Soybean Seed Quality Characteristics in Response to Indigenous Bradyrhizobium Inoculation and N Fertilization in Kashmir–Pakistan

The objective of this study was to quantify changes in soybean seed quality characteristics in response to indigenous Bradyrhizobium inoculation and N fertilization applied under field conditions during the years 2009 and 2010. Seven indigenous Bradyrhizobium isolates were isolated from the different locations under the foothills of great Himalayas Rawalakot Kashmir, Pakistan. The field isolates were compared to a reference strain (exotic) TAL102, three N fertilizer rates and to an un-inoculated control. The seed oil content, fatty acid composition, seed N, P and K concentration and seed N, P and K uptake were quantified. Bradyrhizobium inoculation and N fertilization significantly increased oil content compared to the un-inoculated control. The seed oil content varied between 16.2 and 21.5 %, highest in the seeds treated with indigenous Bradyrhizobium strains NR₂₂, NR₂₅ and NR₃₅, and mainly composed of linoleic acid (47 %), and oleic acid (24 %). Inoculation and N fertilization both decreased the saturated fatty acids (palmitic and stearic) and increased unsaturated fatty acids (linoleic acid and oleic acid). The mineral nutrient content of N, P, and K and their accumulation in seed increased by 2–3-fold compared to the corresponding control. Indigenous Bradyrhizobium strains were able to generate the highest values for seed oil content (NR₂₂, NR₂₅, and NR₃₅), unsaturated fatty acids, i.e. linoleic acid and oleic acid (NR₂₅, and NR₃₅) and N, P and K uptake (NR₂₀, and NR₂₂). There were noticeable differences among the treatments in terms of essential fatty acid, oil, and mineral nutrient content. The study demonstrates the potential benefits of using indigenous Bradyrhizobium strains in order to achieve high quality soybean seeds that can be used as a balanced health product.