Effect of Inoculation with Rhizophagus irregularis on common bean (Phaseolus vulgaris L) under phosphorus level application in South-Kivu, Eastern DRC

The positive effects of arbuscular mycorrhizal fungi (AMF) on yield and phosphorus uptake have already been widely studied. However, the response of common bean (Phaseolus vulgaris L) to mycorrhizal inoculation under phosphorus supply conditions is still poorly documented in South-Kivu where the use of fungal biofertilizers is not yet tested. This study was initiated to determine the effect of mycorrhizal inoculation and increasing phosphorus doses on common bean performance and yield in South Kivu in order to reduce phosphate input. The study was conducted during the A 2021 cropping season at the experimental field of the “Université Evangélique en Afriqu” in Kashusha, Kabare territory. A split plot design was used to compare two levels of mycorrhizal inoculation (with inoculation and without inoculation) and three rates of increasing phosphorus (0, 30, 60 and 120 kg P ha-1). Growth, yield and mycorrhizal colonization parameters were recorded. Inoculation with R irregularis significantly improved root mycorrhization rate, biomass, yield and harvest index of bean at 0 Kg P ha-1 and 30 Kg P ha-1. The performance of bean plants inoculated with R irregularis, in terms of collar diameter, above-ground biomass, total biomass, yield and harvest index at 30 kg P ha-1, was superior to that non-inoculated and inoculated plants at the doses of 60 kg P ha-1 and 120 kg P ha-1, suggesting the potential of AMF in reducing phosphate fertilizer input. The results indicate that P levels significantly affected the mycorrhization rate of the bean plants. The application of 60 and 120 kg P ha-1 drastically reduced the mycorrhization rate of bean confirming the influence of inorganic P on the establishment of mycorrhizal symbiosis. Therefore, the responses evoked by AMF were also dependent on the applied P dose. Mycorrhizal inoculation with R irregularis could be an important lever to boost bean yield and ensure phosphate fertilizer saving in ferralitic soils of Kashusha.