Effects of co-inoculation of Bradyrhizobium japonicum SAY3-7 and Streptomyces griseoflavus P4 on plant growth,nodulation, nitrogen fixation,nutrient uptake,and yield of soybean in a field condition

ABSTRACT

Co-inoculation of nitrogen-fixing bacteria with plant growth-promoting bacteria has become more popular than single inoculation of rhizobia or plant-growth-promoting bacteria because of the synergy of these bacteria in increasing soybean yield and nitrogen fixation. This study was conducted to investigate the effects of Bradyrhizobium japonicum SAY3-7 and Streptomyces griseoflavus P4 co-inoculation on plant growth, nodulation, nitrogen fixation, nutrient uptake, and seed yield of the ‘Yezin-6’ soybean cultivar. Nitrogen fixation was measured using the acetylene reduction assay and ureide methods. Uptake of major nutrients [nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg)] was also measured. This study showed that single inoculation of SAY3-7 significantly increased shoot biomass; nodulation; Relative Ureide Index (RUI %), percent nitrogen derived from N fixation (% Ndfa); N, P, K, Ca, and Mg uptakes; during the later growth stages (R3.5 and R5.5), compared with control. These observations indicate that SAY3-7 is an effective N-fixing bacterium for the plant growth, nodulation, and nitrogen fixation with an ability to compete with native bradyrhizobia. Co-inoculation of SAY3-7 and P4 significantly improved nodule number; nodule dry weight; shoot and root biomass; N fixation; N, P, K, Ca, and Mg uptake; at various growth stages and seed yield in ‘Yezin-6’ soybean cultivar compared with the control, but not the single inoculation treatments. Significant differences in plant growth, nodulation, N fixation, nutrient uptake, and yield between co-inoculation and control, not between single inoculation and control, suggest that there is a synergetic effect due to co-inoculation of SAY3-7 and P4. Therefore, we conclude that Myanmar Bradyrhizobium strain SAY3-7 and P4 will be useful as effective inoculants in biofertilizer production in the future.     

Growth and yield of soybean varieties inoculated with <Emphasis Type="Italic">Bradyrhizobium</Emphasis> spp in N-deficient calcareous soils

This research reports the effect of Bradyrhizobium spp strains on dry matter yield, nodulation and seed yield of soybean varieties grown in N-deficient soil in Uzbekistan in pot and field experiments, in 2001 and 2002. The results of experiments revealed that significant positive effects on growth, nodule number and yield of soybean were obtained after inoculation with Bradyrhizobium spp strains; and, generally, strains S62 and S63 were more effective than strain S61. The protein content of seeds also increased after inoculation. Both Orzu and Uzb2 soybean varieties gave a higher response than the Uzb6 variety.     

Nitrogen Fertilization of Soybean Affects Root Growth and Nodulation on Two Soil Types in Mississippi

Greenhouse studies were conducted to evaluate the influence of nitrogen (N) sources [urea + ?N-(n-butyl) thiophosphoric triamide, NBPT (urease inhibitor) and polymer-coated urea (PCU)] and rates on soybean root characteristics, nodule formation, and biomass production on two soil types (silt loam and clay) commonly cropped to soybean in Mississippi. About 15% less belowground biomass was produced in clay soil than in silt loam soil directly corresponding to all other root parameters including root length, root area, root diameter, and nodule number. Pooled across N rates, N additions resulted in 19% and 52% decrease in belowground biomass and number of nodules, respectively, across soils compared to soybean receiving no N. The N rate was the most critical factor as it influenced all root growth parameters. Number of nodules were 24% greater with PCU than urea + NBPT. Nitrogen additions and clay soil negatively impacted soybean root growth, nodulation, and belowground biomass production.

Abbreviations: Polymer-coated urea, PCU; N-(n-butyl) thiophosphoric triamide, NBPT     

Mineral nitrogen impairs the biological nitrogen fixation in soybean of determinate and indeterminate growth types

Soybean (Glycine max Merrill) crop production in Brazil relies mainly on biological nitrogen fixation (BNF) for nitrogen (N) supply. Recent adoption of indeterminate growth-type genotypes has raised doubts on the need for supplemental mineral N that might negatively affect the BNF. We assessed the effects of mineral N on BNF attributes of soybean genotypes grown in central and southern Brazil. Genotypes were inoculated with Bradyrhizobium sp. and/or received mineral N in three sets of experiments. In the first set, two genotypes received increasing rates of mineral N in nutrient solution, which consistently reduced the BNF. In the second set, mineral N applied at sowing and/or topdressing reduced nodulation and ureides-N in determinate and indeterminate growth-type genotypes. In the third set, mineral N applied at R5.3 stage, foliar or as topdressing, did not increase grain yield in four field experiments. Mineral N impaired BNF irrespective of the growth type and had no effect on grain yield.     

Iron requirement for soybean [Glycine max (L.) Merrill] inoculated with selected exotic and native isolates of Bradyrhizobium sp. under irrigated conditions

A field and greenhouse experiments were conducted to determine the requirement of Fe nutrient supplied through foliar and soil application in soybean inoculated with different selected isolates of exotic and native Bradyrhizobium spp. in saline soils. Six soybean genotypes and three Bradyrhizobium spp. were used for the greenhouse experiments, whereas only two soybean genotypes, namely TGx-1336424 and GIZA, were selected for further study under field conditions. Two levels of FeSO₄ (0 and 4 mg Fe kg^?1 soil) directly supplied to the soil and three levels of Fe-ethylenediaminetetraacetic acid (0–2% of Fe) through foliar application were used for greenhouse and field experiments, respectively. The results of the greenhouse experiment indicated a non-significant effect of Fe application on nodulation and shoot biomass in soybean. Fe application did not improve the grain yield and total biomass yield in soybean inoculated with UK isolate and local isolate but showed remarkable improvement with TAL-379. High soil native N might be the cause for insignificant effect of Fe applied at 2% in highly effective inoculated plants. Therefore, it can be concluded that the symbiotic effectiveness of Bradyrhizobium sp. and the native soil N would affect the soybean Fe requirement supplied through foliar application.     

Potential for enhancement of root growth and nodulation of soybean co-inoculated with Azospirillum and Bradyrhizobium in laboratory systems

The potential enhancement of root growth and nodulation in vegetable soybean (AGS190) was studied with application of Azospirillum brasilense (Sp7) and A. lipoferum (CCM3863) co-inoculated with two Bradyrhizobium japonicum strains (TAL102 and UPMR48). Significant root growth stimulation and nodulation were observed in Azospirillum as well as during its co-inoculation with Bradyrhizobium. Nodule formation is linked with the initiation of new roots; nodules were almost absent even in Bradyrhizobium inoculated plant due to the absence of new roots development in clipped rooted seedlings. Total root length, root number, specific root length, root dry matter, root hair development and shoot dry matter were significantly increased by Azospirillum alone and its co-inoculum. Co-inoculated plants significantly influenced the number of nodules and its fresh weight. A. brasilense seemed to perform better in root growth and nodule development compared to A. lipoferum.     

Effects of residual and applied κ on soybean nodulation,root growth,pod formation and K and N composition

Abstract

Inoculated soybeans (Glycine max L. Merr. cv. Eragg) were grown in an intensively managed cabbage (Brassica oleracea L. Capitata group)‐ sweetcorn (Zea mays L.) multiple‐cropping sequence on a tile‐drained Arenic Haplaquod having variable residual K levels. The study was conducted to assess the effect of residual and applied K on soybean K and N composition, nodulation, root growth, and pod formation. Sidedress treatments of 0 and 100 kg K/ha were applied at bloom to plots that received either 0 or 300 kg K/ha/acre that had been applied previously to other crops in the sequence. Treatments were arranged in a randomized complete block design witn six replications. Although leaf N conc, was uniform at bloom (R2), leaf N at pod‐fill (R6) ranged from 2.8 to 4.3% and wasquadratically related to leaf K (r² = 0.92). Without residual K fertilizer from cabbage and sweet corn applications sidedress application of K increased leaf and nodule K and N. Root K conc. was correlated with root dry wt. (r = 0.35) at bloom stage, and with root 10 dry wt. (r = 0.54), pod number (r = 0.43), and pod dry wt. (r = 0.39) at pod‐fill stage. Root K conc. was negatively correlated with nodule number (r = ‐0.34) and nodule dry wt. (r = ‐0.41). Sidedress‐applied K did not increase root growth and pod number whereas residual fertilizer K did. A curvilinear relationship between leaf K and N conc. and a linear relationship between leaf N and soybean yield indicated that K deficiency limited the capacity of the soybean plant to supply N to the developing grain during pod‐fill, and that this response was not due to inadequate nodulation.     

Silicon effect on growth,nutrient uptake,and yield of peanut (Arachis hypogaea L.) under aluminum stress

Abstract

The objective of this study was to investigate the effect of silicon (Si) on growth, nutrient uptake, and yield of peanut under aluminum (Al) stress. Peanut (Arachis hypogaea L. cv. Zhonghua 4) raised with or without Si (1.5?mM) in the growth chamber under 0 and toxic Al (0.3?mM) levels. Aluminum stress significantly decreased the biomass and root dry weight by 12.9% and 10.7%, and the pod yield, number of mature pod per plant and seed number of per pod by 16.7%, 10.7%, and 13.9%. The content of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg) was significantly decreased, but that of Al increased markedly in shoots and roots of peanut after Al exposure at seedling, flower-needle and pod-setting stage. Under Al stress condition, Si application protected peanut by improving nutrient uptake at different growth stages and favoring the partitioning of dry mass to pod and the allocation of tissue N, P, K, Ca, and Mg to shoots and pod and decreasing Al uptake and accumulation.     

CO-INOCULATION OF SOYBEAN (GLYCINE MAX) WITH ACTINOMYCETES AND BRADYRHIZOBIUM JAPONICUM ENHANCES PLANT GROWTH,NITROGENASE ACTIVITY AND PLANT NUTRITION

The aim of this study was to determine the potential of the endophytic actinomycetes that produce plant growth promoters used as co-inoculants with Bradyrhizobium japonicum to promote the growth of soybean. These endophytes exhibited the potential to enhance plant growth, nitrogenase activity of root nodules and plant nutrient uptake. Co-inoculum of B. japonicum with Nocardia alba conferred the maximum yield of root and shoot dry weight. All single-inoculated actinomycetes strains had the ability to enhance plant growth. Noc. alba and Nonomuraea rubra increased total plant dry weight up to 2.14-fold and 2.11-fold, respectively, when compared to the uninoculated controls. Co-inoculations of B. japonicum with each of Noc. alba, Non. Rubra, and Actinomadura glauciflava increased acetylene reduction activity up to 1.7 to 2.7-fold. For plant mineral composition, all of co-inoculation treatments significantly increased the nutrient levels of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), iron (Fe) and zinc (Zn) within a soybean plant.     

Magnesium and zinc interaction in four soybean cultivars with different nutritional requirements

Abstract

In the last decades, soybean (Glycine max (L.) Merrill) was the crop with the highest acreage in Brazil. Soybean has been cropped under unfertile soils as sandy soils and those under pasture decaying where applying high fertilizer levels have significant responses. The presence of calcium (Ca) and magnesium (Mg) concentration in the upper layers promotes ions imbalanced concentration in soil solution because the soil acidity correction reduces the uptake of other cations as zinc (Zn). The objective of this study was to evaluate under nutritive solution conditions, the Mg influence in Zn distribution and mobilization into plants from four soybean cultivars with different nutritional requirements. The experimental design was complete randomized blocks in factorial scheme 4?×?2?×?4 being with four soybean cultivars (FT Estrela, DM Nobre, IAC 17, and IAC 15-1), two Mg rates (0.1 and 1.0?mmol?L^?1), four Zn rates (0, 1, 2, and 5?µmol?L^?1), and four replicates. The IAC 17 and FT Estrela cultivars with determinate growth and high nutritional requirements, and the IAC 15-1 and DM Nobre with tolerance to soils partially corrected, average fertility, or both were investigated. In the highest Mg rates, we verified increase in grain yield (GY) as well as in the Zn rates up to 2.0?µmol?L^?1. The Mg?×?Zn interaction was significant and the IAC 17 cultivar was the most responsive to Zn under nutritive solution. The foliar nutrient concentration was significantly modified by Mg rates. The Mg at 1.0?mmol?L^?1 presented the lowest nutrient concentration in soybean plants and increased the shoot dry weight yield (SDWY) in plant and grain no matter the nutritional requirement from every cultivar.     

EFFICIENCY OF RHIZOBIUM INOCULATION AND P FERTILIZATION IN ENHANCING NODULATION,SEED YIELD,AND PHOSPHORUS USE EFFICIENCY BY FIELD GROWN SOYBEAN UNDER HILLY REGION OF RAWALAKOT AZAD JAMMU AND KASHMIR,PAKISTAN

A field experiment was conducted in continuity of our previous study to assess the effect of Rhizobium inoculation (RI) and phosphorus fertilization (P) on growth, yield, nodulation, and P use efficiency of soybean. Different treatments were i) Rhizobium strains (0, S₃₇₇, S₃₇₉, and the mixture of S₃₇₇+S₃₇₉ i.e. S₀, S₁, S₂, S₃); ii) phosphorus fertilizer (0, 50, 100 kg ha^?1 i.e. P₀, P₁, P₂). Soybean variety NARC-1 was as used as a testing crop. Results indicated that root and shoot growth increased by RI treatments whether used alone or in combination with P. Rhizobium inoculation increased plant height up to 12% while P did not show significant effect. Increases in soot dry weight, root length and root dry weight due to RI and P was 57 and 22%, 42 and 7%, 55 and 25%, respectively, over the control treatment. Number of nodules increased from 73 in the control to a maximum of 151 in S₂ while the number increased from 90 in the control to 147 in P₂. Combine application of strains and P increased nodules number from 65 at S₀P₀ to a maximum of 183 at S₂P₂. Similar response was also observed for nodules mass. Soybean seed yields ranged between 1710 and 2335 kg ha^?1 against 1635 kg ha^?1 in the control indicating a maximum of 43% increase over control. Concentration of N and P in plants and their uptake was significantly increased by RI and P. RI also increased the N and protein content of soybean seed. Apparent recovery efficiency (ARE) of applied P was 10?12% and the agronomic, agrophysiological, recovery, utilization efficiencies, and harvest index of P decreased with increasing P rates. Nodule number significantly correlated with the DM yield (r² = 0.78) and seed yield (r² = 0.63) while P uptake significantly correlated with root length (r² = 0.48) and root mass i.e. dry weight (r² = 0.65). Also a significant correlation existed between N uptake and DM yield (r² = 0.98) and N uptake and seed yield (r² = 0.65), P uptake and DM yield (r² = 0.73), and P uptake and seed yield (r² = 0.83). The results of present study indicated a substantial growth and yield potential of soybean under the hilly region and increase in yield and N₂ fixing potential (nodulation) can be achieved by applying Rhizobium inoculation with P fertilization.     

Enhanced soybean (Glycine max L.) plant growth and nodulation by Bradyrhizobium japonicum-SB1 in presence of Bacillus thuringiensis-KR1

Abstract

Nodulation and subsequent nitrogen fixation are important factors that determine the productivity of soybean (Glycine max L.). The beneficial effects of nodulation can be enhanced when rhizobial inoculation is combined with plant-growth-promoting bacteria (PGPB). The PGPB strain Bacillus thuringiensis-KR1, originally isolated from the nodules of Kudzu vine (Pueraria thunbergiana), was found to promote growth of soybean plants (variety VL Soya 2) under Jensen's tube and growth pouch conditions, when co-inoculated with Bradyrhizobium japonicum-SB1. Co-inoculation with Bacillus thuringiensis-KR1 (at a cell density of 10 cfu) provided the highest and most consistent increase in nodule number, shoot weight, root weight, root volume, and total biomass, over rhizobial inoculation and control, under both conditions. The results demonstrate the potential benefits of using nonrhizobial nodule occupants of wild legumes for the co-inoculation of soybean, with Bradyrhizobium japonicum-SB1, in order to achieve plant-growth promotion and increased nodulation.     

Nodulation and nitrogen fixation of Lupinus species with Bradyrhizobium (lupin) strains in iron-deficient soil

 The effect of six Bradyrhizobium sp. (lupin) strains (WPBS 3201D, WPBS 3211D, USDA 3040, USDA 3041, USDA 3042 and CB 2272) and Fe supply on nodulation, N₂-fixation and growth of three lupin species (Lupinus termis, L. albus and L. triticale) grown under Fe deficiency in an alkaline soil, were examined in sterilized and non-sterilized pot experiments. When inoculated with USDA 3040, 3041, 3042 and CB2272 without Fe addition, the three lupin species had a very low nodule number and mass, low shoot and root dry matter accumulation and lower N yield. However, inoculation with WPBS 3201D and 3211D without Fe treatments increased all these parameters substantially. The ability of WPBS 3201D and 3211D to form nodules on the three lupin species under conditions of Fe stress could be attributed to their ability to scavenge Fe from Fe-deficient environments through their siderophore production. Addition of Fe to the other four strains significantly increased nodulation and N₂-fixation of the three lupin species, indicating that the poorer nodulation and N₂-fixation of these strains in the absence of Fe, resulted from a low ability to obtain Fe from alkaline soils. Bradyrhizobium strains WPBS 3201D and 3211D were superior to the other four strains in terms of promoting greater nodulation, N₂-fixation, plant growth and N accumulation of L. termis and L. albus. However, the other four strains were more efficient in symbiotic association with L. triticale. The greater variations in nodule efficiencies (specific nitrogenase activity) under different levels of Fe supply could be attributed to the quantities of bacteroid protein and leghaemoglobin in the nodules. The results suggested that Bradyrhizobium (lupin) strains differ greatly in their ability to obtain Fe from alkaline soils, and that the selection of bradyrhizobial strains which are tolerant of Fe deficient soils could complement plant breeding for the selection of legume crops for Fe-deficient soils. Received: 5 January 1998     

Effects of co-inoculation of Bradyrhizobium elkanii BLY3-8 and Streptomyces griseoflavus P4 on Rj4 soybean varieties

Co-inoculation of selected nitrogen-fixing bacteria with plant growth-promoting bacteria is the promising way for the improvement of soybean production through enhancing plant growth, nodulation, and N₂ fixation. Therefore, this experiment was conducted to study the effects of co-inoculation of Bradyrhizobium elkanii BLY3-8 with Streptomyces griseoflavus P4 on plant growth, nodulation, N₂ fixation, N uptake, and seed yield of Rj₄ soybean varieties. Two experiments with completely randomized design and three replicates were done in this study. N₂-fixation ability of soybean was evaluated by acetylene reduction activity (ARA) and relative ureide method. In the first experiment, synergetic effect in N₂ fixation and nodulation was occurred in co-inoculation treatment (BLY3-8 + P4) in Yezin-3 and Fukuyutaka. Based on these results, co-inoculation effect of BLY3-8 and P4 was assessed on Yezin-3 and Fukuyutaka varieties at three different growth stages, using Futsukaichi soil under natural environmental conditions. This study shows that co-inoculation of BLY3-8 and P4 significantly increased N₂ fixation at V6 stage; plant growth, nodulation, N₂ fixation, and N uptake at R3.5 stage; and shoot growth, N uptake, and seed yield at R8 stage, in Rj₄ soybean varieties compared with the control. Significant difference in plant growth, nodulation, N₂ fixation, N uptake, and yield between co-inoculation and control, not between single inoculation and control, suggests that there is a synergetic effect due to co-inoculation of BLY3-8 and P4.     

东北黑土区大豆生长、结瘤及产量对氮、磷的响应

氮肥和磷肥显著影响大豆的结瘤和产量。然而在土壤肥力较高、速效养分有效性差的东北地区,有关氮肥和磷肥施用量对大豆结瘤和产量影响的研究较少。本试验采用裂区田间试验,设置3个氮（N）水平（0、20 和 50 kg/hm2）和 3 个磷（P）水平（0、 20 和 40 kg/hm2）,研究氮、 磷及其交互作用对大豆生长发育、 结瘤特征及产量的影响。结果表明, 单施氮肥大豆生物量和产量随着施氮量的增加而增加,而根瘤数量、 干重、 大小和结瘤指数呈逐渐下降的趋势。单施磷肥促进大豆生物量、 产量、 根瘤数量、 干重、 大小和结瘤指数的增加,但其增幅低于施氮处理下的增幅。氮磷对大豆生长和产量促进作用高于单施氮和单施磷处理,但差异不显著;氮磷处理下的根瘤数量、 干重、 大小和结瘤指数低于单施磷处理;氮磷处理下N2（N 50 kg/hm2）处理下的大豆根瘤数量、 干重、 大小和结瘤指数高于N1处理（N 20 kg/hm2）下的,随着施磷量的增加大豆根瘤数量、 干重、 大小和结瘤指数增加,施磷能够抵消氮对大豆根瘤产生和形成的抑制。氮、 磷及其交互作用对大豆根瘤的影响都是直接的,并且不是通过促进大豆生长间接促进的。因此氮和磷均是限制东北地区大豆结瘤和产量的因素,但氮是主导因素。若要获得大豆高产,氮肥施用量需要控制在50 kg/hm2,磷肥在40 kg/hm2;但若想最大的发挥大豆的结瘤固氮功能,那么应该不施或者减少氮肥的施用量到20 kg/hm2,磷肥仍在40 kg/hm2。     

Silicon stimulates initial growth and chlorophyll a/b ratio in rice seedlings,and alters the concentrations of Ca,B, and Zn in plant tissues

Abstract

Silicon (Si) is considered a beneficial element for plants due to the far-reaching benefits it confers, including enhanced growth, yield, and crop quality, as well as stress resistance. In this study, we evaluated the effect of Si during germination and initial growth (0.0, 0.5, 1.0, or 1.5?mM Si) and during vegetative growth (0, 1, 2, or 3?mM Si) in rice (Oryza sativa) cv. Morelos A-98. Si did not affect germination but stimulated seedling height, root length, number of roots, as well as fresh and dry biomass weight of shoots and roots during initial growth. During vegetative growth, the application of 3?mM Si significantly increased the chlorophyll a/chlorophyll b ratio, but no major changes were observed either in growth or in concentrations of most nutrients, with the exception of Ca (which increased with 3?mM Si), and B and Zn (which decreased in the presence of Si). In conclusion, applying Si had positive effects during the initial stage of growth, increasing seedling height, root length, root number, and fresh and dry biomass weight. Under our experimental conditions, Si did not affect germination and vegetative growth, but increased Ca concentrations and decreased B and Zn concentrations.     

Effect of placement of coated urea fertilizer on root growth and rubidium uptake activity in soybean plant

Abstract

We reported in the previous paper (Takahashi et al. 1991) that the deep placement of slow release N fertilizer (coated urea) contributed to a stable increase of soybean (Glycine max L. Merr.) yield. In the previous study we observed that the deep placement of coated urea did not depress appreciably the nitrogen fixation by root nodules although fertilizer N was efficiently utilized. We assumed that the N absorbed from the roots in the deep layers did not cause nodule senescence, contributed to the maintenance of the leaf activity during the maturation stage, and that the increase in the availability of carbohydrate and N improved seed production. In the current report the effects of placement of coated urea fertilizer on the root growth and activity were studied by measuring the root dry weight and Rb absorption activity.     

Selection of type A and type B strains for improving symbiotic effectiveness on non-Rj and Rj4 genotype soybean varieties

The selection of effective rhizobia for higher efficiency nitrogen fixation is one of the most important steps for inoculant production. Therefore, this experiment was conducted to select the most effective type A and type B strains for specific Rj-gene harboring soybean varieties and to test the symbiotic effectiveness of selected strains on different Rj-gene harboring soybean varieties. Screening experiments using the specific soybean varieties were done with a completely randomized design and three replications in this study. Evaluation of the effective Myanmar Bradyrhizobium strains for plant growth, nodulation and N₂ fixation were studied in pot experiments using sterilized vermiculite in the Phytotron (controlled-environmental condition). Then, a pot experiment was conducted using Futsukaichi soil in the screen house (natural environmental condition). The N₂ fixation ability of soybean was evaluated by acetylene reduction activity (ARA) and the relative ureide index method. In the first screening experiment, type A and type B strains with higher nitrogen fixation and proper nodulation on their respective soybean cultivars were selected for the next screening. In the second screening, Bradyrhizobium elkanii AHY3-1 (type A), Bradyrhizobium japonicum SAY3-7 (type A), B. elkanii BLY3-8 (type B) and B. japonicum SAY3-10 (type B) isolates, which showed higher nitrogen fixation and nodulation in Yezin-3 (Rj₄) and Yezin-6 (non-Rj), were selected for the next experiment. In the third screening experiment, SAY3-7 and BLY3-8, which had higher nitrogen fixing potential and proper nodulation, were selected as effective isolates. These two isolates were compatible with non-Rj and Rj₄ soybean varieties for nodulation and nitrogen fixation. Based on the results of the screening experiment, these two strains were tested for their symbiotic efficacy in Futsukaichi soil. This study shows that inoculation treatment of SAY3-7 and BLY3-8 significantly increased plant growth, nodulation, and N₂ fixation at the V6, R3.5 and R8 stages in Yezin-3 (Rj₄) and/or Yezin-6 (non-Rj), and the seed yield at R8 stage, in Yezin-3 (Rj₄) and Yezin-6 (non-Rj) soybean varieties compared with the control treatment. It can be concluded that SAY3-7 and BLY3-8 are suitable for inoculant production because of their higher nitrogen fixation ability, proper nodulation and better productivity of Myanmar soybean cultivars.     

Soybean nodulation and nitrogen fixation on soil previously amended with sewage sludge

Summary A greenhouse study was conducted to examine the residual effects of sewage sludge on soybean Glycine max (L.) Merr., nodulation, and N fixation. Nodulating and nonnodulating isolines of Clark soybean were grown to the R2 stage in soils (Typic Paleudults) obtained from plots where heat-treated sludge had been applied in 1976 at rates equal to 0, 56,112, and 224 Mg ha^–1 high (7.0) and low (6.2) soil pH regimes were established by CaCO₃ additions. Sludge and soil pH treatments resulted in clearly defined differences in metal uptake by soybean shoots. Plant Zn, Cd, and Ni concentrations were greater on pH 6.2, sludge-amended soil than on the pH 7.0, amended soil. At low soil pH, soybean Zn and Cd concentrations, respectively, increased from 41 and 0.19 mg kg^–1 (control) to 120 and 0.58 mg kg^–1 at the 224 Mg hat sludge rate. At the high soil pH and 224 hg hat sludge rate, Zn and Cd concentrations were 45 and 0.15 mg kg^–1, respectively.Symbiotic N fixation provided 90% of the total N accumulation. Total N accumulation, shoot N concentration, dry matter, and N fixation by nodulating soybeans exhibited a significant linear increase with sludge rate. Total N accumulation, dry matter, and N fixation were significantly greater at high soil pH. For high and low soil pH, respectively, N fixation increased from 422 and 382 mg N per plant (control) to 614 and 518 mg N per plant at the 224 Mg ha^–1 sludge rate. While soybean nodulation also increased linearly on sludge-amended soil, a significant rate times pH interaction for nodule number indicated that nodulation was less strongly enhanced by sludge at low soil pH.