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

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 N 2 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 N 2 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 N 2 fixation was evaluated using the 15 N natural abundance isotope method. Key factors influencing root nodulation and N 2 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 N 2 fixation, leading to improved plant N nutrition. The nodulation and N 2 fixation were severely limited by water deficiency stress. Improved phosphorous supply favoured nodulation and N 2 fixation by A. auriculiformis plants under water deficiency stress. Conclusions These findings suggested that A. auriculiformis could grow in early tailings technosols and fixed N 2, and proper water and phosphorous fertilizer management could improve Acacia plant’s performance and N 2 fixation functions. It is possible to introduce tolerant native legumes such as A. auriculiformis to improve N supply in the early technosols.