Rhizobium Inoculation Research Articles

Additive Response of Biofertilizers on Seed Yield and Quality in Cowpea

Background: Cowpea is a precious crop for farmers with limited resources. The crop’s yield potential was constrained coupled with poor seed management methods, a lack of high yielding varieties and improper input use. Seed inoculation with biofertilizer is critical for increasing nutrient utilization efficiency and crop yield via nitrogen fixation and nodulations. With this in mind, a study was performed to appraise the influence of pre-sowing seed inoculation on initial seed quality, crop growth, seed yield, seed biochemical content and seed quality in cowpea, both in the laboratory and field. Methods: Cowpea seeds were imposed with different bio-inoculants viz., Rhizobium @ 600 g/ha, PSB @ 600 g/ha, VAM @ 600 g/ha and Pseudomonas @ 10 g/kg as single treatment and in combined inoculations. The above treated seeds along with control were evaluated for seed quality under laboratory condition and crop growth and yield potential under field condition. Result: Rhizobium inoculation (600 g/ha) and phosphate solubilizing bacteria inoculation (600 g/ha) were added to the seeds before they were sown. This led to better growth, yield and seed quality.

The Rhizobium tropici CIAT 899 NodD2 protein promotes symbiosis and extends rhizobial nodulation range by constitutive nodulation factor synthesis.

In the symbiotic associations between rhizobia and legumes, the NodD regulators orchestrate the transcription of the specific nodulation genes. This set of genes is involved in the synthesis of nodulation factors, which are responsible for initiating the nodulation process. Rhizobium tropici CIAT 899 is the most successful symbiont of Phaseolus vulgaris and can nodulate a variety of legumes. Among the five NodD regulators present in this rhizobium, only NodD1 and NodD2 seem to have a role in the symbiotic process. However, the individual role of each NodD in the absence of the other proteins has remained elusive. In this work, we show that the CIAT 899 NodD2 does not require activation by inducers to promote the synthesis of nodulation factors. A CIAT 899 strain overexpressing nodD2, but lacking all additional nodD genes, can nodulate three different legumes as efficiently as the wild type. Interestingly, CIAT 899 NodD2-mediated gain of nodulation can be extended to another rhizobial species, since its overproduction in Sinorhizobium fredii HH103 not only increases the number of nitrogen-fixing nodules in two host legumes but also results in nodule development in incompatible legumes. These findings potentially open exciting opportunities to develop rhizobial inoculants and increase legume crop production.

3D-printed biological habitats for the protection and persistence of <em>Rhizobia</em> species in compacted soils

Microorganisms in soils are responsible for many ecosystem services. However, in degraded soils microbial abundance and function are limited which compromises several biologically facilitated processes. Inoculating soils with desirable microbes can help to re-instate or initiate a viable functioning microbial community. However, establishment success is reliant on the survival of the microorganism in an adverse environment. In this proof-of-concept study, artificial microbial refugia have been developed using resin and light-emitting diode array (LED) 3D printing technology. We assessed whether the artificial refugia, termed a Rhiome, would support better microbial growth in degraded soils. Soil compaction, a form of soil degradation, and Rhizobium, an important microorganism for global agriculture, were both selected as the use case application for this assessment. Different materials together with resin were assessed for their suitability as a 3D printing material and for supporting rhizobial growth. The best result was found in materials constructed with a combination of polylactic acid (PLA) resin, yeast extract and mannitol. In a soil compaction experiment with inoculation of rhizobia, the addition of Rhiome significantly increased bacterium survival in the compacted soil to a level similar to, or higher than, the rhizobial loading in non-compacted soils. Augmentation of the resin with yeast extract and mannitol increased Rhizobium growth significantly compared with the Rhiome constructed only with resin. These results indicate that the Rhiome was highly beneficial for instigating and maintaining significant rhizobia survival and growth in compacted soils. Further work, including near-to-field assessments, are required to assess Rhiome performance in a range of applications and to refine material properties relative to important context-specific performance metrics such as degradation rate. We propose the Rhiome concept as a promising asset in the toolbox for soil ecological restoration as a means of improving soil resiliency.

Elite Bradyrhizobium strains boost biological nitrogen fixation and peanut yield in tropical drylands.

Peanut (Arachis hypogaea L.) is an important crop for the family-based systems in the tropics, mainly in Brazil. In the Brazilian drylands, peanuts are cropped in low technological systems, and cheap and efficient technologies are needed to improve crop yield and sustainability. Despite this importance, few data are available on selecting efficient peanut rhizobia in experiments under different edaphoclimatic conditions. This work evaluated the agronomic efficiency and the biological nitrogen fixation (BNF) by two elite Bradyrhizobium strains under four different fields in the Brazilian semiarid region. We compared a new efficient strain Bradyrhizobium sp. ESA 123 with the reference strain B. elkanii SEMIA 6144, currently used in peanut rhizobial inoculants in Brazil. Besides the inoculated treatments, two uninoculated controls were assessed (with and without 80kgha-1 of N-urea). The BNF was estimated by the δ15N approach in three out of four field assays. BNF contribution was improved by inoculation of both Bradyrhizobium strains, ranging from 42 to 51% in Petrolina and 43 to 60% in Nossa Senhora da Glória. Peanuts' yields benefited from the inoculation of both strains and N fertilization in all four assays. Nevertheless, the results showed the efficiency of both strains under different edaphoclimatic conditions, indicating the native strain ESA 123 as a potential bacterium for recommendation as inoculants for peanuts in Brazil, mainly in drylands.

Effects of Stand Density and N Fertilization on the Performance of Maize (Zea mays L.) Intercropped with Climbing Beans (Phaseolus vulgaris L.)

Maize is Germany’s most important fodder and energy crop. However, pure maize cultivation has ecological disadvantages. Moreover, its yield is low in crude protein, an important feed quality parameter. Maize–bean intercropping can potentially address both issues. A bean variety specially developed for intercropping was first introduced in 2016. Using this variety, a network of institutions conducted 13 field trials from 2017 to 2020 on four sites in Germany. We sought to determine the effects of stand density and nitrogen (N) fertilization on dry matter yield, crude protein yield, and soil mineral N content (Nmin) at harvest of intercropped vs. pure maize. The three intercropping bean densities we tested (7.5, 5.5, and 4 plants/m2) produced non-significantly different yields of dry matter or crude protein, given a maize density of 7.5–8 plants/m2. Intercropping was inferior to pure maize in dry matter yield, but non-significantly different in crude protein yield. Under neither cropping strategy were significant losses in dry matter or crude protein yield recorded with reduced compared to full N fertilization. At full fertilization, however, both pure maize systems and the 8/4 maize–bean intercrop system left significantly higher Nmin at harvest than the other variants of the corresponding system or N fertilization level and thus an increased risk of nitrate leaching. We encourage further optimization of yield performance in maize–bean intercropping, e.g., through breeding or promotion of biological N fixation via rhizobia inoculation. Furthermore, we recommend reducing N fertilization levels in maize cultivation.

Full-Length Transcriptome Sequencing Reveals Alternative Splicing and lncRNA Regulation during Nodule Development in Glycine max.

Alternative splicing (AS) is a ubiquitous phenomenon among eukaryotic intron-containing genes, which greatly contributes to transcriptome and proteome diversity. Here we performed the isoform sequencing (Iso-Seq) of soybean underground tissues inoculated and uninoculated with Rhizobium and obtained 200,681 full-length transcripts covering 26,183 gene loci. It was found that 80.78% of the multi-exon loci produced more than one splicing variant. Comprehensive analysis of these identified 7874 differentially splicing events with highly diverse splicing patterns during nodule development, especially in defense and transport-related processes. We further profiled genes with differential isoform usage and revealed that 2008 multi-isoform loci underwent stage-specific or simultaneous major isoform switches after Rhizobium inoculation, indicating that AS is a vital way to regulate nodule development. Moreover, we took the lead in identifying 1563 high-confidence long non-coding RNAs (lncRNAs) in soybean, and 157 of them are differentially expressed during nodule development. Therefore, our study uncovers the landscape of AS during the soybean-Rhizobium interaction and provides systematic transcriptomic data for future study of multiple novel directions in soybean.

Yield Response of Faba Bean to Lime, NPSB, and Rhizobium Inoculation in Kiremu District, Western Ethiopia

Faba bean (Vicia faba L.) is one of the most important winter legume crops for human consumption as a green or dried, fresh, or canned. Low soil fertility and acidity are the major constraints of faba bean production in Ethiopia. A field experiment was conducted in the Kiremu district of West Oromia, Ethiopia, under rain-fed conditions on a farmer's field to evaluate the effect of different rates of lime and NPSB-blended fertilizer application with and without inoculation on yield components and yield of faba bean. The three factors, lime rates (0, 2, and 4 t ha−1), mineral fertilizer rates (0, 60, 120, and 180 kg·ha−1 NPSB), and rhizobium inoculation (with and without), were combined in 3 x 4 x 2 factorial arrangement of RCBD in three replications. The data were collected on yield and yield components and subjected to the analysis of variance (ANOVA). The ANOVA results revealed that the number of pods per plant, number of seeds per pod, hundred seeds weight, harvest index, aboveground biomass, and grain yield were significantly affected by the treatment. Therefore, the highest faba bean yield was obtained from the application of 2 t limes ha−1, 120 NPSB ha−1, and 500 g·ha−1 rhizobium inoculation, and thus, the integrated application of the aforementioned rates of lime, NPSB, and rhizobium inoculation could be recommended for maximizing the productivity profitability of faba bean production in the study area and similar agro-ecologies.

Impact of Integrated Nutrient Management on Physico-chemical properties of soil in Pea (Pisum sativum L.) var. GS 10

During the rabi season of 2021-2022, a field experiment was conducted at the soil science research farm of the Sam Higginbottom University of Agriculture, Technology and Sciences in Prayagraj, UttarPradesh, India. Three different parameters viz., three levels of NPK, FYM at 0%, 50%, and 100% ha-1, and three levels of rhizobium inoculation at 0%, 25%, and 50% ha-1 were used in the study. The result obtained with treatment T9[I3@100% + F3@ 100% + R3@50%] had a bulk density (1.17 Mg m-3) at 0-15cm and (1.18 Mg m-3) at 15-30 cm, particle density (2.41 Mg m-3) at 0-15cm and (2.42 Mg m-3) at 15-30, pore space (58.26%) at 0-15cm and (58.09%) at 15-30cm, water holding capacity (58.60%) at 0-15cm and (58.13%) at 15-30, pH (7.75) at 0-15cm and (7.75) at 15-30cm, EC (0.47dSm-1) at 0-15cm and (0.48 dSm-1) at 15- 30cm, soil organic Carbon (0.58%) at 0-15cm and (0.49%) at 15-30cm as regards soil available nutrients, available nitrogen (280.86 kg ha-1) at 0-15cm and (286.40) at 15-30cm, available phosphorus (16.56 kg ha-1) at 0-15cm and (17.26 kg ha-1), available potassium (178.13 kg ha- 1) at 0-15cm and (172.80 kg ha-1). The use of FYM and Rhizobium, as well as its blend with complete NPK, significantly improves the growth and overall production of Pea.

Role of rhizobia in promoting non-enzymatic antioxidants to mitigate nitrogen-deficiency and nickel stresses in Pongamia pinnata

The contribution of rhizobia in the mitigation of non-enzymatic antioxidants against nitrogen deficiency and heavy metal toxicity for legume plant is not clear. Therefore, it is hypothesized that the inoculation of rhizobia could mitigate nitrogen deficiency and nickel (Ni) stresses in P. pinnata tissues by enhancing the formation of certain non-enzymatic antioxidants. The effect of symbiotic nitrogen-fixing rhizobia on the mitigation of nitrogen-deficiency and Ni stresses in P. pinnata was evaluated by inoculating two different rhizobia, i.e., Rhizobium pisi PZHK2 and Ochrobacterium pseudogrignonense PZHK4, around the rhizosphere of P. pinnata grown in soil containing 40 mg kg−1 Ni2+ and without nitrogen addition. The inoculation with both rhizobial strains promoted the growth of P. pinnata under nickel stress or nitrogen-deficiency condition, increased nitrogen content in all plant tissues and nickel content in shoots and leaves, but reduced nickel accumulation in roots. The four non-enzymatic antioxidants including glutathione (GSH), proanthocyanidin (OPC), ascorbic acid (ASA) and flavonoids (FLA) distributed in roots, shoots and leaves were followed in descending order: GSH > OPC > ASA > FLA. The four non-enzymatic antioxidants showed different levels of change under the nitrogen-deficiency and nickel stresses and in the non-stress control. The inoculation of PZHK2 and PZHK4 significantly (p < 0.05) increased the four non-enzymatic antioxidants in P. pinnata tissues, especially in roots. Some non-enzymatic antioxidants showed correlations with nickel or nitrogen in P. pinnata tissues, and the four non-enzymatic antioxidants also had correlations among each other. Therefore, this research revealed an excellent role of rhizobia in promoting non-enzymatic antioxidants to mitigate nitrogen-deficiency or nickel stress for P. pinnata.

Grain Yield and Economic Benefit of Soybean as Affected by Integration of Rhizobium Inoculation and Phosphorus Application in Chuka Sub-County, Kenya

Soybean (Glycine max [L.] Merrill) yields are far below the potential yield on most smallholder farms in Kenya. This necessitates suitable interventions to bridge this yield gap and result to profitable soybean production. An experiment was conducted in Chuka University demonstration farm, Chuka Sub County to determine the effect of integration of rhizobium inoculation (R) and phosphorus (P) on yields and net economic returns in soybean cultivation. The experiment was laid out in a randomized complete block design in a split-split plot arrangement with each treatment replicated three times. The experiment which was conducted between 2018 and 2019 was repeated once and the treatments included; three P rates (0, 20 and 30 kg/ha), three rhizobium rates (0, 100 and 200 g/ha) and two soybean genotypes (SB19 and SB24). Triple superphosphate (0:46:0) was used as the source of the phosphorus. The soybean genotypes, rhizobium and phosphorus rates were assigned to the main plot, sub-plot and the sub-sub plots respectively. Data collected included soybean yields (kg/ha) and economic analysis was calculated. The data collected was subjected to analysis of variance using Statistical Analysis System® 9.4 and significantly different means separated using Tukeys test at (p≤0.05). The results showed statistically significant difference in soybean yields and net economic benefit within SB19 and SB24 genotypes in both trials at (p≤0.05). Integration of R and P at the rate of 200 g and 30 kg/ha increased soybean yield by 101% and 98%, and 158% and 138% for SB19 and SB24 in trial I and II respectively. This earned a net economic benefit of ksh. 239,496 and 192,730, and ksh. 297,930 and 239,330 for SB19 and SB24 in both trials I and II, respectively. Both genotypes performed well in yield and net economic benefit and application of R and P at the rate of 200 g/ha and 30 kg/ha promoted yield and net economic benefit of soybean.

EFFECT OF INOCULATING Bradyrhizobium liaoningense ON GROWTH, CHLOROPHYLL CONCENTRATION, NODULATION AND YIELD OF SOYA BEANS

Soya bean is important staple food crops in Western Kenya. Legumes play a significant role in agriculture by fixing nitrogen. Currently Kenya is experiencing low yield of soya beans. Approximately 0.8 t/ha is under production and this is due to low soil fertility. This has posed a threat to agricultural productivity. Symbiotic rhizobia inoculation increases crop yields through biological nitrogen fixation. However, the potential of Bradyrhizobium liaoningense in improving yield and productivity of soya beans has not been documented. Rhizobia bacteria are known to improve growth and yield of several other crops but the effect of inoculating soya beans with B. liaoningense on growth, chlorophyll concentration, nodulation and yields has not been determined. This study was conducted at Maseno University under greenhouse conditions. Previously purified local isolates of B. liaoningense (S3) from wild soya beans plants were used to inoculate the soya bean seeds. 4.5 litre plastic pots were filled with 7kg of top soil. Ten seeds of Soya beans coated with Bradyrhizobium liaoningense inoculants were sown in each pot except the control. The seeds were treated with the isolates inoculants as: un-inoculated (control), 1.07x107 cfu/ml, 1.19x107 cfu/ml, 1.31x107 cfu/ml and 2.67x107 cfu/ml inoculation of B. liaoningense. The experiment was laid out as Completely Randomised Design (CRD). The treatments were replicated three times. After two weeks of germination, the seedlings were thinned to three plants per pot. Watering was done daily with 200 ml of water per pot up to the end of the experiment. Data on plant height, number of leaves, leaf area, shoot and root fresh weight and dry weight, chlorophyll concentration, number of nodules and number of pods were determined. Data was subjected to Analysis of Variance (ANOVA). Treatments means were separated using Fisher’s Least Significant Difference at (P = 0.05). Soya bean growth, chlorophyll concentration, number of nodules and number of pods after inoculation treatments were significantly different among the treatments (P ≤ 0.05). Plant height, number of leaves and leaf area were highest in 2.67 x 107 cfu/ml of B. liaoningense inoculation followed by 1.31x 107 cfu/ml inoculation, 1.19x107 cfu/ml, 1.07x107 cfu/ml and lowest in un-inoculated. Inoculation at 2.67 x 107 cfu/ml significantly increased soya bean root and shoot fresh weight and dry weights. Chlorophyll concentration was found to be highest in 2.67 x 107 cfu/ml treatment and lowest in un-inoculated control treatment. Inoculation at 2.67 x 107 cfu/ml increased the number of nodules of soya beans. Number of pod per plant were highest at 2.67 x 107 cfu/ml treatment and lowest in un-inoculated (control treatment). These findings showed that B. liaoningense inoculation was effective in enhancing growth, chlorophyll synthesis, formation of root nodules and pods in soya beans. From the study it can be recommended that B. liaoningense from wild soya bean may be used as a biofertiliser to improve productivity of soya beans by smallholder farmers in Kenya.

The Effect of Different Fertilizer Treatments of Plant Traits on Faba Bean during Flowering Periods

The experiment was conducted at Dicle University Field Crops Department, Southeast Anatolia, Diyarbakir Turkey in the 2018-2019 early spring growth periods. The study aimed to determine the effect of fertilizer treatments (control, phosphorus, nitrogen, organic, and Rhizobium) on plant traits of different faba bean cultivars (Filiz 99, Eresen 87, and Salkim). Plants were harvested in three different periods pre-flowering (43-62 days after sowing), full-flowering (52-75 days), and post-flowering (78-98 days), and shoot and root traits were evaluated. Fresh plant biomass, stem height, fresh and dry root weight, fresh and dry nodule weight, fresh leaf weight, and fresh and dry pod weight were responding to nitrogen fertilizer treatments depending on flowering periods. The number of nodules and fresh and dry nodule weight was affected to a different degree in both nitrogen and phosphorus fertilizer treatments. Nodule weight showed a negative response to rhizobium inoculation. We determined that nitrogen (40 kg ha-1) and phosphorus (80 kg ha-1) fertilizer treatments on faba beans were important. However, we have not belied that fertilizer applications should not be applied for sustainable agriculture because of their high environmental efficiency.

Effects of Rhizobium inoculum compared with mineral nitrogen fertilizer on nodulation and seed yield of common bean. A meta-analysis

Effects of Rhizobium inoculum compared with mineral nitrogen fertilizer on nodulation and seed yield of common bean. A meta-analysis

Socioeconomic drivers of inoculant technology and chemical fertilizer utilization among soybean farmers in the Tolon District of Ghana

Soybean farming is an important source of income for smallholder farmers in Ghana, particularly in the northern savanna ecological zones, where soil infertility is a challenge. To increase soybean production and farm revenue, farmers must adopt improved soybean production technologies. Smallholder soybean farmers' decisions to embrace high-yielding technology are influenced by various socioeconomic factors. The factors driving the adoption of rhizobium inoculant and mineral fertilizer technologies in Ghana's Tolon district were evaluated using a multinomial logit model with 200 smallholder soybean farmers. According to the findings, the likelihood of using inoculants and inorganic fertilizers increased with herd size, farm size, and access to extension services. In addition, female soybean producers were more likely than their male counterparts to use inoculants and chemical fertilizers. The study also found that soybean producers were less likely to use inoculants and chemical fertilizers because of their distance from the local market. To encourage technology adoption, the study recommends that agricultural extension services to farmers be increased. Farmers should also be encouraged to join farmer-based groups to increase inoculant technology uptake.

Promotion effect of AM fungi and rhizobia co-inoculations on alfalfa (Medicago Sativa L.) growth

Arbuscular mycorrhizal fungi (AMF) and rhizobia have been widely used in agriculture in recent years to increase production, reduce fertilizer consumption and control plant diseases. However, it is unclear whether there are differences in the effects of AMF and rhizobia inoculation alone and in combination. In this study, alfalfa seedlings were inoculated with AMF Glomus mosseae (G.m), Glomus intraradices (G.i) and co-inoculated with AMF and rhizobia Sinorhizobium meliloti (S.m) before being transplanted outdoors. The growth characteristics, fine root yield and fine root death of alfalfa were measured throughout the experiment, and the results showed that co-inoculation with AMF and rhizobia promoted alfalfa growth, while increasing plant height, branch number and total biomass. However, the growth promoting effects of AMF and rhizobia differed; AMF inoculation displayed no advantage over S.m inoculation in increasing aboveground biomass (P > 0.05) but did lead to an increase in underground biomass (P < 0.05). Compared with that observed following the single inoculations with G.m or S.m, the annual fine root production following co-inoculation with G.m and S.m increased by 15.38% and 47.06%, respectively, although there was less effect following co-inoculation with G. i and S.m. These results indicated that there was mutual selectivity and interaction between AMF and rhizobia. G.m and S.m inoculation treatment has a positive effect on alfalfa growth, on the one hand, it is because that AMF-Rhizobia synergically promoted alfalfa root system to absorb nutrients (N), then improve the plant growth, on the other hand, their vaccination can reduce the death of alfalfa fine roots, significantly improve the alfalfa biomass of underground part.

Deciphering the Potential Role of Symbiotic Plant Microbiome and Amino Acid Application on Growth Performance of Chickpea Under Field Conditions.

The unprecedented rise in the human population has increased pressure on agriculture production. To enhance the production of crops, farmers mainly rely on the use of chemical fertilizers and pesticides, which have, undoubtedly, increased the production rate but at the cost of losing sustainability of the environment in the form of genetic erosion of indigenous varieties of crops and loss of fertile land. Therefore, farming practices need to upgrade toward the use of biological agents to maintain the sustainability of agriculture and the environment. In this context, using microbial inoculants and amino acids may present a more effective, safer, economical, and sustainable alternative means of realizing higher productivity of crops. Therefore, field experiments were performed on chickpea for two succeeding years using Rhizobium and L-methionine (at three levels, i.e., 5, 10, and 15 mg L–1) separately and in combinations. The results show that the application of Rhizobium and all the three levels of L-methionine increased the growth and yield of chickpea. There was a higher response to a lower dose of L-methionine, i.e., 5 mg L–1. It has been found that maximum grain yield (39.96 and 34.5% in the first and second years, respectively) of chickpea was obtained with the combined use of Rhizobium and L-methionine (5 mg L–1). This treatment was also the most effective in enhancing nodule number (91.6 and 58.19%), leghemoglobin (161.1 and 131.3%), and protein content (45.2 and 45%) of plants in both years. Likewise, photosynthetic pigments and seed chemical composition were significantly improved by Rhizobium inoculation. However, these effects were prominent when Rhizobium inoculation was accompanied by L-methionine. In conclusion, utilizing the potential of combined use of L-methionine and microbial inoculant could be a better approach for developing sustainable agriculture production.

Effects of Phospholipase Dε Overexpression on Soybean Response to Nitrogen and Nodulation.

Nitrogen is a key macronutrient to plant growth. We found previously that increased expression of phospholipase Dε (PLDε), which hydrolyzes phospholipids into phosphatidic acid (PA), enhanced plant growth under nitrogen deficiency in Brassicaceae species Arabidopsis and canola. The present study investigated the effect of AtPLDε-overexpression (OE) on soybean (Glycine max), a species capable of symbiotic nitrogen fixation. AtPLDε-OE soybean plants displayed increased root length and leaf size, and the effect of AtPLDε-ΟΕ on leaf size was greater under nitrogen-deficient than -sufficient condition. Under nitrogen deficiency, AtPLDε-OE soybean plants had a higher chlorophyll content and activity of nitrogen assimilation-related enzymes than wild-type soybean plants. AtPLDε-OE led to a higher level of specific PA species in roots after rhizobium inoculation than wild type. AtPLDε-OE soybean plants also increased seed production under nitrogen deprivation with and without nodulation and decreased seed germination in response to high humidity storage and artificial aging. These results suggest that PLDε promotes nitrogen response and affects adversely seed viability during storage.

Effect of Rhizobium Inoculation and Phosphate Rock Fertilizer Application on Biomass Production, Nutrient use Efficiency and Yield Parameters of Green Gram (Vigna radiata)

The research was focused on an ecologically sound and highly production of legumes particularly green gram through the application of Rhizobium and rock phosphate fertilizer. Therefore, biomass production, nutrient use efficiency and yield parameters were determined for two growing seasons (November 2019 - January 2020 and February - April 2020), at Chuka university horticultural research farm. Biological nitrogen fixation (BNF) in green grams can improve sustainable soil fertility management and increased production. In Kenya, green gram is a major source of food security particularly in Tharaka Nithi County. However, green gram yields are usually low due to low phosphorous and nitrogen levels of the soil. A factorial experiment of 2 x 2 x 2 was laid out in a randomized complete block design. There were three factors, varieties (N26-nylon and KS20-uncle), phosphate rock (0 and 30 kg P ha-1) and Rhizobium MEA 716 (0 and 100 g ha-1) making a total of eight treatments which were replicated three times. Soil sampling and analyses were done before planting and after harvesting of green grams. Data on grain yield, total dry biomass, shoot and root dry weights. Phosphorus use efficiency (PUE) and nitrogen use efficiency (NUE) were done. Data was analysed using Statistical Analysis Software (SAS). Significant means were separated using Least Significant Difference (LSD) at probability level of 5 %. Results for both wet and dry seasons indicated that variety KS20 under Rhizobium inoculation and phosphate rock fertilizer (R1P1V2) showed significantly (P&lt;0.05) higher increase in shoot dry biomass (52.01 g plant-1), root dry biomass (7.60 g plant-1), total dry biomass (146.4 g plant-1), number of pods (84 plant-1) and yield (2158 kg ha-1). Also, there was significant (P&lt;0.05) higher phosphorous use efficiency of 279.32 Kg/ha and nitrogen use efficiency of 1732 kg/ha in treatment R1P1V2 over other treatments. From these results it was concluded that variety KS20 (V2) performed better compared to N26 (V1) under combined application of Rhizobium and phosphate rock fertilizer. Hence, based on the findings, for sustainable and improved green gram production farmers in Tharaka Nithi County.

Effects of Rhizobium Inoculation and P Fertilizer Levels on Selected Soil Properties, Yield, and Yield Components of Faba Bean (Vicia faba L.): The Case of Abuna Gindeberat, West Shewa Zone, Ethiopia

Poor soil fertility status and inappropriate agronomic practices are the major factors for low crop productivity like legumes. Thus, the experiment was conducted to evaluate the effect of the P fertilizer rate and rhizobium inoculation on selected soil properties and yield of faba bean. In order to achieve this objective, a field experiment was laid out in a randomized complete block design in a factorial arrangement with replication. The treatments consisted of five P levels (0, 23, 46, 69, and 92 kg P2O5 ha−1) and two rhizobium inoculants (Fb17 and Fb18). Faba bean (Moti variety) was used as the test crop. Soil samples were collected before and after planting for laboratory analysis. All soil and agronomic data were subjected to the analysis of variance (ANOVA) using statistical analysis software version 9.2. The main effect of strain positively improved soil porosity, but soil bulk density was negatively influenced. Soil chemical parameters such as organic carbon, total N, available P, available sulfur, Ca, Mg, and K were positively influenced. The interaction effects of the P fertilizer rate and rhizobium inoculation significantly influenced organic carbon, total N, available P, and yield parameters (pod per plant, numbers of nodules per plant, biomass yield, straw yield, and grain yields). The combined application of 69 kg P2O5 ha−1 and Fb18 rhizobium inoculants gave the highest grain yield (4.4 t ha−1) of faba bean. Thus, the integrated application of strain and P2O5 fertilizer improved soil fertility and faba bean crop yield. Therefore, reducing soil fertility constrains of the soils through the integrated application of strain and P2O5 fertilizer could be a possible option to reduce the yield gap seen between smallholder farmers and experimental fields. So as to maintain soil fertility and sustain faba bean crop production, farmers of the study area are advised to make integrated use of strain type Fb18 and P2O5 fertilizer at 69 kg/ha−1 with appropriate agronomic practices.

Dependence on Nitrogen Availability and Rhizobial Symbiosis of Different Accessions of Trifolium fragiferum, a Crop Wild Relative Legume Species, as Related to Physiological Traits.

Biological nitrogen fixation by legume-rhizobacterial symbiosis in temperate grasslands is an important source of soil nitrogen. The aim of the present study was to characterize the dependence of different accessions of T. fragiferum, a rare crop wild relative legume species, from their native rhizobia as well as additional nitrogen fertilization in controlled conditions. Asymbiotically cultivated, mineral-fertilized T. fragiferum plants gradually showed signs of nitrogen deficiency, appearing as a decrease in leaf chlorophyll concentration, leaf senescence, and a decrease in growth rate. The addition of nitrogen, and the inoculation with native rhizobia, or both treatments significantly prevented the onset of these symptoms, leading to both increase in plant shoot biomass as well as an increase in tissue concentration of N. The actual degree of each type of response was genotype-specific. Accessions showed a relatively similar degree of dependence on nitrogen (70–95% increase in shoot dry mass) but the increase in shoot dry mass by inoculation with native rhizobia ranged from 27 to 85%. In general, there was no correlation between growth stimulation and an increase in tissue N concentration by the treatments. The addition of N or rhizobial inoculant affected mineral nutrition at the level of both macronutrient and micronutrient concentration in different plant parts. In conclusion, native rhizobial strains associated with geographically isolated accessions of T. fragiferum at the northern range of distribution of the species represent a valuable resource for further studies aimed at the identification of salinity-tolerant N2-fixing bacteria for the needs of sustainable agriculture, as well as in a view of understanding ecosystem functioning at the level of plant-microorganism interactions.