Avaliação agronômica de fontes e doses de fósforo para o capim-Tifton 85
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Data
2003-06-23
Autores
Franco, Henrique Coutinho Junqueira [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
Com o objetivo de avaliar a eficiência agronômica de fontes de fósforo (P) para o capim-Tifton 85 em três crescimentos, na produção de massa seca da parte aérea e das raízes, e perfilhamento, conduziu-se um experimento em vasos contendo amostras de um LATOSSOLO VERMELHO-AMARELO textura média. Os fertilizantes fosfatados utilizados foram: o superfosfato triplo-ST (fonte referência), os fosfatos naturais reativos de Gafsa e Arad e o termofosfato magnesiano (pó e grosso), aplicados nas doses de fósforo 30, 60, 90 e 120 mg kg-1. A adubação fosfatada promoveu incrementos significativos na produção de massa seca (parte aérea) e no perfilhamento da forrageira durante todo período experimental, assim como na produção de massa seca de raízes (1° e 3° crescimentos). A eficiência dos fosfatos reativos (Arad e Gafsa) aumentou significativamente quando se considerou seu efeito residual. O aumento da granulometria do termofosfato prejudicou a sua atuação. O método do equivalente em ST médio foi o que melhor avaliou os resultados de eficiência agronômica, mostrando através dos resultados, que se deve obter a curva de resposta completa de cada fonte e avaliar o seu efeito residual. Quando se considerou a soma dos três crescimentos, o fosfato natural Arad foi o único fertilizante fosfatado que superou a fonte de referência (ST), em termos econômicos. O nível crítico de fósforo no solo e na planta foram respectivamente 18 mg dm-3 e 2,4 9 kg-1. A adubação fosfatada aumentou as concentrações de fósforo e de proteína bruta na parte aérea da forrageira durante todo o período experimental.
This research evaluated the agronomic effectiveness of phosphorus (P) sources for the Tifton 85 grass (three cuttings) on the productíon of the dry mass (shoot and roots) and tillering of Tifton 85 grass. The experiment was conducted in pots containg samples of a LA TOSSOLO VERMELHO AMARELO (Oxisol). The phosphate fertilizers used were: triple superphosphate - TSP (reference source), Gafsa and Arad phosphates rock, and fused magnesium phosphate (powder and coarse). The fertílization with phosphorus promoted significant increments in the dry mass yield (shoot) and on tillering of the forage troughout the experimental period as well as on the production of the roots dry mass (1st and 3rd cutting). The effectiveness of the phosphates rock (Arad and Gafsa) increased significantly when considering its residual effect. The increase of the particle size of the fused magnesium phosphate decreased its effectiveness. The agronomic effectiveness was better evaluated by the method equivalent medium TSP. It was observed that the complete response curve of each source must be obtained and its residual effect evaluated. When the sum of the three cuttings was considered, the Arad phosphate rock was the only fertilizer that overcame the reference source (TSP) in economic terms. The critical levels of the soil and plant were respectively 18 mg dm-3 and 2,4 9 kg-1. The fertilization with phosphorus raised the concentration of phosphorus and the crude protein content in the shoot of the forage troughout the experimental period.
This research evaluated the agronomic effectiveness of phosphorus (P) sources for the Tifton 85 grass (three cuttings) on the productíon of the dry mass (shoot and roots) and tillering of Tifton 85 grass. The experiment was conducted in pots containg samples of a LA TOSSOLO VERMELHO AMARELO (Oxisol). The phosphate fertilizers used were: triple superphosphate - TSP (reference source), Gafsa and Arad phosphates rock, and fused magnesium phosphate (powder and coarse). The fertílization with phosphorus promoted significant increments in the dry mass yield (shoot) and on tillering of the forage troughout the experimental period as well as on the production of the roots dry mass (1st and 3rd cutting). The effectiveness of the phosphates rock (Arad and Gafsa) increased significantly when considering its residual effect. The increase of the particle size of the fused magnesium phosphate decreased its effectiveness. The agronomic effectiveness was better evaluated by the method equivalent medium TSP. It was observed that the complete response curve of each source must be obtained and its residual effect evaluated. When the sum of the three cuttings was considered, the Arad phosphate rock was the only fertilizer that overcame the reference source (TSP) in economic terms. The critical levels of the soil and plant were respectively 18 mg dm-3 and 2,4 9 kg-1. The fertilization with phosphorus raised the concentration of phosphorus and the crude protein content in the shoot of the forage troughout the experimental period.
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Palavras-chave
Capim-das-bermudas, Plantas - Efeito do fosforo
Como citar
FRANCO, Henrique Coutinho Junqueira. Avaliação agronômica de fontes e doses de fósforo para o capim-Tifton 85. 2003. x, 92 f. Dissertação (mestrado) - Universidade Estadual Paulista, Faculdade de Ciências Agrárias e Veterinárias, 2003.