Immobilization of trace elements and lettuce growth in soil amended with activated dolomite phosphate rock fertilizers

Abstract

Activation of low-grade phosphate rocks such as dolomite phosphate rock (DPR) with organic molecules of humic acid (HA) and sodium lignosulfonate (SLS) holds promise for developing slow release P fertilizers. Consequently, activated DPR fertilizers also contains multiple essential plant elements, including P, Ca, Mg, Zn, and Fe, while minimizing leaching losses of nutrients and heavy metals. Greenhouse experiments were conducted to examine the availability of Ca, Mg, and trace metals in soils applied with activated DPR fertilizers and subsequent response of lettuce (Lactuca Sativa L.) as compared with original DPR and water-soluble P fertilizers including superphosphates (SP) and diammonium phosphates (DAP). Application of activated DPR fertilizers stimulated the uptake of Ca, Mg, Zn, Fe, B by lettuce plants relative to original DPR and DAP. Potential toxic elements such as Cr, Cd, Ni, Pb, and Cu were mostly immobilized in soil without uptake by lettuce when applied with activated DPRs primarily due to increased soil pH, as compared with water soluble fertilizers such as DAP and SPs. Apparently, the activated DPR fertilizers offer advantages over original DPR materials and water-soluble P fertilizers in providing multiple nutrients with minimal adverse effects on soil and environmental quality.

Keywords:

• activation of dolomite phosphate rock
• essential elements
• immobilization
• lettuce
• trace elements

Acknowledgments

The authors expressed gratitude to the Mosaic Fertilizer Company for assistance with collection of DPR samples, and Brian M. Cain for his assistance in the analysis of plant and soil samples.

Disclosure statement

The authors certify that they have no conflicts of interest with any individual/organization for the present work.

Data availability statement

All data generated or analyzed during this study are included in this published article.

Additional information

Funding

This study was, in part, supported by a grant from the Florida Institute of Phosphate Research (FIPR no. 15-01-208) and a scholarship from China Scholarship Council provided to Dr. Yune Cao for her conducting one year visiting research at the University of Florida-IFAS, Indian River Research and Education Center.