Submitted to: Communications in Soil Science and Plant Analysis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/10/1996
Publication Date: N/A
Interpretive Summary: Several chemicals, when added to poultry litter, have shown effectiveness in reducing both ammonia volatilization from litter and phosphorus runoff from litter applied to pastures. This study was conducted to determine the long-term stability of phosphorus forms created by adding the various chemicals to poultry litter, and then adding the treated litter to soils. We found that addition of litter to soil increased phosphorus concentrations, and water soluble phosphorus decreased with time in all treatments. After 98 days, little change was observed in phosphorus concentrations. The lowest phosphorus levels were observed with additions of either ferrous sulfate or aluminum sulfate. These amendments, especially alum, have been demonstrated to greatly decrease ammonia volatilization in poultry houses. This can lead to healthier, heavier birds, while at the same time greatly decreasing phosphorus solubility. Use of chemical amendments to limit phosphorus solubility in litter has great potential to reduce phosphorus loading to sensitive surface waters where poultry litter is applied as a fertilizer.
Technical Abstract: Phosphorus (P) runoff from field-applied poultry litter can adversely impact water quality. The Majority of P in runoff from poultry litter is soluble, so decreasing the solubility of P could lessen the impact of poultry litter on water quality. The objective of this study was to determine long-term P solubility in soils receiving poultry litter treated with Al, Ca, and Fe amendments at various soil pHs. Soil pH was adjusted t 4, 5, 6, 7, and 8 using elemental S or CaCO3 with some soil left at its native pH. The pH-adjusted soil was incubated with no litter (control), litter alone (litter control),or litter amended with alum, Al2(SO4)3.16H20, (100 or 200 g/kg), Ca(OH)2 (25 or 50 g/kg, or FeSO4.7H2O (100 or 200 g/kg). The soil was then allowed to equilibrate in the dark at room temperature for 0, 7, 49, 98, and 294 days. After equilibration, soils were extracted with deionized water and soluble reactive P levels were determined. Water soluble P levels decreased with time in all treatments, including the control and litter control treatments. Soil pH also affected soluble reactive P levels, with the lowest levels generally observed at pH 8. Addition of both unamended and chemically-amended litter to soil significantly increased P concentrations at all combinations of pH and sampling time. Addition of chemically-amended litter to soil significantly reduced soluble reactive P compared to unamended litter. With all treatments, an apparent equilibrium was reached at 98 d. Litter ammended with FeSO4.7H2O or alum resulted in the lowest soluble reactive P levels after 294 days. Use of chemical amendments to limit P solubility has potential and should be pursued as a means of reducing eutrophication of sensitive surface waters where poultry litter is applied as a fertilizer.