Root-soil-microbe interactions mediate phosphorus and iron uptake from lithium iron phosphate nanomaterials

Addressing the critical challenge posed by the rapidly increasing amount of end-of-life lithium iron phosphate (LiFePO₄) batteries from electric vehicles and various industries, the presence of iron (Fe) and phosphorus (P), both essential plant nutrients in LiFePO₄, provides an opportunity to transform waste into valuable resources. This study explores an innovative strategy to sustainably utilize LiFePO₄ nanoparticles (n-LiFePO₄) as a fertilizer in a peanut (Fe-deficiency) and maize (P-deficiency) intercropping system to enhance crop productivity. We chose 50 and 250 mg/kg of n-LiFePO₄ mixed with soil and applied in monocropping maize, monocropping peanut and intercropping. The same content of P and Fe of ionic groups as n-LiFePO₄ was added as P and Fe fertilizer control. The final control group (CK) received no amendments. The results showed that n-LiFePO₄ at 50 mg/kg significantly increased root dry weight by 80 % compared to the control. While n-LiFePO₄ at 250 mg/kg still exhibited positive effects, the same concentration of Fe²⁺ reduced peanut root biomass by 23 %. Mechanistically, the improvements are attributed not only to the sustained release of P and Fe from n-LiFePO₄ but also to the stimulation of maize root exudation. This altered exudate profile positively influenced rhizosphere soil pH and enhanced the enrichment of Fe-solubilizing and P-mobilizing bacteria. These findings demonstrate that n-LiFePO₄ effectively enhances agricultural productivity, and intercropping systems further amplify these benefits through root-soil-microbe interactions, providing a promising strategy for sustainable crop management.