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Apr 30, 2022Keywords:
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Main Article Content
Assessment of Nitrogen Fixation of Soybean [Glycine max (L). MERR] in a Sodic Ferric Luvisol of the Nigerian Sudan Savanna
Abstract
Agricultural practices under irrigation have negatively affected production of grain legumes due to salt stress; because ability to fix nitrogen is hampered by either salinity, sodicity or both. A field study was undertaken with Soybean (TGx 1904-6F) at the Irrigation Research Farm of Institute for Agricultural Research (IAR), Kadawa, Kano in the Sudan savanna to assess the effect of soil sodicity, nitrogen and phosphorus fertilizer application on biological nitrogen fixation (BNF). Sodic and non- sodic soils (control) each were cultivated. The treatments consist of two levels of nitrogen (0 and 20kgNha-1) applied as urea, and four levels of phosphorus fertilizers (0, 6.6, 13.2, 26.4 kgPha-1) applied as single super phosphate, while maize (Zea mays) variety SAMMAZ 14) was used as reference crop for estimating biological nitrogen fixation. The treatments were laid out in a randomized complete block design with levels of N and P in a factorial combined and replicated thrice. Nodule number and nodule weight of soybean was increased in sodic soils at 6WAP by 64.94% (nodule number)and at 8 WAP (88.12% and 50%) for nodule number and weight respectively; suggesting tolerance of native levels of Bradyrhizobium sp. were much higher. Nitrogen fixation was depressed by 13.10% and 64.67% and Ndfa increased at 6WAP by 15% and decreased by 3.22% at 8WAP due to sodicity. Increasing levels of N increased soybean nodulation by 52.94% and 51.32% and N2 fixation by 13.87% and 2.77% at 6 and 8 WAP respectively. Application of 26.4kgPha-1 gave the highest nodulation and %Ndfa at both at 6 and 8WAP, while13.2 kgPha-1gave the highest amount of N2 fixed (103.10 and 102.99 kgNha-1) respectively. This suggests that the soil P level was adequate for the indigenous strains of rhizobia to produce nodules.
