Inoculation of indigenous nitrogen-fixers isolated from the Kuwait desert enhances seedling growth and nutrient uptake in a greenhouse bioassay

Abstract

Desert soil degradation, primarily caused by anthropogenic disturbance and desertification, poses significant challenges for ecosystem restoration in degraded ecosystems. Soil microbial communities, particularly diazotrophs, play a crucial role in different soil system processes, including nutrient cycling, and can improve nitrogen-limited characteristics of nutrient-poor soil systems. Free-living and root-associated nitrogen-fixing bacteria have great potential to enhance nitrogen availability in the nitrogen-limited soil and support host plant growth and nutrient acquisition. Free-living nitrogen-fixing bacteria and root-associated rhizobacteria contribute a substantial amount of nitrogen to ecosystems, including arid lands. This study evaluated the growth performance and nutrient uptake ability of four native plant species of Kuwait inoculated with a consortium of selected indigenous putative diazotrophs isolated from the Kuwait desert. The seedlings of Vachellia pachyceras were inoculated with both indigenous root-nodule bacteria isolated from Kuwait desert and a commercial inoculum to evaluate their symbiotic efficiency. The seedlings were cultivated under greenhouse conditions in both native desert soils and in potting mix to assess the extent to which growth medium influenced inoculation response. The primary objective was to determine whether the inoculated indigenous N2 fixing bacteria could contribute early seedling development and nutrient acquisition, thereby supporting their potential use them as biofertilizer in future large-scale restoration efforts. Bacterial inoculation significantly enhanced plant dry mass and nutrient uptake across all tested plant species compared to the non-inoculated controls. The magnitude of improvement varied with bacterial density, plant species, and growth medium used. These findings are consistent with evidence that isolated indigenous N2-fixers have the potential to enhance plant growth and nutrient uptake in selected native plant species, supporting their use as biofertilizers for restoration and revegetation efforts in arid environments. This study represents the first evaluation of Kuwaits native seedlings inoculated with indigenous diazotrophs, highlighting their potential for sustainable ecosystem restoration.