Formas de fósforo em solos tropicais adubados com lodo de esgoto em experimento de longa duração
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Data
2020-05-25
Autores
Delarica, Denise de Lima Dias [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
O uso de adubos orgânicos afeta os teores totais e disponíveis de fósforo (P) do solo, suas formas e transformações, e constitui uma maneira de prolongar a sustentabilidade dos sistemas de produção. Os objetivos com este estudo foram: (i) avaliar as formas de P inorgânico e P orgânico em Latossolo Vermelho eutroférrico (LVef) e Latossolo Vermelho distrófico (LVd) adubados com lodo de esgoto por vinte anos; (ii) comparar a distribuição de P nos Latossolos adubados com fertilizantes fosfatados solúveis e lodo de esgoto (LE). Nos experimentos conduzidos em campo, em esquemas de blocos casualizados, os tratamentos são adubo mineral (controle), mais três doses LE que acumularam 100, 200 e 365 t ha-1 nos vinte anos de aplicação. Na dose acumulada de 365 t ha-1, o teor de P inorgânico nas frações solúvel, ligada ao alumínio e ao ferro aumentou nos dois Latossolos. As frações ocluída e ligada ao cálcio, mesmo tendo seu teor aumentado, não apresentaram diferença significativa em função do tipo de adubação. A aplicação de LE teve efeito pequeno no aumento dos reservatórios de P orgânico nas menores doses (100 e 200 t ha-1), que apresentaram, em muitas frações, comportamento semelhante à fertilização mineral. Os efeitos mais pronunciados foram notados nos reservatórios ligados aos ácidos fúlvicos (P-AF) e húmicos (P-AH) na maior dose acumulada, 365 t ha-1. A aplicação de LE por vinte anos em solos tropicais mantém maior teor de P inorgânico em formas com maior solubilidade e de P orgânico em formas com maior labilidade. A distribuição do P inorgânico nas formas avaliadas, no LVef, foi: P-ocluído>P-Fe>P-Al>P-Ca>P-solúvel. No LVd foi: P-Al>P-Fe>P-ocluído>P-Ca>P-solúvel. A distribuição de P orgânico seguiu a mesma ordem para os dois Latossolos: P-H2SO4>P-AF>P-AH>P-NaHCO3>P-HCl. A manutenção de maiores teores de P em frações solúveis, lábeis e moderadamente lábeis é vantajosa e fortalece a sustentabilidade da aplicação do LE como adubo orgânico em regiões tropicais, ao prevenir o esgotamento das reservas do nutriente e ao diminuir a dependência de fertilizantes fosfatados provenientes de reservas internacionais.
The use of organic fertilizers affects the total and available levels of phosphorus (P) in the soil, its forms and transformations, and constitutes a way to prolong the sustainability of production systems. The objectives of this study were: (i) to evaluate the forms of inorganic P and organic P in Oxisols (LVef) and (LVd) fertilized with sewage sludge for twenty years; (ii) to compare the distribution of P in the Oxisols fertilized with soluble phosphate fertilizers and sewage sludge (LE). In experiments conducted in the field, in randomized block schemes, the treatments are mineral fertilizer (control), plus three LE doses that accumulated 100, 200 and 365 t ha-1 in the twenty years of application. At the accumulated dose of 365 t ha-1, the content of inorganic P in the soluble fractions, linked to aluminum and iron increased in the two Oxisols. The fractions occluded and bound to calcium, even though their content increased, did not show significant difference depending on the type of fertilization. The application of LE had little effect on the increase of the organic P reservoirs in the lowest doses (100 and 200 t ha-1), which presented, in many fractions, a behavior similar to mineral fertilization. The most pronounced effects were noted in reservoirs linked to fulvic (P-AF) and humic (P-AH) acids in the highest accumulated dose, 365 t ha-1. The application of LE for twenty years in tropical soils maintains a higher content of inorganic P in forms with greater solubility and organic P in forms with greater lability. The distribution of inorganic P in the evaluated forms, in LVef, was: P-occluded> PFe> P-Al> P-Ca> P-soluble. In LVd it was: P-Al> P-Fe> P-occluded> P-Ca> P-soluble. The distribution of organic P followed the same order for the two Oxisols: P-H2SO4> PAF> P-AH> P-NaHCO3> P-HCl. Maintaining higher levels of P in soluble, labile and moderately labile fractions is advantageous and strengthens the sustainability of the application of LE as an organic fertilizer in tropical regions, by preventing the depletion of nutrient reserves and by decreasing the dependence on phosphate fertilizers from international reserves.
The use of organic fertilizers affects the total and available levels of phosphorus (P) in the soil, its forms and transformations, and constitutes a way to prolong the sustainability of production systems. The objectives of this study were: (i) to evaluate the forms of inorganic P and organic P in Oxisols (LVef) and (LVd) fertilized with sewage sludge for twenty years; (ii) to compare the distribution of P in the Oxisols fertilized with soluble phosphate fertilizers and sewage sludge (LE). In experiments conducted in the field, in randomized block schemes, the treatments are mineral fertilizer (control), plus three LE doses that accumulated 100, 200 and 365 t ha-1 in the twenty years of application. At the accumulated dose of 365 t ha-1, the content of inorganic P in the soluble fractions, linked to aluminum and iron increased in the two Oxisols. The fractions occluded and bound to calcium, even though their content increased, did not show significant difference depending on the type of fertilization. The application of LE had little effect on the increase of the organic P reservoirs in the lowest doses (100 and 200 t ha-1), which presented, in many fractions, a behavior similar to mineral fertilization. The most pronounced effects were noted in reservoirs linked to fulvic (P-AF) and humic (P-AH) acids in the highest accumulated dose, 365 t ha-1. The application of LE for twenty years in tropical soils maintains a higher content of inorganic P in forms with greater solubility and organic P in forms with greater lability. The distribution of inorganic P in the evaluated forms, in LVef, was: P-occluded> PFe> P-Al> P-Ca> P-soluble. In LVd it was: P-Al> P-Fe> P-occluded> P-Ca> P-soluble. The distribution of organic P followed the same order for the two Oxisols: P-H2SO4> PAF> P-AH> P-NaHCO3> P-HCl. Maintaining higher levels of P in soluble, labile and moderately labile fractions is advantageous and strengthens the sustainability of the application of LE as an organic fertilizer in tropical regions, by preventing the depletion of nutrient reserves and by decreasing the dependence on phosphate fertilizers from international reserves.
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Palavras-chave
Adubação orgânica, Biossólido, Extração sequencial do fósforo