Optimizing the Amount of Nitrogen and Seed Inoculation to Improve the Quality and Yield of Soybean Grown in the Southeastern Baltic Region

The cultivation of soybeans, especially where this species has not been grown in large areas, requires the determination of the optimal mineral nitrogen fertilization and seed inoculation with Bradyrhizobium japonicum. The purpose of the study was to determine the optimal dose of mineral N fertilization and seed inoculation treatments with B. japonicum under field conditions in the southeastern Baltic region. The objective of this study was to achieve nitrogen supply and/or inoculation with B. japonicum: check-0 kg N ha−1, 30 kg N ha−1, 60 kg N ha−1, HiStick® Soy + 0 kg N ha−1, Nitroflora + 0 kg N ha−1, HiStick® Soy + 30 kg N ha−1, HiStick® Soy + 60 kg N ha−1, Nitroflora + 30 kg N ha−1, Nitroflora + 60 kg N ha−1. Higher yields of seeds, protein and fat were found after application HiStick® Soy compared to Nitorflora. The inoculation with B. japonicum together with nitrogen fertilization improved crude protein content in seeds, biometrical features, yield components and especially the seed yield of ‘Aldana’ soybean. The highest seed yield was found after the application of HiStick® Soy and nitrogen fertilization in doses 30 kg N ha−1 or 60 kg N ha−1. Compared to the control, combined B. japonicum inoculation and nitrogen fertilization in soybean cultivation proved to be a significant factor in improving the productivity of this species in southeastern Baltic conditions.