Aumento da disponibilidade de fósforo em solo cultivado com Brachiaria em rotação com soja
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Data
2011-12-07
Autores
Merlin, Alexandre [UNESP]
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
O fornecimento de P para as culturas em solos tropicais é geralmente deficiente devido à sua natureza pouco solúvel no solo, e a adição de fertilizantes P tem sido obrigatória para se atingir rendimentos elevados. Uma abordagem possível é a adoção de sistemas de cultivo com plantas de alta eficiência no uso do P. O objetivo deste estudo foi determinar os mecanismos da braquiária (Brachiaria ruziziensis), cultivada em rotação, aumentando a disponibilidade de P no solo. Foram desenvolvidos dois experimentos: para o ensaio de campo os tratamentos foram doses de fosfato solúvel e natural aplicadas à lanço, com e sem cultivo de braquiária (Brachiaria ruziziensis). A gramínea foi cultivada por 289 dias e após esse período o solo foi amostrado de 0-5 e 5-10 cm de profundidade. O segundo experimento, em casa de vegetação, Brachiaria ruziziensis e Brachiaria brizantha foram cultivadas em solução nutritiva com complexos de P em óxidos de Ferro e Alumínio. À campo, os níveis de fósforo disponível foram superiores após o cultivo da gramínea. No experimento em casa de vegetação, o desenvolvimento das espécies de braquiária foi normal nos tratamentos onde o fósforo estava adsorvido pelos óxidos de Ferro e Alumínio, indicando a capacidade dessas duas espécies em acessar formas indisponíveis de P tornandoas disponíveis para outras culturas
Phosphorus supply to crops in tropical soils is usually deficient due its sparingly soluble nature in soil, and the addition of P fertilizers has been mandatory in order to achieve high yields. One potential approach is to adopt cropping systems that could increase plant available P in soil. The objective of this study was to examine the mechanisms of cover crop (Congo grass - Brachiaria ruziziensis) rotation in enhancing soil and fertilizer P availability using long-term field trials and laboratory chemical fractionation approaches. The first experiment was a field cropped under no-till for five years. No P or 35 kg ha-1 of P was applied on the soil surface as triple superphosphate or Arad rock phosphate and Congo grass was grown for 289 days. After this, soil samples were taken down to 10 cm and soil P was fractionated. The second experiment was carried out in a green house where the treatments were Brachiaria species (Brachiaria brizantha and Brachiaria ruziziensis) and two mineral-P complexes (goethite and amorphous Al-oxide) plus two controls with and without P as regular nutrient solution. In the first experiment, soil available P, as estimated by resin extraction was increased by congo grass down to10 cm when P fertilizers were applied. At the nutrient solution experiment, after 14 days of cultivation, the dry matter yields of both Brachiaria species were not affected by oxide-P (goethite-P or Al oxide-P) as sole P source, demonstrating that Brachiaria species could access non-labile adsorbed when P was supplied with Al oxide-P and goethite-P
Phosphorus supply to crops in tropical soils is usually deficient due its sparingly soluble nature in soil, and the addition of P fertilizers has been mandatory in order to achieve high yields. One potential approach is to adopt cropping systems that could increase plant available P in soil. The objective of this study was to examine the mechanisms of cover crop (Congo grass - Brachiaria ruziziensis) rotation in enhancing soil and fertilizer P availability using long-term field trials and laboratory chemical fractionation approaches. The first experiment was a field cropped under no-till for five years. No P or 35 kg ha-1 of P was applied on the soil surface as triple superphosphate or Arad rock phosphate and Congo grass was grown for 289 days. After this, soil samples were taken down to 10 cm and soil P was fractionated. The second experiment was carried out in a green house where the treatments were Brachiaria species (Brachiaria brizantha and Brachiaria ruziziensis) and two mineral-P complexes (goethite and amorphous Al-oxide) plus two controls with and without P as regular nutrient solution. In the first experiment, soil available P, as estimated by resin extraction was increased by congo grass down to10 cm when P fertilizers were applied. At the nutrient solution experiment, after 14 days of cultivation, the dry matter yields of both Brachiaria species were not affected by oxide-P (goethite-P or Al oxide-P) as sole P source, demonstrating that Brachiaria species could access non-labile adsorbed when P was supplied with Al oxide-P and goethite-P
Descrição
Palavras-chave
Rotação de cultivos, Capim-braquiaria, Solos - Teor de fosforo, Phosphate, Crop rotation
Como citar
MERLIN, Alexandre. Aumento da disponibilidade de fósforo em solo cultivado com Brachiaria em rotação com soja. 2011. viii, 53 f. Tese (doutorado) - Universidade EStadual Paulista, Faculdade de Ciências Agronômicas, 2011.