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Manure-component Effects on P Release from Manure-amended Sandy Soils

Manure-component Effects on P Release from Manure-amended Sandy Soils. M. S. Josan. Introduction. Active and abandoned dairies Continuous release of P from these soils even years after abandonment (Nair et al., 2003) Paucity of P retaining minerals

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Manure-component Effects on P Release from Manure-amended Sandy Soils

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  1. Manure-component Effects on P Release from Manure-amended Sandy Soils M. S. Josan Josan

  2. Introduction • Active and abandoned dairies • Continuous release of P from these soils even years after abandonment (Nair et al., 2003) • Paucity of P retaining minerals • Manure components are important in the fate of P in dairy manure-impacted soils • Importance of Mg in P dynamics in these soils has not been recognized

  3. Properties of Manure Impacted and Unimpacted Soils

  4. Rationale • High Ca concentrations and pH should favor the formation of relatively stable calcium phosphates • Stable Ca-P minerals (such as apatite) have not been found in heavy manure-impacted soils (Wang et al. 1995) • Non-formation of Ca-P minerals could be due to inhibition by Mg, biogenic Si, and DOC

  5. Hypotheses • The release of phosphorus (P) in dairy manure-impacted soils is controlled by sparingly soluble Ca and/or Mg-phosphate phases • Magnesium phosphate is a manure component rather than a component formed in soil after manure application

  6. Objectives • Assess the release of Ca, Mg and P in soil solution from dairy manure-impacted soils • Evaluate Ca and/or Mg-P association in dairy manure and manure-impacted soils

  7. Materials and Methods • Soil and manure sampling • Particle size fractionation and chemical characterization of soil and manure samples • Repeated water extractions • Column leaching

  8. Materials and Methods • Chemical equilibrium modeling (V-MINTEQ) • Soil and dairy manure column effluents • Saturation paste extracts • Chemical fractionation

  9. Fractionation Scheme Soil (2g) NH4Cl-P 20 mL 1M NH4Cl 2-h shaking NaOH-P 20 mL 0.1M NaOH 17-h shaking HCl-P 20 mL 0.5M HCl 24-h shaking Residual-P Ignition at 550o C Acid solubilization Mainly organic -P Labile -P Fe/Al -P Ca/Mg -P Total P Org. –P= (Total P- In -P) Josan Nair et al., 1995

  10. Residual -P NH4Cl -P Al/Fe -P Org. -P Ca/Mg -P Percentage of P Fractions in A-horizon of a Heavily Manure-impacted soil (TP= 2900 mg kg-1) 1st NH4Cl Extraction Hieltjes and Lijklema (1980) Nair et al. (1995) Josan

  11. NH4Cl -P Residual -P Al/Fe -P Org. -P Ca/Mg -P Percentage of P Fractions in A-horizon of a Heavily Manure-impacted soil (TP= 2900 mg kg-1) 2nd NH4Cl Extraction Josan

  12. Percentage of P Fractions in A-horizon of a Heavily Manure-impacted soil (TP= 2900 mg kg-1) 3rd NH4Cl Extraction NH4Cl -P Residual -P Al/Fe -P Org. -P Ca/Mg -P Josan

  13. Percentage of P Fractions in A-horizon of a Heavily Manure-impacted soil (TP= 2900 mg kg-1) ‘n’ Extractions Residual -P Al/Fe -P Org. -P Ca/Mg -P NH4Cl -P Josan

  14. Modified Fractionation Scheme Soil (2g) NH4Cl-P 20 mL 1M NH4Cl 2-h shaking NH4Cl-P 20 mL 1M NH4Cl 2-h shaking NH4Cl-P 20 mL 1M NH4Cl 2-h shaking NH4Cl-P 20 mL 1M NH4Cl 2-h shaking 1st Extraction 2nd Extraction 3rd Extraction 10th Extraction or Greater NaOH-P 20 mL 0.1M NaOH 17-h shaking HCl-P 20 mL 0.5M HCl 24-h shaking Residual-P Ignition at 550o C Acid solubilization Ca, Mg, and P concentrations will be determined in each extraction Josan

  15. Materials and Methods • Solid state assessments: • Density separation • X-ray diffraction (XRD) • Thermogravimetery (TG) • Scanning electron microscopy (SEM) and Energy dispersive X-ray analysis (EDS)

  16. Air-dried manure Air-dried soil Particle size fractionation and pre-concentration Silt Clay Density separation <2.0 g cm-3 >2.0 g cm-3 Density separation <2.0 g cm-3 >2.0 g cm-3 ? P with Mg or Ca Solid State Assessment XRD TG SEM Josan

  17. Statistical Analysis • Analysis of variance (ANOVA) • The Student-Newman-Keuls • Non-parametric statistics (the Kruskal-Wallis test)

  18. Preliminary Results Josan

  19. SRP, Mg and Ca Relationships for Active Dairy Manure Soils during Repeated Water Extractions Josan Josan et al. 2005 (in press)

  20. SRP, Mg and Ca Relationships for Abandoned Dairy Manure Soils during Repeated Water Extractions Josan Josan et al. 2005 (in press)

  21. Speciation Data from Column Leachates Josan Josan et al. 2005 (in press)

  22. Dot Map Images of Dairy Manure Clay Size Fraction

  23. Expected Results and Implications • P stabilization via crystallization of calcium phosphates (even at near-neutral pH) may be preempted by Mg-P association • Mg-P association is a key factor for high P activities in these soils • Approaches to minimize P release • P-retaining soil amendments • Management of animal diet to eliminate Mg-P formation.

  24. Acknowledgments • Supported in part by the USDA-NRI • Committee Members • Dr. Vimala Nair (Chair) • Dr. Willie Harris • Dr. George O’Connor • Dr. Dean Rhue • Dr. Tom Obreza • Dr. Amelia Dempere (Materials Science & Engineering Department) • Thanks are also due to several people in SWSD who have helped me since my joining the department

  25. Comments and Suggestions Thanks

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