Épocas de la aplicación de desecantes en el cultivo de la soja: tenor de agua y productividad

Abstract

Épocas de la aplicación de desecantes en el cultivo de la soja: tenor de agua y productividad RESUMEN -Los herbicidas glifosato y paraquat son utilizados por los productores de soja con el objetivo de desecar las plantas, anticipar y uniformizar la cosecha. Sin embargo, el uso indiscriminado de herbicidas puede causar problemas eventualmente en las características agronómicas y fisiológicas del cultivo. El presente trabajo tuvo por objetivo evaluar la utilización de los herbicidas glifosato y paraquat como desecantes para el cultivo de la soja. El experimento fue llevado a cabo en el año agrícola 2005/06, en un delineamiento experimental de bloques al azar, con cuatro repeticiones. Los tratamientos fueron dispuestos en dos esquemas factoriales, 3x3x5x2 y 3x2x5x2: dos desecantes (glifosato y paraquat) y un testigo (sin desecación), aplicación de los desecantes en tres y dos estadios fenológicos de las plantas (R 6 , R 7 y R 8 ) y (R 7 y R 8 ), para las variedades MSOY 6101 de ciclo superprecoz, y MG/BR 46 (Conquista) de ciclo precoz, respectivamente, cinco épocas de muestreo (2; 4; 6; 8 y 10 días después de la aplicación) y evaluación en dos posiciones en la planta (ápice y base). Fue evaluada la producción de semillas, masa y tenor de agua de 100 semillas. Los desecantes evaluados fueron eficientes en la reducción del tenor de agua de las semillas, sin afectar la productividad y la masa de 100 semillas. Palavras-chave:Desecante. Glifosato. Paraquat. Humedad. ABSTRACT -The herbicides glyphosate and paraquat have been used by Brazilian soybean producers to obtain crop desiccation and to anticipate and uniformity at harvest. However, improper use of herbicides can to occasion problems in agronomic and physiologic characteristics of crop. This study aimed to evaluate the use of the glyphosate and paraquat herbicides as a desiccant for growing soybeans. The experiment was conducted in 2005/06 crop year, in an experimental design of randomized blocks with four replications. Treatments were arranged in two factorial design, 3x3x5x2 and 3x2x5x2: two desiccants (glyphosate and paraquat) and control (without drying), three and two growth stages (R6, R7 and R8) and (R7 and R8) for varieties MSOY 6101 of superprecocious cycle, and MG / BR 46 (Conquista) of precocious cycle, respectively, five sampling times (2, 4, 6, 8 and 10 days after application) and two positions in the plants on the ground assessment (apex and base). Was evaluated for seed production, mass and water content of 100 seeds. Desiccants tested were effective in reducing the water content of seeds, without affecting productivity and mass of 100 seeds.

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

“…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 high seed yield reduction caused by desiccation is due to the action of the herbicide used. Paraquat acts by contact, which results in rapid water loss from the dried plant, similar with other herbicides used as desiccants (Malaspina et al, 2012). Consequently, photoassimilate translocation to seeds is probably disrupted, if they are still at the dry matter accumulation stage at the desiccation time.…”

“…This practice is not new in the production system; it was previously studied for several years by Rahman et al (2004), for example. Recently, the study of pre-harvest desiccation has resumed as some issues still require resolution, especially concerning the appropriate desiccation time (Kappes et al, 2008;Griffin et al, 2010;Boudreaux and Griffing (2011); Malaspina et al, 2012) and the influence of the growth type of the cultivar (Inoue et al, 2003). 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.…”

Physiological Quality of Salvia hispanica L. Seeds at Differents Paraquat Application Moments

“…The seeds quality decreases from the physiological maturity depending on the climatic conditions, an alternative to minimize the deterioration of the seed's quality in the field or to anticipate the harvest in commercial areas of production is the use of desiccant herbicides (Malaspina et al, 2012).…”

“…The same author mentions that there is no unanimous agreement regarding the application time of the desiccant, he also mentions that the stage in which this practice is performed is essential for the seed quality obtained and has an important relationship with the possibility of product adverse effects that are used as desiccant on the seed. Malaspina et al (2012), mention as a classic contact herbicide example, the paraquat, inhibitor of the photosynthetic system, which drastically reduces the water content of the plants green biomass. The mechanism of action is through the blocking of electrons from photosynthesis, preventing the reduction of NADP + to NADPH 2.…”