Abstract
Sequential fractionation coupled with phosphatase hydrolysis allows a greater understanding of the effects of animal manure on the chemical distribution of soil P. Concentrations of specific soil P fractions were determined after long-term (>10 yr) poultry litter application at rates of 4.5, 6.7, 9.0, 11.2, and 13.4 Mg manure ha⁻¹ yr⁻¹ to watershed-scale plots (cultivated and grazed–ungrazed pasture) on a calcareous Texas Blackland Vertisol. Soil total extractable P (Pₜ) and inorganic P (Pᵢ) were quantified following sequential extraction with H₂O, NaHCO₃, NaOH, and HCl. Hydrolyzable organic P (Pₑ) and non-hydrolyzable organic P (Pₙₑ) were determined in the extracted fractions following enzymatic hydrolysis. Litter application increased Pₜ regardless of land-use type compared with the control. Concentrations of H₂O-extractable Pᵢ in litter-amended plots increased by 9 to 34% (cultivated) and 7 to 30% (pasture) over the control, indicating substantial risk of soluble P runoff. Labile organic P (Pₒ) extracted with H₂O and NaHCO₃ decreased in the order monoester > nucleic acid > phytate > Pₙₑ. An average of 68% of Pₜ was extractable with HCl. Organic P comprised the majority (95%) of HCl-Pₜ; however, only trace levels of HCl-Pₒ were hydrolyzable, and litter application increased HCl-Pₙₑ up to 217%. Thus, litter application increased levels of both soluble Pᵢ and stable Pₙₑ, but the specific response varied with application rate and land management. This study increased understanding of P chemical distribution with time in litter-amended soil with high clay and CaCO₃ contents under differing land-use scenarios.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call