and to increase its production, farmers apply excessive dose of chemicals which adversely affect environment and soil as well as human health. To overcome these negative effects, researchers advocate the use of bio-inoculants which may enhance crop yield. Present study, comprising of three bio-inoculants, namely arbuscular mycorrhiza (AM) fungi, rhizobial (Rhi) and phosphate-solubilizing bacteria (PSB), was carried out to test their efficacy in enhancing yield of Phaseolus mungo and Vigna radiata . In first phase, both crops were inoculated with nine purified fungi. To test the inherent ability of AM fungi, experiment was conducted in autoclaved soil, and to examine competitive ability of the fungi, plants were grown in non-autoclaved soil. Further, in second phase, mixture of better performed AM species ( Acaulospora scrobiculata and Rhizophagus irregularis ) was used with bacterial inoculants (Rhi and/or PSB) in pot (net-house) and field (irrigated and rainfed) experiments. Almost all AM species significantly increased crop yield in autoclaved as well as non-autoclaved soils; however, their efficacy was relatively better in autoclaved soil. Integration of AM fungi with Rhi and PSB significantly increased yield in both pot and field experiments. Maximum yield was recorded in the treatment comprising of AM fungi, Rhi and PSB simultaneously. Rhi and AM fungi showed better efficiency under irrigated and rainfed field conditions, respectively. Per cent increase in plot yield in different treatments over control ranged from 20–36% ( P. mungo ) and 26–44% ( V. radiata ) under irrigated and from 23–57% ( P. mungo ) and 20–37% ( V. radiata ) under rainfed field conditions. The results of present study suggested that application of bio-inoculants (AM fungi, Rhi and PSB) can efficiently enhance the yield of both test crops which may bridge the demand and supply gap of pulse crops. However, extrapolation of the results to real field conditions should be done with precaution, because present study was conducted in nutrient-poor soil (Alfisol), and nutrient-rich soil (Vertisol) may affect the outcome of application of bio-inoculants. Therefore, it will be worthwhile to test the efficacy of AM fungi, Rhi and PSB in enhancing the yield of P. mungo and V. radiata in different soil types.