Variability of soybean response to rhizobia inoculant, vermicompost, and a legume-specific fertilizer blend in Siaya County of Kenya

Open Access JournalRhizobia inoculation can increase soybean yield, but its performance is influenced by among others soybean genotype, rhizobia strains, environment, and crop management. The objective of the study was to assess soybean response to rhizobia inoculation when grown in soils amended with urea or vermicompost to improve nitrogen levels. Two greenhouse experiments and one field trial at two sites were carried out. The first greenhouse experiment included soils from sixty locations, sampled from smallholder farms in Western Kenya. The second greenhouse experiment consisted of one soil selected among soils used in the first experiment where inoculation response was poor. The soil was amended with vermicompost or urea. In the two greenhouse experiments, Legumefix (inoculant) + Sympal (legume fertilizer blend) were used as a standard package. Results from the second greenhouse experiment were then validated in the field. Analysis of variance was done using SAS statistical software and mean separation was done using standard error of the difference for shoot biomass, grain yield nodulation, nodule effectiveness and nutrient uptake. In the first greenhouse trial, soybean response to inoculation was significantly affected by soil fertility based on nodule fresh weight and shoot biomass. Soils with low nitrogen had low to no response to inoculation. After amendment, nodule fresh weight, nodule effectiveness, nodule occupancy, and shoot dry biomass were greater in the treatment amended with vermicompost than those amended with urea (Legumefix + Sympal + vermicompost and Legumefix + Sympal + urea) respectively. Under field conditions, trends were similar to the second experiment for nodulation, nodule occupancy and nitrogen uptake resulting in significantly greater grain yields (475, 709, 856, 880, 966 kg ha −1) after application of vermicompost at 0, 37, 74, 111, and 148 kg N ha −1 respectively. It was concluded that soybean nodulation and biological nitrogen fixation in low fertility soils would not be suppressed by organic amendments like vermicompost up to 148 kg N ha −1

Co-inoculation effect of rhizobia and plant growth promoting rhizobacteria on common bean growth in a low phosphorus soil

Open Access JournalNitrogen (N) fixation through legume-Rhizobium symbiosis is important for enhancing agricultural productivity and is therefore of great economic interest. Growing evidence indicates that other soil beneficial bacteria can positively affect symbiotic performance of rhizobia. Nodule endophytic plant growth promoting rhizobacteria (PGPR) were isolated from common bean nodules from Nakuru County in Kenya and characterized 16S rDNA partial gene sequencing. The effect of co-inoculation of rhizobium and PGPR, on nodulation and growth of common bean (Phaseolus vulgaris L.) was also investigated using a low phosphorous soil under greenhouse conditions. Gram-positive nodule endophytic PGPR belonging to the genus Bacillus were successfully isolated and characterized. Two PGPR strains (Paenibacillus polymyxa and Bacillus megaterium), two rhizobia strains (IITA-PAU 987 and IITA-PAU 983) and one reference rhizobia strain (CIAT 899) were used in the co-inoculation study. Two common bean varieties were inoculated with Rhizobium strains singly or in a combination with PGPR to evaluate the effect on nodulation and growth parameters. Co-inoculation of IITA-PAU 987 C B. megaterium recorded the highest nodule weight (405.2 mg) compared to IITAPAU 987 alone (324.8 mg), while CIAT 899 C B. megaterium (401.2 mg) compared to CIAT 899 alone (337.2 mg). CIAT 899 C B. megaterium recorded a significantly higher shoot dry weight (7.23 g) compared to CIAT 899 alone (5.80 g). However, there was no significant difference between CIAT 899 C P. polymyxa and CIAT 899 alone. Combination of IITA-PAU 987 and B. megaterium led to significantly higher shoot dry weight (6.84 g) compared to IITA-PAU 987 alone (5.32g) but no significant difference was observed when co-inoculated with P. polymyxa. IITA-PAU 983 in combination with P. polymyxa led to significantly higher shoot dry weight (7.15 g) compared to IITA-PAU 983 alone (5.14 g). Plants inoculated with IITA-PAU 987 and B. megaterium received 24.0 % of their nitrogen demand from atmosphere, which showed a 31.1% increase compared to rhizobium alone. Contrast analysis confirmed the difference between the co-inoculation of rhizobia strains and PGPR compared to single rhizobia inoculation on the root dry weight. These results show that co-inoculation of PGPR and Rhizobia has a synergistic effect on bean growth. Use of PGPR may improve effectiveness of Rhizobium biofertilizers for common bean production. Testing of PGPR under field conditions will further elucidate their effectiveness on grain yields of common bean

Performance of cowpea as influenced by native strain of rhizobia, lime and phosphorus in Samaru, Nigeria

Open Access Article; Published online: 14 Sept 2017The complimentary effects of a native rhizobia strain (SAMFIX 286), lime and single superphosphate (SSP) as components of ISFM were evaluated on the biomass, nodulation and N2 fixation of cowpea (Vigna unguiculata L.). Lime was applied at the rate of 250 kg (Ca(OH)2) ha−1, while SSP was applied at 30 kg P ha−1. The trial was carried out in a screen house with the treatments arranged in randomized complete block design. Results obtained show that the performance of SAMFIX 286 inoculated plants did not significantly (p < 0.05) differ from that of the un-inoculated treatment. Application of lime significantly increased root dry weight, shoot dry weight, nodule number and dry weight by 42.5%, 35.3%, 65.6% and 50%, respectively. Nodulation was significantly (p < 0.05) increased by SSP. The complimentary effect of lime with SSP significantly increased total shoot N concentration. Similarly, combined inoculation of SAMFIX 286 with lime and SSP increased N concentration by 31.9% and N derived from atmosphere (Ndfa) by 16.3% compared to the un-inoculated treatment. Inoculation of SAMFIX 286 with SSP was also effective on Ndfa by cowpea. It was concluded that lime and SSP were good combination with native rhizobia strain in improving cowpea nodulation and biological N2 fixation

Production and use of arbuscular mycorrhizal fungi inoculum in sub-Saharan Africa: challenges and ways of improving

Article purchasedUse of inorganic fertilizer is an essential practice to optimize crop productivity in the poor fertility soils in sub-Saharan Africa, but it has been linked to high cost of crop production, contamination of surface and/or ground water by nitrate leaching and eutrophication of surface water by phosphate run-off. Besides, secondary effects on soil biotic community and soil impoverishment have weakened cropping systems making them increasingly dependent on external chemical fertilizers. Efficient plant nutrition management should ensure both enhanced and sustainable agricultural production and safeguard the environment. Improved production and adoption of bio-inoculants such as arbuscular mycorrhizal fungi is an emerging soil fertility management practice with potential to increase and cheaply improve crop yields. Arbuscular mycorrhizal fungi inoculum production and adoption in sub-Saharan Africa smallholder systems is however, still limited mainly by research capacity and technological challenges. This study provides the state of the art in production and use of the technology and highlights the challenges and opportunities for its advancement. To experience the benefits of arbuscular mycorrhizal fungi, sound investment on research in low input systems and technical support from the government, the public and the private sectors should be considered. Nevertheless, adequate training of extension workers, agro-dealers and smallholder farmers through agricultural, academic and research institutions will solve the challenges of production and adoption of arbuscular mycorrhizal fungi inoculum technology hence improve crop production

Phenotypic, host range and symbiotic characteristics of indigenous soybean nodulating rhizobia from Ethiopian soils

Open Access ArticleSoybean is an exotic crop to Ethiopia and may not necessarily have a specific endosymbiont in the soil. However, since it is a promiscuous host, nodulated by cross nodulating rhizobia, it is likely that some compatible endosymbionts exist from heterologous hosts that could nodulate it with effective nitrogen fixation. This necessitated the search for effective indigenous rhizobia isolates and/or compatible and effective cross-inoculating rhizobia that are already adapted to local conditions. To this end, a total of 67 bacterial isolates were trapped from different soil samples using two soybean varieties (Clark-63K and Awassa-95) and one cowpea variety (Bole), to evaluate their diversity and screen for their symbiotic effectiveness. Accordingly, the majority of isolates (93%) were tentatively categorized into alkali producing slow growing Bradyrhiobium spp. and the others (7%) were fast growing and acid producing rhizobia. The isolates showed differences in utilizing various carbon and nitrogen sources and tolerance to acidity, salinity and temperature. The isolates were also diverse in their inherent antibiotic and heavy metal resistance. All the isolates were able to nodulate soybean variety Clark-63K with significant difference in their capacity to infect and effectively fix nitrogen evidenced from variations in nodulation parameters and shoot dry weights. Accordingly, the isolates induced nodulation with nodule number ranging from 2 to 49 nodules plant-1; nodule dry weight of 16 mg plant-1 to 94 mg plant-1 and shoot dry weight between 585 and 1012 mg plant-1. Using shoot dry weight as an indicator of the relative effectiveness of the isolates, 12% of the isolates were highly effective (SE > 80%) and 88% were effective (SE from 50 to 80%) on soybean. Furthermore, the isolates showed narrow and broad host ranges on four legume species viz., cowpea, mung bean, pigeon pea, and peanut. Accordingly, many isolates (67%) formed nodules with effective nitrogen fixation with cowpea (Vigna unguiculata), pigeon pea (Cajanus cajan) (47%), and on few cases with mung bean (Vigna radiata) showing different level of effectiveness. However, the data showed very narrow host range on peanut (Arachis hypogaea) where, only one isolate formed effective nodules