Abstract
Abstract: This study aimed to compare the results of germination, vigor, and yield of high- and low-vigor soybean seeds submitted to on-farm application of biostimulant with its application via industrial treatment 60 days before sowing. The experimental design was a factorial arrangement of 6 × 2 × 2 (technology × vigor level × strategy of biostimulant application) for the laboratory experiment and of 6 × 2 (technology × strategy of biostimulant application) for the field experiment. Germination, accelerated aging, emergence in sand, seedling dry biomass, and electrical conductivity were assessed in the laboratory, while stand, one thousand-grain weight, and yield were assessed in the field. Biostimulant application in soybean seeds not coated with pesticides did not affect the physiological quality regardless of the application moment (at the day of sowing or at 60 days before sowing). However, when applied in seeds coated with fungicides and insecticides, better results of germination, vigor, and yield were obtained with the on-farm use of biostimulant.
Highlights
The use of kinetin, auxin, and gibberellic acid-based biostimulants in soybean cultivation via seed treatment or foliar spraying in the V5–V6 or R1 stages are cultural practices considered equivalent both in crop yield and in obtaining high-quality grains (Bertolin et al, 2010; Embrapa, 2013a)
In relation to the physiological quality, no adverse effects of the biostimulant were observed on the germination and vigor of high-vigor seeds not treated with fungicide and insecticide (Table 2)
With the exception of germination and seedling dry biomass in treatments 2 (Bio OF) and 3 (Bio BS), the early biostimulant application in low-vigor seeds resulted in reductions of the physiological quality, as observed by means of the tests of germination, emergence in sand, electrical conductivity, accelerated aging, field emergence, and seedling dry biomass
Summary
The use of kinetin, auxin, and gibberellic acid-based biostimulants in soybean cultivation via seed treatment or foliar spraying in the V5–V6 or R1 stages are cultural practices considered equivalent both in crop yield and in obtaining high-quality grains (Bertolin et al, 2010; Embrapa, 2013a). Auxins influence cell expansion mechanisms, cytokinins are linked to nutrient mobilization and floral development, while gibberellins are associated with the promotion of stem growth (Taiz and Zeiger, 2013). In this sense, the observation of the positive response of soybean crop to biostimulant application in three different phenological stages (seeds, V5–V6 or R1) is explained by the difference in the metabolic processes in which each of the hormones participates. In the most recent survey, it is estimated that 95% of the soybean seeds sown in the country’s producing regions were treated with fungicides and/or insecticides so that approximately 66% of the total commercialized corresponded to the industrial treatment (França-Neto et al, 2015)
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