Interaction Amongst Soybean [Glycine max (L.) Merrill] Genotype, Soil Type and Inoculant Strain with Regard to N2 Fixation |
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| Authors: | C M van Jaarsveld M A Smit & G H J Krüger |
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| Institution: | School of Environmental Sciences and Development, Potchefstroom University for Christian Higher Education, Potchefstroom 2520, South Africa,;A.R.C. Grain Crops Institute, P/Bag X1251, Potchefstroom 2520, South Africa,;present address: Department of Botany, University of Zululand, P/Bag X1001, Kwadlangezwa 3886, South Africa,;present address: SASEX, P/Bag 02, Mount Edgecombe, South Africa |
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| Abstract: | The nitrogen (N2)‐fixing bacterial inoculant strain for soybean Glycine max (L.) Merrill] is not indigenous to South African soils. The interaction between soybean genotype, soil type and inoculant strain, however, has a definite influence on soybean production and compatibility should be optimized. This paper reports a growth chamber study using three different soybean genotypes (Barc‐9, Avuturda and Talana), three Bradyrhizobium japonicum inoculant strains (WB108, WB112 and WB1) and three soil types (Avalon, Arcadia and sand) to evaluate the effectiveness of N2 fixation by different genotype × soil type × inoculant strain combinations, using different measuring parameters. These parameters included nodule fresh mass (NFM), amount of N2 fixed (Pfix), as determined by the ureide method, seed protein content (SPC), average seed mass per plant (SMP) and average foliar N content (FNC). The comparison amongst the three‐way interactions, genotype × soil type × inoculant strain, did not differ significantly for the parameters used. Significant two‐way interactions were soil × inoculant for FNC, Pfix and SMP; soil × genotype for FNC and SMP, and inoculant × genotype for FNC (P < 0.05). The soil × inoculant strain interaction was significant for Pfix (P < 0.05). NFM, Pfix, FNC, SMP and SPC correlated positively with soil pH and negatively with soil clay content and soil NO3– and NH4+ content (P < 0.05). SPC was significantly different (P < 0.05) for soil type, genotype and inoculant strain. Pfix and NFM did not reflect the protein content of the seeds, indicating that nodule evaluation should be used with caution as a N2 fixation parameter. Low soil pH and high mineral N content inhibited N2 fixation. NFM correlated negatively with the clay content of the soil. This finding confirms that soybean production in South Africa can be improved by appropriate selection of genotypes and inoculant strains for their compatibility in different soils. |
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| Keywords: | Bradyrhizobium inoculant strains N2 fixation nodulation protein content soil types soybean [Glycine max (L ) Merrill] genotypes |
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