Anna ILIEVA and Viliana VASILEVA
Abstract: Effect of pre-sowing treatment of seeds with insecticide preparations on parameters related to nodulation and nitrate reduction in soybean was studied in pot trial at the Institute of Forage Crops, Pleven, Bulgaria (2003–2004). It was found that insecticide preparations Gaucho 600 FS (imidacloprid), Carbodan 35 ST (carbofuran) applied for pre-sowing treatment of seeds at the doses of 1, 2 and 3 L/100 kg seeds, and Promet 400 CS (furathiocarb) (standard) at the dose of 3 L/100 kg seeds, had no suppressive effect on the root length, dry root mass and specific nodulating ability of plants. When used Gaucho 600 FS at the dose of 1 L/100 kg seeds, root mass was most developed, the largest number of nodules was formed, and specific nodulating ability was highest. The common tendency for decrease of nitrate reductase activity in leaves and significant increase in stems was found. Nitrate reductase activity increased in leaves, stems and roots in treatment with Carbodan 35 ST applied at the dose of 3 L/100 kg seeds. Chlorophylls а+b/carotenoids ratio exceeded this of the control only in treatment with Gaucho 600 FS at the dose of 1 L/100 kgseeds.