Dessecação pré-colheita e efeitos sobre a produtividade e qualidade fisiológica de sementes de soja

Abstract

RESUMO -A antecipação da colheita da soja é possível com uso da prática de dessecação pré-colheita, a qual reduz o tempo de permanência das sementes no campo, após a maturação fisiológica. O objetivo deste trabalho foi avaliar o efeito da época de aplicação do herbicida paraquat, como dessecante na pré-colheita da soja, sobre a produtividade e qualidade fisiológica de sementes. O trabalho constou de duas etapas: um experimento em campo, conduzido no município de Jaboticaba-RS, safra 2010/2011, e uma análise da qualidade fisiológica das sementes. Os tratamentos consistiram de três épocas de aplicação do paraquat (240 g i.a. ha -1 ), R6, R7.1 e R7.3, bem como de um tratamento testemunha (sem dessecação). Foram avaliados a produtividade de grãos e os componentes da produtividade. A análise da qualidade das sementes foi conduzida no Laboratório de Produção e Tecnologia de Sementes da UFSM, Campus de Frederico Westphalen, RS, onde se realizaram os seguintes testes: germinação; primeira contagem de germinação, comprimento de parte aérea e radicular, matéria seca de plântulas, envelhecimento acelerado, condutividade elétrica, emergência em campo e índice de velocidade de emergência. A aplicação de paraquat como dessecante na pré-colheita da soja, nos estádios R6 e R7.1, provoca queda acentuada na produtividade da cultura. A dessecação sem perda de potencial produtivo da soja só é viável a partir do estádio R7.3. Sementes oriundas de plantas com dessecação nos estádios R6 e R7.1 apresentam percentual superior e maior velocidade de germinação. Entretanto, sementes de plantas com dessecação no estádio R6 possuem menor vigor de plântulas. Palavras-chave:Glycine max, paraquat, estádio fenológico, vigor de sementes. Jaboticaba-RS, in 2010/2011 and the analysis of the physiological quality of seeds. The treatments consisted of three times of paraquat (240 g a.i. ha -1 ) application, R6, R7.1 and R7.3, as well as one untreated (without burn-down ABSTRACT -The anticipation of soybean harvest is possible with the use of pre-harvest burn-down practice, which reduces the time of permanence of seeds in the field, after reaching physiological maturation. The objective of this work was to evaluate the effect of time of application of the herbicide paraquat as burn-down during soybean pre harvest on yield and physiological quality of the seeds. The work consisted of two steps: one field experiment, conducted in

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

“…Therefore, it is extremely important that the soybean producer knows the stages of plant development. 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).…”

“…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).…”

“…A similar result was also observed by Toledo et al (2012) who found glyphosate effect on root length, hypocotyl length and total height of the seedlings. Lamego et al (2013) obtained a higher rate of soybean seedling emergence when seeds were derived from plants desiccated in R6.0. Kappes et al (2009) verified that soybean seed batches desiccated with Paraquat performed better than controls in seed quality tests.…”

“…It is well known that in plants of determinate growth type, the maturation of pods in the lower third is delayed compared with other parts of the plant. Several studies have shown that earlier desiccation results in a greater loss in seed yield (Bastidas et al, 1971;Kappes et al, 2008;Lamego et al 2013). In a premature desiccation, the seed has not yet reached physiological maturity i.e.…”

“…For the producer, choosing the right time to desiccate is the most difficult decision, because the maintenance of physiological quality and especially the yield must be considered of paramount importance. Some works have shown that the earlier the desiccation the greater the losses in seed weight (Kappes et al, 2008;Lamego et al, 2013). Kappes et al (2008) reported reductions of 17.5, 39 and 44% respectively, when desiccation was performed at the R7.2, R7.1 and R6.0 stages.…”