Interaction of Mechanical Damage and Chemical Treatment and Its Effects on Soybean Seed Physiological Quality

The objective was to evaluate the effects of chemical treatment and levels of mechanical damage and the lignin content of seed coat on soybean seed physiological quality. Two soybean cultivars were used- BMX Lança (58I60 RSF IPRO) and BMX Zeus (55I57 RSF IPRO), with different levels of mechanical injury identified by the tetrazolium test. The chemical treatments used were- control; Carbendazim + Thiram; Carbendazim + Thiram + Dry Powder; Imidacloprid + Thiodicarb; Imidacloprid + Thiodicarb + Dry Powder. A completely randomized design was used, in an 8 × 5 factorial scheme (Types of Samples × Seed Treatment). Physiological quality was evaluated by germination, primary root length, seedling dry mass, accelerated aging and seedling emergence tests. Also, the lignin content in seed coat, one-thousand-seed weight and uniformity test were performed. Data were submitted to analysis of variance (F test) and the mean comparison by the Tukey’s test (p < 0.05). Cultivars showed differences in the tegument lignin content. The treatment with Imidacloprid + Thiodicarb + dry powder promoted greater reduction in seed physiological potential, intensifying in seeds with more severe damage levels. The lignin content in soybeans seed coat influences the occurrence of mechanical injuries. Seeds with greater intensities of mechanical damage are more susceptible to phytotoxic effects promoted by chemical treatment, since such effects are intensified with the incorporation of dry powder in the seed treatment.