Natural nodulation and nitrogen fixation of Acacia Auriculiformis grown in technosol eco-engineered from Fe ore tailings

Abstract

Aims: Nitrogen deficiency in eco-engineered technosol from iron (Fe) ore tailings limits the productivity of colonising soil microbes and pioneer plants, which are critical to further development of the technosol. Symbiotic biological N2 fixation may be a strategy to supply N in the moderately alkaline early technosols since native legumes such as Acacia auriculiformis are tolerant of saline and alkaline soil conditions as those in the technosol. It is hypothesized that tolerant native legume A. auriculiformis could form functional nodules to fix N2 when grown in early eco-engineered technosols. Methods: A. auriculiformis growth and root nodulation in the early tailing technosols were investigated using a glasshouse experiment, and plant N2 fixation was evaluated using the 15 N natural abundance isotope method. Key factors influencing root nodulation and N2 fixation have also been evaluated, including water supply and phosphorous nutrition. Results: The results indicated that A. auriculiformis grew well in the tailing technosols and naturally formed nodules with rhizobia. The nodules were functional in N2 fixation, leading to improved plant N nutrition. The nodulation and N2 fixation were severely limited by water deficiency stress. Improved phosphorous supply favoured nodulation and N2 fixation by A. auriculiformis plants under water deficiency stress. Conclusions: These findings suggested that A. auriculiformis could grow in early tailings technosols and fixed N2, and proper water and phosphorous fertilizer management could improve Acacia plant’s performance and N2 fixation functions. It is possible to introduce tolerant native legumes such as A. auriculiformis to improve N supply in the early technosols.