Single and Multistrain Rhizobial Inocula for Pinto and Black Bean Cultivars

ABSTRACT

Common bean (Phaseolus vulgaris L.) is relatively poor in dinitrogen (N₂) fixation, so selecting compatible host cultivar and Rhizobium strain combinations may offer an improvement. The effectiveness of six rhizobial strains was evaluated using five bean cultivars of bean (three pinto and two black bean) in a growth-room experiment. We subsequently selected the three best strains to assess whether multi-strain inoculation had advantages over single-strain inoculation in growth-room and field experiments. In the first-growth-room experiment, Rhizobium strains UMR 1899, RCR 3618, and USDA 2676 were selected for high nodulation, plant dry weight, shoot nitrogen (N), and N₂ fixation. In a second growth-room experiment, the individual strains and a mixture of the three strains generally did not differ in the parameters evaluated. Total shoot N accumulated ranged from 172.9 to 162.8 mg plant^?1, of which 32.1% to 33.6% (equivalent to 54.0 to 59.2 mg plant^{? 1}) was fixed. In field experiments, plant biomass and seed N₂ fixed did not differ among the inoculants at any site. These results suggest that the three strains were equally effective and that the multi-strain inoculant offered no consistent advantage over the single-strain inoculants.     

Comparative efficieny of Rhizobium/Bradyrhizobium spp. strains in nodulating Cajanus cajan in relation to characteristic metabolic enzyme activities

The comparative symbiotic properties of Rhizobium spp. and Bradyrhizobium spp. strains infecting pigeon pea were evaluated. Bradyrhizobium strains (Cajanus) were found to be superior to Rhizobium strains (Cajanus) and the superiority was ascertained to be due to the higher enzyme activity of the tricarboxylic acid (TCA) cycle in comparison to Rhizobium spp. strains. Moreover, metabolic superiority or rapid growth rate does not necessarily correlate with symbiotic effectiveness. The symbiotic performance of isolates varied with the host cultivar. The dry matter accumulation could be correlated with the total acetylene reduction activities rather than nodule number or nodule fresh weight per plant. Received: 3 March 1993     

Host specificity and phenotypic diversity of Rhizobium strains nodulating Leucaena, Acacia, and Sesbania in Egypt

Phenotypic diversity was studied among 13 Rhizobium strains selected from a total of 160 Rhizobium isolates from root nodules of Leucaena leucocephala. Two strains from Acacia saligna and two strains from Sesbania sesban plants were included in the examination for host range in the greenhouse. The Rhizobium sp. (Leucaena) strains were different from the reference strains and fell into three distinct groups for the utilization of 95 different carbon sources. Four of the best symbionts constituted a group, the majority of the strains fell into a second group, and strain DS 91 was the only member of the third group. Strains were effective symbionts for their original hosts. Nine strains were tolerant to elevated temperature (>42°C), and three strains were resistant to high salinity (>3% NaCl). All Rhizobium sp. (Leucaena) strains effectively nodulated L. leucocephala and L. culensii, but nitrogen fixation was greater with L. leucocephala than with L. culensii. These strains failed to form effective symbioses with two other species of Leucaena (L. retusa and L. divursiflora) or with alfalfa, Medicago sativa. Rhizobium sp. (Leucaena) strains DS 65, DS 78, and DS 158 nodulated and efficiently fixed nitrogen with Phaseolus vulgaris, with DS 65 showing the highest symbiotic capability. Strain DS 65 also nodulated and fixed nitrogen with Glycine max and Vigna sinensis. Nodulation of Leucaena by two Bradyrhizobium sp. (Acacia) strains was sparse. Strain DS 101 from Sesbania formed nodules on Leucaena, whereas the other strain from Sesbania, DS 110, failed to nodulate this genus. Received: 30 September 1996     

Efficiency of N2 fixation in Vicia faba L. in combination with different Rhizobium leguminosarum strains

The efficiency of symbiotic dinitrogen (N₂) fixation in Vicia faba L. in combination with 3 different Rhizobium leguminosarum strains was studied in a pot experiment during vegetative and reproductive growth. The objective of the experiments was to assess variability among Rhizobium strains inoculated on single legume species and determine possible reasons for observed variations. Dry matter formation, N₂ fixation and the carbon (C) costs of N₂ fixation were determined in comparison with nodule free plants grown with urea. Nodule number and the capacity of different respiratory chains in the nodules were also measured. The plants inoculated with the Rhizobium strain A 37 formed less dry matter and fixed less N compared to the other two Rhizobium strains (Vic 1 and A 150). This coincided with a lower number of nodules and higher C costs of N₂ fixation. The C costs for N₂ fixation were in all cases significantly lower during reproductive growth compared to vegetative growth. Neither the latter nor the differences in C expenditure for N₂ fixation between the Rhizobium strains could be explained in terms of differences or shifts in the capacity of different respiratory chains in the nodules.     

PLANT GROWTH PROMOTING RHIZOBACTERIA INCREASE GROWTH,YIELD AND NITROGEN FIXATION IN PHASEOLUS VULGARIS

Nitrogen (N) fixation by legume-Rhizobium symbiosis is important to agricultural productivity and is therefore of great economic interest. Growing evidence indicates that soil beneficial bacteria can positively affect symbiotic performance of rhizobia. The effect of co-inoculation with plant growth-promoting rhizobacteria (PGPR) and Rhizobium, on nodulation, nitrogen fixation, and yield of common bean (Phaseolus vulgaris L.) cultivars was investigated in two consecutive years under field conditions. The PGPR strains Pseudomonas fluorescens P-93 and Azospirillum lipoferum S-21 as well as two highly effective Rhizobium strains were used in this study. Common bean seeds of three cultivars were inoculated with Rhizobium singly or in a combination with PGPR to evaluate their effect on nodulation and nitrogen fixation. A significant variation of plant growth in response to inoculation with Rhizobium strains was observed. Treatment with PGPR significantly increased nodule number and dry weight, shoot dry weight, amount of nitrogen fixed as well as seed yield and protein content. Co-inoculation with Rhizobium and PGPR demonstrated a significant increase in the proportion of nitrogen derived from atmosphere. These results indicate that PGPR strains have potential to enhance the symbiotic potential of rhizobia.     

Diversity of <Emphasis Type="Italic">Trifolium ambiguum</Emphasis>—nodulating rhizobia from the lower Caucasus

Kura clover (Trifolium ambiguum M.B.) is a perennial rhizomatous forage legume whose use is currently limited by difficulties in its establishment in part attributable to nodulation problems and very specific rhizobial requirements. A limited number of Kura clover-nodulating rhizobial strains are currently available and many have a limited effectiveness. In this study, 128 rhizobia were isolated from four sites in the center of origin of Kura clover (i.e., two in Azerbaijan, one in Armenia, and one in Northwest Iran) using the three ploidy levels of Kura clover (diploid, tetraploid, and hexaploid), red clover (Trifolium pratense L.), and white clover (Trifolium repens L.) plants as trap hosts. Rhizobia were fingerprinted using repetitive extragenic palindromic polymerase chain reaction (BOXA1R primer) and their genetic diversity was measured using the Shannon-Weaver diversity index. The nodulation specificity and phenotypic diversity of a subset of 13 isolates was determined. Genetic diversity among the 128 isolates was large and similar for rhizobia grouped according to their geographic origin or original host plant. Phenotypic diversity was significant; percentage of similarity among 13 isolates ranging between 38 and 92%. Nodulation specificity of the Kura clover-nodulating rhizobial isolates studied was less complex and not as clearly delineated as previously reported. Some strains originally isolated from Kura clover could effectively nodulate more than one ploidy level of Kura clover and even one or both of two other Trifolium species (i.e., red clover and white clover). Three strains formed effective nodules on both Kura clover and white clover; however, none promoted plant growth of both species to levels currently obtained with commercial inoculants when evaluated in a growth chamber. Rhizobial isolates that are highly effective with both species have yet to be identified.     

Response of the pigeonpea-Rhizobium symbiosis to salinity stress: variation among Rhizobium strains in symbiotic ability

Summary There were significant differences among pigeonpea [Cajanus cajan (L.) Millsp] Rhizobium sp. strains (IC 3506, IC 3484, IC 3195, and IC 3087) in their ability to nodulate and fix N₂ under saline conditions. Pigeonpea plants inoculated with IC 3087 and IC 3506 were less affected in growth by salinity levels of 6 and 8 dS m^-1 than plants inoculated with the other strains. For IC 3506, IC 3484, and IC 3195, there was a decrease in the number of nodules with increasing salinity, while the average nodule dry weight and the specific nitrogenase activity remained unaffected. However, in IC 3087, the number of nodules increased slightly with increasing salinity. Leaf-P concentrations increased with salinity in the inoculated plants irrespective of the Rhizobium sp. strain, and leaf-N concentrations decreased with increasing salinity in IC 3484 and IC 3195 only. Shoot-Na and-Cl levels were further increased in these salt-sensitive strains only at 8 dS m^-1. Therefore there may be scope for selecting pigeonpea Rhizobium sp. symbioses better adapted to saline conditions. The Rhizobium sp. strains best able to form effective symbioses at high salinity levels are not necessarily derived from saline soils.Submitted as JA No. 919 by the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT)     

<Emphasis Type="Italic">Rhizobium</Emphasis>,<Emphasis Type="Italic"> Bradyrhizobium</Emphasis> and<Emphasis Type="Italic"> Agrobacterium</Emphasis> strains isolated from cultivated legumes

The present study was conducted to isolate and characterize rhizobial strains from root nodules of cultivated legumes, i.e. chickpea, mungbean, pea and siratro. Preliminary characterization of these isolates was done on the basis of plant infectivity test, acetylene reduction assay, C-source utilization, phosphate solubilization, phytohormones and polysaccharide production. The plant infectivity test and acetylene reduction assay showed effective root nodule formation by all the isolates on their respective hosts, except for chickpea isolate Ca-18 that failed to infect its original host. All strains showed homology to a typical Rhizobium strain on the basis of growth pattern, C-source utilization and polysaccharide production. The strain Ca-18 was characterized by its phosphate solubilization and indole acetic acid (IAA) production. The genetic relationship of the six rhizobial strains was carried out by random amplified polymorphic DNA (RAPD) including a reference strain of Bradyrhizobium japonicum TAL-102. Analysis conducted with 60 primers discriminated between the strains of Rhizobium and Bradyrhizobium in two different clusters. One of the primers, OPB-5, yielded a unique RAPD pattern for the six strains and well discriminated the non-nodulating chickpea isolate Ca-18 from all the other nodulating rhizobial strains. Isolate Ca-18 showed the least homology of 15% and 18% with Rhizobium and Bradyrhizobium, respectively, and was probably not a (Brady)rhizobium strain. Partial 16S rRNA gene sequence analysis for MN-S, TAL-102 and Ca-18 strains showed 97% homology between MN-S and TAL-102 strains, supporting the view that they were strains of B. japonicum species. The non-infective isolate Ca-18 was 67% different from the other two strains and probably was an Agrobacterium strain.     

Ex planta nitrogenase induction and uptake hydrogenase in Rhizobium Sp. (cowpea miscellany)

Rhizobium strains of the cowpea miscellany nodulating green gram [Vigna radiata (L.) (Wilczek)], black gram [V. mungo (L.) (Hepper)], cowpea [V. mguiculata (L.)], pigeon pea [Cajanus cajan (L.)], cluster bean [Cyamposis tetragonoloba (L.) (Taub.)] and chick pea [Cicer wietinum (L.)] were studied to find a method to detect uptake hydrogenase (Hup) under cultural conditions. Triphenyl tetrazolium chloride and methylene blue reduction tests were found to be ambiguous as known Hup⁺ and Hup⁻Rhizobium strains of these crops reduced the dyes non-specifically in a culture medium with the addition of different carbon substrates. Hydrogen uptake studies in cultures grown in medium containing low concentrations of carbon substrates showed that uptake of H₂ was below the detection limits. It was found that Hup⁺Rhizobium strains of these legumes invariably expressed nitrogenase under cultural conditions but not the Hup⁻ strains. Characterization of native Rhizobium on the basis of ex planta nitrogenase induction showed that 94% of the ex planta nitrogenase positive isolates were of Hup⁺ phenotype, whereas all the ex planta nitrogenase negative isolates were of Hup⁻ phenotype in nodules. The expression of nitrogenase under cultural conditions was therefore, found to be a reliable method for identification of Rhizobium strains for Hup⁺ phenotype among the rhizobia of the “cowpea miscellany”.     

Synergistic effects of plant-growth promoting rhizobacteria and Rhizobium on nodulation and nitrogen fixation by pigeonpea (Cajanus cajan)

Plant‐growth promoting rhizobacteria (PGPR), in conjuction with efficient Rhizobium, can affect the growth and nitrogen fixation in pigeonpea by inducing the occupancy of introduced Rhizobium in the nodules of the legume. This study assessed the effect of different plant‐growth promoting rhizobacteria (Azotobacter chroococcum , Azospirillum brasilense, Pseudomonas fluorescens, Pseudomonas putida and Bacillus cereus) on pigeonpea (Cajanus cajan (L) Milsp.) cv. P‐921 inoculated with Rhizobium sp. (AR‐2–2 k). A glasshouse experiment was carried out with a sandy‐loam soil in which the seeds were treated with Rhizobium alone or in combination with several PGPR isolates. It was monitored on the basis of nodulation, N₂ fixation, shoot biomass, total N content in shoot and legume grain yield. The competitive ability of the introduced Rhizobium strain was assessed by calculating nodule occupancy. The PGPR isolates used did not antagonize the introduced Rhizobium strain and the dual inoculation with either Pseudomonas putida, P. fluorescens or Bacillus cereus resulted in a significant increase in plant growth, nodulation and enzyme activity over Rhizobium‐inoculated and uninoculated control plants. The nodule occupancy of the introduced Rhizobium strain increased from 50% (with Rhizobium alone) to 85% in the presence of Pseudomonas putida. This study enabled us to select an ideal combination of efficient Rhizobium strain and PGPR for pigeonpea grown in the semiarid tropics.     

Co-selection of compatible rhizobia and vesicular-arbuscular mycorrhizal fungi for cowpea in sterilized and non-sterilized soils

Summary We selected two isolates of Rhizobium for cowpea (Vigna unguiculata) with sterilized soil tests and two different isolates by non-sterilized soil testing. The four rhizobia were then paired individually with either Glomus pallidum, Glomus aggregatum, or Sclerocystis microcarpa in separate, sterilized, or non-sterilized soil experiments. The purpose of the experiments was to determine the effect of soil sterilization on the selection of effective cowpea rhizobia, and to see whether these rhizobia differed in their effects on cowpea growth when paired with various vesicular-arbuscular mycorrhizal (VAM) fungi. Our experiments showed that the rhizobia selected in sterilized soil tests produced few growth responses in the cowpea compared to the other introduced rhizobia, irrespective of pairing with VAM fungi in sterilized or non-sterilized soil. In contrast, the two rhizobia initially selected by non-sterilized soil testing significantly improved cowpea growth in non-sterilized soil, especially when paired with G. pallidum. Our results suggest that it is important to select for effective rhizobia in non-sterilized soil, and that pairing these rhizobia with specific, coselected VAM fungi can significantly improve the legume growth response.     

The Effect of Soil pH on Nodulation and N2-Fixation of Winged Bean Psophocarpus tetragonolobus (L) D.C. Rhizobium Strains

Nine effective Rhizobium strains of winged bean were tested for their symbiotic performance under different soil pH levels. In general, they performed best at soil pH 5.5. The performance of all the strains was poor when soil pH was either extremely low as 4.5 or high as 7.5. The strains RRIM 56, KUL-JN, KUL-Z₃ were suitable for soils with a pH range of 5.5 to 6.0. The strains KUL-Z₁, KUL-Z₂ and KUL-GP could be only used in soils with a pH of 5.5. The strains KUL-BH, KUL-6.2Z and KUL-6.9Z could be used for inoculation of soils with high pH. Isolating strains of Rhizobium by altering the original pH of the soil of Rhizobium isolation would be a good practice to obtain strains with desirable pH tolerance.     

Competition between Winged Bean Psophocarpus tetragonolobus (L) D.C. Rhizobium Strains for Nodulation

The competitiveness of several effective winged bean Rhizobium strains for nodulation was assessed in a glass house experiment with paired and multi-strain inoculations. The strains varied in their competitive abilities when applied as mixed inocula. The strains KUL-BH, KUL-Z₃, KUL-JN and KUL-GP were more competitive than the strain RRIM 56. The strain KUL-GP was more competitive than the strain KUL-JN. The strains KUL-BH and KUL-GP had relatively high competitiveness. The multi-strain inoculum consisting of Rhizobium strains RRIM 56, KUL-BH, KUL-JN, KUL-GP and KUL-Z₃ was equally effective as the single strain inoculations and thus the multi-strain inoculum could be used in field practice. The broth and the peat multi-strain inocula were equally effective.     

Comparison of symbiotic effectiveness of Rhizobium sp. with positive hydrogen-uptake activity compared with negative mutants in relation to nitrogen fixation in mungbean (Vigna radiata L.)

H₂ uptake activity was well distributed in Rhizobium sp. strains isolated from nodules of mung-bean (Vigna radiata L.). Two effective strains, RMP1 und RMP2, exhibiting significantly higher H₂ uptake activity were subjected to mutagenesis with nitrosoguanidine. The respective mutation frequencies were 0.18 and 0.19%. Three Hup^- mutants each of RMP1 und RMP2 were compared with the wild-type parent strains under pot culture experiments to evaluate the significance of the H₂ uptake system in biological N₂ fixation. Nodulation capabilities, plant growth characteristics, and the chlorophyll content of the leaves were significantly reduced in the plants treated with Hup^- mutants. Nitrogenase activity in Hup^- nodules was reduced by 8–41%. Similarly, N accumulation was also reduced singificantly.     

Nitrogen-fixing potential of Acacia mangium and Acacia auriculiformis seedlings inoculated with Bradyrhizobium and Rhizobium spp.

Summary Two Australian Acacia species, A. mangium and A. auriculiformis were inoculated in vitro with eight strains of Bradyrhizobium spp. and two strains of Rhizobium spp. On the two plant species, only Bradyrhizobium spp. strains formed effective N₂-fixing nodules. A. mangium, which nodulates effectively with a restricted range of Bradyrhizobium spp. strains, is a specific host compared to A. auriculiformis. A. auriculiformis is assumed to be a promiscuous host because it nodulates effectively with a wide range of Bradyrhizobium spp. strains. Nodule efficiency as expressed by the ratio of N₂ fixed to nodule dry weight appeared to be higher in A. auriculiformis (0.44–0.81) than in A. mangium (0.23–0.55).     

Antifungal and Plant Growth Promoting Activities of Indigenous Rhizobacteria Isolated from Maize (Zea mays L.) Rhizosphere

Plant growth promoting rhizobacteria (PGPR) enhance the plant growth directly by assisting in nutrient acquisition and modulating plant hormone levels, or indirectly by decreasing the inhibitory effects of various pathogens. The aim of this study was to select effective PGPR from a series of indigenous bacterial isolates by plant growth promotion and antifungal activity assays. This study confirmed that most of the isolates from maize rhizosphere were positive for PGPR properties by in vitro tests. Azotobacter and Bacillus isolates were better phosphate solubilizers and producers of lytic enzymes, hydrocyanic acid (HCN), and siderophores than Pseudomonas. Production of indole-3-acetic acid (IAA) and antifungal activity were the highest in Azotobacter, followed by Bacillus and Pseudomonas. The most effective Azotobacter isolates (Azt₃, Azt₆, Azt₁₂) and Bacillus isolates (Bac_10, Bac₁₆) could be used as PGPR agents for improving maize productivity. Further selection of isolates will be necessary to determine their efficiency in different soils.     

Nodulation and growth of black locust (Robinia pseudoacacia) on a desurfaced soil inoculated with a local Rhizobium isolate

Nodulation and nitrogen fixation of black locust (Robinia pseudoacacia L.), a legume tree broadly used in Argentina for urban and agricultural afforestation, was studied in hydroponic culture. The development of seedlings inoculated with a local strain of Rhizobium, highly specific for R. pseudoacacia, was also compared with respect to non-inoculated but N-fertilised seedlings. This strain produced fast nodulation and high crop yield and leaf N content. Already nodulated plants with the local Rhizobium strain were assayed for growth in a greenhouse pot experiment with soil from a field where topsoil has been removed for industrial purposes, whilst pots with non-desurfaced soil from the same field were used as control. Non-inoculated plants were also grown in either control or desurfaced soil. Inoculated plants developed better than non-inoculated plants in desurfaced soil, and in control soil as well, suggesting that the symbiosis was able to overcome the nutrient limitation of the desurfaced soil. Non-inoculated plants were nodulated by native soil born Rhizobium, either in control or desurfaced soil, but they showed low final nitrogen leaf content and low nitrogen fixation activity, suggesting that native rhizobia were ineffective.     

Alleviation of drought stress in the common bean (Phaseolus vulgaris L.) by co-inoculation with Paenibacillus polymyxa and Rhizobium tropici

A greenhouse experiment was performed to evaluate the influence of Rhizobium when co-inoculated with each of two Paenibacillus polymyxa strains, singly and in mixture on growth, nitrogen content, phytohormone levels and nodulation of the common bean (Phaseolus vulgaris L.) under three levels of drought stress. Stress was applied continuously by the control of matric potential (ψ_m) through a porous cup. Bean plants cv. Tenderlake were grown in pots with Fluvic Neosol eutrophic soil under three different ψ_m (S₁ −7.0; S₂ −70.0 and S₃ < −85 kPa). The seeds were inoculated with Rhizobium tropici (CIAT 899) and each of P. polymyxa (DSM 36) and P. polymyxa Loutit (L) singly and in mixture (CIAT 899 + DSM36 + Loutit). Co-inoculation of bean with Rhizobium and both Paenibacillus strains resulted increased plant growth, nitrogen content and nodulation compared to inoculation with Rhizobium alone. This was particularly evident at the most negative ψ_m (S₃ < −85 kPa) we used. Drought stress triggered a change in phytohormonal balance, including an increase in leaf abscisic acid (ABA) content, a small decline in indole acetic acid (IAA) and gibberellic acid (GA₃) and a sharp fall in zeatin content in bean leaves. The content of endogenous Cks decreased under water stress, possibly amplifying the response of shoots to increasing ABA content. We hypothesize that co-inoculation of bean with R. tropici (CIAT 899) and P. polymyxa strains (DSM 36) and Loutit (L) mitigates some of the negative effects of drought stress on bean.     

A microcosm study on the influence of pH and the host-plant on the soil persistence of two alfalfa-nodulating rhizobia with different saprophytic and symbiotic characteristics

The acid tolerance of Sinorhizobium meliloti in culture media and in soils is considered a useful criteria to select for strains with improved survival in agricultural acidic soils. Using a glass tube system with gamma-irradiated soil at different pH values, we analysed the survival of two different alfalfa-nodulating rhizobia: S. meliloti (pH_limit for growth 5.6–6.0) and the acid-tolerant Rhizobium sp. LPU83, closely related to the strain Rhizobium sp. Or191 (pH_limit for growth below 5.0). Although the acid-tolerant rhizobia showed a slightly better survival during the first months in acid soil (pH=5.6), none of the strains could be detected 2 months after inoculation (bacterial counts were below 10³ colony-forming units (cfu)/30 g of soil). The inclusion of two alfalfa plants/glass tube with soil, however, supported the persistence of both types of rhizobia at pH 5.6 for over 2 months with counts higher than 9×10⁶ cfu/30 g of soil. Remarkably, in the presence of alfalfa the cell densities reached by S. meliloti were higher than those reached by strain LPU83, which started to decline 1 week after inoculation. Although more acid-sensitive in the culture medium than the Or191-like rhizobia, in the presence of the host plant the S. meliloti strains showed to be better adapted to the free-living condition, irrespective of the pH of the soil.     

Soil fertility effects with tripartite symbiosis for growth,nodulation and nitrogenase activity of vicia faba L

Fababean (Vicia faba L.) is one of the oldest known important grain legume food crops grown within the temperate and subtropical regions of the world. This species is adapted for both forage and food grain production as a cool season annual crop on a wide range of soil and climatic conditions with effective tripartite symbiosis. Both Rhizobium and endophyte mycorrhiza are essential for high levels of production and symbiotic N₂ fixation. The objective of these greenhouse and field studies was to determine effects of Glomus fasciculatum colonization with soil fertility treatments to a Psammentic Paleustalf (Eufaula series) on growth, nodulation, nitrogenase activity and nodule composition for V. faba, var. Major, fuh Rumi (Nile) inoculated with R. leguminosarum Frank.

Top growth and nodule mass were increased approximately 10 fold and nitrogenase activity about 7 fold with the highly significant effect of mycorrhiza and response to low soluble Ca₃(PO₄)₂ fertilization in greenhouse studies. With both effective mycorrhiza and Rhizobium inoculation in the field experiments, seed yields were correlated with top growth (r = 0.841). Phosphorus and Ca fertilization resulted in highly significant increases in seed yields. Nitrogenase activity was correlated with nodule wt. (r = 0.958) and highly significant increases resulted with P and Ca soil amendment. Plant nutrient element composition of nodules increased with the fertilization treatments for P, Ca and increased K levels. Sodium content decreased significantly with increased K fertilization (r = ‐0.846). Potassium composition increased significantly with P content (r = 0.523). Enhanced N₂‐fixation along with increased high protein forage and food grain production with Fababeans have much potential. However, soil fertility and management techniques for improved production include effective mycor‐rhizal colonization.