Potassium Solubilizing Bacteria Research Articles

Impact of Organic and Natural Farming Practices on Growth, Yield Attributes and Yield of Joha Rice

Aims: The aim of the experiment was to study the impact of organic and natural farming practices on the growth, yield attributes and yield of Bokul Joha variety of rice Study Design:  The experiment was laid in a randomized block design with three replications. Place and Duration of Study: Assam Agricultural University-Assam Rice Research Institute, Titabar, Assam, India, during the kharif season of 2022-2023 Methodology: The number of treatments used were eight in total including control which were T1 [Absolute control], T2 [(Natural farming, Beejamrit as root dip treatment (3%) (100 L ha-1) + Jeevamrit as spray (3%) (100 L ha-1) + Ghanajeevamrit as soil treatment at 100 kg (Jeevamrit and Ghanajeevamrit at 30, 60 and 90 DAT)], T3 [(Enriched compost (5 tha-1) + Biofertilizer (Azospirillum, PSB as seedling root dip) (4 kg ha-1)], T4 [Enriched compost (5 t ha-1)], T5 [Vermicompost (5 t ha-1)], T6 [Enriched compost (2.5 t ha-1) + Vermicompost (2.5 t ha-1)], T7 [Fresh azolla as dual crop (400 kg ha-1) + Biofertilizers (Azospirillum, PSB and KSB mix as seedling root dip) (4 kgha-1)] and T8 [Vermicompost (1 tha-1), mixed inocula of Azospirillum amazonense A-10 and Bacillus megaterium P-5 (4 kg ha-1), rock phosphate (10 kg P2O5  ha-1)]. The experiment was laid in a randomized block design with three replications. Where T= Treatment, PSB = Phosphate Solubilizing Bacteria, KSB=Potassium Solubilizing Bacteria, DAT = Days After Transplanting and NF=Natural Farming.  Results: Plants that were noticeably taller were observed with treatment T8: application of vermicompost (1 tha-1), mixed inocula of Azospirillum amazonense A-10 and Bacillus megaterium P-5 (4 kg ha-1), rock phosphate (10 kg P2O5) i.e., at 45 DAT (81.78 cm),90 DAT (128.15 cm) and at harvest (145.71 cm). The same treatment recorded the highest no. of tillers 45 DAT (8.31m-2), at 90 DAT (13.79 m-2) and at harvest (10.40 m-2). Also, dry weight was noted to be highest for the same treatment, at 45 DAT (29.34 g plant-1), 90 DAT (79.11 g plant-1) and at harvest (92.29 g plant-1). Additionally, the same treatment resulted in highest grain (34.62 qha-1) and straw (70.30 q ha-1) yield. Conclusion: Combined application of vermicompost (1 t/ha) along with inocula of Azospirillum amazonense A-10 and Bacillus megaterium P-5 (4kg/ha) and rock phosphate (10 kg P2O5) can be used as a suitable treatment for attaining higher growth, yield attributes and yield in Bokul Joha variety of rice.

Isolation, and selection of indigenous potassium solubilizing bacteria from Vietnam Mekong Delta rhizospheric soils and their effects on diverse cropping systems

Potassium (K) is an essential nutrient for plant growth, biosynthesis, and metabolism. It enhances plant tolerance to salinity and acidity by triggering various defense mechanisms. These characteristics are particularly important to agricultural production in the Vietnam Mekong River Delta, experiencing increased saltwater intrusion, precipitation extremes and unpredictable drought. This study isolated and selected indigenous potassium-solubilizing bacteria (PSB) from Vietnam Mekong Delta rhizospheric soils collected from three different ecological systems producing rice, maize, kumquat, and green onion. Experiments were conducted to evaluate the effect of indigenous PSB on rice seedlings and future potential as biostimulants for commercial field application. To isolate PSB, solid Aleksandrov medium supplemented with 0.2% muscovite was used. The soluble K was quantified using the atomic absorption method at a wavelength of 766.5 nm. Among 24 isolates, Burkholderia vietnamiensis L1.1 and Staphylococcus hominis T7.3 exhibited the highest K solubilization, releasing 567 μg L−1 and 488 μg L−1 liquid medium, respectively. The study explored the optimal conditions for K release, revealing that a temperature of 35 °C, a pH 5, and NaCl concentration up to 1 % in a medium favored K solubilization. B. vietnamiensis L1.1 significantly enhanced rice seed germination (95.3 %) compared to the control treatment without PSB (82 %). Furthermore, the combined application of B. vietnamiensis L1.1 and S. hominis T7.3 notably improved rice growth under K deficient conditions. This research suggests that these indigenous PSB can effectively increase plant available K and improve the productivity of rice and other crops grown under saline and acidic stresses.

Sustainable basmati rice yield and quality enhancement through long-term organic nutrient management in the Indo-Gangetic Plains

Context or problemThe extensive use of chemical fertilizers and pesticides in modern agriculture, particularly since the green revolution, has led to profound consequences for agricultural ecosystems. This approach, while initially boosting yields, has disrupted soil health, biodiversity, and environmental balance. Moreover, it contributes silently to global climate change by releasing greenhouse gases. These challenges underscore the urgent need for a shift towards sustainable agricultural practices to safeguard soil health, biodiversity, and human nutrition while mitigating the impacts of climate change. Objective or research questionThe primary objective of this study is to assess the impact of the long-term (seventeen years) application of organic nutrient management on the physicochemical properties of basmati rice soil and its nutritional quality. The study aims to understand the effectiveness of different organic nutrient management practices in mitigating the negative consequences associated with conventional agricultural practices. MethodsThe experiment used a strip-plot design with three replications, assigning two cropping systems (basmati rice-wheat-green gram and basmati rice-wheat-sesbania) to vertical strips. Seven nutrient management practices, including control, farmyard manure (FYM), vermicompost, farmyard manure + crop residues, vermicompost + crop residues, farmyard manure + crop residues + biofertilizers, and vermicompost + crop residues + biofertilizers [nitrogen-fixing Azospirillum, phosphorus-solubilizing bacteria (PSB), potassium-solubilizing bacteria (KSB), and a cellulolytic culture (Aspergillus awamori, Trichoderma viride, Phanerochaete chrysosporium, and Aspergillus wululens)] were applied to the horizontal strips. ResultsThe findings show that the cropping system with sesbania green manure significantly improved soil physicochemical attributes, nutritional content, and basmati rice yield compared to the green gram-based system. Continued application of organic manures, crop residues, and biofertilizers notably enhanced soil fertility, grain quality, and basmati rice productivity. The combined use of vermicompost, wheat residue, biofertilizers, and sesbania green manure treatment increased organic carbon content by 78.7% over the control, and soil available nitrogen, phosphorus, and potassium by 38.3–54.9%, 57.6–143.8%, and 27.9–64.1%, respectively. Additionally, it augmented diethylenetriamine pentaacetic acid extractable iron, zinc, manganese, and copper content by up to 44.2%, 28.5%, 57.9%, and 71.0%, respectively. Co-application of the above organic sources also significantly enhanced grain and straw yields by 74.5–80.1% and 46.1–50.0%, respectively, compared to the control. ConclusionsEnhancing Basmati rice yield and quality in the Indo-Gangetic Plains can be sustainably achieved through sesbania green manuring and organic practices. Positive correlations with key soil parameters emphasize the significance of organic farming for long-term sustainability. Implications and significanceThe study suggests that adopting organic practices, including sesbania green manuring and combining organic inputs, can alleviate the adverse effects of conventional farming on soil health, biodiversity, and climate change. This aligns with the broader goal of establishing sustainable production and consumption in basmati rice-based cropping systems.

Release of Potassium Ions from Feldspar by Organic Acids Present in Potassium-Solubilizing Bacteria

Agricultural production and quality are determined by the nutrient levels in the soil. Permanent agricultural lands are usually nutrient deficient and it is compensated by fertilization. Recent studies have found that potassium-bearing chemical fertilizers caused some environmental issues and these fertilizers are expensive. Therefore, the development of a new method for supplying potassium to plants using ingredients found in Sri Lanka is important. In this respect, the bioconversion of feldspar using biotechnological processing to obtain potassium fertilizers is very promising. The overall objective of this study is to explore the release of potassium ions from feldspar (Microcline- KAlSi3O8) found in Sri Lanka by organic acids present in potassium-solubilizing bacteria to improve the efficiency of these minerals to use in more sustainable agricultural practices. In this research, the solubilization of feldspar with citric, oxalic, succinic, and tartaric acids (the main acids that are produced by potassium solubilizing bacteria) was studied, concerning the effect of acid type, the effect of each acid concentration, the effect of particle size of feldspar, the effect of incubation time, and the changes in pH over time. Ground feldspar (0.150–0.300 mm and 0.075– 0.150 mm) was separately shaken with 0.01, 0.02, 0.03, 0.04 and 0.05 M of each organic acid for different periods (1, 2.5 and 4 hours) and the released potassium ion concentration was measured using a flame photometer and pH change was measured using a pH meter. The extent of solubilization of feldspar was shown to be influenced by the type of organic acid used. In comparison to inorganic acids (H2SO4), some organic acids were more successful in solubilizing feldspar. Both oxalic and tartaric acids showed a higher capability of releasing potassium from the feldspar than other acids by up to 9 folds. The solubilization was insignificant for the same acid when the acid concentration was changed. The solubility of feldspar in all acids increased as the particle size decreased. The solubilization of feldspar was increased practically in almost all acids as time increased. pH was increased in almost all acids when the reaction time was increased. These findings show that both oxalic and tartaric acids are the most successful acids in solubilizing feldspar. Finding bacteria that secrete these acids as their major byproducts and conditions that secrete these acids would be beneficial for agriculture and feldspar can be used to supply potassium to agricultural lands. 
 Keywords: Organic acids, Feldspar, Solubilization 

Potassium Ions Release from Mica by Organic Acids Present in Potassium Solubilizing Bacteria

Plants require a variety of life-building ingredients to grow properly and optimally. Plants that lack essential nutrients are unable to reach their full potential, have lesser yields, and are more susceptible to diseases. The primary macronutrients are nitrogen (N), phosphorus (P), and potassium (K), which are the three most critical nutrients without which plants wouldn‘t survive. Fertilizers must be added to K-depleted soil to produce a feasible soil environment for plant growth. Chemical K fertilizers are costly and cause soil pollution. Bio-fertilizers gaining popularity because of their low harmful effects. In Sri Lanka, new ways of producing Bio K-fertilizer are convenient in the field of agriculture. Phlogopite mica is a natural mineral that contains K as a major component (7.22% of mass as K2O) that can be used as the source of Bio-K fertilizer production. In this research, the solubilization of phlogopite mica (sample was obtained from Matale district, Sri Lanka) by major types of organic acids which are mainly released from bacteria was determined. In this study special attention was paid to the following main factors: Type of organic acids (Citric, Oxalic, Succinic and Tartaric acid), Acid concentrations (0.01 M, 0.02 M, 0.03 M, 0.04 M, and 0.05 M), Effect of ground mica particle sizes (0.300 mm-0.150 mm and <0.150 mm), the effect of time on solubilization in three shaking time intervals (1 hour, 2.5 hours, 4 hours) the indicated solubilization patterns and pH changes were observed. The current findings show that Citric acid is the most efficient K solubilizer because at 0.04 M, citric releases the 17.00 mg/L of K whereas the lowest value of released K 2.33 mg/L was observed for oxalic acid which is determined by Flame Photometer using 50.00 mg/L of standard K+ solution. Therefore, Citric acid has a significant potential for the solubilization of K in mica. When particle size increases, the rate of solubilization appears to decrease with each acid. Also, when shaking time was increased the amount of soluble K released has been increased. Future studies of this research will be extended to find and isolation of citric acid-releasing bacteria for solubilizing mica to produce K Biofertilizer to improve soil fertility thereby increasing the crop yield in Sri Lanka. 
 Keywords: Phlogopite mica, Bioconversion, Bio-fertilizers, Chemical K-fertilizers 

Species Diversity, Nitrogen Fixation, and Nutrient Solubilization Activities of Endophytic Bacteria in Pea Embryos

Endophytic bacteria, especially those that participate in nitrogen fixation, play critical roles in supplying essential nutrients for legume plant growth. Despite that there have been numerous investigations targeting bacterial microbiomes in legume roots and nodules, little is known about embryonic bacteria that facilitate plant nutrient utilization after seed germination. Here, we collected and investigated endophytic bacterial microbiome in edible pea (Pisum sativum) embryos using five representative cultivars and a pea sprout (shoot of pea [SHP]) control. Twenty-six nitrogen-fixing bacteria (NFB) were isolated from pea embryos, with three strains found in fresh grain pea (FGP) and snow pea (SP) exhibiting the strongest nitrogenase activity of above 85 nmol C2H4/mL/h. Some NFB isolates are also potassium-solubilizing bacteria (KSB) or phosphorus-solubilizing bacteria (PSB) utilizing inorganic and/or organic phosphorus. All 26 NFB showed variable levels (0.41 to 7.10 μg/mL) of indole-3-acetic acid (IAA) secretion. The nutrient-solubilizing NFB identified in our research are potential targets for biofertilizer development. They could be useful in converting nitrogen, potassium, and/or phosphorus into usable forms for the plants. At the microbiome level, high-throughput 16S ribosomal RNA (rRNA) sequencing of 40 bacterial collections from pea embryos generated 4234 operational taxonomic units (OTUs) using 97% identity as the threshold for clustering high-quality effective reads (valid tags). Analysis of OTU annotation results revealed similar species community structures, abundance, and diversity in most samples. Our embryo-derived endophytic bacterial pool provides a microbiome platform for seed dormancy and germination research of edible peas, as well as for digging new biofertilizer resources in general.

Peranan Pseudomonas aeruginosa ATCC 15442 terhadap Pertumbuhan Tanaman Cabai Rawit (Capsicum frutescens L.) Varietas Bonita pada Kondisi Salin

Hot pepper (Capsicum frutescens L.) is one of the food crop commodities that is widely cultivated in Indonesia. Salinity stress can reduce the bioavailability of potassium and its uptake by plants, which will ultimately reduce plant growth and production. One way to reduce the effect of salinity and increase potassium uptake by plants is to use potassium-solubilizing bacteria. One of the bacteria that can solubilize potassium is Pseudomonas aeruginosa. This research aims to study the role of Pseudomonas aeruginosa ATCC 15442 on the growth of the Bonita variety of hot pepper under saline conditions. This study used a completely randomized factorial design with four concentration levels of NaCl treatment: 0, 4, 8, and 12 g/L, as well as two levels of bacteria administration: without bacteria and with bacteria. The results showed that the application of bacteria, salt concentration, and the interaction of the two had no effect (p-value> 0.05) on the growth of hot pepper plants with the observed parameters namely plant height, number of leaves, shoot fresh weight, root fresh weight, shoot dry weight, root dry weight, and chlorophyll content.

Effect of Micronutrients and Biofertilizer Treatments on Yield and it`s Attributes of Coriander (Coriandrum sativum L.) cv. RCR-41

The current study, named "effect of micronutrients and biofertilizer on yield parameters of coriander Coriandrum sativum (L.) cv. RCR-41," is planned to be carried out in the Research Field, Department of Horticulture, College of Agriculture, Gwalior, M.P., during Rabi 2020-21 and 2021-22. The experiment was designed in a Completely Randomized Block Design (CRBD) with two factors concepts i.e., Micronutrients (ZnSO4 (0.5%), FeSo4 (0.5%), CuSo4 (0.5%), Biofertilizers (Phosphorus Solubilizing Bacteria (PSB), Azotobacter, Potassium Solubilizing Bacteria (KSB) and replicated three times and included three replications. At the time of coriander seeding, treatments combinations including RDF doses of fertilisers and biofertilizers were used. The results showed that treatment M1 (ZnSO4 @ 0.5%) was the optimum micronutrient level treatment for coriander production. Treatment B2 (Azotobacter) was shown to be the optimal biofertilizer level for coriander production. The treatment combination M1B2 (ZnSO4 @ 0.5% x Azotobacter) was shown to be considerably better among all treatment combinations, yielding the highest coriander yield characteristics.

Potassium Solubilizing Bacteria (KSB) and Osmopriming Mediated Morphological Changes and Triggers in Yield of Green Gram (Vigna radiata L.) Under Water-Limiting Conditions

A field-based experiment was conducted to know the relevance of potassium solubilizing bacteria (KSB), and Osmo-priming mediated morphological changes and yielded recovery in green gram (Vigna radiata L.) under water-limiting conditions. Hence, the experiment was carried out at the research farm of Lovely Professional University. The characters like plant height, number of leaves, leaf area plant-1, and LAI were considered to track the morphological changes, while the primary branches, nodules, pods plant-1, seeds pod-1, the average length of the pod, test weight, biological yield, grain yield, and harvest index (HI) were used to determine the recovery of yield as compared to control. Among the treatments, T8 was recorded as one of the best treatments for all the morphological parameters studied, i.e., plant height (51.80 cm), number of leaves (42 plant-1), leaf area (577.27 cm2.plant-1) and LAI (1.92) while most of the yield contributing characters were found better in T6 i.e. nodules (8.3 plant-1), seeds pod-1 (10) and length of the pod (7.65 cm) except for the primary branches and the number of pods plant-1 which was remain recorded maximum in T8 (6.0 and 22). The yield of green gram and its biological yield were recorded as highest in T6 and T2 (6.83 and 24.23 g.plant-1), while HI and test weight were also noted in T6 (32.0% and 5.90 g). This study has concluded that the KSB, combined with KNO3, showed a strong potential to modify the morphological structure while the yield of green gram was in KSB + Ca(NO3)2 under water scarcity.

Screening of rhizosphere nitrogen fixing, phosphorus and potassium solubilizing bacteria of Malus sieversii (Ldb.) Roem. and the effect on apple growth

Nitrogen, phosphorus and potassium inorganic fertilizers are commonly used when growing apples, but their excessive application has resulted in a decline in soil fertility and therefore an inability to maintain sustainable cultivation systems. It is possible to compensate for this with biofertilizers. Nitrogen-fixing, phosphorus solubilizing, and potassium solubilizing bacteria are biofertilizers with a broad range of possible uses. In this study, beneficial microorganisms were screened from the rhizosphere soil of the apple tree, Malus sieversii (Ldb.) Roem., which is rich in microbial diversity in natural environments. It was essential to investigate their effects on the growth of apple seedlings. Eight populations of organic phosphorus solubilizing bacteria (56), inorganic phosphorus solubilizing bacteria (13), nitrogen-fixing bacteria (22), and potassium solubilizing bacteria (24) were isolated from eight populations of Xinjiang wild apple rhizosphere in Ili by medium culture. Their morphological characteristics were recorded and their activity was determined. The most active strains were Pseudomonas migulae, Pseudomonas poae, and Pseudomonas extremaustralis, which was determined by physiological and biochemical properties and 16S rDNA sequence analysis. The L16 (45) orthogonal experiment, which used the three strains as testing materials, was created to assess the effects of the strains on apple physiological indicators, soil nutrients, leaf nutrients, and biomass, as well as to identify the ideal combination, concentration, timing, and application method. The results indicated that the peroxidase (POD) and catalase (CAT) activities of apple seedlings increased significantly under the 10 treatment, and the (SOD) activities of the 0 (control) and 1 (inorganic fertilizer only) treatments were significantly lower than the other treatments; soluble sugar, soluble protein and chlorophyll contents increased in all treatments compared to 0 and 1, while malondialdehyde and proline contents increased or decreased compared to 0 and 1; apple seedlings in treatment 10 had the highest soil N, P, and K content, leaf N, P, and K content and biomass were also all highest in treatment 10. In summary, the strains screened for the test can be used as biofertilizers and the optimum application was determined for treatment 10, meaning that the results also provide a theoretical basis for their application in artificially grown orchards.

Effect of Plant Growth Regulators and Bio-Fertilizer on Growth and Quality of Fenugreek (Trigonella foenum-graecum L.)

The present investigation entitled “Effect of plant growth regulators and bio-fertilizer on growth and quality of fenugreek (Trigonella foenum-graecum L.)” was carried out at the Experimental field, College of Agriculture, RVSKVV, Gwalior during 2020-21 under agro-climatic and soil conditions of Northern Madhya Pradesh. The experiment was laid out in Randomized Block Design (RBD) with three replications. Each replication consists of ten treatments of biofertilizers viz., Rhizobium, Phosphate solubilizing bacteria (PSB) and Potassium solubilizing bacteria (KSB) and plant growth regulators viz., Gibberellic acid (GA3) and Naphthalene acetic acid (NAA). All the treatments were randomized separately in each replication. Result showed that the different biofertilizers (i.e. Rhizobium, PSB and KSB) and plant growth regulators (i.e. GA3 and NAA) treatments significantly influenced the growth and quality parameters of fenugreek. Treatment T4 (Rhizobium + NAA) gave the maximum growth, it was found best treatment combination as compared to all other treatment combinations of biofertilizers and PGRs, while the minimum growth, yield and economical parameters were recorded in treatment T1 (Control).

Impact of Potassium Inoculants and Biotite on Soil Microbial Population and Enzymatic Activity under Maize (Zea mays L.) Cultivation in Gangetic Plains

The study explores the impact of potassium inoculants and black mica on soil microbial populations and enzymatic activity in maize cultivated soils. Microbial communities fueled by root exudates play essential roles in nutrient cycling, plant health, and soil structure. This study investigates the effects of potassium-solubilizing bacteria (KSB) and mineral potassium on microbial populations and enzymatic activity across different growth stages of maize. The experiment was conducted in randomized block design with 14 treatments, including combinations of KSB isolates, mineral potassium, and inorganic potassium. Microbial populations (bacteria, fungi, actinomycetes, and KSB) were quantified using serial dilution and plating techniques. Enzymatic activities (dehydrogenase, phosphatase, and urease) were assessed to understand nutrient interactions and microbial influences. The findings indicate that all treatments exhibited increased microbial populations compared to the control. Notably, treatment 75% recommended potassium dose + 25% potassium from Biotite + OVPS 05 consistently demonstrated the highest microbial growth. The presence of KSB appeared crucial in enhancing bacterial and fungal populations. Additionally, enzymatic activities were significantly influenced by treatments, with 75% recommended potassium dose + 25% potassium from Biotite + OVPS 05 showing the highest dehydrogenase, alkaline phosphatase, and urease activities. These results suggest that the combination of KSB isolates and mineral potassium contributes to enhanced microbial populations and soil enzymatic activities, offering insights into sustainable agriculture practices that balance productivity and soil health. The study sheds light on the intricate relationships between microorganisms, nutrients, and soil biochemical processes, providing valuable guidance for future agricultural strategies.

Identifikasi Bakteri Pelarut Kalium Indigenus Asal Perkebunan Nanas

The use of relatively high doses of inorganic fertilizers to increase yields in plantation-scale pineapple (Ananas comosus) cultivation can lead to new problems, such as being toxic to plants, polluting the environment, and increasing production costs. The utilization of rhizosphere microbes, such as potassium solubilizing bacteria (KSB) is expected can reduce the dose of inorganic K fertilizer application because it can dissolve potassium-fixed Al and Fe soil so that it is available to plants. This study aims to assess and characterize the potential of BPK in pineapple plantation areas. KSB evaluation was carried out based on the Potassium Solubility Index (IKK), besides that, it also carried out the characterization of bacteria that have the potential as CPC isolates. CPC was isolated from planting blocks with low and high production levels in the vegetative (V) and generative (G) phases with 5 replications. As many as 20 isolates from the CPC population on pineapple plantations were successfully isolated in this study. The lowest K solubility index of 0.6 was obtained in isolate RV1 and the highest, namely 1.2 in isolate RG1. Among these isolates, RG1 is Gram-positive and grows optimally at pH 5, temperature 30°C. Based on the results of the phylogenetic analysis, it is known that this potassium solubilizing isolate has the same level of similarity with the bacterium Bacillus subtilis.
  
 Keywords: Bacillus, indigenous, potassium, solubilizing index, temperature

Seed Priming for Enhancement of Seed Quality in Quality Protein Maize (QPM) (Zea mays L.)

An investigation was carried out with HQPM-5 maize hybrid and its parental lines HKI-163 and HKI-161 seeds during rabi 2022-23 to evaluate the effect of liquid biofertilizers (Azospirillum, Phosphorus solubilizing bacteria and Potassium solubilizing bacteria) on seed quality attributes in Quality Protein Maize (QPM) genotypes. The seeds were subjected to different concentration and duration of hydropriming and biopriming (Concentration: 10,15 and 20%; Duration: 6,12,18 and 24h). The non primed seeds were used as control. HQPM-5 seeds bioprimed with combination of Azospirillum @ 20 % + Phosphorous solubilizing bacteria @ 20 % + Potassium solubilizing bacteria @ 20 % at 12h (T9) recorded higher seed quality i.e., germination, field emergence, root length, shoot length, seedling length, seedling fresh weight, root dry weight, shoot dry weight, seedling dry weight, seed vigour index I & II, nitrogen and protein content and lower EC of seed leachates than the parental lines, HKI-163 and HKI-161. The overall performance of female parent was found to be better compared to the male parent.

Analysis of the Potassium-Solubilizing Priestia megaterium Strain NK851 and Its Potassium Feldspar-Binding Proteins.

Potassium-solubilizing bacteria are an important microbial group that play a critical role in releasing mineral potassium from potassium-containing minerals, e.g., potassium feldspar. Their application may reduce eutrophication caused by overused potassium fertilizers and facilitate plants to utilize environmental potassium. In this study, a high-efficiency potassium-solubilizing bacterium, named NK851, was isolated from the Astragalus sinicus rhizosphere soil. This bacterium can grow in the medium with potassium feldspar as the sole potassium source, releasing 157 mg/L and 222 mg/L potassium after 3 days and 5 days of incubation, respectively. 16S rDNA sequencing and cluster analysis showed that this strain belongs to Priestia megaterium. Genome sequencing further revealed that this strain has a genome length of 5,305,142 bp, encoding 5473 genes. Among them, abundant genes are related to potassium decomposition and utilization, e.g., the genes involved in adherence to mineral potassium, potassium release, and intracellular trafficking. Moreover, the strong potassium-releasing capacity of NK851 is not attributed to the acidic pH but is attributed to the extracellular potassium feldspar-binding proteins, such as the elongation factor TU and the enolase that contains potassium feldspar-binding cavities. This study provides new information for exploration of the bacterium-mediated potassium solubilization mechanisms.

Effect of Potassium Solubilizing Bacteria (KSB) on the Performance of Sweet Corn (Zea mays L. saccharata) in Potassium Sufficient Soils of Semi-arid Tropic

An experiment was conducted on potassium sufficient sandy loam soil (Alfisols) to evaluate the impact of potassium solubilizing bacteria (KSB) on the performance of rabi sweet corn. The study consisted of 10 treatments with different doses of potassium with and without KSB treatment [Seed treatment (ST) + Soil drenching (SD) at Knee height (KH) stage]. Result of this experiment indicated that sweet corn yield was gradually reduced with reduction of recommended dose of potassium (RDK) irrespective of KSB treatment. Amongst all treatments, application of 100% RDK in 2 equal splits at sowing and KH stage + KSB (ST + SD) (T10) resulted in highest growth, yield (19.7 t ha-1) and yield attributes. However, T10 was on par with the result of [100% RDK + KSB (ST) + KSB (SD) at KH stage], (50% RDK at basal + 50% RDK at KH stage), [100% RDK+ KSB (ST) +KSB (SD) at KH stage] and [75% RDK at basal + KSB (ST) +KSB (SD) at KH stage] treatments. Whereas, implication of 25% or 50% reduction of RDK was significantly inferior to 100% RDK. The study revealed that KSB could substitute 25% of RDK supplied to nutrient exhaustive crop like rabi sweet corn without compromising the economic yield in potassium rich alfisols of semi-arid tropic.

Agronomic Characteristics of Maize Grown in Paddy Soil, Along with Root Zone Soil Chemical Properties and Soil Bacterial Numbers

Maize is being considered as an alternative crop for off-season rice production in Thailand due to increasing water scarcity. The objective of this study was to evaluate the agronomic characteristics and root-zone soil properties of 4 hybrid maize varieties grown in paddy soil during off-season rice cultivation, in order to assess their growth and development after the flooded-rice harvest and the associated soil microorganisms. The randomized complete block design with 4 treatments and 4 replications was used. The 4 treatments were 2 new maize varieties (Suwan 5731 and Suwan 5819), 1 check variety (Suwan 4452), and 1 local use variety (PAC 789). Suwan 5819 showed significantly higher plant height than Suwan 4452, Suwan 5731 and PAC 789, with the highest plant height recorded for Suwan 5819 (221 cm). Similarly, Suwan 5819 exhibited significantly higher estimated leaf area index than Suwan 4452, Suwan 5731 and PAC 789, with differences of 32.67, 42.57 and 29.29 % at VT, respectively. These superior performances of Suwan 5819 could be attributed in part to increased dry matter and nutrient accumulation at the VT stage. The grain yield for PAC 789 was 13.71 t ha–1, Suwan 4452 was 13.23 t ha–1, Suwan 5731 was 12.83 t ha–1, and Suwan 5819 was 12.25 t ha–1. However, there was no significant difference in the grain yields among the 4 varieties. The soil in the root zone of Suwan 5819 at VT was significantly less acidic (pH 5.08) than Suwan 4452 (pH 4.58), PAC 789 (pH 4.61) and Suwan 5731 (pH 4.75). The nitrogen-fixing bacteria were most abundant in PAC 789 (84 %), phosphate-solubilizing bacteria in Suwan 4452 (15 %), and potassium-solubilizing bacteria in Suwan 5819 (16 %). Overall, the study suggests that Suwan 5819 is a promising maize variety for agronomic performance in the tested region. HIGHLIGHTS Maize is a viable alternative to rice for off-season cultivation in water-scarce regions. One new maize hybrid (Suwan 5819) showed better growth and nutrient accumulation during the vegetative transition stage. Soil properties, including beneficial microorganisms, did not differ significantly among the four maize varieties studied. Suwan 5819 new maize hybrid had less acidic root zone soil conditions than the other tested varieties. Commercial maize hybrid had the highest counts of N-fixing and K-solubilizing bacteria in the root zone soil, but there was no significant difference in bacterial count compared to the Suwan maize GRAPHICAL ABSTRACT  

Visual screening of potassium solubilizing bacteria for increasing the solubilization of potassium minerals

Research on potassium solubilizing bacteria (KSB) has recently gained attention, most of it has been focused on the size of the halo zone; however, information regarding KSB growth duration and their potential to reduce the use of chemical fertilizers for sustainable agriculture and to be used as a biofertilizer are still lacking. The aim of this study was to offer a complete, long-term observation of KSB growth. We monitored the growth of two KSB strains that were isolated from the rhizosphere for 7 days on Modified Aleksandrov Medium (MAM) plates. We specifically designed the observation times. These methods were used to distinguish KSB’s capability to solubilize potassium minerals. The results indicated that KSB-12 isolate was capable of producing organic acid and thus solubilizing potassium faster than KSB-19 isolate at 1-4 days of incubation. Interestingly, the solubilizing zone of the KSB-12 isolate decrease after 5 days of incubation, while KSB-19 isolate continued to grow, maintain cell numbers, produce organic acids, and continuously release potassium. Different types of volatile and non-volatile organic acids have an effect on this phenomenon. In conclusion, we provided a well-designed time series study regarding the potassium solubilization efficiency of KSB, determining the fastest and longest strains of potential KSBs.

Contribution of potassium solubilizing bacteria in improved potassium assimilation and cytosolic K+/Na+ ratio in rice (Oryza sativa L.) under saline-sodic conditions.

Sodium-induced potassium (K+) deficiency is more prevalent in salt-affected soils. Plants experience K+ starvation thus cytosolic K+/Na+ ratio is lowered, which is a prerequisite for their survival. K+ enrichment in crops can be acquired via K-solubilizing bacteria as a sustainable green agriculture approach. This study was conducted to explore potent K-solubilizing bacteria from the rhizosphere of wheat, rice, and native flora grown in salt-affected soils in two distinct regions of Pakistan. The aim of this work was to evaluate the contribution of microbial consortiums to the improvement of K+ assimilation and cytosolic K+/Na+ ratios in rice crops under saline-sodic conditions. Among 250 bacterial isolates, 9 were selected based on their salt (11% NaCl) and alkali (9) tolerance and K-solubilization indices (1.57-5.67). These bacterial strains were characterized for their plant growth-promoting traits and identified based on 16S rRNA gene sequencing. A consortium of five strains, namely, Enterobacter hormaechei, Citrobacter braakii, Pseudomonas putida, Erwinia iniecta, and Pantoea agglomerans, was used as a bio-inoculant to evaluate its role in K+ assimilation, cytosolic K+/Na+ ratio, and subsequent yield enhancement in rice grown under saline-sodic conditions. The impact of applied consortium on rice was assessed under variable salt levels (Control, 40, 80, and 120 mM) in a pot experiment and under natural saline-sodic conditions in the field. Plant agronomical parameters were significantly higher in the bacterial consortium-treated plants, with a concomitant increase in K+-uptake in root and shoot (0.56 and 0.35 mg g-1 dry wt.) of the salt-tolerant rice variety Shaheen. The root K+/Na+ ratio was significantly improved (200% in 40 mM and 126% in 80 mM NaCl) and in the shoot (99% in 40 mM and 131% in 80 mM) too. A similar significant increase was also observed in the salt-susceptible variety Kainat. Moreover, grain yield (30.39 g/1,000 grains wt.) and biomass (8.75 g) of the rice variety Shaheen, grown in field conditions, were also improved. It can be concluded that K-solubilizing bacteria can be used as bio-inoculants, contributing to growth and yield increment via enhanced K-assimilation and cytosolic K+/Na+ ratio in rice crops under salt stress.

Isolation and molecular characterization of potassium-solubilizing bacteria from limestone mountain of Bahorok, Langkat District, Indonesia

Abstract. Bangun IH, Hanum H, Sabrina T. 2023. Isolation and molecular characterization of potassium-solubilizing bacteria from limestone mountain of Bahorok, Langkat District, Indonesia. Biodiversitas 24: 4175-4184. In agricultural practices, ensuring an adequate supply of potassium to plants is crucial for optimal growth and productivity. However, the exchangeable K is tightly bound to soil minerals such as mica, feldspar, and clay minerals, making it unavailable for plant uptake. K-solubilizing bacteria K can dissolve potassium from the mineral layer and be available to plants. The Previous study has found 11 bacterial isolates capable of solubilizing K in Aleksandrov solid media. This study aimed to select the best K-solubilizing bacteria for solubilizing K in soil and to perform molecular identification of these bacteria. A novel finding from this study is that specific KSBs enhance the levels of exchangeable K in the soil through various mechanisms, as evidenced by increased exchangeable Ca, Mg, and soil pH. Additionally, the research identified two newly discovered bacterial species capable of potassium solubilization: Paraburkholderia phymatum and Burkholderia paludis. Furthermore, the study suggests the existence of an unknown mechanism for K solubilization, indicated by the observed increase in soil pH during the process.