Produção da mamoneira submetida a combinações com fontes de fósforo e calagem

A mamoneira é considerada cultura exigente em fósforo haja vista que a nutrição fosfatada adequada com a utilização de fontes solúveis em conjunto com fontes naturais, pode aumentar a eficiência de absorção do fósforo e a produtividade de mamona. Objetivou-se avaliar os componentes de produção da mamoneira após a combinação de adubações com fosfato solúvel e natural, na ausência e na presença de calagem. O estudo foi conduzido em esquema fatorial 2 x 5 envolvendo duas doses de calcário (com e sem calcário) e cinco combinações de adubação fosfatada: testemunha (0 kg ha-1 de P2O5); 100% de fosfato natural (560 kg ha-1), fosfato natural (560 kg ha-1 ) + MAP (188 kg ha-1); fosfato natural (560 kg ha-1 ) + ½ MAP (94 kg ha-1) e 100% MAP (188 kg ha-1) com quatro repetições em blocos ao acaso. As características avaliadas foram o comprimento dos racemos primário e secundário, o número de bagas, a massa de casca, a massa de bagas, a massa de grãos, a massa de 100 grãos e a relação entre massa de grãos/massa de bagas. A combinação de fosfato natural + MAP propiciou, na presença de calcário, maior produção de grãos de mamoneira (1.455 kg ha-1) e incrementou a maioria dos demais componentes de produção estudados

Sorghum yield after liming and combinations of phosphorus sources

ABSTRACT Phosphate fertilization has increased sorghum yield, but few studies are available on sorghum production and efficient fertilizer management related to liming and phosphorus (P) sources. This work evaluates production, dry matter partitioning and agronomic efficiency (AEI) in successive sorghum cycles after application of limestone and combinations of phosphorus sources. Two cycles were conducted in sequence in the same experimental field, in a 2 x 6 factorial scheme, corresponding to soil with or without liming and six combinations of P2O5 sources: control (0 kg ha-1 P2O5), 100% Itafós natural phosphate (NP), 75% NP + 25% single superphosphate (SS), 50% NP + 50% SS, 25% NP + 75% SS and 100% SS. Pots with capacity for 8 dm3 were used in a randomized block design with four replicates. The first cycle, conducted in the summer/autumn season, reached the highest dry matter production and P accumulation in treatments with higher SS proportions, leading to higher AEI. Subsequently, in the second cycle, conducted considering only the residual phosphate fertilization of the first cycle, highest dry matter production and AEI were obtained in the treatment with 100% or higher proportions of natural phosphate in the presence of liming, most likely due to the gradual release of P

Sorghum yield after liming and combinations of phosphorus sources

<div><p>ABSTRACT Phosphate fertilization has increased sorghum yield, but few studies are available on sorghum production and efficient fertilizer management related to liming and phosphorus (P) sources. This work evaluates production, dry matter partitioning and agronomic efficiency (AEI) in successive sorghum cycles after application of limestone and combinations of phosphorus sources. Two cycles were conducted in sequence in the same experimental field, in a 2 x 6 factorial scheme, corresponding to soil with or without liming and six combinations of P2O5 sources: control (0 kg ha-1 P2O5), 100% Itafós natural phosphate (NP), 75% NP + 25% single superphosphate (SS), 50% NP + 50% SS, 25% NP + 75% SS and 100% SS. Pots with capacity for 8 dm3 were used in a randomized block design with four replicates. The first cycle, conducted in the summer/autumn season, reached the highest dry matter production and P accumulation in treatments with higher SS proportions, leading to higher AEI. Subsequently, in the second cycle, conducted considering only the residual phosphate fertilization of the first cycle, highest dry matter production and AEI were obtained in the treatment with 100% or higher proportions of natural phosphate in the presence of liming, most likely due to the gradual release of P.</p></div