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Vaughan, Canada

Audette Y.,University of Guelph | Voroney R.P.,University of Guelph | O'Halloran I.P.,University of Cuelph
Soil Science Society of America Journal

Various methods for quantifying and characterizing organic P in Turkey litter compost (TLC) were compared. The standard extractant used, both for the NaOH-Ethylenediaminetetraacetic acid (EDTA) method measuring organic P and for solution 31P NMR spectroscopy, is a mixture of 0.25 M NaOH and 0.05 M Na2EDTA, however these methods underestimated organic P in TLC compared with the ignition and the sequential fractionation methods. Approximately 83% of the total organic P in TLC was extracted with a weak acid extractant, ammonium acetate (pH 4.2), by the sequential fractionation method. Acid soluble phytates, such as Ca(Mg)-phytates, usually present in animal manure composts would be insoluble at pH above 6.0. These organic P fractions can be important sources of plant available P, however, neither direct quantification nor solution 31P NMR spectroscopy of organic P extracted by the NaOH-EDTA would be able to detect them. To avoid underestimation of organic P in animal manure composts, modifications to either the concentration of EDTA or the compost to solution ratio may be necessary. These changes would allow for complete chelation of the Ca2+ and Mg2+ present in animal manures and composts. Otherwise, an analysis of organic P in both alkaline and acid extracts by solution 31P NMR spectroscopy may be necessary. © Soil Science Society ot America, 5585 Guiltord Rd., Madison WI 53711 USA. All Rights reserved. Source

Ramnarine R.,University of Cuelph | Ramnarine R.,University of the West Indies | Voroney R.P.,University of Cuelph | Wagner-Riddle C.,University of Cuelph | Dunfield K.E.,University of Cuelph
Soil Science Society of America Journal

Tillage management on agricultural soils is important because of its effect on soil organic matter (SOM) dynamics. The decomposition of fresh crop residues to stabilized organic matter by soil microbes results in a continuum of intermediary SOM fractions or pools. The light fraction organic matter (LFOM) represents one of The SOM pools formed in The early stages of decomposition and is distinguished as a potential labile SOM pool which is sensitive to changes in management practices. The objective of this study was to measure The quantity, distribution, and δ13C signature of The LFOM pool in farmland soils managed under a conventional tillage (CT) and no-tillage (NT) system. The study uses The δ13C natural abundance technique which involved a crop rotation of C3 and C4 species on a calcareous Typic Hapludalf soil. The LFOM was obtained using density fractionation, while The organic C, N, and δ13C of whole soil and light fraction were measured using high-temperature combustion coupled with isotope ratio mass spectrometry. Our findings showed that The re was a significant increase in The light fraction C and N pools in The NT soils compared with The CT soils after 6 yr of NT. There was a higher proportion of corn-derived C in The light fraction in The 0- to 10- and 10- to 20-cm depth of NT soils. The differences in The isotopic signature of The whole soil and SOM fractions also show a preservation of newly derived C in The NT soils compared with The CT soils. © Soil Science Society of America, 5585 Guilford Rd., Madison WI 53711 USA. All rights reserved. Source

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