Properties of Fe-oxides and Fe fractionation in an Oxisol amended over long term with lime and phosphogypsum

Autor(es)

Firmano, Ruan Francisco ^[1] ; Alleoni, Luis Reynaldo Ferracciu ^[1]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Luiz Queiroz Coll Agr ESALQ, Soil Sci Dept, Padua Dias Av 11, BR-13418000 Sao Paulo - Brazil

• Tipo de documento: Artigo Científico
• Fonte: APPLIED GEOCHEMISTRY; v. 135, DEC 2021.
• Citações Web of Science: 0

Resumo

Iron (Fe) is present in the structure of (hydr)oxides directly linked to phosphorus (P) cycles in natural and agricultural environments. However, changes in the properties of these Fe-(hydr)oxides caused by the continuous addition of Ca-based amendments (e.g. lime or phosphogypsum) to the soil have not been widely studied. The objective was to evaluate the long-term effects of soil acidity neutralization on Fe fractions and the properties of Fe-(hydr)oxides. X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), Fe fractionation procedures, and X-ray absorption spectroscopy (XAS) were performed in soil samples from a long-term (18 years) experiment in which the soil was amended with lime and/or phosphogypsum. Hematite and goethite were the dominant Fe-(hydr)oxides in the soil, and their diffraction patterns were unaffected by the application of the amendments. However, diffuse reflectance spectroscopy revealed low crystallinity and a slightly higher structural Al con-centration in Fe-(hydr)oxides from soil samples collected from a native forest near the experimental area. With the exception of the Fe fraction associated with SOM, all others were influenced by treatments, including Fe fractions with higher and lower crystallinities, which influenced the P retention capacity of the samples. The proportions of Fe-species obtained by XAS with low structural order were lower in soil samples from the experimental area than in samples from an adjacent native forest, indicating that the soil used in agriculture does not favor permanence of this type of Fe-species. However, Fe-species have suffered little influence from the application of long-term lime and phosphogypsum. Soil management practices may have more significant effects on Fe-(hydr)oxide properties than the continuous addition of Ca-based amendments in highly weathered tropical Oxisols. This study also provided insights into how P retention estimates may be affected in soil samples with high Ca content and how carbon-bound Fe fractions should be further studied. (AU)

• Processo FAPESP: 18/08586-8 - Aplicação superficial de calcário e de fosfogesso e formas de fósforo em um latossolo sob semeadura direta
• Beneficiário: Ruan Francisco Firmano
• Modalidade de apoio: Bolsas no Brasil - Doutorado
• Processo FAPESP: 18/11063-7 - Calagem e gessagem em sistema plantio direto de longa duração: qualidade do solo melhorando a fisiologia das culturas e a recuperação do 15N-fertilizante no sistema solo-planta
• Beneficiário: João William Bossolani
• Modalidade de apoio: Bolsas no Brasil - Doutorado