Produtividade e qualidade de sementes de soja em função de estádios de dessecação e herbicidas

Abstract

O objetivo deste trabalho foi avaliar a melhor época de aplicação de dessecantes, de forma a permitir antecipação da colheita sem prejudicar a produtividade e qualidade de sementes de soja. O delineamento experimental foi de blocos ao acaso em esquema fatorial (3x3) + 1, com quatro repetições. Um dos fatores foi constituído pelos herbicidas dessecantes paraquat, glufosinato de amônio e glyphosate, nas doses de 400, 400 e 960 g i.a. ha-1, respectivamente. Outro fator constituiu-se de três estádios de aplicação dos herbicidas, via pulverização (R6, R7.2 e R8.1). Avaliaram-se a antecipação da colheita, massa de 100 sementes, produtividade, germinação e vigor das sementes. A utilização de herbicidas, aliada aos estádios fenológicos de aplicação, permitiu antecipar a colheita de um a seis dias. A dessecação de plantas de soja em pré-colheita com os herbicidas nos diferentes estádios fenológicos não afetou a produtividade. O herbicida glufosinato de amônio reduziu a germinação de sementes de soja quando aplicado no estádio R6. O herbicida glyphosate reduziu o vigor das sementes de soja quando aplicado nos estádios R6 e R7.2. O herbicida paraquat promoveu os melhores índices de germinação e vigor de sementes de soja quando utilizado nos estádios R6 e R7.2.

Productivity and quality of soybean seeds of determinate and indeterminate growth types desiccated in pre-harvest

“…As the desiccation time of the crop approached the R8.0 stage, a smaller reduction in the normal cycle time for the cultivar was verified, corroborating Guimarães et al (2012). Crop cycle anticipation depends on the desiccation stage, so choosing the right moment is an important step in the process.…”

“…The premature death of the plant results in disruption of photoassimilate accumulation in seeds (Marcos Filho, 2005). In contrast, some other studies have reported that there is no influence of desiccant application time on seed weight (Guimarães et al, 2012;Malaspina et al, 2012).…”

“…The seed yield results are in accordance with Lamego et al (2013) who reported that desiccation without loss of production occurred only with desiccation at the R7.3 stage. Desiccant application time is crucial, because when desiccation is performed before physiological seed maturity, it may result in reduction of the crop yield (Bastidas et al, 1971;Kappes et al, 2008;Guimarães et al, 2012;Lamego et al, 2013). However, if the desiccation is appropriately performed at physiological maturity there will be uniformity in plant maturity and harvest anticipation, with no effect on the productive potential (Lacerda et al, 2001;Inoue et al, 2012;Guimarães et al, 2012).…”

“…Desiccant application time is crucial, because when desiccation is performed before physiological seed maturity, it may result in reduction of the crop yield (Bastidas et al, 1971;Kappes et al, 2008;Guimarães et al, 2012;Lamego et al, 2013). However, if the desiccation is appropriately performed at physiological maturity there will be uniformity in plant maturity and harvest anticipation, with no effect on the productive potential (Lacerda et al, 2001;Inoue et al, 2012;Guimarães et al, 2012). Reductions in seed yield found in this study were 27% with desiccation at R5.7, 20% with desiccation at R6.5, and 6% with desiccation at R7.3, compared to harvest at stage R8 (Table 1).…”

“…Kappes et al (2009) verified that seeds produced by nondesiccated plants showed the highest germination percentage, higher than plants desiccated at the R6.0, R7.1 and R7.2 stages, showing that desiccation at these stages causes damage to seed germination. On the other hand, according to Guimarães et al (2012), the use of paraquat herbicide promoted better germination and strength in soybean seeds when used at the R6.0 and R7.2 stages, compared with ammonium glufosinate and glyphosate at the same stages. The harvest delay for the plants desiccated at R7.3 seriously decreased seed germination.…”