Effects of micronutrients on biological nitrogen fixation and soyabean productivity

Abstract

The effects of micronutrients on biological nitrogen fixation (BNF) and on soyabean yield were studied in two sets of field experiments. The effects of Zn, Co, B and Mo were tested at three sites (soils LRe, LEa and, LRd) where soyabean had been cultivated for more than eight years. In the other set, the effects of Mo (9.0 g) were tested at two sites of acid soils (LBd and LRa), in a first-year soyabean crop production, at different levels of lime. The micronutrients were applied on the seeds, just before inoculation with Bradyrhizobium elkanii, using 80 kg of seeds by hectare: 15 g of Zn, 0.75 g of Co, 4.5 and 9.0 g of Mo and 3.0 g of B. In soils already cultivated with soyabean, Zn, Co and B did not increase BNF and soyabean yield, but Mo increased BNF and soyabean yield in two of these soils. Mo did not increase BNF and soyabean yield in LBd soil. In the other soil (LRa soil), Mo increased BNF and soyabean yield, but only without lime.