Modeling mycorrhizae-rhizobacteria interactions through PLS-SEM to enhance okra growth in compost-amended soil

Soil fertility, soil quality, and crop yield decline due to the misuse of chemical fertilizers. Eco-friendly strategies based on biological or organic procedures can mitigate the harmful effects of agrochemicals on the environment. A more effective option for boosting plant development and production is the use of Arbuscular mycorrhizae fungi (AMF) and plant growth-promoting bacteria (PGPR). Therefore, a fully randomized design (CRD) pot experiment was carried out to assess the efficacy of AMF, PGPR, and their interaction in enhancing okra's growth, physiology, nutrient absorption, and yield, with and without the addition of compost. While both AMF and PGPR improved the traits that were tested, the results showed that combined inoculation of the two was far more effective than either inoculation alone or the control treatment at increasing fresh and dry weight, plant length, fruit yield per plant, chlorophyll a and b, and carotenoids. The combined application of AMF and PGPR significantly enhanced the plant height (48.4%), the number of okra fruits (87.4%), fresh weight (60.7%), dry weight (83.2%), and P (63.2%) without compost but the maximum increase in N (55.5%) and K (64%) concentrations, stomatal conductance (22.1%), transpiration rate (2.7 times), photosynthetic (1.4 times), water use efficiency (1.1 times) was found under combined inoculation of AMF and PGPR in compost amended soil. Pearson correlation showed that the plant height, number of okra fruits, and fresh and dry weight were significantly associated with chlorophyll a, chlorophyll b, carotenoid, water use efficiency, and P concentration. The PLS-SEM analysis revealed that microbial inoculation accounted for 88% of the variation in nutrient concentrations and indirectly explained 98.5% of the variation in plant growth and yield under compost amendment. Consistently, PCA results indicated that all measured attributes were markedly enhanced by the integrated application of AMF and PGPR, particularly in compost-amended soil.