Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/5/2002
Publication Date: N/A
Interpretive Summary: The chemical composition of phosphorus (P) in animal manure influences the transport and availability of P to plants. Methods used to study P in soils have recently been used to investigate P in animal manure. However, physical and chemical properties of animal manure and soils may differ considerably. Therefore, interpretation of test results based on soil studies may not be applicable for manure P. In this study we determined that the chemical compositions of manure and soil were indeed different and these differences could impact interpretation of P tests. Our data show that the soil was inorganic mineral-based, and the animal manure was organic residue-based. These differences should be taken into account when applying a soil-based method to investigate animal manure P.
Technical Abstract: Sequential fractionation is one of the most common methods to investigate phosphorus forms in soils. Recently, the strategy of sequential fractionation has been used to investigate manure and compost P and their changes after application to soils. However, the physico-chemical characteristics of animal manure may differ from those of soils. Evaluation nis therefore needed to determine if sequentially extracted P forms based o soil studies are applicable for manure. In this study we fractionated P in a sandy loam soil and a swine manure with H2O, 0.5 M NaHCO3, 0.1 M NaOH, and 1.0 M HCl. The P distribution in soil was 0.2% H2O-extractable, 11 % NaHCO3-extractable, 58 % NaOH-extractable, 14% HCl-extractable, and 16% residual P. In contrast, P distribution in swine manure was 48% H20-extrac- table, 19 % NaHCO3-extractable, 18 % NaOH-extractable, 11% HC1-extractable, and 3% residual P. Elemental analyses, UV/visible spectra, and FT/IR spectra revealed distinct differences in chemical composition between soil and swine manure. The soil was inorganic mineral-based, and the animal manure was organic residue-based. These data indicate it is inappropriate to apply the soil based fractionation scheme to swine manure by exclusively assigning NaOH-extractable inorganic P, Pi to Al- and Fe-P, and HCl-extractable-Pi to Ca-P. We attribute the distinctly different P distribution patterns observed with sequential fractionation of soil and manure to their different physico-chemical properties. These differences must be recognized when developing and interpreting fractionation procedures for manure.