Transport, retention and release of phytate in soil with addition of Mg-Al layered double hydroxides

Organic fertilizers have been excessively used for agricultural production, raising P loss risk to river systems. Phytate is the most abundant organic phosphorus (OP) in organic fertilizers. In this study, Mg-Al layered double hydroxides (LDHs) as environmentally friendly materials were applied to soils to control phytate loss from soil and improve the sustainable utilization of phytate. Adsorption kinetic experiments, XRD, and zeta potential measurements were conducted to investigate adsorption mechanisms of phytate on LDHs. Saturated soil column experiments and numerical modeling were conducted to investigate the transport, retention, and release behaviors of phytate in natural soil with and without LDHs. The KCl and CaCl2 solutions were chosen as leachate to simulate different types of soil solutions. Adsorption modes of phytate on LDHs contained electrostatic attraction and surface complexation but not interlayer anion exchange. Retention of phytate in the soil increased with the addition of LDHs or the presence of Ca2+ due to irreversible retention. The retention of phytate in soil-LDHs column reduced with increasing ionic strength (IS) of KCl due to the competition of Cl(-)with anionic groups of phytate on the LDHs (M-eff: 1 mM, 12.1% of total phytate; 20 mM, 16.6% of total phytate; 100 mM, 20.7% of total phytate). On the other side, the release of phytate from soil-LDHs occurred by the competition of phosphate but was not obvious by IS reduction. The injection of phytate brought release of organic substances from soil and the dissolution of LDHs with increasing IS of KCl.

Automated summary

Organic fertilizers have been overused, increasing the risk of phosphorous loss in river systems. This study explores the use of environmentally friendly Mg-Al layered double hydroxides (LDHs) to reduce phytate loss from soil and improve its sustainable utilization. The findings suggest that adding LDHs or Ca2+ increases phytate retention in soil, while increasing KCl ionic strength reduces phytate retention. Additionally, the injection of phytate leads to the release of organic substances and the dissolution of LDHs.