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ARS Home » Pacific West Area » Kimberly, Idaho » Northwest Irrigation and Soils Research » Research » Publications at this Location » Publication #227158
Title: Effectiveness of recovered magnesium phosphates as fertilizers in neutral and slightly alkaline soils

Author
item MASSEY, M - COLORADO STATE UNIVERSITY
item DAVIS, J - COLORADO STATE UNIVERSITY
item Ippolito, James
item SHEFFIELD, R - LOUISIANA STATE UNIV

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/24/2008
Publication Date: 3/9/2009
Citation: Massey, M., Davis, J., Ippolito, J.A., Sheffield, R. 2009. Effectiveness of recovered magnesium phosphates as fertilizers in neutral and slightly alkaline soils. Agronomy Journal. 101(2):323-329.

Interpretive Summary: In this study, Massey et al. determined whether recovered dairy waste struvite (MgNH4PO4x6H2O) and dittmarite (MgNH4PO4xH2O) were effective P fertilizers in alkaline soils. Dissolution kinetics for triple superphosphate (TSP), certified organic rock phosphate (RP), recovered struvite, dittmarite, and a heterogeneous recovered phosphate, and material fertilizer effectiveness for spring wheat (Triticum aestivum L.) were studied. Struvite and dittmarite were more soluble than RP, but less soluble than TSP, and dissolution kinetics occurred within ~24 hours. At a soil pH of 6.5, both dittmarite and struvite increased the average plant P concentration over the control, yet struvite and dittmarite performance was similar to TSP. In a limed soil (pH 7.6), many treatments had plant P concentrations significantly lower than the control, but most fertilizers increased DM production over the control; all fertilizers generally performed similarly to one another. Recovered Mg phosphates could be a useful P fertilization alternative in arid and semi-arid environments.

Technical Abstract: Magnesium phosphates such as struvite (MgNH4PO4x6H2O) can be recovered from municipal, industrial and agricultural wastewaters. However, minimal research has been conducted on the beneficial reuse of these recovered products; conducted research has focused on low pH soils. This study determined whether recovered struvite and dittmarite (MgNH4PO4xH2O) were effective P fertilizers in alkaline soils. In addition to commercially available triple superphosphate (TSP) and certified organic rock phosphate (RP), recovered struvite, dittmarite, and a heterogeneous recovered phosphate were evaluated in a laboratory dissolution study and as fertilizers for spring wheat (Triticum aestivum L.) in a greenhouse study. Struvite and dittmarite were much more soluble than RP, but less soluble than TSP. Laboratory dissolution kinetics were fast, with most materials nearing equilibrium within 24 hours. At a soil pH of 6.5, both dittmarite and struvite increased the average plant P concentration over the control. Struvite and dittmarite performance was similar to TSP. There were no significant differences in plant dry matter (DM) production or total P uptake at pH 6.5. In the limed soil (pH 7.6), many treatments had plant P concentrations significantly lower than the control, but most fertilizers increased DM production over the control; all fertilizers generally performed similarly to one another. These findings support previous work showing recovered Mg phosphates to be effective in acidic soils, and provide evidence that they are also effective in alkaline soils. Recovered Mg phosphates could become a useful alternative for P fertilization in arid and semi-arid environments.