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Solubilization of Bayóvar Natural Phosphate Rock under the Drain Effect of Calcium and Phosphorus at Two Levels of Acidity

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Open Journal of Soil Science 2017年第8期7卷 173-180页

作者： sarah vieira novais Edson Marcio Mattiello Leonardus Vergutz Elizio Ferreira Frade Junior Roberto Ferreira novais Department of Soil Science University of S&#227o Paulo S&#227o Paulo Brazil Department of Soil Science Federal University of Vi&#231osa Vi&#231osa Brazil Department of Soil Science Federal University of Vi&#231osa Rio Paranaíba Brazil

Natural phosphate rock (NP) solubilization in soils is dependent on the soil pH and its power to remove or drain (sink effect) P and Ca of the solution that is in equilibrium with the NP. The aim of this work was to evaluate the effect of acidity and P- and Ca-sinks on the solubilization of bayóvar reactive rock phosphate (a phosphorite). Samples of this NP in aqueous suspension were placed in a cassette (Slide-A-Lyzzer G2 Dialysis Cassette) compartment and immersed in a beaker containing 150 mL of an aqueous solution with pH adjusted at 4.5 or 6.0, where P- and Ca-sinks individually or in their combinations, were applied. The tested sinks were: Anionic Resin (AR);Cationic Resin (CR);Mixed Resin (MR: AR + CR);Goethite (Goe);Goe + AR;Goe + CR and one control (NP only) in five replicates. Beakers (experimental units) were shaken for 12 h daily, at 130 rpm, until completing 30 days of equilibrium. The suspensions were filtered to extract solution-P from the residue on the filter paper;the labile-P was extracted from this residue using 0.8 mol·L-1 NH4Cl in 2 mol·L-1 HCl and, finally, the remainder P in the same residue together with the filter paper were subjected to nitric-perchloric acid digestion, to determine the P-residual in the extract. Goe caused greater solubilization of the NP, indicating that this P-sink was more effective than AR, causing similar or greater solubilization than CR. AR and CR, in a similar way, significantly restricted the trait characteristic of Goe (p < 0.05), at both pH values, in the solubilization of NP. Although Goe generally caused greater solubilization of the NP, it also caused the lower formation of labile-P. The CR presented, in general, the highest contents of solution-P, thus it triggered solubilization of NP without the immobilization of the solution-P, unlike the one with the AR that adsorbs it. In the lower pH condition (4.5), the solubilization of NP tended to be higher than at pH 6.0, although in a little effective way, compa

关键词： Anionic Resin Cationic Resin Goethite P-Sink Ca-Sink

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Mitigation of Greenhouse Gas Emissions from Tropical Soils Amended with Poultry Manure and Sugar Cane Straw Biochars

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Agricultural Sciences 2017年第9期8卷 887-903页

作者： sarah vieira novais Mariana Delgado Oliveira Zenero Elizio Ferreira Frade Junior Renato Paiva de Lima Carlos Eduardo Pelegrino Cerri Department of Soil Science Escola Superior de Agricultura Luiz de Queiroz University of S&#227 o Paulo Piracicaba Brazil Department of Environmental Sciences Federal Institute of Mato Grosso Barra do Gar&#231 a Brazil

Increases in greenhouse gases (GHG) emissions, upon changes in land use and agricultural management, lead to a search for techniques that enhance carbon residence time in soil. Pyrolysis increases the recalcitrance of organic materials and enhances their activities as physical, chemical and biological soil conditioners. Emissions of CO2, CH4 and N2O quantified from a sandy soil that was treated with three rates (12.5, 25 e 50 Mg·ha-1) of either non-pyrolysed poultry manure and sugarcane straw or biochars, pyrolysed at two contrasting temperatures (350°C and 650°C). Subsequently, the flux of the three gases was converted and compared in a standard unit (CO2eq). The added biochars, significantly reduced GHG emissions, especially CO2, relative to the non-pyrolysed materials. The greatest differences between applied rates of poultry manure, relative sugarcane straw, both to biochar and raw material, and the positive response to the increase of pyrolysis temperture, confirm the importance of raw material choice for biochar production, with recalcitrance being an important initial characteristic. Greater emissions occurred with intermediate rate of biochars (25 Mg·ha-1) amendment to the soil. These intermediate rates had higher microbial biomass, provided by an intermediate C/N ratio derived from the original soil and the biochar, promoting combined levels of labile C and oxygen availability, leading to an optimal environment for microbiota.

关键词： CO2 CH4 N2O Weathered Soil

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