Abstract
The reduction in the leaf area is one of the causes in the fall in soybean (Glycine max) productivity as it depends on the production of photoassimilates generated by the leaves, so any factor that interferes in its leaf area may affect the production. The attack of defoliating insects is among such factors. They cause a marked drop in grain yield due to its direct action, therefore, reducing the leaf area, consequently reducing the photosynthetic rate of the plant. The agronomic characteristics of the cultivars may interfere on the level of tolerance of the plant to this type of stress. The objective of this study was to evaluate the influence of defoliation levels on the vegetative and reproductive stages on the development and yield of grains in soybean cultivars. The experimental design was in randomized blocks, in a 2×11×2 factorial scheme, with four replicates. Factors consisted of defoliation stage (vegetative and reproductive), treatment levels (T1-control plant and ten treatments of artificial defoliation) and soybean cultivars (BRS 9090 RR and BRS 8890 RR). The following variables were evaluated: grain yield, dry mass of the pod, leaf dry mass, stem and root dry mass, plant height, stem diameter, number of leaves per plant, length and width of roots. It was observed that the defoliation had a negative effect on the productivity components of the cultivars, with the highest decrease in the reproductive stage, except for the treatment R5, 100% defoliation at the R5 stage, which was also reduced. In relation to the cultivars, the BRS 8890 RR was 27% better in grain yield in relation to BRS 9090 RR.
Highlights
Soybean (Glycine max (L.) Merril) is one of the crops with the greatest growth in planted area in the Brazilian agro-industrial segment
The productivity of the soybean is directly related to the photosynthesis performed by the leaves, and the production of photoassimilates from the photosynthetic complex
The capacity of the soybean to avoid reduction in the productivity after defoliation depends on factors such as the defoliation intensity itself, the phenological stage in which it occurs, the ability of the cultivar to tolerate or to compensate for defoliation (Costa et al, 2003; Parcianello et al, 2004) besides the environmental factors, among them, the solar radiation (Andrade et al, 2002). In their early stages of development, soybean plants have a great recovery capacity in relation to defoliation, and reductions in the production are only caused when the defoliation is sufficient to cause the death of the plant, significantly reducing the plant stand
Summary
Soybean (Glycine max (L.) Merril) is one of the crops with the greatest growth in planted area in the Brazilian agro-industrial segment. Its expansion and establishment of agricultural frontiers was only possible due to the development of cultivars with high productivity, wide adaptation to the different edaphoclimatic conditions and resistance to pests and diseases (EMBRAPA, 2008). The factor that limits the leaf area may compromise crop productivity (Peluzio et al, 2002; Li et al, 2006). The attack of a large variety of defoliating insects (Timsina et al, 2007), the incidence of diseases such as soybean rust (Debona et al, 2009) and the occurrence of inclement weather (Fazolin & Estrela, 2003) are some of the factor that limits its production. Studies that evaluate the influence of early defoliation on soybean yield through the analyses of the phenological stages in which the soybean was found (from the initial vegetative stage to the end of the reproductive period) and levels of defoliation (ranging from 0 to 100%) have demonstrated since the non-occurrence of the response until 87% of grain yield (Ribeiro & Costa, 2000; Parcianello et al, 2004)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
