Solubilidade e eficiência de fontes de fósforo em sistemas de pastagem com Uroclhoa brizantha cv Marandu
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Data
2018-06-21
Autores
Ferreira-Eloy, Natalia Rodrigues [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
Uma das limitações no estabelecimento e na manutenção de pastagens nos solos tropicais consiste em baixos níveis de fósforo (P) disponível aliado ao alto custo dos fertilizantes fosfatados solúveis. Por isso a utilização de fontes alternativas como fosfatos naturais e resíduos tem ganho espaço na agricultura. Assim, objetivou-se integrar métodos químicos e espectroscópicos para avaliar a dinâmica do P a longo prazo e o produto de reação de fertilizantes fosfatados em diferentes condições de saturação por bases em um Latossolo Vermelho distrófico. O primeiro experimento foi conduzido a campo, em blocos ao acaso no esquema fatorial 3x5, com 4 repetições, totalizando-se 60 parcelas, com 30 m2 cada. Os tratamentos foram compostos por quatro fontes de fertilizantes fosfatados: fosfato precipitado 1 (FP1), fosfato precipitado 2 (FP2), fosfato reativo (FNR) e superfosfato triplo (SFT), além do tratamento sem aplicação de fósforo e o outro fator correspondeu a 3 condições de acidez do solo, V% original, V% intermediário (45) e V% recomendado (60). Foram aplicados 100 kg ha-1 de P2O5 correspondendo a uma única dose de cada fonte, de acordo com as recomendações para a cultura. Os dados obtidos foram submetidos ao teste de Tukey ao nível de 5% de probabilidade. O segundo experimento foi conduzido em laboratório simulando as mesmas condições de V% no campo sem a vegetação e foram realizadas análise expectroscopia de raio – X do P na borda K de absorção, pela linha de SXS do Laboratório Nacional de Luz e Síncroton. No primeiro experimento as fontes alternativas proporcionaram altos índices de eficiência agronômica (IEA) e alta produção de massa de matéria seca (MMS) da Urochloa brizantha. O FP1 promoveu melhores rendimentos de produção deMMS e maior IEA em condições de acidez intermediária sendo em geral superior a todas as outras fontes analisadas. A longo prazo as fontes FP2 e FNR proporcionaram rendimentos tão eficientes quanto as fontes SFT e FP1, demonstrando o potencial efeito residual da fonte FP2 em todas as condições de solo e a maior solubilidade que FP1 apresenta quando comparado a FP2. A diferença da IEA primeiros cortes foi expressa em valores maiores encontrados na FP1 e com o passar do cultivo a fonte FP2 foi a mais expressiva nos últimos cortes. No geral, as fontes testadas proporcionaram teores de fósforo maiores que o nível crítico específico para este solo, satisfazendo, portanto, a necessidade da cultura. No segundo experimento, os resultados de XANES apontaram para a predisposição de fósforo ligado ao Ferro, demonstrado pela correlação entre as amostras e o padrão de Ferridrita, para ambos os tratamentos, em todas as fontes de P.
One of the limitations in establishing and maintaining pastures on tropical soils is low levels of available phosphorus coupled with the high cost of soluble phosphate fertilizers. Due to these factors the use of alternative sources such as natural phosphates and residues has gained space in agriculture. The objective of this study was to integrate chemical and spectroscopic methods to evaluate the long-term P dynamics and the reaction product of phosphate fertilizers under different soil saturation conditions in a Dystrophic Red Latosol (Oxisol), simulating different technical conditions in pasture areas. The first experiment was carried out in field, randomized blocks, in a 3x5 factorial scheme, with 4 replicates, totaling 60 plots, with 30 m2 each. The treatments were composed of four sources of phosphate fertilizers: precipitated phosphate 1 (FP1), precipitated phosphate 2 (FP2), reactive phosphate and triple superphosphate, besides the treatment without application of phosphorus and the other factor corresponded to 3 acidity conditions, V % of soil, V% intermediate (45) and V% corrected (60). 100 kg ha-1 of P2O5 corresponding to a single dose of each source was applied according to the recommendations for the culture. The data were submitted to the Tukey test at the 5% probability level. The second experiment was carried out in the laboratory simulating the same conditions of V% in the field without vegetation and spectroscopy analysis of X-ray of P at the K edge of absorption, by the SXS line of the National Laboratory of Light and Synchroton. In the first experiment. The first experiment, the alternative sources provided high levels of agronomic efficiency (IEA) and high dry matter mass (DMS) production of Urochloa brizantha. The FP1 promoted better yields of production of MMS and higher IEA in conditions of intermediate acidity, being in general superior to all other sources analyzed. In the long term, the FP2 and FNR sources provided yields as efficient as the SFT and FP1 sources, demonstrating the potential residual effect of the FP2 source in all soil conditions and the higher solubility that FP1 presents when compared to FP2. The difference in the IEA in the first cuts was expressed in higher values found in FP1 and with the passage of cultivation, the FP2 source was the most expressive in the last cuts. In general, the tested sources provided phosphorus contents higher than the specific critical level for this soil, satisfying, therefore, the crop's need. In the second experiment, the results of XANES pointed to the predisposition of phosphorus bound to Iron, demonstrated by the correlation between the samples and the Ferhydrite pattern, for both treatments, in all P sources.
One of the limitations in establishing and maintaining pastures on tropical soils is low levels of available phosphorus coupled with the high cost of soluble phosphate fertilizers. Due to these factors the use of alternative sources such as natural phosphates and residues has gained space in agriculture. The objective of this study was to integrate chemical and spectroscopic methods to evaluate the long-term P dynamics and the reaction product of phosphate fertilizers under different soil saturation conditions in a Dystrophic Red Latosol (Oxisol), simulating different technical conditions in pasture areas. The first experiment was carried out in field, randomized blocks, in a 3x5 factorial scheme, with 4 replicates, totaling 60 plots, with 30 m2 each. The treatments were composed of four sources of phosphate fertilizers: precipitated phosphate 1 (FP1), precipitated phosphate 2 (FP2), reactive phosphate and triple superphosphate, besides the treatment without application of phosphorus and the other factor corresponded to 3 acidity conditions, V % of soil, V% intermediate (45) and V% corrected (60). 100 kg ha-1 of P2O5 corresponding to a single dose of each source was applied according to the recommendations for the culture. The data were submitted to the Tukey test at the 5% probability level. The second experiment was carried out in the laboratory simulating the same conditions of V% in the field without vegetation and spectroscopy analysis of X-ray of P at the K edge of absorption, by the SXS line of the National Laboratory of Light and Synchroton. In the first experiment. The first experiment, the alternative sources provided high levels of agronomic efficiency (IEA) and high dry matter mass (DMS) production of Urochloa brizantha. The FP1 promoted better yields of production of MMS and higher IEA in conditions of intermediate acidity, being in general superior to all other sources analyzed. In the long term, the FP2 and FNR sources provided yields as efficient as the SFT and FP1 sources, demonstrating the potential residual effect of the FP2 source in all soil conditions and the higher solubility that FP1 presents when compared to FP2. The difference in the IEA in the first cuts was expressed in higher values found in FP1 and with the passage of cultivation, the FP2 source was the most expressive in the last cuts. In general, the tested sources provided phosphorus contents higher than the specific critical level for this soil, satisfying, therefore, the crop's need. In the second experiment, the results of XANES pointed to the predisposition of phosphorus bound to Iron, demonstrated by the correlation between the samples and the Ferhydrite pattern, for both treatments, in all P sources.
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Palavras-chave
formas de fósforo, Urochloa brizantha, latossolo vermelho distrófico, XANES, fontes alternativas, fertilizantes fosfatados, phosphorus forms, dystrophic red latosol, alternative sources, phosphate fertilizers