Biochar and PGPR: A Winning Combination for Peanut Growth and Nodulation under Dry Spell

Purpose: Drought stress is one of the major abiotic stresses for optimal peanut production in semi-arid regions. Use of various organic amendments have been shown to mitigate drastic damage caused by drought. This study explores the effect of the use of cotton straw biochar and Plant Growth Promoting Rhizobia (PGPR) based biofertilizer on plant physiology and as a potential remedy for drought tolerance in plants. Methods: The experiment was conducted using a randomized complete block design in a greenhouse setting. Two variable ratios of biochar (1% and 2%) with and without PGPR formulation (Biozote-Max) were evaluated for improvement in drought tolerance in peanut. Plant growth was measured through morphological and physiological parameters. Further, Gas Chromatography Mass Spectrometry (GS-MS) was carried out to analyze changes in plant metabolome for 2% biochar and PGPR treatment group in comparison to controls. Results: Root fresh weight (RFW), root dry weight (RDW), root length (RL) and nodule number (NN) found to be improved by solo or combined application of biochar and PGPR. A similar trend was observed in shoot growth parameters. However, plant physiology measured through SPAD value and relative water content (RWC) was superior in solo biochar (1% or 2%) application. Corresponding to this, reactive oxygen species (ROS) mitigating enzymes levels and respective metabolites were attenuated better by 2%biochar + PGPR than the individual application. Conclusions: These results illustrate the importance of organic amendments in protecting plants from damage caused under dry spell. Furthermore, synergistic application of biochar and PGPR further enhances the plant growth under aridity stress than the ones growing in sufficient moisture.