Population Of Azospirillum Research Articles

Tracking maize colonization and growth promotion by Azospirillum reveals strain-specific behavior and the influence of inoculation method

Inoculation of Azospirillum in maize has become a standard practice in Latin America. However, information on the behavior and population survival of the Azospirillum post-inoculation is scarce, making standardization difficult and generating variations in inoculation efficiency across assays. In this study, we tracked the colonization of three agriculturally relevant Azospirillum strains (Ab-V5, Az39, and the ammonium excreting HM053) after different inoculation methods in maize crops by qPCR. Besides, we assessed their ability to promote maize growth by measuring biometric parameters after conducting a greenhouse essay over 42 days. Inoculated plants exhibited Azospirillum population ranging from 103 to 107 cells plant−1 throughout the experiment. While all strains efficiently colonized roots, only A. argentinense Az39 demonstrated bidirectional translocation between roots and shoots, which characterizes a systemic behavior. Optimal inoculation methods for plant growth promotion varied among strains: soil inoculation promoted the best maize growth for the Ab-V5 and Az39 strains, while seed inoculation proved most effective for HM053. The findings of this study demonstrate that the inoculation method affects the behavior of Azospirillum strains and their effectiveness in promoting maize growth, thereby guiding practices to enhance crop yield.

Revitalizing sub-optimal drylands: Exploring the role of biofertilizers

Abstract Indonesia has a dry land area of 79.69%, with low soil productivity (physical, chemical, and biological), as well as uneven and unpredictable rainfall. The dryland potential is optimally utilized using biofertilizers that can produce microbes to increase soil fertility. This research aims to determine the effects of biofertilizers on dryland improvement and crop production. The study was conducted from February to May 2021 in Central Java, Indonesia. Using a randomized block design in peanut cultivation. Six biofertilizers (Controlled, Agrimeth, BioNutrient, Gliocompost, Agrimeth + BioNutrient, Agrimeth + BioNutrient + Gliocompost) were applied with four replications. The performance of each biofertilizer was assessed based on chemical soil parameters, soil microbe population, plant growth, and yields. The soil in the study area belonged to the Inceptisols group and exhibited moderately acidic pH, low organic carbon content, and low nitrogen levels. However, it had high potential and available phosphorus, as well as moderate potential and high available potassium. BioNutrient and Gliocompost increased available phosphate by 12 and 19%, respectively, due to the presence of Pseudomonas fluorescens and Aspergillus sp. Agrimeth influenced the population of Azospirillum (45–63%) and enhanced phosphate-solubilizing bacteria. Agrimeth + BioNutrient + Gliocompost promoted the growth of the Azospirillum and Trichoderma populations (17–18%), resulting in a 45.04% increase in profits. Biofertilizer inoculation positively affected peanut development, root nodule formation, and yield. This novelty showed the potential of biofertilizers in improving dryland conditions, increasing crop productivity, and contributing to sustainable agriculture in the long term.

Studies on the Effect of Integrated Nutrient Management on Soil Health of Tea (Camellia sp.)

A field trial was conducted at Parry Agro Industries Ltd., Valparai, Coimbatore district in two varieties of tea viz., Assam jat and ATK clone. On Eighteen treatments with different combinations of 100, 75, 62.5 and 50 per cent of the recommended doses of fertilizers along with DCC and biofertilizers. The DCC at a rate of three and six tonnes ha-1 and biofertilizers viz., VAM, Azospirillum and Phosphobacteria each @ 50 kg ha-1 were given annually. The soil physical properties viz., bulk density, particle density, porosity and water holding capacity, chemical properties viz., pH, EC, CEC, organic matter, soil N, P, K, Zn, Cu, Fe and Mn and biological properties viz., VAM infection, population of Azospirillum, Phosphobacteria, bacteria, actinomycetes and fungi were greatly improved by the treatments consisting DCC 6 tonnes and biofertilizers along with full or reduced level of recommended dose of the estate practice.

THE EFFECT OF AGRICULTURAL WASTE COMPOST ON THE POPULATION OF AZOTOBACTER, AZOSPIRILLUM, AND PHOSPHATE SOLUBILIZING BACTERIA IN CORN PLANT MEDIA ON INCEPTISOLS JATINANGOR

Plants require nutrients in order to grow. One method is to provide organic fertilizer in the form of compost. rice straw, Oil Palm Empty Fruit Bunch (OPEFB), and sugarcane bagasse can all be used as compost material. The purpose of this study is to see how different types of agricultural waste compost affect the population of beneficial bacteria such as Azotobacter sp., Azospirillum sp., and Phosphate Solubilizing Bacteria (PSB) on maize planting media in Jatinangor. The study was carried out at the screen house of Ciparanje Experimental Garden in Jatinangor District, utilizing a Randomized Block Design with 9 treatments and three replications. The treatments included a control (no treatment) and three dose levels (5 tons.ha-1 , 10 tons.ha-1 , and 15 tons.ha-1 ) of each type of compost (oil palm empty fruit bunch, sugarcane bagasse, and rice straw). The findings revealed that the use of various types of agricultural waste compost influenced the population of Azotobacter sp., Azospirillum sp., and PSB. When compared to the compost treatment of rice straw and bagasse, the application of OPEFB compost at a dose of 15 tons.ha-1 produced a greater population of Azotobacter sp. 106.43 x 107 cfu.g-1 . While the population of Azospirillum sp. increased by 2.20 x 107 cfu.g-1 as a result of the 15 tons.ha-1 compost of OPEFB, the effect was similar to that of rice straw and bagasse compost. PSB population increased at 15 tons.ha-1 of rice straw compost to 3.73 x 104 cfu.g-1 but not different from 15 tons.ha-1 of OPEFB compost. Compost can be used as an environmentally friendly fertilizing alternative to enhance the population of beneficial bacteria in corn growth media and increasing nutrient availability for plants.

ABUNDANCE OF N2-FIXING RHIZOBACTERIA OF DIFFERENT DRYLAND AGRICULTURE ECOSYSTEMS IN DRY CLIMATE ZONE OF LOMBOK-INDONESIA

Soil microbial communities are crucial in ecosystem diversity and are directly related to soil fertility. Lombok is an island in central Indonesia that has low soil fertility and a limited amount of available water. Beneficial microorganisms can be used as a low-cost and environmental friendly tool to increase productivity in dryland agriculture systems. Screening to obtain superior rhizosphere bacteria is one of the options to support the nutrient supply in arid soils. Composites soil samples were taken from five ecosystems in Lombok, West Nusa Tenggara, an arid region in the eastern part of Indonesia to obtain the isolates of nitrogen-fixer rhizobacteria (NFR). Nine Azotobacter and Azopirillium spp were isolated from, rainfed, maize, mixed crop, natural forests, and savanna ecosystems. Abundance of total bacteria and N2-fixers in all ecosystems was relatively high (more than 108 cfu g-1), and the highest total population was recorded in the natural forest. The abundance of N2-fixer rhizobacteria recorded the highest Azotobacter population at 2.64 x 108 cfu g-1 in the maize ecosystem and the highest Azospirillum population at 2.32 x 108 cfu g-1 in the natural forest ecosystem. Additionally, the highest contain of organic C and total nitrogen were obtained in natural forest and savanna ecosystem. Eighteen isolates were obtained and characterized microscopic and macroscopically, consisted of nine Azotobacter sp and nine Azospirillium isolates which are potentially to be used as biogent for improving the growth of upland rice on dry climate zone.

Pemanfaatan Limbah Pertanian dalam Menurunkan Dosis Pupuk Anorganik, Meningkatkan Populasi Azospirillum sp. , Nitrogen tanah, Serapan Nitrogen, dan Hasil Jagung pada Inceptisols Jatinangor

Balanced fertilizer is a solution to increase Inceptisols fertility and maize productivity. The aim of this study was to determine the effects and interactions between various fertilizers organic fom agriculture waste with inorganic fertilizers to increase the total population of Azospirillum sp., nitrogen uptake, soil nitrogen and the yield of maize (Zea mays) in Inceptisols Jatinangor. The research was conducted from July 2020 to January 2021 in the experimental screen house at Ciparanje, Agriculture Faculty, Universitas Padjadjaran, Jatinangor, Sumedang, West Java, 724 meters above the sea level. This research design used a randomized block design (RBD) factorial with 16 treatments and three replicates. The first factor was the type of organic fertilizer (O) of four levels: without organic fertilizer (control), 10 tons ha1 of rice straw compost, sugarcane bagasse compost, and oil palm empty fruit bunche compost. The second factor was the dosage of inorganic fertilizers (A) of four levels: without inorganic fertilizer (control), 50%, 75% and 100% dose recommendation inorganic fertilizer. The results showed that no interaction between organic fertilizers and inorganic fertilizers against all the parameters. The independent effect of organic fertilizers had a significant effect on the parameters of the total population of Azospirillum sp., nitrogen uptake and maize yields. The independent effect of inorganic fertilizers has a significant effect on nitrogen uptake and maize yields. Treatment of 10 ton ha-1 of oil palm empty bunche compost and inorganic fertilizer (50% recommendation dose) was the best treatment for dry shelled weight per maize plant on Inceptisols, equal to 88.52 g and 87.96 g each plants.

Coinoculaton of endophytic diazotroph with PGPR and AM fungi for enhancing sugarcane production

The field experiment was conducted at Sugarcane Research Station, Cuddalore during 2010 – 2012, to evaluate the response of sugarcane variety CoC 24 to the application of bioinoculants viz., Gluconoacetobacter diazotrophicus, AM fungi and Azophos (Azospirillum and phosphobacteria), under different levels of N, P2O5 and K2O inorganic fertilizer in plant and ratoon crop. The results revealed that the application of mycorrhizae, G. diazotrophicus, Azospirillum and phosphobacteria significantly produced higher cane yield in plant crop. The application of Gluconoacetobacter diazotrophicus @10 kg + AM fungi + Azophos @10 kg + 75 % NPK recorded the maximum germination and tiller population and also maximum mean millable cane population of 1.32 lakhs /ha, cane yield (137.45 t/ha) and sugar yield (16.96 t/ha). Similar results were recorded with the ratoon crop. The population of Azospirillum and Pseudomonas are higher compared to that of Glucanoacetobacter diazotrophicus and phosphobacteria. The application of bioinoculants improves soil microbial biomass and their by enhancing soil organic matter content. The applied bacterial sources helps in nitrogen fixation and also in continuous mobilizing and solubilisation of nutrients and their persistence and colonization in soil is an added advantage and also enhances the soil fertility. The usage of these bioinoculants inturn reduces the inorganic fertilizer input and thereby reduces the cost of cultivation.

Azospirillum brasilense increases corn growth and yield in conventional low input cropping systems

AbstractThe supplementation of nitrogen can be increased by the use of nitrogen-fixing, diazotrophic bacteria such as Azospirillum brasilense. These bacteria can act to promote plant growth in various plant species, including corn (Zea mays L.). However, there is a need to understand the behavior of these bacteria in different agricultural systems. The objective of this study was to evaluate the effect on the growth and yield of corn inoculated with A. brasilense, and to identify the type of farming system which benefited most from the use of A. brasilense-based inoculants. The experiment conducted over two corn crop seasons was arranged in a 6 × 2 factorial scheme, consisting of six farming systems and the presence or absence of inoculation with the bacteria A. brasilense. The farming systems were derived from a long-term experiment with different fertilization systems that has been conducted since 1984. Among these systems, there were three conventional systems (CNT1: conventional no-till without fertilizer; CNT2: conventional no-till with 150 kg ha−1 of mineral fertilizer + 50 kg ha−1 of urea; CNT3: conventional no-till with 300 kg ha−1 of mineral fertilizer + 100 kg ha−1 of urea), and three organic systems (ONT1: organic no-till with 40 m3 ha−1 of organic compost; ONT2: organic no-till with 20 m3 ha−1 of organic compost; ONT3: organic no-till with 40 m3 ha−1 of organic compost and intercropped with Canavalia ensiformis). Although the Azospirillum population in the soil before planting was the same for all six systems, the count in the rhizospheric soil was higher in the organic systems, and there was no increase in that count due to inoculation. In this study, the only difference observed was within the CNT1 system, between the inoculated (CNT1-I) and uninoculated (CNT1-NI) treatments. In this system, inoculation resulted in an increase in plant height, in addition to higher concentrations of foliar N and P, and a higher plant survival rate, which culminated in higher yield. Corn inoculated with A. brasilense in the CNT1-I treatment showed a significant increase in yield—2839 kg ha−1 higher than that recorded for CNT1-NI. This study shows that, in the conventional low input treatment CNT1-I, inoculation with A. brasilense resulted in an increase in corn growth and yield.

Potensi Jenis Bahan Organik Sebagai Biostimulan dalam Meningkatkan Populasi Azospirillum sp, dan Hasil Kedelai (Glycine Max. L.) pada Inceptisol Jatinangor

Azospirillium is a genus of non-symbiotic N fixer bacteria, known as a biological fertilizer inoculant. The quality of Azospirillum sp. inoculant often decrease when applied outside its original habitat. Therefore, it is necessary to maintain the viability and increase its effectiveness. One way that can be done is by adding organic material as additives as a source of energy for bacteria. Potential organic materials can be used as additives to stimulate the viability, activity and effectiveness of Azospirillium sp. are coconut water, molasses and bran. The organic material contained elements such as C, N and P as the source of nutrients for Azospirillium sp. which was inoculated in Soybean (Glycine max L.) plants. This experiment aimed to examine the effect of additive application on Azospirillum sp. population, root nodules, and seed weight of soybean plants (Glycine max L.) on Jatinangor Inceptisols. The experimental design used was Randomized Block Design (RBD) consisted of combination between of Azospirillum sp. and additives type, namely molasses, coconut water and bran. The results showed that the application of a mixture of bran, molasses, and coconut water attracted the population of Azospirillum sp. higher than the control treatments. Meanwhile molasses, coconut water, and additive mixtures have the potential to increase the number of root nodules and soybean pods yields. Coconut water, molasses and bran are organic materials that have the potential as additives that stimulate the activity and increase the population of Azospirillium sp. and soybean pods.

Enzyme Activity and Rhizosphere Microflora under Sugarcane Monocropping as Influenced by Integrated Nutrient Management

Sugarcane is one of the lead crops in North Coastal Andhra Pradesh. Farmers in North Coastal Zone are opting for raising more number of ratoons owing to its substantially low cost of production. Ratoon crops however seldom receive proper care and inputs due to considered it as a bonus crop by majority of farmers. Field experiments were conducted consecutively for six years in the same field (2012-13 to 2018-19) at RARS, Anakapalle to study the monocropping effect on soil biology under the influence of different nutrient management practices. Irrespective of the year of ratooning, plots which received 50% recommended dose of chemical fertilizers + 25% nitrogen though vermicompost + 25% nitrogen through green manure incorporation resulted in higher microbial population over chemical fertilizers alone. Activity of dehydrogenase and active carbon pool also showed similar trend in multi-ratooning system of sugarcane. Rhizosphere microbial population at different growth stages revealed that, azospirillum population was observed highest followed by azotobacter while lowest population counts of phosphorus solubilizing bacteria were observed. Highest population counts were recorded in INM plots and population was highest at formative later reduced to harvest. INM with 50% RDFN + 50% through organics (66.80 t ha-1) recorded at par yields with 100% RDF (67.28 t ha-1).

Isolation and identification of Azospirillum and Azotobacter species from Acacia spp. at Riyadh, Saudi Arabia

Populations of Azospirillum and Azotobacter isolated and identified from the soil rhizosphere of Acacia ehernbergiana, A. gerrardii and A. tortilis from three sites varied widely irrespective of tree species, size and site. Azospirillum strains were purified and characterized through morphological, microscopic and biochemical tests for motility, cell shape, pigmentation, colony color, gram reaction, optimal temperatures, biotin requirement, pH growth, acidification of peptone glucose medium, ability of nitrogen fixation, growth on 3% NaCl, and D-glucose and D-ribose utilization. Twenty Azospirillum isolates were divided into four matching characters. They were identified as A. lipoferum, A. brasilense, A. dobereinerae and A. zeae. The same above tests with omission of temperatures, biotin requirement, and acidification of peptone and addition of starch hydrolysis, H2S, urease, oxidase and sucrose, maltose and mannitol as carbon source were applied to Azotobacter strains. Azotobacter isolates were divided into three matching characters. They were identified as A. chroococcum, A. beijerinckii and A. salinestris.

Influence of Pesticides on Azospirillum sp. Population and Its Nitrogen Fixation in Groundnut (Arachis hypogaea L.) Soils

Aim: To study the impact of selected pesticides on Azospirillum sp. population and its nitrification in groundnut (Arachis hypogaea L.) soils. 
 Study Design: Black clay and red sandy loam soils with known pesticide history were collected from groundnut (Arachis hypogaea L.) cultivated fields and were investigated to elucidate the impact of pesticides on Azospirillum sp. population and its nitrification in both the soils.
 Place and Duration of Study: The soil samples were collected from groundnut cultivated fields of Anantapur District, Andhra Pradesh (A.P) and the study was carried out for 3 months.
 Methodology: Ten gram portions of each soil sample were placed in (25 × 150 mm) test tubes and treated with different concentrations of pesticides, (10, 25, 50, 75 and 100 µg g-1 soil) which were equivalent - 1.0, 2.5, 5.0, 7.5 and 10 kg ha-1. Soil samples without pesticides served as controls. The soils with and without pesticides were incubated at room temperature (28 ± 4°C) in the laboratory and moisture content was maintained at 60% water holding capacity (WHC) throughout the experimental period. After 7 and 14 days of incubation, triplicate soil samples were used to estimate the population size of Azospirillum sp. using the MPN method. Five ml aliquots of semi – solid malate medium were added to five MPN tubes and inoculated with 0.5 ml of a soil suspension from 10-1 to 10-5 soil dilutions, and incubated at 37°C.
 Results: The population of Azospirillum sp. in both soils increased when pesticides were applied @ 2.5 - 5.0 kg ha-1 and incongruity, when the pesticides concentration increased from 7.5 - 10.0 kg ha-1, the Azospirillum sp. population gradually decreased in both soils.
 Conclusion: The present study aimed at determining the influence of selected pesticides such as oxydemeton methyl, emamectin benzoate, dithane Z-78 and benomyl on the population of Azospirillum sp. and nitrogen fixation in black clay soil and red sandy loam soils in groundnut cultivated fields of Anantapur District, Andhra Pradesh, India. Insecticides and fungicides applied up to 5.0 kg ha-1, enhanced the population of Azospirillum sp. and its nitrogen fixation also increased significantly after 7 and 14 days of incubation in both soils. However, the population of Azospirillum sp., decreased with increasing period of soil incubation in both treated and untreated soils.

Analysis of physico-chemical parameters of soil and population density of Azospirillum isolates from paddy fields of Theni district, Tamilnadu

The rhizosphere region of eight different paddy field areas of Theni district was studied for their physico-chemical analysis of soil and the population density of Azospirillum sp. The study results showed range of values of pH (7.4-7.9), bulk density (1.13g/cm3 -1.60g/cm3), water holding capacity (34.31% - 18.25%), electrical conductivity (1.31 – 1.11), organic carbon (0.93% - 0.71%) . The macronutrient values namely total nitrogen (1.72% - 0.78%), phosphorus content (0.177% - 0.122%) and potassium (1.364% - 1.273%) were observed. Also micronutrients of various paddy fields like Zn (0.9% - 0.5%), Cu (2.3% - 1.7%), Fe (10.9% -8.2%), Mn (6.7% - 5.2%) were recorded, whereas the values of available macronutrients namely nitrogen (295kg/ha - 223kg/ha), phosphorous (89Kg/acre - 49kg/acre), potassium (790kg/acre - 490kg/acre) were noted. The Azospirillum population density was highest in Chinnamanur (192 x105 CFU/g) and lowest in Royyanpatti (91 x105 CFU/g). Thus through this work we were able to isolate and identify novel high yielding Azosprillium sp from paddy fields of Theni district.

Microbial characterization of on-farm produced bio-enhancers used in organic farming

Different bio-enhancers commonly used in organic production of various crops were prepared for microbial characterization. Panchagavya had been utilized since long time by the farmers to provide nutrients to the plants and soil micro-organisms. Microbial analysis of bio-enhancers revealed that Panchagavya contained highest number of total bacteria (6.25 × 109 cfu/ml) as compared to Jeevamrita (3.24 × 109 cfu/ml), biodynamic liquid pesticide (2.27 × 109 cfu/ml) and Amritpani (5.49 × 109 cfu/ml). Panchagavya had also higher number of Pseudomonas (4.7 × 109 cfu/ml), Rhizobium (2.43 × 109 cfu/ml), Azotobacter (1.4 × 109 cfu/ml) and Azospirillum (1.03 × 105 cfu/ml). Fungi population was highest in Jeevamrita (1.20 × 107 cfu/ml) as compared to biodynamic liquid pesticide (2.64 × 106 cfu/ml), Amritpani (0.46 × 105 cfu/ml) and Panchagavya (0.20 × 105 cfu/ml). Actinomycetes, Pseudomonas, p-solubilizing microbes, Azotobacter and Azospirillum population were highest in biodynamic liquid pesticide (1.37 × 108, 3.28 × 108, 8.50 × 106, 2.00 × 106 and 1.40 × 105 cfu/ml). Similarly, gram positive bacteria, gram negative bacteria and Rhizobium were highest in Jeevamrita (1.60 × 108, 2.20 × 108, 7.51 × 107 cfu/ml). Amritpani had higher number of actinomycetes (1.31 × 107 cfu/ml), gram negative bacteria (1.35 × 108 cfu/ml) and p-solubilizing microbes (4.80 × 106 cfu/ml). Among all bio-enhancers, Panchagavya was rated most effective bio-enhancer followed by biodynamic liquid pesticide, Jeevamrita and Amritpani. Results reveal that these bio-enhancers could play a potent source of beneficial microbes which could improve soil fertility, crop productivity and produce quality.

Crop establishment and nitrogen management affect greenhouse gas emission and biological activity in tropical rice production

The comprehensive impacts of different nitrogen management and crop establishment on greenhouse (GHG) fluxes are not well documented. GHG emissions from rice paddies under different nitrogen management and crop establishment merit attention because nitrogen fertilizer is indiscriminately used for the intensification of rice cultivation. Field trials were conducted to assess methane (CH4), nitrous oxide (N2O) and carbon dioxide (CO2) emissions, labile C pools, microbial population and enzymatic activities in rice soil under different crop establishment and nitrogen (N) management practices. The crop establishment methods included aerobic rice (AR) that involved dry direct seeding under non puddled and non-flooded situation and puddled transplanted rice (PTR) under flooded condition. Nitrogen management practices were control, 100kgNha−1 as prilled urea (PU) and applied conventionally, 100kgNha−1 as neem coated urea (NCU), applied conventionally, 100kgNha−1 as PU, applied on the basis of customized leaf colour chart (CLCC) recommendation, 100kgNha−1 as NCU, applied on the basis of CLCC recommendation, 100kgNha−1 as PU and farm yard manure (FYM) in 1:1 ratio, applied conventionally. Cumulative seasonal CH4 emission was 73–75% less in AR as compared to PTR. But seasonal N2O and CO2 emissions from soils were significantly higher in AR. Global warming potential of AR was comparatively less than PTR but yield loss in AR caused greenhouse gas intensity (GHGI) of AR to be at par with that of PTR. Inclusion of FYM along with PU reduced N2O emission and maintained significantly higher (P≤0.05) microbial biomass carbon concentration, nitrifiers, Azotobacter and Azospirillum population and dehydrogenase, β-glucosidase and urease activities in soils of AR and PTR. Real time N application according to leaf colour chart and use of slow release N fertilizers can reduce N2O emission, minimize yield loss and lower GHGI of AR.

Studi Populasi Mikrob Fungsional pada Tanah Gambut yang Diaplikasikan Dua Jenis Pestisida

Agricultural land expansion necessity for food security in Indonesia has been faced by the fact in utilizing marginal land such as shallow peat soil in Central Kalimantan. Among problems encountered in such marginal land are pests and diseases incidence. Farmers practice in dealing with those problems is the chemical pesticides application. Unintended chemical pesticides that fall on/into the soil might have an adverse effect to soil microbes activity. This research aimed to assess the effect of pesticides on functional soil microbes population in peat soil. The research used completely randomized factorial design with two factors. First factor was 7 combinations of types (paraquat and buthylphenylmethyl carbamat (BPMC)) and dosages (50, 100, and 200% of recommended dosage) of pesticides. Second factor was 4 incubation times (1, 7, 14, and 28 days). Following the each of incubation times, the soil samples treated and analyzed for population of phosphate solubilizing microbes, cellulolytic microbes, and N2 fixing bacteria. The results show that phosphate solubilizing fungi population decrease by pesticides treatment. In contrast, pesticides significantly increased the Azospirillum population. Adverse effect to microbes population was found on the first day of incubation, however it recovered at 7 days and longer incubation times. In general, functional microbes population with paraquat application lower than BPMC application.

English

Availability of heterotrophic soil bacteria and an associative micro-aerophilic nitrogen fixing Azospirillum, from the rhizosphere of different crop plants, was studied. Microorganisms were reported from root and rhizospheric soil (from twenty-seven different samples collected from Chhattisgarh, India) of different crop plants. The amount of total heterotrophic bacteria, in different samples, varied significantly from 3.01×108 to 4.90×108 in rhizosphere and from 1.11×108 to 2.91×108 in root tissues. Azospirillum population significantly varied from 3.81×108 to 4.90×108 in rhizosphere and from 2.09×108 to 2.88×108 in root tissues. Rhizospheric soils were found to harbor the highest population of heterotrophic soil bacteria and Azospirillum in comparison with plant tissues. Nitrogen, phosphorus, potash, organic matter (OM) and pH value have significant positive correlation but electrical conductivity (EC) have non-significant effect with total heterotrophic bacterial population. Based on the correlation co-efficient (r) value, all significant positive correlation has been grouped in three categories viz; strong (r = >0.5), medium (r = >0.4 but <0.5) and weak (r = <0.4). Thus, in the present study, N, OM and rhizospheric pH have strong significant positive correlation with total heterotrophic bacterial population while P and K content have medium correlation with bacterial population.   Key words: Heterotrophic bacteria, rhizosphere, Azospirillum, nitrogen fixing bacteria, correlation, regression.

Population dynamics and identification of efficient strains of Azospirillum in maize ecosystems of Bihar (India)

Information on inoculum load and diversity of native microbial community is an important prerequisite for crop management of microbial origin. Azospirillum has a proven role in benefiting the maize (Zea mays) crop in terms of nutrient (nitrogen) supply as well as plant growth enhancement. Bihar state has highest average national maize productivity although fertilizer consumption is minimum, indicating richness of Azospirillum both in terms of population and diversity in soils. An experiment was planned to generate basic information on Azospirillum population variation in maize soils under different agricultural practices and soil types of Bihar, to identify suitable agricultural practices supporting the target microorganism and efficient Azospirillum strain(s). No tillage, growing traditional maize cultivar, land use history (diara soil having history of maize cultivation), soil organic carbon (>1%) and intercrop with oat supported prevalence of Azospirillum in maize rhizosphere. Native Azospirillum population varied from 1 million to 1 billion/g soil under diverse agricultural practices and soil types. Such richness, however, does not necessarily mean that artificial inoculation of Azospirillum is not required in Bihar soils as 92% of Azospirillum isolates (50 isolates) were poor in nitrogen-fixing ability and 88% were poor on IAA production. Efficient strains of Azospirillum based on growth (three), acetylene reduction assay (three), IAA production (three), broad range of pH (two) and temperature tolerance were identified. The findings suggested that maize crop in Bihar should be inoculated in universal mode rather than site-specific mode.

Impact of Fertigation on Soil Microbial Community and Enzyme Activities Cropped with Maize (cultivar. COMH 1) under Precision Farming System

Precision farming is an integrated plant nutrient management system attempt to deliver the inputs actual crop needs without disturbing the entire farming area. The fertilizers in liquid state will be delivered through laterals directly to the root zone at high concentrations. Soil microorganisms are potential resources for soil productivity and sustainability, intended to be influenced by various anthropogenic-and farming activities. Hence in present study, we have investigated that the effect of different dose of liquid fertilizers on changes in soil microbial populations and enzyme activities of maize in comparison with conventional practice of fertilization. The results clearly revealed that all the fertilization reduced the microbial population and enzyme activities of maize rhizosphere and among the fertigations, 75 per cent of recommended NPK in the form of liquid fertilizer had a less reduction in the population of Azospirillum, P solubilising bacteria and total diazotrophs, soil respiration and enzyme activities. Hence it is evident from the study that the use of more organic manures and microbial inoculants along with inorganic chemicals fertilizers, as integrated approach is needed for precision farming.

Effect of pesticides on soil microbial community

According to guidelines for the approval of pesticides, information about effects of pesticides on soil microorganisms and soil fertility are required, but the relationships of different structures of pesticides on the growth of various groups of soil microorganisms are not easily predicted. Some pesticides stimulate the growth of microorganisms, but other pesticides have depressive effects or no effects on microorganisms. For examples, carbofuran stimulated the population of Azospirillum and other anaerobic nitrogen fixers in flooded and non-flooded soil, but butachlor reduced the population of Azospirillum and aerobic nitrogen fixers in non-flooded soil. Diuron and chlorotoluron showed no difference between treated and nontreated soil, and linuron showed a strong difference. Phosphorus(P)-contains herbicides glyphosate and insecticide methamidophos stimulated soil microbial growth, but other P-containing insecticide fenamiphos was detrimental to nitrification bacteria. Therefore, the following review presents some data of research carried out during the last 20 years. The effects of twenty-one pesticides on the soil microorganisms associated with nutrient and cycling processes are presented in section 1, and the applications of denaturing gradient gel electrophoresis (DGGE) for studying microbial diversity are discussed in section 2.