Efeito dos diferentes níveis de injúria inicial e de desfolha no desenvolvimento da cultura da soja

Abstract

The soybean crop may suffer injury and / or defoliation by insect pests throughout its development cycle. This study aimed to evaluate different levels of injuries in the early stages and defoliation during the vegetative and reproductive stage of soybean FT Campo Mourao and Brasmax Potência. The experiments were conducted at the experimental field of Embrapa Western Region Agriculture, in Dourados, Mato Grosso do Sul State, during season of 2012/2013. In one experiment , was evaluated the effect of injuries carried in the early stages of culture development (height , number of pods/plant, green weight of aerial part) and grain yield , represented by the following treatments: 1) Removal of one cotyledon , 2) removal of two cotyledons, 3) removal of two cotyledons and leaf unifoliada, 4) removal of two cotyledons and two unifoliate leaves , 5) Removal of one unifoliate leaves, 6) Removal of the two unifoliate leaves, 7) Cut bellow of the unifoliate leaf; 8 ) Cut the leaf bud of the trifoliada, 9) Control (without injury). In another experiment was evaluated the effect of two levels of defoliation when applied at the vegetative and / or reproductive stages of soybean, represented by the following treatments: 1) control - no defoliation, 2) 16.7% defoliation in the vegetative period; 3) 33.3 % defoliation in the vegetative period; 4)16.7% defoliation on reproductive period; 5) 33.3 % defoliation on reproductive period; 6)16.7% defoliation throughout the cycle of the plant, 7) 33.3 % defoliation throughout the plant cycle . In both trials conducted the Potência cultivar showed higher plant height (cm), number of pods/plant and fresh weight of aerial part compared to FT Campo Mourão cultivar. Grain yield (kg /ha) was similar in both cultivars in both trials conducted. The weight of 100 seeds (g) was higher in cultivar Campo Mourão compared to that observed in cultivar Potência. Reduction were observed in plant height of soybean at early stage in treatments 3, 4, 6 and 7 when compared with the control. And for the levels of defoliation, there was smaller plants with 33.3 % of defoliation throughout the crop cycle in both cultivars. The number of pods/plant, fresh weight of aerial part, weight of 100 seeds and grain yield showed no difference between the different treatments of injuries caused in plants, the same occurring with the different levels of defoliation studied. It was concluded that both cultivars have great capacity of recover to the damage in their leaf area, not reducing the grain yield.