Plant growth-promoting Rhizobacteria (PGPR) and Rhizobia as multi-strain biofertilizers for improved growth and yield of rice

Recently, there has been much interest on the application of PGPR and rhizobia as multi-strain biofertilizer for crops to benefit from the consortium of biochemical characteristics. Several laboratory and glasshouse studies were conducted to assess the beneficial effects of locally isolated PGPR and rhizobia on Malaysian rice variety, MR219. Based on 16S rDNA gene sequencing, these bacterial strains were identified as Lysinibacillus xylanilyticus, Alcaligenes faecalis, Bradyrhizobium japonicum, Rhizobium etli and Bacillus subtilis. These isolates were selected as a potential strains in the development of multi-strain biofertilizer for having multiple beneficial abilities namely biological nitrogen fixation, solubilization of phosphate and potassium, production of phytohormone, hydrolyzing enzymes and iron siderophore. Laboratory study has demonstrated the effectiveness of these strains on early growth and vigor of rice seedlings under controlled condition. A subsequent glasshouse studies have showed a significant improvement of rice growth and yield with bacterial inoculations, particularly when supplied with minimal fertilizer-N rate (33% from the recommended rate). Single and multi-strain inoculations also significantly promoted plant and root growth, tiller numbers, plant dry weight, nutrient accumulations and produced a lower 15N enrichment than uninoculated control that received similar N-fertilizer (33% N). The lower 15N enrichment indicates the occurrence of biological N2 fixation. The proportion of N uptake from atmosphere was estimated at 22% Ndfa. The study revealed a possible new and beneficial biofertilizer formulation to promote growth and yield of rice plants at reduced chemical N-fertilizer input in a sustainable and environmental-friendly agricultural system

Impact of chemical and organic fertilizer on the yield and nutritional composition of bambara groundnut (vigna subterranea l. Verde.)

A pot experiment was conducted to find out the effects of chemical and organic fertilizer on the yield and nutritional composition of bambara groundnut (Vigna subterranea). The size of the pot was 65.94 cm2. Different rates of compost, biofertilizer, gypsum was used along with the combination of different doses of nitrogen and phosphorus fertilizer. N and P fertilizers were found to play dominating role to increase yield and nutritional composition of the plant. Number of pod (41.75), 100-seed weight (34.25 g), protein (22.15%), Ca (803.25 mg/ka) increased with the application of N and P 30 and 60 kg/ha, respectively which was better than all other treatments. The application of N30 + P60 kg/ha increased yield and nutritional composition of bambara groundnut

Fermentation of washed rice water Increases beneficial plant bacterial population and nutrient concentrations

Washed rice water (WRW) is said to be a beneficial plant fertilizer because of its nutrient content. However, rigorous scientific studies to ascertain its efficiency are lacking. The purpose of this study was to determine the effect of fermenting WRW on the bacterial population and identification, and to measure how fermentation affects the nutrient composition of WRW. Rice grains were washed in a volumetric water-to-rice ratio of 3:1 and at a constant speed of 80 rpm for all treatments. The treatments were WRW fermented at 0 (unfermented), 3, 6, and 9 days. Bacterial N fixation and P and K solubilization abilities in the fermented WRW were assessed both qualitatively and quantitatively. The isolated bacterial strains and the WRW samples were also tested for catalase and indole acetic acid (IAA) production ability. Significantly greater N fixation, P and K solubilization, and IAA production were recorded after 3 days of fermentation compared with other fermentation periods, with increases of 46.9–83.3%, 48.2–84.1%, 73.7–83.6%, and 13.3–85.5%, respectively, in addition to the highest (2.12 × 108 CFU mL−1) total bacterial population. Twelve bacteria strains were isolated from the fermented WRW, and the gene identification showed the presence of beneficial bacteria Bacillus velezensis, Enterobacter spp., Pantoea agglomerans, Klebsiella pneumoniae and Stenotrophomonas maltophilia at the different fermentation periods. All the identified microbes (except Enterobacter sp. Strain WRW-7) were positive for catalase production. Similarly, all the microbes could produce IAA, with Enterobacter spp. strain WRW-10 recording the highest IAA of up to 73.7% higher than other strains. Generally, with increasing fermentation periods, the nutrients N, S, P, K, Mg, NH+4, and NO−3 increased, while pH, C, and Cu decreased. Therefore, fermentation of WRW can potentially increase plant growth and enhance soil health because of WRW’s nutrients and microbial promotional effect, particularly after 3 days of fermentation

Impact of nitrogen and phosphorus fertilizer on growth and yield of bambara groundnut

Bambara groundnut (Vigna subterranea) is an indigenous African crop which belongs to the family fabacea and sub-family of faboidea. It seeds contain 63% carbohydrate, 19% protein and 6.5% oil and good source of fibre, calcium, iron and potassium. Hence, this study aimed to determine the effect of nitrogen (N) and phosphorus (P) on growth and yield bambara groundnut. A pot experiments was conducted in ladang 15 at the Faculty of Agriculture; Universiti Putra Malaysia. The experiment was performed Randomized Complete Block Design (RCBD). The size of the pot was 65.94 cm2. The experiment was conducted in a factorial design with four levels of N (0, 10, 20, 30 kg/ha) and P (0, 20, 40 and 60 kg/ha). In this study, N and P fertilizer was played dominating role for vegetative growth of the plant. Plant height (20.65 cm), leaves number (262), leaf area (2140.54 cm2), number of pod (47.25) and pod weight (22.8 g) increased with the application of level of N and P. Vegetative growth and yield of the plant was better at N30P60 kg/ha than the all other treatments. It can be concluded that by using N30P60 kg/ha growth and yield of bambara groundnut is maximum

Wastewater from washed rice water as plant nutrient source: current understanding and knowledge gaps

A significant wastewater source in every household is washed rice water (WRW) because it contains leached nutrients (from washing the rice prior to cooking) that could be used as fertilizer. The paper reviewed the current understanding of the potential use of WRW as a plant nutrient source. WRW was shown to increase vegetables growth, such as water spinach, pak choy, lettuce, mustard, tomato, and eggplant. Different researchers have used various amounts of WRW, and their results followed a similar trend: the higher the amount of WRW, the higher the plant growth. WRW has also been used for other purposes, such as a source of carbon for microbial growth. WRW from brown rice and white rice had nutrients ranging from 40-150, 43-16306, 51-200, 8-3574, 36-1425, 27-212, and 32-560 mg L-1 of N, P, K, Ca, Mg, S, and vitamin B1 (thiamine), respectively. Proper utilization of WRW could reduce chemical fertilizer use and prevent both surface and groundwater contamination and environmental pollution. However, only a few of the studies have compared the use of WRW with the use of conventional NPK fertilizer. The major drawback of WRW studies is that they lack depth and scope, such as determining the initial and (or) final soil physico-chemical properties or plant nutrient contents. Considering the rich nutrient content in WRW, it will impact plant growth and soil fertility when used as both irrigation water and plant nutrient source. Therefore, it is recommended that studies on WRW effect on soil microbial population, plant, and soil nutrient contents to be carried out to ascertain the sustainability of WRW use as a plant nutrient source

Growth and yield responses of rice CV. MR219 to rhizobial and plant growth-promoting rhizobacterial inoculations under different fertilizer-N rates

Effects of locally isolated plant growth-promoting rhizobacteria (PGPR) and rhizobial inoculations on growth and yield of local Malaysian rice variety MR219 experiments were conducted in glasshouse. The treatments consisted of three PGPR (UPMB10, UPMB19 and UPMB20) and two rhizobial (UPMR30 and UPMR31) inoculations, each with three levels of nitrogen fertilizer (0, 33, 100% of recommended rate), laid in CRD. Results showed that bacterial inoculations significantly improved rice growth and yield parameters, particularly when supplied with minimal N rate (33). Bacterial inoculations increased chlorophyll content at 43 and 67 days after planting (DAP). Similar trend for tiller numbers (except inoculation with UPMB20) at 43 DAP. UPMB10 significantly increased filled spikelet percentage (87.33) and UPMB19 produced highest straw dry weight (114.34 g/plant), spikelet weight (107 g/plant) and biological yield (220.11 g/plant) with minimal fertilizer-N. The positive effects of bacterial inoculations appeared to be due to N2-fixing ability, solubilize phosphate and potassium, produce IAA, siderophore, cellulase and pectinase. Thus, locally isolated indigenous PGPR and rhizobial strains have the potential for using as liquid biofertilizer to increase growth and yield of rice minimizing N-fertilizer use

Aerobic Methanotrophy and Co-occurrence Networks of a Tropical Rainforest and Oil Palm Plantations in Malaysia

Oil palm (OP) plantations are gradually replacing tropical rainforest in Malaysia, one of the largest palm oil producers globally. Conversion of lands to OP plantations has been associated with compositional shifts of the microbial community, with consequences on the greenhouse gas (GHG) emissions. While the impact of the change in land use has recently been investigated for microorganisms involved in N2O emission, the response of the aerobic methanotrophs to OP agriculture remains to be determined. Here, we monitored the bacterial community composition, focusing on the aerobic methanotrophs, in OP agricultural soils since 2012, 2006, and 1993, as well as in a tropical rainforest, in 2019 and 2020. High-affinity methane uptake was confirmed, showing significantly lower rates in the OP plantations than in the tropical rainforest, but values increased with continuous OP agriculture. The bacterial, including the methanotrophic community composition, was modified with ongoing OP agriculture. The methanotrophic community composition was predominantly composed of unclassified methanotrophs, with the canonical (Methylocystis) and putative methanotrophs thought to catalyze high-affinity methane oxidation present at higher relative abundance in the oldest OP plantation. Results suggest that the methanotrophic community was relatively more stable within each site, exhibiting less temporal variations than the total bacterial community. Uncharacteristically, a 16S rRNA gene-based co-occurrence network analysis revealed a more complex and connected community in the OP agricultural soil, which may influence the resilience of the bacterial community to disturbances. Overall, we provide a first insight into the ecology and role of the aerobic methanotrophs as a methane sink in OP agricultural soils

Isolation and characterization of encapsulated plant growth-promoting Enterobacter sp. SA10 for enhancing chili growth

Introduction: Plant growth-promoting rhizobacteria (PGPR) can increase plant growth and encapsulation of PGPR with biochar ensures the viability and survival of PGPR. However, this approach is still underexplored. Objectives: The objectives of this study: 1) to isolate and select a potential PGPR from rice rhizosphere based on plant growth-promoting characterization, 2) encapsulate the selected PGPR strain SA-10 using biochar and sodium alginate, and 3) assess the effect of encapsulated and non-encapsulated SA-10 on chili plant growth compared to a non-inoculated SA-10 and control. Methodology: SA-10 was isolated from rice rhizosphere and characterized for plant growth promoting traits including, the nitrogen fixation, phosphate solubilization, production of siderophore, production of indole acetic acid and production of cellulose degradation enzyme. SA-10 was encapsulated in alginate beads along with biochar. A pot experiment conducted using encapsulated SA-10, non-encapsulated SA-10, and a control group to assess the effects of encapsulated SA-10 application on chili plants using complete randomized design (CRD) experimental design with four replications. Results: About 28 bacteria isolates were isolated from the rhizosphere and endospheric of rice crops to determine their effects on the growth of chili plants. The isolates were characterized with zinc, phosphate, and potassium solubilization, siderophores production, and cellulose degradation. The findings showed isolate SA-10 solubilized zinc at a rate of 41.6 %, phosphate at 50 %, and potassium at 76.9 %. It also fixed nitrogen, produced siderophores and degraded cellulose. The isolate also produced the highest IAA at 4.007 mg/L. Isolate SA-10 was then encapsulated in a mixture of biochar and sodium alginate. The results showed that plants treated with encapsulated SA-10 had significantly higher leaf area (3.68 cm2), leaf diameter (6.55 cm), and dry weight (0.39 g) compared to those treated with non-encapsulated and the control treatment. Through 16S rRNA gene sequencing, it was identified that SA-10 belongs to the Enterobacter genus, closely resembling Enterobacter chuandaensis. Conclusion: The findings suggest that Enterobacter sp. SA-10 enhances plant growth, and the use of encapsulated SA-10 with biochar contributes to the growth of chili plants. The encapsulated Enterobacter sp. SA-10 has a promising potential in enhancing crop yield production and promoting sustainable agriculture

Effects of fish stocking density on water quality, growth performance of Tilapia and yield of butterhead lettuce grown in decoupled recirculation aquaponic systems

This study was conducted over a period of 52 days to determine the effects of fish stocking density on the water quality, growth performance of tilapia and yield of butterhead lettuce cultivated in decoupled recirculation aquaponic systems (DRAPS). In this study, three respective tilapia stocking densities (treatments) of 8 Kg m-3, 10 Kg m-3, and 12 Kg m-3 were used to evaluate the butterhead lettuce in the DRAPS, which consist of two independent loops. All treatments were done in triplicates. The results showed with increased stocking density, the electrical conductivity, total dissolved substances and salinity increased and dissolved oxygen decline. The results showed that the highest stocking density produced the highest nutrients accumulation of ammonia-nitrogen (NH3-N), ammonium (NH4), nitrite-nitrogen (NO2-N) and nitrate-nitrogen (NO3-N) and potassium (K) except for phosphorus (P). Nevertheless, based on the conversion of fish feed to NO3-N and P per kilogram of feeds, the lowest stocking density provided the highest concentration of NO3-N and P. It was documented that DRAPS relied solely on the fish waste produced an insufficient concentration of N, P, K and iron. The average survival rate of tilapia in all treatments was above 94% and was not a significant difference among the treatments