Soybean Biological Nitrogen Fixation Research Articles

Exploring microbial symbionts for improving soybean production andsoil carbon sequestration

To meet UN 2030’s agenda for Sustainable Development Goals (SDGs), the use of non-renewable bioresources is being campaigned globally to ensure food security and resource sustainability while minimizing environmental impact. Among oilseeds, soybean is the most important leading oilseed crop worldwide and being a high rich seed protein (40%) crop requires high N for its growth. Its requirement is largely met through biological nitrogen fixation (BNF) and to certain extent from native pool. BNF in soybean takes place via specific N fixing symbiotic bacteria (e.g., bradyrhizobia) inside the root nodules of the plant-soil rhizosphere (rhizobiome) wherein other microbes such as arbuscular mycorrhizal (AM) fungi are also actively involved in performing various soil functions. However, during crop growth, BNF activity is limited by number of environmental and ecological factors. Amongst all, drought and nutritional stress are the most limiting factors affecting the productivity of soybean. Hence to mitigate the adverse conditions, improve soil biological health and overall productivity there is need to have well adapted microbial symbionts such as super nodulating and moisture tolerant soybean rhizobia and AM fungi for sustaining the productivity of soybean.

Biological nitrogen fixation in soybean with different levels of drought tolerance

Biological nitrogen fixation in soybean with different levels of drought tolerance

Phosphorus and Potassium Cycling, Biological Nitrogen Fixation in Soybean, and Soil Microbial Activity in an Oxisol Fertilized with Wastewater from Heparin Production

Phosphorus and Potassium Cycling, Biological Nitrogen Fixation in Soybean, and Soil Microbial Activity in an Oxisol Fertilized with Wastewater from Heparin Production

Biochar application increases biological nitrogen fixation in soybean with improved soil properties in an Ultisol

Biochar application increases biological nitrogen fixation in soybean with improved soil properties in an Ultisol

Soybean Seed Enrichment with Cobalt and Molybdenum as an Alternative to Conventional Seed Treatment

Biological nitrogen fixation in soybean is enhanced when seed is treated with cobalt (Co) and molybdenum (Mo) prior to planting. In this study, our objective was to verify if Co and Mo application during the reproductive phase of the crop increases seed Co and Mo concentration without adverse effects on seed quality. Two experiments were conducted. First, we investigated foliar and soil Co and Mo application under greenhouse conditions. Next, we validated the results obtained in the first study. The treatments for both experiments consisted of Co doses combined with Mo, and a control without Co and Mo application. The foliar application was more efficient in producing enriched Co and Mo seed; meanwhile, as Co doses increased so did Co and Mo concentrations in the seed. There were no adverse effects on nutrition, development, quality, and yield of parent plants and seed when these micronutrients were applied. The seed showed higher germination, vigor, and uniformity for the development of soybean seedlings. We concluded that the application of 20 g ha-1 Co and 800 g ha-1 Mo via foliar application at the reproductive stage of soybean increased germination rate and achieved the best growth and vigor index of enriched seed.

White-rot fungus Ceriporia lacerata HG2011 improved the biological nitrogen fixation of soybean and the underlying mechanisms

White-rot fungus Ceriporia lacerata HG2011 improved the biological nitrogen fixation of soybean and the underlying mechanisms

Potentially harmful effects of seed treatment and pre-inoculation on soybean biological nitrogen fixation and yield

Biological nitrogen fixation (BNF) is a crucial process for the successful development of soybean plants. Nevertheless, many management decisions can affect the symbiosis between the bacteria and the plant, impacting soybean growth and yield. The use of pesticides in soybean seed treatment and the application of Bradyrhizobium sp. inoculant to the seeds a few days or even weeks before sowing are two management practices that can have a detrimental effect on the BNF process and always raise concerns. To shed light on the potential impact of these two management practices, the objective of this study was to evaluate under laboratory, greenhouse, and field conditions the effects of pre-inoculating soybean seeds with Bradyrhizobium sp. for up to 30 days prior to sowing with and without common pesticides used for seed treatment. One laboratory, one greenhouse, and six field experiments were conducted from 2016 to 2019. Pre-inoculation time (3 h and 30 days before sowing) and pesticides seed treatment (control - without pesticide application; pyraclostrobin + thiophanate-methyl + fipronil; thiabendazole + fludioxonil + metalaxyl-M; and carbendazim + thiram) were the two fixed effects controlled by the experimental design. Results from laboratory and greenhouse trials showed that pre-inoculation and pesticide seed treatment can negatively affect the recovery of colony-forming units of Bradyrhizobium elkanii inoculated to the seed, ureides concentration in plant shoots, BNF efficiency, and plant growth. Pooled analysis of the six field experiments demonstrated that although none of the BNF variables assessed were affected by pre-inoculation or pesticide seed treatment compared to the control, thiabendazole + fludioxonil + metalaxyl-M caused significant yield loss, whereas the weight of thousand grains for inoculation 3 h before sowing was significantly higher than inoculation 30 days before sowing.

Soybean relay‐cropped with winter camelina reduces biological nitrogen fixation

AbstractThe contribution of biological nitrogen fixation (BNF) in soybean [Glycine max (L.) Merr.] to plant nutrition and its N credit for the next crop is significant. The amount of N fixed via BNF in monocropped soybean is well documented, but it is unknown when soybean is relayed into winter camelina [Camelina sativa (L.) Crantz]. Therefore, BNF in soybean relayed into fertilized (WCFerti) and unfertilized (WCUnfert) winter camelina grown for seed, and soybean seeded after winter camelina terminated as a cover crop (WCCC) were compared with a monocrop (control) soybean. The results showed that N‐fixing bacteria successfully infected soybean roots and were potentially active in N fixation for all treatments. Ureide‐N abundance was in the order of control > WCFerti = WCUnfert > WCCC. The control had 38 and 44% more ureide‐N (indicating greater BNF) than WCFerti and WCUnfert, respectively. Relayed soybean had the same grain protein and oil concentrations as the control. However, the control had greater soybean grain, protein, and oil yields than relayed treatments due to grain yield differences. Fertilized winter camelina resulted in greater total (soybean + camelina) oil yield (859 kg ha–1) than the control (587 kg ha–1). The lower ureide‐N abundance and grain yields for relayed soybean than the control was due to differences in belowground and aboveground biomass. Further research is needed to develop earlier‐maturing winter camelina genotypes, better row spacing, and more shade‐tolerant soybean cultivars to minimize competition between the two species, enhance BNF, and increase relayed‐soybean yield.

Biochar-Induced Soil Available Mo Enhancement to Increase Biological Nitrogen Fixation in Soybean in an Ultisol

Biochar-Induced Soil Available Mo Enhancement to Increase Biological Nitrogen Fixation in Soybean in an Ultisol

An Overview of the Morphological, Genetic and Metabolic Mechanisms Regulating Phosphorus Efficiency Via Root Traits in Soybean

Phosphorus (P) is an essential macronutrient for optimum productivity of several crops including soybean, but it is largely limited in most arable lands. The persistent depletion of phosphate rocks is a major constraint for plant growth and development. Improved P efficiency (PE, uptake and use efficiency) drives an enhanced biological nitrogen fixation in soybean, which could consequently lead to an increased grain and biomass production. Thus, to mitigate P limitation in soybean production, a wide range of genetic approaches have been deployed. These approaches have unravelled the morphological, genetic, phytohormonal and metabolic mechanisms involved in soybean adaptations to P-deficient conditions. Most of the approaches are targeted at root modifications due to the importance of roots in the mediation of early responses to P-deficient conditions. PE among soybean genotypes in P-deficient conditions is mostly dependent on the root plasticity, development of shallow root architecture, symbiosis with arbuscular mycorrhizal fungi and exudation of phosphatases and organic acid anions. Genetic manipulation of soybean has revealed a number of important genes (GmPAPs, GmPTs, GmPLDZ2, GmIPS1 and GmExPB2), transcription factors (C2H2 zinc finger protein, WRKY and MYB) and quantitative trait loci (q14-2 and q19-2) modulating P mobilisation, uptake and utilization under P limiting conditions. Through the modification of root traits, the hormonal (biosynthesis, transport and secretion of ethylene, auxin and jasmonic acid) and metabolic (phenylpropanoid biosynthesis and phenylalanine metabolisms) pathways also modulate PE in soybean. Recent advances in genetic manipulations of root traits offer promising ways for enhancing soybean production, particularly in a P limiting environment.

Biochar can improve biological nitrogen fixation by altering the root growth strategy of soybean in Albic soil

Albic soil is a low-yielding soil that is widely distributed in Northeast China. The high viscosity and acidity and the lack of nutrients in the Albic layer limit the growth of crop. In our previous studies, we found that applying biochar as a soil amendment could improve the properties of Albic soil and promote soybean growth. Increases in the nitrogen contents of the soil and the soybeans were key aspects of these improvements. Soybean is a nitrogen-fixing crop, the increase in nitrogen in the Albic soil may have been due to an improvement in biological nitrogen fixation by the soybean with biochar amendment, but the function mechanism was still uncertain. We hypothesized that biochar could improve biological nitrogen fixation of soybean by affecting soybean root growth in the Albic soil. Therefore, we conducted pot experiments with five treatment levels (0, 10, 20, 30, and 40 g·kg−1 biochar) for two years to study how biochar affects the root growth strategy and biological nitrogen fixation of soybean based on its root structure and root nutrient acquisition ability at different stages. The soybean root structure and activity indexes, nodulation ability and nitrogen uptake were measured at different growth stages; in the second year, at the late seed-filling stage, the stable 15N isotope method was used to elucidate the biological nitrogen fixation process. Regarding root structure at the pod-setting stage, biochar resulted in increases in root length density, specific root length, root diameter and specific tip density but a decrease in root tissue mass density at the pod-setting stage. Biochar improved root nutrient acquisition by increasing root activity, root tip number and root-bleeding sap amount. The change in root growth strategy contributed to the promotion of biological nitrogen fixation by the rhizobia that live symbiotically with soybean, thereby increasing crop yield.

Nodulation and biological nitrogen fixation in soybean (Glycine max L.) as influenced by phosphorus fertilization and arbuscular mycorrhizal inoculation

Abstract Arbuscular mycorrhizal fungi (AMF) can be used to promote the productivity of legumes on phosphorus- (P) deficient soils. The present study investigates the inoculation effects of three AMF species (Funneliformis mosseae, Rhizophagus intraradices, and Claroideoglomus etunicatum) and the control (uninoculated) on nitrogen fixation efficiency and growth performance of tropical soybean cultivar (TGx1448-2E) under varying P fertilizer rates (0, 20, and 40 kg P2O5 ha−1) in a derived savannah of Nigeria. The results showed that shoot and root dry matter, number of nodules, relative ureide abundance (RUA), nitrogen derived from atmosphere (Ndfa), total N fixed, shoot P uptake, grain, and biomass yield significantly increased with AMF inoculation, with better performance observed in plants inoculated with Rhizophagus intraradices and Funneliformis mosseae compared to Claroideoglomus etunicatum. Similarly, the soybean growth variables, P uptake, and nitrogen fixation activities increased with increasing P application rates. Conversely, AMF root colonization significantly reduced with increasing P rate. Interaction of AMF inoculation and P rates significantly influenced soybean growth and nitrogen fixation. R. intraradices inoculation with 20 kg P2O5 ha−1 resulted in the highest amount of RUA, Ndfa, N fixed, and grain yield. It could be concluded from this study that R. intraradices with moderate P rate could be used to enhance nodulation, nitrogen fixation, and soybean yield in P-deficient soils.

Nutritional and environmental effects on biological nitrogen fixation in soybean: A meta-analysis

Biological N2 fixation (BNF) and mineral soil absorption are complementary N sources for soybean growth. BNF is sensitive to nutrient and environmental conditions, though a comprehensive synthesis of the studies underlying these conclusions is currently lacking. Our objective was to conduct a meta-analysis of nutrient and environmental effects on BFN. Articles reporting manipulative treatments and BNF estimations were compiled, and data and metadata were extracted. N fertilization reduced BNF ∼70% relative to the unfertilized control in greenhouse experiments and ∼44% in field experiments. This effect was higher for vegetative than for reproductive stage applications. Fertilization with other nutrients stimulated BNF relative to the unfertilized treatments. Water stress reduced BNF 40% relative to the unstressed control. The negative impact of water stress was larger when stress was applied at vegetative (-70%) compared to reproductive (-30%) stages. Flooding reduced BNF by 40% relative to the non-flooded control with highest effect when applied during vegetative stage (-82%). Increased temperature reduced BNF nitrogenase activity. Carbon dioxide enrichment has a stimulatory effect on BNF. With the exception of N fertilization, soybean and Rhizobium fitness showed a high positive correlation across nutrients and environmental factors. This work summarizes for the first time the impact and relative response of BNF to different nutrient and environmental factors. Results showed an initial critical stage (i.e. vegetative stage) for BNF that is common to most environmental factors negatively affecting BNF. This suggests that common strategies might exist to increase BNF that are independent of the specific identity of the stressor. Also, the positive correlation between host and Rhizobium fitness suggest that strategies to increase BNF potential are the same that those required to increase crop performance. We observed publication bias for some variables, suggesting that effect sizes might be inflated compared to true effect sizes. The only way to solve this problem is to find venues for publication of no significant results when sound experimental approaches and reasonable statistical power can be proved.

Interplay between nitrogen fertilizer and biological nitrogen fixation in soybean: implications on seed yield and biomass allocation

Legumes rely on soil mineral nitrogen (N) and biological N fixation (BNF). The interplay between these two sources is biologically interesting and agronomically relevant as the crop can accommodate the cost of BNF by five non-mutually exclusive mechanisms, whereby BNF: reduces shoot growth and seed yield, or maintains shoot growth and seed yield by enhanced photosynthesis, or reduced root:shoot ratio, or maintains shoot growth but reduces seed yield by reducing the fraction of shoot biomass allocated to seed (harvest index), or reducing concentration of oil and protein in seed. We explore the impact of N application on the seasonal dynamics of BNF, and its consequences for seed yield with emphasis on growth and shoot allocation mechanisms. Trials were established in 23 locations across the US Midwest under four N conditions. Fertilizer reduced the peak of BNF up to 16% in applications at the full flowering stage. Seed yield declined 13 kg ha−1 per % increase in RAUR6. Harvest index accounted for the decline in seed yield with increasing BNF. This indicates the cost of BNF was met by a relative change in dry matter allocation against the energetically rich seed, and in favor of energetically cheaper vegetative tissue.

New Insights into Soybean Biological Nitrogen Fixation

Core Ideas As N2 fixation (%) increased, seed production per N2 fixation decreased. The N‐gap between crop N uptake and N supplied by N2 fixation rose when contribution from biological N2 fixation increased. The partial N balance revealed negative values across all N derived from the atmosphere levels. Yield was negatively related to partial N balance when N derived from the atmosphere was below 42%. Soybean biological N2 fixation (BNF) relationships with fertilizer N and yield response have been comprehensively reviewed in the scientific literature. However, the study of the N‐gap between N uptake and N supplied by N2 fixation, and the partial N balance (fixed N in aboveground biomass – N seeds) needs further investigation. Therefore, the goals of this synthesis–analysis were to (i) quantify seed production per unit of fixed N under different amounts of N derived from the atmosphere (NDFA, %), (ii) study the N‐gap and explore limitations of N2 fixation (kg ha−1) for satisfying plant N demand, and (iii) calculate a partial N balance for soybean and determine its relationship with the N2 fixation process. Data was gathered from 1955 through 2016 using studies reporting BNF, seed yield, and plant N uptake (n = 733 data points). The main outcomes of this review were (i) as NDFA increased, seed production per N2 fixation decreased (from 0.033 to 0.017 Mg yield kg−1 N from low, 28%, to high, 80%, NDFA); (ii) N‐gap increased faster when NDFA values were above 80% and after plant N content was above 370 kg N ha−1 suggesting that the crop needs additional N for coping yield potential; and (iii) when excluding roots, the partial N balance calculation revealed negative values across all NDFA levels. Future studies should consider a holistic approach to quantify the contribution of BNF in overall N cycling, including N contribution from roots, and to better understand the soil × plant × rhizobia interactions.

Characterization of Genetic Basis on Synergistic Interactions between Root Architecture and Biological Nitrogen Fixation in Soybean.

Soybean [Glycine max (L.) Merr] is an important legume crop and its yield largely depends on root architecture (RA) and biological nitrogen fixation (BNF). However, the relationship between RA and BNF, and its genetics behind remain unclear. Here, two soybean genotypes contrasting in RA and their 175 F9:11 recombinant inbred lines (RILs) were evaluated in field. The shallow-root parent, JD12, had better nodulation and higher yield than the deep-root parent, NF58. Strong correlations between shoot dry weight (SDW) and RA or BNF traits existed in the RILs, and the shallow-root group had more and heavier nodules, as well as higher SDW. After inoculating with rhizobia, roots became shallower and bigger, showing strong synergistic interactions between RA and BNF. In total, 70 QTLs were identified for the 21 tested traits. Among them, qBNF-RA-C2, qBNF-RA-O, and qBNF-RA-B1, were newly identified QTLs for BNF and/or RA traits in soybean, which co-located with the QTLs for SDW detected presently, and with the QTLs for yield identified previously. The results together suggest that there are synergistic interactions between RA and BNF, and the QTLs identified here could be used for breeding new soybean varieties with higher yields through optimization of RA traits and BNF capacity.

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

ABSTRACTSoybean (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.

Biological nitrogen fixation in soybean under water restriction and exposed to 1-methylcyclopropene

Abstract: The objective of this work was to assess the effects of 1-methylcyclopropene (1-MCP) on traits related with biological nitrogen fixation on 'BRS 268' soybean (Glycine max) subjected to water restriction. Plants were either exposed to drought between 32 (R2) and 47 (R3) days after sowing (DAS) or kept well-watered, in combination with exposure or not to 1-MCP. On the second day under drought (34 DAS), plants from both water conditions were exposed to 1-MCP in a hermetically sealed chamber for 15 hours. Control plants, dry or well-watered, that were not exposed to 1-MCP were kept in a separate chamber. At 36 (R2) and 47 (R3) DAS, shoot and root dry weights, leaf area index, number and dry weight of nodules, total ureides in sap, and N concentration in leaves were assessed. From 47 DAS on, extra plants were well watered until physiological maturity (R8) and assessed for yield components. Water restriction increased ureides in sap and reduced N in leaves in R2; reduced the number and mass of nodules, shoot dry weight, and leaf area index in R3; and reduced the number of pods and seed mass of plants not exposed to 1-MCP. However, when plants are exposed to 1-MCP, there is an attenuation of water restriction effects.

Biological nitrogen fixation in soybean in Argentina: relationships with crop, soil, and meteorological factors

Aims This study aims to (i) asses the contribution of biological N fixation (%Ndfa) in the soybean production area of Argentina, (ii) build a model for predicting %Ndfa using crop, soil, and meteorological variables, and (iii) estimate %Ndfa at the country level using values obtained in this study.

Gas Exchanges and Biological Nitrogen Fixation in Soybean under Water Restriction

Biological nitrogen fixation (BNF) in soybean is vulnerable to drought; however, there are genotypic variations among soybean cultivars regarding the ability to keep BNF under moderate water restriction. The aim of this study was to evaluate parameters related to gas exchanges and regulation of BNF in soybean genotypes BNF drought-tolerant (R01-581F and R01-416F), or drought-susceptible (CD 215 and BRS 317), submitted to adequate water supply or restriction between 45 and 55 days after emergence. We searched for traits associated with tolerance/susceptibility to drought, which might be useful in the selection of drought-tolerant soybean genotypes. Plant biomass was not affected under water restriction, but the number and dry weight of nodules reduced by 33% and 12%, respectively, in the average of genotypes. Drought-tolerant genotypes were more effective in maintaining gas exchanges under water restriction. Under water restriction, all genotypes increased the concentration of ureides in nodules, but only the susceptible genotypes showed that in leaves. The maintenance of gas exchanges and N metabolism regulation under water restriction in genotype R01-581F suggests that these parameters may be used to characterize soybean genotypes that can be sources of drought tolerance in genetic breeding programs.