Iron-modified biochar enhances cotton growth and iron uptake in saline-alkali soil by reducing salinity and facilitating root colonization of beneficial bacteria

Background and aims

Biochar modification is an innovative approach to enhance its amelioration effect on saline-alkali soil. However, limited studies have compared the effects of different modified biochar on the improvement of saline-alkali soil.

Methods

A pot experiment was conducted to evaluate the comparative effect of different biochar materials, including pristine biochar (PBC), acid-modified biochar (HBC), iron-modified biochar (FBC), and acid-iron-modified biochar (HFBC), on plant growth, chemical properties of saline-alkali soil, and the composition of soil bacterial and endophytic bacterial communities.

Results

The results demonstrated that FBC was the most effective in promoting cotton growth and reducing soil salinity and alkalinity among the four biochar materials. Compared to the CK (non-biochar) treatment, the application of FBC increased the biomass of cotton seedlings by 2.9 folds. Additionally, the lowest Na⁺ content in the 0–15 cm soil depth was observed in the FBC treatment, showing a 36.5% decrease compared to CK. Importantly, FBC amendment significantly increased soil available Fe content as well as Fe content in cotton shoot. Furthermore, FBC application enhanced soil bacterial diversity and increased the abundance of Proteobacteria and Bacteroidota. Moreover, FBC addition facilitated the colonization of beneficial endophytes (e.g., Alcaligenaceae) in roots.

Conclusions

The findings indicate that FBC is a promising and novel material for improving saline-alkali soil due to its multiple effects, including reducing salinity, providing essential nutrients, and promoting root colonization by beneficial bacteria.