Abstract
ABSTRACT: Nitrogen fertilization is a common practice used to increase the yield of winter bean crops. However, this practice leads to excessively tall and prostrate plants that have too many leaves, resulting in self-shading, and low yield and grain quality. The use of growth regulators could minimize the undesired effects of nitrogen fertilization. This study aims to determine the optimal concentration of paclobutrazol (PBZ) for inhibiting bean growth using the cultivars BRS Pontal and BRS Supremo. The plants were treated with PBZ at different concentrations, and also in combination with ammonium sulfate ten days after fertilization. The height and yield of plants were evaluated. It was observed that PBZ at 8 mg L-1 effectively inhibits the growth of bean plants, and increases the number of pods and grains. Higher concentrations of PBZ proved to be phytotoxic. Additionally, the application of PBZ ten days after fertilization with ammonium sulfate did not suppress the overgrowth of bean plants, and did not affect their yield.
Highlights
MATERIAL AND METHODSThe cultivation of bean plants during the winter, or third-season irrigated, especially in the Cerrado region, has already accounted for more than 16% of the Brazilian production of the grain
Paclobutrazol (PBZ) is an important regulator known to inhibit vegetative growth. It inhibits the synthesis of gibberelin by blocking the monooxygenase activity of cytochrome P-450, which in turn inhibits the oxidation of ent-kaurene to entkaurenoic acid in their biosynthetic pathway (HEDDEN; GRAEBE, 1985; RADEMARCHER, 2000)
This study aimed to determine, in the first experiment, the best concentration of PBZ for beans, and assess, in the second experiment, its effects when combined with nitrogen fertilization, in terms of plant height, pods per plant, total mass of 100 grains, and grain production for the cultivars BRS Pontal and BRS Supremo of Phaseolus vulgaris L
Summary
MATERIAL AND METHODSThe cultivation of bean plants during the winter, or third-season irrigated, especially in the Cerrado region, has already accounted for more than 16% of the Brazilian production of the grain. The bean is a leguminous vegetable, able to fix atmospheric nitrogen (N) via a symbiotic association, naturally or through inoculation, it cannot fully meet the demand for N when farmers aim to increase productivity (COMISSÃO TÉCNICA SUL-BRASILEIRA DE FEIJÃO, 2009). Bean producers during this season apply excessive doses, above 80 kg ha-1 of nitrogen, resulting in overgrown plants, which grow flatter and demonstrate self-shading, creating a disease-prone environment, resulting in a fall in productivity and grain quality (FAGERIA et al, 2014; PORTES, 2012). It inhibits the synthesis of gibberelin by blocking the monooxygenase activity of cytochrome P-450, which in turn inhibits the oxidation of ent-kaurene to entkaurenoic acid in their biosynthetic pathway (HEDDEN; GRAEBE, 1985; RADEMARCHER, 2000)
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