Effect of nitrogen on the yield response of Pennisetum americanum,Triticum aestivum and Zea mays to inoculation with Azospirillum brasilense under temperate conditions

Summary A nitrate-respiring strain, a denitrifying strain, and a non-nitrogen-fixing strain of Azospirillum brasilense were compared for their effect on the growth of pearl millet (Pennisetum americanum), wheat (Triticum aestivum) and maize (Zea mays) under temperate conditions in nitrogen-limited pot cultures. Increases in yield of Z. mays shoots occurred with all three strains when inoculation coincided with the addition of low levels of combined nitrogen. The inoculation of A. brasilense did not show any effect on the yield of P. americanum and T. aestivum. Increased numbers of A. brasilense became associated with Z. mays roots following the addition of low levels of combined nitrogen. Low and very variable rates of acetylene reduction activity were observed from excised roots of inoculated Z. mays plants without preincubation. Results indicate that inoculation of cereals with A. brasilense under temperate conditions has only a limited effect on plant growth.     

Association of Azospirillum brasilense with pearl millet (Pennisetum americanum (L.) Leeke)

Summary Microscopic observations of the root system of pearl millet (Pennisetum americanum (L.) Leeke) var. BJ 104 after surface sterilization and incubation in phosphate malate triphenyl tetrazolium chloride (TTC) revealed extensive colonization by Azospirillum spp. when plants were grown in sterile, partially sterile and field conditions as evidenced by the TTC-reducing property of active cells of the bacterium. Quantitative studies showed the need to standardize the techniques further to ensure more precise monitoring of the bacteria in the rhizosphere, as large numbers of soil bacteria were found capable of growth on specific media, thus interfering with the plate counts. Seed inoculation with A. brasilense increased the mean grain yield of pearl millet under different agroclimatic conditions in India. The mean increase in grain yield due to inoculation over uninoculated controls was also noticed with graded levels of fertilizer nitrogen (urea). Inoculation alone contributed to increased nitrogen uptake of plants with varying levels of fertilizer nitrogen application under sandy loam soil conditions (pH 7.3). The effects of inoculation were more prominent under lower levels of nitrogen than at the higher levels. The root biomass under field conditions was increased with Azospirillum spp. inoculation at 10 and 20 kg N/ha than their corresponding uninoculated controls.     

Potential for enhancement of root growth and nodulation of soybean co-inoculated with Azospirillum and Bradyrhizobium in laboratory systems

The potential enhancement of root growth and nodulation in vegetable soybean (AGS190) was studied with application of Azospirillum brasilense (Sp7) and A. lipoferum (CCM3863) co-inoculated with two Bradyrhizobium japonicum strains (TAL102 and UPMR48). Significant root growth stimulation and nodulation were observed in Azospirillum as well as during its co-inoculation with Bradyrhizobium. Nodule formation is linked with the initiation of new roots; nodules were almost absent even in Bradyrhizobium inoculated plant due to the absence of new roots development in clipped rooted seedlings. Total root length, root number, specific root length, root dry matter, root hair development and shoot dry matter were significantly increased by Azospirillum alone and its co-inoculum. Co-inoculated plants significantly influenced the number of nodules and its fresh weight. A. brasilense seemed to perform better in root growth and nodule development compared to A. lipoferum.     

Field performance of a liquid formulation of Azospirillum brasilense on dryland wheat productivity

The beneficial effects of inoculating with Azospirillum brasilense on crop productivity have been widely described, but extensive use in typical agricultural field environments is scarcely documented. The objective of this study was to quantify the productivity of wheat (Triticum aestivum L.) whose seed was inoculated with a liquid formulation containing Azospirillum brasilense INTA Az-39 strain under typical dryland farming conditions. The study was performed in the 2002–2006 growing seasons, evaluating inoculated and non-inoculated seed at 297 experimental locations in the Pampas region of Argentina. The inoculated crops exhibited more vigorous vegetative growth, with both greater shoot and root dry matter accumulation (12.9 and 22.0%, respectively). The inoculation increased the number of harvested grains by 6.1%, and grain yield by 260 kg ha^?1 (8.0%). Positive responses were determined in about 70% of the sites, depending mostly on the attainable yield and independently of fertilization and other crop and soil management practices. In general, more response to inoculation was observed in the absence of major crop growth limitations, suggesting the complementary contribution of the Azospirillum brasilense treatment to more efficiently developing higher yielding wheat.     

Cadaverine production by Azospirillum brasilense and its possible role in plant growth promotion and osmotic stress mitigation

Polyamines are considered as plant growth regulating compounds; among them, cadaverine has been correlated with root growth promotion or osmotic stress mitigation in some plant species. The purpose of this study was to evaluate the capacity of bacterial Azospirillum brasilense Az39 strain to produce cadaverine in chemically defined medium and inoculated plants, and to correlate this capacity with root growth promotion or osmotic stress mitigation in hydroponics conditions. To evaluate cadaverine production in chemically defined medium A. brasilense Az39 was cultivated aerobically at 30 °C and 80 rpm in NFb medium or NFb-l supplemented with the precursor l-lysine. To evaluate the bacterial cadaverine production and growth promotion in plants, rice (Oryza sativa L.) cv. El Paso 144 seedlings were inoculated and hydroponically cultured under optimal conditions in growth chamber. In both, cadaverine was identified and quantified by dansyl-derivative method using a fluorescence-HPLC system, and lysine decarboxylase (LDC) activity was determined by ¹⁴CO₂ production in a closed tube system fed with [¹⁴C]-lysine. To evaluate the possible role of bacterial cadaverine in osmotic stress conditions, abscisic acid (ABA) production was analyzed in rice seedlings hydroponically cultured under 0 (no stress), ?0.47 (stress) or ?0.82 (severe stress) MPa osmotic potential generated by mannitol, with the addition of 1 nM or 1 μM cadaverine or A. brasilense Az39 inoculation. Our results indicate that A. brasilense Az39 promoted root growth and helped mitigate osmotic stress in rice seedlings, due in part to cadaverine production.     

Azospirillum brasilense mitigates water stress imposed by a vascular disease by increasing xylem vessel area and stem hydraulic conductivity in tomato

Water stress, with its negative consequences on plant growth and survival, can be mitigated by Azospirillum brasilense inoculation. In tomato, A. brasilense delays wilting caused by a vascular pathogen, Clavibacter michiganensis subsp. michiganensis, by yet unknown mechanisms. We studied morphological, anatomical and physiological changes induced by A. brasilense in tomato that relate to water stress tolerance, which could explain the deferral in symptom expression. For this purpose, tomato seeds were treated or not with A. brasilense BNM65, and 5 weeks later plants were challenged with C. michiganensis subsp. michiganensis or mock inoculated with water. There was a large growth promotion associated to Azospirillum: treated plants had higher total biomass and leaf area. In relation to water stress tolerance, Azospirillum treated plants had larger xylem vessel area, higher stem specific hydraulic conductivity, thicker stems, and lower shoot/root dry matter and specific leaf area. These changes were opposite to those induced by C. michiganensis subsp. michiganensis. We conclude that A. brasilense favoured a better adjustment of plant-water relations by several mechanisms, and thus, transitorily alleviated symptoms expression of a vascular disease.     

Azospirillum inoculation and nitrogen fertilization effect on grain yield and on the diversity of endophytic bacteria in the phyllosphere of rice rainfed crop

We assessed the Azospirillum inoculation and N-fertilization effect on grain yield and on the phyllosphere endophytic diversity of nitrogen-fixing bacteria in a rice rainfed crop. We used cultivation-based techniques and cultivation-independent methods involving PCR-16S rRNA and denaturing gradient gel electrophoresis (DGGE). In general, we observed that grain yield was improved when inoculated with Azospirillum (depending on the genotype) and/or fertilized with urea. A similar behavior was observed in total N-content in grain and the MPN determination, as the highest values occurred when seeds were inoculated with A. brasilense REC3 (S1) than with A brasilense 13-2C (S2). A positive nitrogenase activity and PCR-nifH amplification suggests that the bacteria associated to inner tissues of rice phyllosphere could have contributed to the different N-contents detected. The bacterial diversity, observed in the number and intensity of DGGE profiles, showed a higher number of bands when total DNA was obtained using only CTAB than with CTAB + PVP. The DGGE profiles revealed great stability in the dominating bands, which presumably represent numerically dominant species. Application of A. brasilense strains as inoculants did not influence the dominant members of the endophytic microbial communities in the phyllosphere, but improved N-content and production of rainfed rice crop.     

Response of neem (Azadirachta indica A. Juss) to indigenous arbuscular mycorrhizal fungi, phosphate-solubilizing and asymbiotic nitrogen-fixing bacteria under tropical nursery conditions

Neem (Azadirachta indica A. Juss) seedlings were inoculated with arbuscular mycorrhizal (AM) fungi, Glomus intraradices Schenck and Smith and G. geosporum (Nicol. and Gerd.) Walker, Azospirillum brasilense, and phosphate-solubilizing bacteria (PSB) individually or in various combinations in unsterile soil under nursery conditions. Seedlings were harvested at 60 and 120 days after transplantation. Microbial inoculation resulted in increased mycorrhizal colonization, greater plant height, leaf area and number, root collar diameter, biomass, phosphorus, nitrogen and potassium content, and seedling quality. Inoculated seedlings also had low root/shoot ratios and low nutrient utilization efficiencies. Populations of PSB declined with seedling growth; contrarily populations of A. brasilense increased. A. brasilense and PSB populations were related to each other and influenced root colonization by AM fungi. Microbial inoculation effects were greatest when seedlings were inoculated with a combination of microbes rather than individually. This clearly indicates that these microorganisms act synergistically when inoculated simultaneously, with maximum response being when both AM fungi were coinoculated with A. brasilense and PSB. The results emphasize the importance of microbial inoculations for the production of robust, rapidly growing seedlings in nurseries and illustrate the advantage of inoculating soils of a low microbial population with indigenous microbes.     

Effect of Azospirillum brasilense inoculation on rhizobacterial communities analyzed by denaturing gradient gel electrophoresis and automated ribosomal intergenic spacer analysis

Nucleic acid-based techniques allow the exploration of microbial communities in the environments such as the rhizosphere. Azospirillumbrasilense, a plant growth promoting rhizobacterium (PGPR), causes morphological changes in the plant root system. These changes in root physiology may indirectly affect the microbial diversity of the rhizosphere. In this study, the changes in the rhizobacterial structure following A. brasilense inoculation of maize (Zea mays) plants was examined by PCR-denaturating gradient gel electrophoresis (DGGE) and automated ribosomal intergenic spacer analysis (ARISA), using two universal primers sets for the 16S rRNA gene, and an intergenic 16S-23S rDNA primer set, respectively. Similar results were obtained when using either ARISA or DGGE performed with these different primer sets, and analyzed by different statistical methods: no prominent effect of A. brasilense inoculation was observed on the bacterial communities of plant roots grown in two different soils and in different growth systems. In contrast, plant age caused significant shifts in the bacterial populations.     

Effects of Azospirillum brasilense on root morphology of common bean (Phaseolus vulgaris L.) under different water regimes

 The effects of inoculation with Azospirillum brasilense Cd on root morphology and growth of common bean (Phaseolus vulgaris L.) were studied under different growth systems and water regimes. The root systems were evaluated by image analysis. In a PVC-tube growth system, inoculation with A. brasilense at 10⁷ colony forming units (CFU) ml^–1 increased root length, root projection area, specific root length (m g^–1) and specific root area (cm² g^–1), as compared with non-inoculated controls, resulting in root systems with longer and thinner roots. Water stress induced similar root responses to those observed after inoculation with A. brasilense. No increase in plant biomass was observed in inoculated plants, suggesting that under the tested growth conditions, a relatively larger amount of resources is required for the maintenance of the thinner roots. In water-stressed potted plants, the effect of A. brasilense on tap root length was inoculum-concentration dependent. At 10⁷ CFU ml^–1 this effect was significant as compared to non-inoculated controls. In a pouch system without water stress, inoculation with A. brasilense at a concentration of 10⁵–10⁷ CFU ml^–1 2 days after germination resulted initially (2 days after inoculation) in an increase in root length (95%) and root fresh weight (66%), but reduced root diameter (20%), compared to controls. At this early stage of growth the distribution of root length among the different root diameter classes changed: the thinner-root classes had the largest proportion of longer roots. Received: 3 January 2000     

Nitrogen fixation by Azospirillium brasilense in soil and the rhizosphere under controlled environmental conditions

Summary Acetylene reduction activity by Azospirillum brasilense, either free-living in soils or associated with wheat roots, was determined in a sterilised root environment at controlled levels of O₂ tension and with different concentrations of mineral N. In an unplanted, inoculated soil nitrogenase activity remained low, at approximately 40 nmol C₂H₄ h^-1 per 2kg fresh soil, increasing to 300 nmol C₂H₄ h^-1 when malic acid was added as a C source via a dialyse tubing system. The N₂ fixation by A. brasilense in the rhizosphere of an actively growing plant was much less sensitive to the repressing influence of free O₂ than the free-living bacteria were. An optimum nitrogenase activity was observed at 10 kPa O₂, with a relatively high level of activity remaining even at an O₂ concentration of 20 kPa. Both NO _inf3 ^sup- and NH _inf4 ^sup+ repressed nitrogenase activity, which was less pronounced in the presence than in the absence of plants. The highest survival rates of inoculated A. brasilense and the highest rates of acetylene reduction were found in plants treated with azospirilli immediately after seedling emergence. Plants inoculated at a later stage of growth showed a lower bacterial density in the rhizosphere and, as a consequence, a lower N₂-fixing potential. Subsequent inoculations with A. brasilense during plant development did not increase root colonisation and did not stimulate the associated acetylene reduction. By using the ¹⁵N dilution method, the affect of inoculation with A. brasilense in terms of plant N was calculated as 0.067 mg N₂ fixed per plant, i.e., 3.3% of the N in the root and 1.6% in the plant shoot were of atmospheric origin. This ¹⁵N dilution was comparable to that seen in plants inoculated with non-N₂-fixing Psudomonas fluorescens.     

Influence of ammonium: Nitrate ratios on the growth and nitrogen uptake of pearl millet

Pearl millet [Pennisetum glaucum (L.) R. Br.] is a potentially high‐yielding grain crop for the Southern Coastal Plain region of the USA. Information on the growth and N nutrition of pearl millet is limited; therefore, this study was initiated with the objective of studying pearl millet growth, N content, N uptake patterns and N‐form preference. Plants were grown in solution culture using a modified Hoagland's solution. Solutions were changed weekly and transpirational losses replaced daily. The N‐form ratios were 1:0, 3:1, 1:1, 1:3 and 0:1 NH₄ ⁺ to NO₃ ^‐ Uptake was determined by difference between the initial and final solutions. Nitrate and NH₄ ⁺ uptake patterns were different from each other and were influenced by the ratio of NH₄ ⁺ to NO₃ ^‐. After the plants had been transferred to the solutions, ammonium was preferred for the first two weeks, with NO₃ ^‐ preferred thereafter. Nitrate uptake was highest during the grain filling period. Plant growth as measured by leaf, stem, root, and seed weight, plant height, average seed weight, and head length was generally reduced as NH₄ ⁺ increased. The largest reduction was observed between the 3:1 and 1:0 ratios. Ammonium nutrition had an overall negative effect on pearl millet growth. Ammonium fertilization of pearl millet under conditions that increase absorption of NH₄ ⁺ over NO₃ ^‐ may have a negative effect on pearl millet growth and development.     

Implications of Azospirillum brasilense inoculation and nutrient addition on maize in soils of the Brazilian Cerrado under greenhouse and field conditions

The combination of nitrogen and Azospirillum can ensure greater nutrient absorption and crop yield in agricultural areas using high technology. Thus, the objective was to evaluate maize response to Azopirillum brasilense (AZ) inoculation and nutrient (macronutrients and micronutrients) application under greenhouse and field conditions in clay and sandy soils of the Brazilian Cerrado. In the greenhouse assays, the following parameters were measured: shoot dry weight (SDW), root dry weight (RDW), and root volume (RV). In the field experiments, the maize yield was determined after drying the grains at 60 °C for 48 h. In clay soil, there was a significant increase in the SDW, RDW and RV in the treatment with AZ concentrated (10¹¹ cells ml⁻¹ of inoculum) when compared with the control treatment and the treatment with AZ diluted (10⁶ cells ml⁻¹ of inoculum). In this soil, adding micronutrients did not affect the maize response under greenhouse conditions. In sandy soil, there was no difference between the AZ treatment and the control, except for treatments where nutrients and AZ were both added leading to a significant increase in the maize response. In both soils, the RV:RDW ratio was higher in the treatment with AZ concentrated compared to that in the treatment with AZ diluted, but the yield response depended on the addition of nutrients. Inoculation with A. brasilense gave comparable yield to the nitrogen treatment. The grain production was increased by 29% in the treatment with A. brasilense and nitrogen compared to nitrogen fertilization alone. In this study, the yield response was affected significantly when maize was inoculated with A. brasilense, but this response was dependent on the soil type under greenhouse conditions.     

Natural occurrence of Pseudomonas aeruginosa,a dominant cultivable diazotrophic endophytic bacterium colonizing Pennisetum glaucum (L.) R. Br.

Endophytic microbial communities can have strong influence on the growth of their host plants. The present study reports a diazotrophic endophytic bacterial species that colonizes predominantly Pennisetum glaucum (pearl millet) and remains stabilized throughout the latter's various growth stages under field conditions. Qualitative and quantitative changes in the endophytic bacterial population structure were examined during the plant growth period at regular intervals of 7 days up to harvesting. DNA fingerprinting (ERIC-PCR) was used as a biomarker to track the identity of various isolates obtained at different time intervals. Identification of representative bacterial species corresponding to different ERIC types was made on the basis of 16S rRNA gene sequence analysis. Based on the colony forming unit (cfu) count of bacterial isolates observed at various growth stages, Pseudomonas aeruginosa PM389 was found to be the dominant diazotrophic species among the cultivable endophytes colonizing pearl millet. The population of P. aeruginosa was detected in the host 21 days after sowing (DAS), indicating its entry in plant roots from soil and suggesting its non-vertical transfer in pearl millet. Moreover, an upward migration of this dominant diazotrophic bacterial species to shoots was observed with the plant growth. Further evaluation of P. aeruginosa PM389 revealed its various plant growth promoting properties viz. nitrogen fixation, mineral phosphate solubilization, siderophore production and antagonistic properties.     

Seedlings growth promotion by Azospirillum brasilense under normal and drought conditions remains unaltered in Tebuconazole-treated wheat seeds

The wide use of pesticides in modern agriculture may cause side effects on the non-target microflora. Data on the fungicide Tebuconazole effects on Azospirillum-wheat association are scarce. We analyzed the effects of Tebuconazole on: (a) Azospirillum brasilense Sp245 growth in pure culture, (b) A. brasilense Sp245 colonization of Triticum aestivum cv ProINTA Oasis roots, (c) A. brasilense Sp245-inoculated seedlings growth under normal and water stress conditions in the presence of 20% polyethylene glycol 8000. Seeds were separated in Tebuconazole-free and Tebuconazole-treated lots. Inoculated and non-inoculated seedlings were grown in hydroponics in the dark at 20 °C for 72 h. Root surface, coleoptile length, fresh and dry (DW) weights in both tissues and diazotrophic bacterial most probable number in roots were determined. Water contents and shoot-to-roots DW ratio were calculated. Neither Azospirillum growth nor root colonization was affected by Tebuconazole. Under normal growth conditions most of the growth parameters analyzed, revealed a clear positive effect of A. brasilense on wheat seedlings up to 72 h treatments. The characteristic Azospirillum enhancing effects observed on roots remained unaltered by Tebuconazole. The present study shows that Tebuconazole is compatible with A. brasilense Sp245-wheat inoculation.     

Nitrogen transfer from warm‐season annual legumes to pearl millet

A glasshouse study was conducted to determine and quantify direct transfer of nitrogen (N) between 3 selected warm‐season annual legumes and a warm‐season annual grass during the growing season, ‘Tifleaf’ pearl millet [Pennisetum americanum (L.) Leeke] was grown in pots as a monoculture with and without N applied as inorganic fertilizer, or with either ‘Iron and Clay’ cowpeas [Vigna unguiculata (L.) Walp], common alyceclover [Alysicarpus vaginalis (L.) DC.], or ‘Comanche’ partridge pea (Cassia fasciculata Michx.). Sixty‐three percent of the N contained in pearl millet grown with alyceclover was derived directly from alyceclover as determined by the ¹⁵N dilution technique. Partridge peas and cowpeas transferred 34% and 32%, respectively, of the N contained in companion pearl millet plants. Pearl millet grown with partridge peas produced dry matter yields similar to pearl millet that received the equivalent of 112 kg N/ha. Pearl millet grown with legumes contained lower levels of neutral detergent fiber than did pearl millet that received inorganic fertilizer. Nitrogen content of pearl millet grown with legumes was not as great as pearl millet that received N‐fertilizer.     

Effects of organic manure and chemical fertilizer on soil fertility and productivity of plant and ratoon crops of sugarcane

A long-term field experiment was initiated in November, 1967 at Research Area of Department of Soil Science to study the response of nitrogen to pearl millet-wheat cropping system at various doses and modes of farmyard manure application. The soil organic carbon increased with farmyard manure application and ranged from 0.68% in control to 1.82% in the plot receiving the highest annual dose (90 Mg ha^?1) of farmyard manure. To study the contribution of farmyard manure on the productivity of pearl millet and wheat crops, the constants (intercept and slope) were determined between the grain yield of pearl millet and wheat crops with increasing dose of fertilizer nitrogen. Another linear regression was fitted between the intercept of the linear model and the soil organic carbon content. It has been observed that with each unit increase in the soil organic carbon, the productivity of pearl millet increased by 273 kg ha^?1 and that of wheat by 1591 kg ha^?1. The regression between the slope and soil organic carbon was linear in case of pearl millet (R² 0.49) but in case of wheat there was no relationship.     

Co-inoculation of soybeans and common beans with rhizobia and azospirilla: strategies to improve sustainability

Plant–microorganism associations have long been studied, but their exploitation in agriculture partially or fully replacing chemical fertilizers is still modest. In this study, we evaluated the combined action of rhizobial and plant growth-promoting rhizobacteria inoculants on the yields of soybean and common bean. Seed inoculation with rhizobia (1.2?×?10⁶ cells seed^?1) was compared to co-inoculation with Azospirillum brasilense in-furrow (different doses) or on seeds (1.2?×?10⁵ cells seed^?1) in nine field experiments. The best in-furrow inoculant dose was 2.5?×?10⁵ cells of A. brasilense seed^?1 for both crops. Inoculation with Bradyrhizobium japonicum increased soybean yield by an average 222 kg?ha^?1 (8.4 %), and co-inoculation with A. brasilense in-furrow by an average 427 kg?ha^?1 (16.1 %); inoculation always improved nodulation. Seed co-inoculation with both microorganisms resulted in a mean yield increase of 420 kg?ha^?1 (14.1 %) in soybean relative to the non-inoculated control. For common bean, seed inoculation with Rhizobium tropici increased yield by 98 kg?ha^?1 (8.3 %), while co-inoculation with A. brasilense in-furrow resulted in the impressive increase of 285 kg?ha^?1 (19.6 %). The cheaper, more sustainable inoculated treatment produced yields equivalent to the more expensive non-inoculated + N-fertilizer treatment. The results confirm the feasibility of using rhizobia and azospirilla as inoculants in a broad range of agricultural systems, replacing expensive and environmentally unfriendly N-fertilizers.     

Amendment of degraded desert soil with wastewater debris containing immobilized Chlorella sorokiniana and Azospirillum brasilense significantly modifies soil bacterial community structure, diversity, and richness

The main goal of this study was to expand our knowledge of what happens to the soil bacterial community in an eroded desert soil when improvement of soil fertility is derived from the application of debris of tertiary wastewater treatment containing immobilized microalgae Chlorella sorokiniana and the plant growth-promoting bacterium (PGPB) Azospirillum brasilense. We hypothesized that an “improved” non-agricultural desert soil will exhibit substantial changes in the structure of the bacterial community in a relatively short time after amendment. To assess the effect of the amendments, microalgae and PGPB alone or combined, on the structure of the rhizosphere bacterial community, changes in species richness and bacterial diversity over time were based on sequence differences in the 16S rRNA gene, performed with PCR–denaturing gradient gel electrophoresis (DGGE) and then analyzed by similarity test and non-metric multidimensional scaling analysis. Root surface colonization and persistence in the rhizosphere of A. brasilense was monitored by fluorescent in situ hybridization and sequencing of DGGE bands. Application of waste debris significantly changed the rhizosphere bacterial population structure, whether comparisons were made over time, between inoculated and non-inoculated soil, and among different inoculated microorganisms. Species richness and diversity increased when the waste debris contained the microalgae–bacteria association and also over time. Even as its secondary role as an inoculant after wastewater treatment, A. brasilense colonized the root surface profusely and persisted within the rhizosphere bacterial community. This study demonstrated that small organic amendment to desert soil significantly changed soil bacterial community compared to the original soil and also 2 months after amendments were added.