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Published on: November 28, 2014
Magnesium-enriched poultry manure enhances phosphorus bioavailability in biochars
Aline do Amaral Leite1, Leônidas Carrijo Azevedo Melo1, Luis Carlos Colocho Hurtarte2
1Federal University of Lavras/UFLA - Soil Science Dept., 37200-000, Lavras, Brazil; Soil and Crop Sciences, School of Integrative Plant Science, Cornell University, Ithaca, NY, 14850, USA.
Enriching poultry manure with magnesium (Mg) before pyrolysis enhances biochar phosphorus (P) availability. This Mg enrichment alters P species, forming Mg-P minerals that improve P mobility and plant uptake, contributing to sustainable fertilizer use.
Area of Science:
- Agricultural Science
- Environmental Chemistry
- Soil Science
Background:
- Pyrolysis of calcium-rich poultry manure produces phosphorus (P) species with low short-term plant availability.
- Magnesium (Mg) enrichment prior to pyrolysis may enhance the P-supplying capacity of biochar.
Purpose of the Study:
- To investigate the impact of increasing the Mg/Ca ratio and pyrolysis temperature on P availability and speciation in poultry manure biochar.
- To determine if Mg enrichment can optimize biochar as a P fertilizer.
Main Methods:
- Poultry manure was enriched with magnesium hydroxide [Mg(OH)2].
- Biochar was produced at various pyrolysis temperatures (300°C, 600°C, 700°C).
- Phosphorus availability was assessed using citric and formic acid extraction.
- P speciation was analyzed using P K-edge and L2,3-edge X-ray Absorption Near Edge Structure (XANES) spectroscopy.
Main Results:
- Mg enrichment (∼2.1%) increased P availability by 20% in biochar up to 600°C.
- Mg addition altered P speciation, forming Mg-P minerals (e.g., MgNH4PO4, Mg3(PO4)2·8H2O) instead of predominantly Ca-P species (e.g., Ca3(PO4)2, hydroxyapatite).
- Hydroxyapatite, abundant in non-Mg biochar, was absent in Mg-enriched biochar.
- Mg-P minerals are suggested to enhance P mobility and availability compared to Ca-P.
Conclusions:
- A low level of Mg enrichment is a viable strategy for designing poultry manure biochar as an effective P fertilizer.
- Mg-enriched biochar offers improved P availability, potentially increasing plant P uptake.
- This approach contributes to the sustainable utilization of organic residues as nutrient resources.
