Biochar-based Bradyrhizobium inoculum improves growth of lupin (Lupinus angustifolius L.) under drought stress

- The potential use of biochar as a carrier for Bradyrhizobium sp. inoculants as provided for lupin (Lupinus angustifolius L.), under drought conditions were evaluated.
- The survival of BR populations was higher in hydrochar HTC) carrier material than it was in pyrolysis biochar from maize and pyrolysis biochar from wood.
- A hydrochar-based Bradyrhizobium sp. inoculant significantly enhanced plant growth, N and P uptake, and lupin nodulation under drought conditions.
- Hydrochar-based formulation of Bradyrhizobium sp. is an effective inoculum carrier providing a promising and practical approach for improving growth and symbiotic performance of lupin under drought conditions.

Drought stress has a major abiotic impact on the symbiotic performance of legumes, inhibiting plant growth and nodulation. We evaluated the potential use of biochar as a carrier for Bradyrhizobium sp. inoculants as provided for lupin (Lupinus angustifolius L.), and to determine the response of lupin to the biochar-based inocula of Bradyrhizobium sp. (BR) in pot experiments, under irrigated and drought conditions. The survival of BR populations was higher in HTC-char carrier material than it was in pyrolysis biochar from maize (MBC) and pyrolysis biochar from wood (WBC). An HTC-based Bradyrhizobium sp. inoculant (HTC-BR) significantly enhanced plant growth, N and P uptake, and lupin nodulation under drought conditions in comparison with BR strain inoculation. BR was more likely to survive under drought stress conditions when introduced as HTC-based inocula in comparison with direct inoculation. Overall, this experiment indicates that a HTC-based formulation of Bradyrhizobium sp. is an effective inoculum carrier providing a promising and practical approach for improving growth and symbiotic performance of lupin under stress conditions.