Soil Microbiological Parameters Research Articles

Effects of Weed Management on Soil Microbiological Properties in Groundnut Production

To quantify the efficacy of effective weed control methods and spacing of groundnut on soil microbiological properties, a field experiment was conducted between 2009 and 2010 at the Teaching and Research Farm of the University of Agriculture, Abeokuta, a sub-humid region of southwestern Nigeria. Treatments were five levels of weed control (codal gold 1.6 kg a.i/ha, codal gold 1.6 kg a.i/ha + hoe weeding, codal gold 2.4 kg a.i/ha, hoe weeding and a control (weedy check); two levels of spacing (15 cm and 25 cm) and eight levels of weeding intervals on soil microbial biomass, nodulation, the biomass of root and shoot as well as yield of groundnut in a split-plot design fitted into a randomized complete block design. The results indicated that both levels of spacing have no significant effect on the soil microbiological parameters, groundnut biomass production, nodulation and yield. So, the levels of weed control have no significant effect on groundnut biomass production and nodulation but showed a significant effect on microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), total fungal count, pod count and pod weight of groundnut with plots kept weedy throughout the experiment at 25 cm intra row spacing having 34 % MBC more than plots kept weed free throughout the experiment at the same spacing.

Elevated CO2 along with inoculation of cyanobacterial biofilm or its partners differentially modulates C–N metabolism and quality of tomato beneficially

Diazotrophic cyanobacteria are known to influence nutrient availability in soil, however, their benefits under elevated CO2 environment, particularly on fruit quality attributes, is a less investigated aspect. Laboratory developed cyanobacterium-fungal biofilm (An-Tr), composed of Anabaena torulosa (An) as the matrix with the partner as Trichoderma viride (Tr), along with the individual partners were evaluated under ambient (aCO2-400 ± 50 ppm) and elevated (eCO2-700 ± 50 ppm) conditions, with and without tomato plants. An-Tr inoculation exhibited distinct and significantly higher values for most of the soil microbiological parameters, plant growth attributes and antioxidant/defense enzyme activities measured at 30 and 60 DAI (days after inoculation). Significant enhancement in soil nutrient availability, leaf chlorophyll, with 45–50% increase in the enzyme activities related to carbon and nitrogen assimilation, higher yields and better-quality parameters of tomato, with An-Tr biofilm or An inoculation, were recorded, particularly under eCO2 conditions. The fruits from An-Tr treatments under eCO2 exhibited a higher titrable acidity, along with more ascorbic acid, carotenoids and lycopene content, highlighting the superiority of this inoculant. Multivariate analyses revealed significant (p ≤ 0.05) interactions among cultures, DAI, and CO2 levels, illustrating that cyanobacterial inoculation can be advocated as a strategy to gainfully sequester eCO2. Significant improvement in yield and fruit quality along with 50% N savings, further attest to the promise of cyanobacterial inoculants for tomato crop in the climate change scenario.

Impact of anthropogenic land uses on soil microbiological activity in a peri-urban landscape.

Land use and land cover patterns impact soil properties and negatively affect soil microbial community and related processes. However, the information regarding the influence of urban land use on soil microbial composition and functioning is limited. Here, we investigated the impact of urban land use patterns on soil microbiological parameters by comparing five contrasting anthropogenic land use classes, i.e. agriculture, park, roadside plantation, street green, and bare land. Soil physicochemical properties, basal respiration (BR), microbial biomass carbon (MBC), and enzyme activities were estimated and correlated. The results revealed that soil physicochemical and microbiological properties greatly varied across the five land use classes. Among all the land use types, the roadside plantation had the highest nutrient content, i.e. soil organic carbon (SOC), total nitrogen (TN), and mineral nitrogen (MN) (1.33%, 0.13%, 84.0mgkg-1, respectively), while the soil functional capacities measured in terms of BR, MBC, microbial quotient (QCO2), soil microbial activity (SMA), and dehydrogenase activity (DHA) (9.90 C µg g-1h-1, 300µgg-1, 0.045µgh-1/ µg MBC, 9.0µgml-1, 1.30 TPF g-1h-1, respectively) were highest in the park. Disturbed street greens were markedly nutrient depleted and apparently exhibited lower microbial activity. Variations in soil BR, MBC, and enzyme activity were revealed to be primarily influenced by soil moisture, available phosphorus, and SOC content. We concluded that the negative impacts of anthropogenic land use soil quality and microbiological functioning can be managed by integrating proper management approaches for various land use classes in urban systems.

Impacto dos resíduos de rocha dolomítica na acidez do solo e absorção de Ca e Mg por cevada e trigo

ABSTRACT The dumps of dolomite dropouts from road construction occupy huge arable areas in north-western Russia. Although coarse dolomite particles neglected as a liming material due to its slow solubility, we hypothesise that they can serve as a cheap and long-lasting liming material. The weight loss of dolomite particles of various sizes from the dump applied to Albic Retisol and its effect on assimilation of Ca and Mg by barley and wheat were studied. The pot experiment with 300 g soil was conducted for 30 days in a laboratory phytotron. Results showed that coarse particles of dolomite waste had a positive effect on soil acidity already at the initial phases of the experiment. In the process of dissolution of dolomite, all forms of soil acidity decreased. The cultivation of barley had a stronger effect on the dissolution of dolomite particles than the cultivation of wheat. Barley plants accumulated Ca by 1.1-1.4 times higher than wheat, other factors being identical. The relationship between the yield of green biomass and the accumulation of calcium and magnesium in the plants were empirically described using regression analysis. Results of this preliminary study showed that the by-products from dolomite stone processing can be effectively used for reclamation of strongly acidic soil in north-western Russia. This has the dual benefit of reducing the burden on the environment and reclaiming acidic soils. Further studies should include soil microbiological and biological parameters to trace the effect of root activities and dolomite dissolution rate on a field scale.

Effect of metal fractions on rice grain metal uptake and biological parameters in mica mines waste contaminated soils

Heavy metals from mica waste not only deteriorate the soil quality but also results in the uptake of metals in the crop. The present investigation was conducted to evaluate the effects of different fractions of metals on the uptake in rice, soil microbial and biochemical properties in mica waste-contaminated soils of Jharkhand, India. From each active mine, soil samples were randomly collected at distances of < 50 m (zone 1), 50–100 m (zone 2), and >100 m (zone 3). Sequential metal extraction was used to determine the fractions of different metals (nickel (Ni), cadmium (Cd), chromium (Cr) and lead (Pb)) including water-soluble (Ws) and exchangeable metals (Ex), carbonate-bound metals (CBD), Fe/Mn oxide (OXD) bound metals, organically bound metals (ORG), and residues (RS). The Ni, Cr, Cd and Pb in rice grain were 0.83±0.41, 0.41±0.19, 0.21±0.14 and 0.17±0.08 mg/kg respectively. From the variable importance plot of the random forest (RF) algorithm, the Ws fraction of Ni, Cr and Cd and Ex fraction of Pb was the most important predictor for rice grain metal content. Further, the partial dependence plots (PDP) give us an insight into the role of the two most important metal fractions on rice grain metal content. The microbial and enzyme activity was significantly and negatively correlated with Ws and Ex metal fractions, indicating that water-soluble and exchangeable fractions exert a strong inhibitory effect on the soil microbiological parameters and enzyme activities.

EFFECTS OF THE 2, 4-DICHLOROPHENOXYACETIC ACID (2,4-D) HERBICIDE CONTAMINATION ON SOIL MICROBIOLOGY AT THE COMMUNITY LEVEL

Owing to the knowledge that 2, 4-Dichlorophenoxyacetic Acid (2, 4-D) is rapidly degraded by soil microorganisms, little or no research attention has been given to enhancement of its degradation as a form of environmental remediation. A completely randomized design laboratory incubation experiment was carried out to examine the potentials of organic and mineral fertilizers to stimulate microbial activities in soils under the influence of the 2, 4-D herbicide. Soil contaminated with the field rate of 2, 4-D was separately amended with compost and NPK mineral fertilizer, and the treated samples were incubated for 56 days at room temperature. Soil microbiological parameters were measured in dynamics and eco-physiological quotients were computed at the end of the incubation period to determine responses of soil microbes at the community level of the treatments. Application of 2, 4-D either alone or in combination with fertilizer, regardless of type, raised soil respiration and soil microbial biomass. Addition of NPK to the 2, 4-D contaminated soil increased the microbial metabolic quotient (qCO2) while this parameter was reduced when compost was added. Addition of compost improved all the eco-physiological quotients compared to the sole application of 2, 4-D herbicide. It was therefore concluded that the 2, 4-D herbicide at the field recommended rate has the potential to negatively influence the soil microbial community, application of organic fertilizer may help the soil to regain its microbial competence through enhanced degradation engendered by bio-stimulation of native microorganisms.

Combined Effect of Microplastics and Cd Alters the Enzymatic Activity of Soil and the Productivity of Strawberry Plants

The synergistic effect between heavy metals and microplastics can affect soil properties as well as plant performance and yield. The objective of this study was to evaluate the combined effect of microplastics and cadmium on a soil–plant system. Specifically, we proposed to explore changes in soil microbiological activity, the growth and yield parameters of strawberry plants, and to evaluate the accumulation of these pollutants in the soil and root system. Plants were planted in clay pots under greenhouse conditions. The experiment was set up as a completely randomized design, with four treatments (Control; MPs; Cd; and Cd + MPs) and five replicates. The results showed that MPs and/or Cd affected plant growth, plant biomass, the number of fruits, root characteristics, dehydrogenase activity, acid phosphatase, and microbial biomass, and increased the accumulation of Cd in the roots and soil. The increased bioavailability of Cd, due to the presence of microplastics, could explain the observed negative effects on soil properties and the performance of strawberry plants.

The Effects of Rabbit Manure-Derived Biochar on Soil Health and Quality Attributes of Two Mine Tailings

Biochar amendment is becoming a promising technology for mining soil restoration. The addition of biochar can improve soil microbiological parameters related to soil quality, such as enzyme activities. The aim of the present research was to evaluate the effect of rabbit manure (RM) and two rabbit manure biochars prepared at two pyrolysis temperatures (300 and 600 °C) on the biochemical properties of two mining soils in the Portman area (Spain) in the presence or absence of vegetation. Soils were amended with the RM, the two biochars and a mixture of the rabbit manure and biochars (50/50 w/w) at a rate of 10% in a mesocosms experiment to study the changes in dehydrogenase, phosphomonoesterase, β-glucosidase activities, geometric mean of enzyme activities (GMea) and soil microbial biomass (SMB). Changes in individual enzyme activities were not always consistent. However, when using the GMea as a measure of soil quality, our results showed an increase in the GMea (217–360 times) after the addition of rabbit manure to mining soils, while this increase was from 81–270 times following the addition of rabbit manure with biochar prepared at 300 °C. Therefore, the use of biochar prepared at low temperatures could be a promising direction for the improvement of soil quality and soil carbon sequestration.

Characteristics of Culturable Microbial Community in Rhizosphere/Non-rhizosphere Soil of Potentilla Fruticosa Population in Alpine Meadow Elevation Gradient

Potentilla fruticosa is a typical shrub of alpine meadows with canopy effects that can greatly influence soil fertility and microbiological parameters. Changes in rhizosphere microorganisms can reflect the response of these plants to environmental changes. This study aimed to examine the rhizosphere and non-rhizosphere of P. fruticosa on the amount of selected microorganisms and main environmental factors at different elevation gradients (3,000, 3,250, 3,500, 3,750, and 4,000 m). The results suggested that bacteria were predominant of the microbial soil community in the rhizosphere and non-rhizosphere, while fungi and actinomycetes represented the minority. With the increase of altitude, the total amount of microbial, bacteria, and actinomycetes in the rhizosphere and non-rhizosphere of P. fruticosa showed a downward trend, and microbial functional groups showed that the “hump shape” changed, but the fungi showed the opposite. Variance inflation factor (VIF) screening environmental factors and path analysis were obtained. In the rhizosphere soil, bacteria were affected by Soil organic carbon (SOC), and soil bulk density (SBD) became the main environmental limiting factor with the increase of altitude. The main environmental limiting factor of actinomycetes changed from SBD to Soil total (ST). In the non-rhizosphere soil, the bacteria and actinomycetes changed from ST to SOC and SBD, respectively. The main environmental limiting factor of the fungi was SOC in the rhizosphere and non-rhizosphere. Soil water content (SWC) was the main environmental determinant factor for all microbial groups, microbial functional groups were related to Soil total nitrogen (STN). Our results help to understand the relationship between nutrient cycling and the ecosystem function of alpine meadow plant soil microorganisms and provide theoretical support for alpine meadow ecosystem restoration, biodiversity protection, and the use of microbial resources.

Nonadditive Effects on Decomposition of a Mixture of Rice Straw and Groundnut Stover Applied to a Sandy Soil

Rice straw is an abundant resource, but its use as a sandy soil amendment does not increase soil organic matter (SOM) accumulation. Our study aimed to determine the altered decomposition processes that result from mixing rice straw (RS) (low N, high cellulose) with groundnut stover (GN) (high N) relative to applying these residues singly to a sandy soil to identify the mechanisms underlying decomposition of the mixed residues. A microcosm experiment using the litter bag technique showed synergistic, nonadditive effects (observed &lt; predicted values) of residue mass remaining (31.1% &lt; 40.3% initial) that were concomitant with chemical constituent loss, including C (cellulose, lignin) and N. The nonadditive effects of soil microbiological parameters in response to the applied residues were synergistic (observed &gt; predicted values) for microbial biomass C (MBC) (92.1 &gt; 58.4 mg C kg−1 soil) and antagonistic (observed &lt; predicted values) for microbial metabolic quotient (i.e., the inverse of microbial C use efficiency (CUE)) (0.03 &lt; 0.06 mmol CO2-C • mmol MBC−1 • hr−1) and N mineralization (14.8 &lt; 16.0 mg N kg−1 soil). In the early stage of decomposition (0–14 days), mixed residues increased MBC relative to the single residues, while they decreased N mineralization relative to single GN (p ≤ 0.05). These results indicate an increase in microbial substrate CUE and N use efficiency (NUE) in the mixed residues relative to the single residues. This increased efficiency provides a basis for the synthesis of microbial products that contribute to the formation of the stable SOM pool. The SOM stabilization could bring about the SOM accumulation that is lacking under the single-RS application.

Assessment of the Influence of Pyrogenic Factors on the Biological Properties of Chernozems

Changes in the biological properties of chernozems caused by several pyrogenic agents have been studied in simulation experiments with the low-temperature plasma, infrared irradiation, straw burning, and fume of burning products. It has been shown that the pyrogenic effect has a complex nature, so that worsening of biological parameters depends on temperature, duration of fire episode, intensity of fume, ash impact, and soil moisture. Such integrated effect induced a decrease in microbial biomass by 39%, population of nitrogen-fixating bacteria by 29% versus the control values. The inhibition of dehydrogenase and catalase (oxidoreductase class) was 44–53%; the activity of hydrolase (phosphatase and invertase) was lower (by 16–18%). A maximal effect was recorded for the uppermost soil layer (0–1 сm) as compared to the lower 4–5 сm layer. Microbiological indices went down by 52–56% after placing the sample in the flame of a gas burner for 3 minutes, while soil enzyme activity decreased by 25–26%. For the latter, the duration of flame effect was of special importance; the correlation coefficient for dehydrogenase activity was –0.81; for invertase activity, –0.86; for catalase activity, –0.78; and for phosphatase activity, –0.85 (р < 0.01). Increasing IR irradiation also resulted in growing inhibition of biological indices. Even a minimal impact of fume of straw burning products (3 minutes at temperature 52°С) reliably decreased soil microbiological and biochemical parameters (by 4–19%, р < 0.05). Higher level of impact suppresses the biological activity by 20–30%.

Long‐term legacy of land‐use change in soils from a subtropical rainforest: Relating microbiological and physicochemical parameters

AbstractTropical and subtropical ecosystems are widely affected by the expansion of agriculture over pristine lands. Despite research efforts, knowledge of the impact of land‐use change on soil is still limited by intrinsic variability, inconsistent results and inadequate replication. This study aimed to better understand the consequences of land‐use change by focusing on long‐term effects on both soil biotic and abiotic parameters. For this purpose, we selected three productive farms under similar management, each of them with pristine forest sites and agricultural sites that had been deforested for ~15 and ~30 years. In each site, we analysed soil microbiological (phospholipid fatty acids [PLFAs], biomass and activity) and physicochemical parameters. Long‐term land‐use change caused a detriment in soil microbial biomass, activity and fungal abundance, but only small changes in PLFA composition. In fact, PLFA composition was more affected by soil physicochemical properties such as carbon‐to‐nutrient ratios and labile carbon than by land use. Some physicochemical parameters (e.g., organic carbon and nutrients) were also negatively affected by land‐use change and were more sensitive to time under agricultural use than microbiological parameters. The lower sensitivity of microbiological parameters could be the result of severe drought conditions at sampling, which may have affected soil microbial communities in both land uses. We were also able to detect associations between specific microbiological and physicochemical parameters. Among these, we identified some that seemed to result from their co‐variation in response to land‐use change and others that seemed to be independent of land use. Overall, our results show that soils can suffer further deterioration several years after deforestation. In order to restore soil health in these degraded lands, we need to keep on investigating the physical, chemical and biological mechanisms responsible for this deterioration.Highlights Land‐use change affected soil microbiological and physicochemical parameters. Microbiological parameters seemed to stabilize after continuous agriculture. Soil organic C, total N and fine particles were still reduced after long‐term cultivation. Microbiological parameters were mostly associated with C‐to‐nutrient ratios and labile C. Drought conditions may have affected microbial response to land‐use change.

Influence of organic technology on vegetative growth and production of three climbing edible roses (Rosa sp.)

In the present study, three climbing edible roses (‘Crown Princess Margareta’, ‘Falstaff’ and ‘Brother Cadfael’) were evaluated for total vegetative growth and flowers production, besides correlations with soil microbiological and agrochemical parameters. The applied organic technology included a soil preparatory stage with three ameliorative plants (Sinapis alba L., Phacelia tanacetifolia L. and Tagetes patula L.) and two organic mulch variants (wood chips and wool) after plantation. In variant Sinapis and Tagetes, all three varieties of roses showed the highest values for parameters: total vegetative growth, number of shoots, average shoots length and flowers number. Significant positive correlations between biometric parameters and soil bacteria, phosphorus, mineral nitrogen, potassium (0-20 cm horizon) and humus (20-40 cm horizon) content were observed. Significant positive correlations between the number of flowers and the soil respiration coefficient, soil content in phosphorus, potassium, humus, total soluble salts and mineral nitrogen were noticed. Negative correlations with soil pH have been observed. Taking into account the data obtained in the two flowering stages in 2017, the average yield per hectare cultivated with ‘Crown Princess Margareta’ was 9.44 t petals/ha. For the ‘Falstaff’ and ‘Brother Cadafael’ cultivars, the yields were 7.54 and 5.62 t petals per hectare respectively.

Management Strategies on an Upland Soil for Improving Soil Properties

ABSTRACTUpland soils marginal in organic matter, low in soil quality, vulnerable to water and nutrient losses. This study was conducted to determine whether the integration of winter cover crops and soil amendments into no-till cropping systems improve upland soil quality. The effects of winter cover crops (WCCs), broiler litter (BL) and flue gas desulfurization (FGD) gypsum in no-till (NT) corn-soybean rotation on soil physical and biological properties were investigated at Pontotoc, MS on an upland Falkner silt loam soil (fine-silty, siliceous, active, thermic Aquic Paleudalfs). After harvest, soil samples were collected and analyzed for total C (TC) and selected physical and biological properties. Averaged across fertilization treatments, WCCs increased TC, cumulative infiltration and reduced bulk density (BD) and penetration resistance (PR) at 0–5 cm depth as compared to winter fallow (WF). Averaged across WCCs treatments, BL increased infiltration by 51%, and reduced BD and PR by 3% and 24%, respectively, as compared to unfertilized control. Co-application of FGD gypsum with BL reduced BD and PR at 5 cm soil depth by 4% and 5%, respectively. Interestingly, BL did not affect soil microbiological parameters, but the co-application of FGD gypsum with BL resulted in a significant response in soil dehydrogenase activity. On the other hand, cover crop increased ureC (urease C) genes, probably due to conserved soil moisture by cover crop residues. Integration of WCCs, organic and inorganic amendments into no-till corn-soybean appear to improve soil physical, hydrological and microbial properties, which may enhance the efficiency of cropping systems in upland soils.

Biodiagnostics of Soil under a Low Level of Anthropogenic Impact (by the Example of the Urban Settlement of Stepnoe, Saratov Oblast)

Abstract—Biodiagnostics of soil in a settlement with low technogenic impact was performed by the example of the urban settlement of Stepnoe. The number of microorganisms was evaluated in 30 soil samples by inoculation on solid nutrition media: on meat peptone agar for the calculation of the total heterotrophic microorganisms and on the corresponding selective media for hydrocarbon-oxidizing and iron-oxidizing microorganisms. We also analyzed the activity of several soil redox and hydrolytic enzymes (dehydrogenases, catalases, peroxidases, and invertases). The content of the mobile forms of copper, zinc, lead, cadmium, chromium, and nickel was determined to assess the anthropogenic impact on the soil, and the total soil contamination coefficient (Zc) was calculated. The excess of the MPC of mobile forms of Ni, Cu, and Pb was revealed in the area studied. In general, the total soil contamination coefficient did not exceed 16, indicating favorable environmental and geochemical conditions in the settlement. The analysis of the total number of heterotrophic microorganisms and the amounts of hydrocarbon-oxidizing and iron-oxidizing microorganisms showed deviations from the norm in some regions of the area surveyed, which pointed to anthropogenic transformation of the soil biocenoses. The maximum deviations were typical for the index of hydrocarbon-oxidizing microorganisms, which pointed to soil contamination by hydrocarbons. Our data on the evaluation of the activity of indicator soil enzymes did not exclude possible functional disturbances in the soil. It was found that the activity of soil dehydrogenases and invertases corresponded to low and very low levels of soil enrichment with these enzymes. The activity of soil catalases and peroxidases corresponded to the moderate and high levels of the enzymes, which indicated the absence of pathological changes in the soil. It has been shown that the studied soil microbiological and biochemical parameters are promising for soil health biodiagnostics in areas with low anthropogenic impact.

Effect of Integrated Nutrient Management in Sunflower (&lt;i&gt;Helianthus annuus&lt;/i&gt; L.) on Alluvial Soil

Sunflower, an important oil seed crop, needs a balanced nutrition for its optimum growth and thorough maintenance of soil health. A field experiment was conducted to study the impact of integrated use of organic, inorganic and biofertilizers on soil fertility, soil organic carbon fractions, soil microbiological and biochemical parameters as well as yield of sunflower (cv. GK 2002) in alluvial soil at Agricultural Experimental Farm, University of Calcutta, Baruipur, India, during 2013–14 and 2014–15. There were ten different treatments with three replications. After analysis, the data clearly showed significant difference among treatments in sunflower yield and a prominent impact of integrated use of organic, inorganic and biofertilizers was found under the treatments. Microbial biomass carbon, basal soil respiration, activities of soil enzyme and different carbon fractions showed higher values for those treatments where only organic inputs were given. The best possible combination for higher seed yield was recorded in T 10 /T 6 treatment (vermicompost 2.5 t ha –1 or FYM (5 t ha –1 ) with phosphate solubilizing bacteria @ 8 kg ha –1 soil application + Azotobacter @ 8 kg ha –1 soil application + 50% recommended dose of chemical fertilizers + foliar spray (2% urea)). T 10 /T 6 treatment is thus recommended for sunflower cultivation in alluvial soil considering the soil quality and seed yield of sunflower.

Influence of natural saferock mineral on soil micro-bilogical parameters under rice-wheat cropping system

A field experiment was conducted to study the effect of SafeRock Minerals (SRM) application on soil microbiological parameters in rice-wheat cropping system. The experiments consisted of two methods of rice and wheat establishment and six different levels of crop nutrition including SRM with mineral fertilizers and organic manure (FYM). The rice was grown in kharif (June to October) season through aerobic direct seeded condition and flooded transplanted system. During rabi (October to April) season wheat was cultivated by two establishment methods viz. system of wheat intensification (SWI) and conventional wheat. The high yielding varieties of Basmati rice (Pusa Basmati 1509) and wheat (HD 2967) were used in the experiment. The results revealed that the soils of rice and wheat crops showed significant improvement in available N, P and K and soil microbial parameters (enzymatic activities and microbial biomass carbon) due to the integrated application of 250 kg/ha SRM + 100% recommended dose of fertilizer (RDF) and 250 kg/ha SRM + 50% RDF (chemical) + 25% RDF (organic) and 250 kg/ha SRM + 50% organic-FYM (10.0 t/ha) over the sole SRM application under both the methods of stand establishment of rice as well as wheat.

Microbial inoculants as plant growth stimulating and soil nutrient availability enhancing options for cucumber under protected cultivation.

Protected cultivation of vegetables is often hampered by declining nutrient availability in soil due to year-around farming, which in turn, leads to poor quality and yields, causing serious concern. Our study aimed towards evaluating the potential of novel biofilm formulations-Anabaena or Trichoderma as matrices with Azotobacter sp. as Anabaena-Azotobacter (An-Az) and Trichoderma-Azotobacter (Tr-Az) or together as Anabaena-Trichoderma (An-Tr), on the growth, physiological activities, yield, and changes in the profiles of soil microbial communities in two cultivars (cv. DAPC-6 and cv. Kian) of cucumber (Cucumis sativus). Photosynthetic pigments, evaluated as an index of growth showed two-threefold increase, while elicited activity of defense and antioxidant enzymes was stimulated; this facilitated significant improvement in the plants belonging to the inoculated treatments. Microbial biomass carbon and polysaccharides in soil enhanced by two-threefolds in treatments receiving microbial formulations. Available N in soil increased by 50-90% in An-Az and An-Tr biofilm inoculated treatments, while the availability of P and organic C content of soil improved by 40-60%, over control. PCR-DGGE profiles generated revealed signification modulation of cyanobacterial communities and cultivar-specific differences. Significant enhancement in leaf chlorophyll pigments, soil microbiological parameters and nutrient bio-availabilities along with positive correlation among the analysed parameters, and distinct profiles generated by PCR-DGGE analyses illustrated the promise of these novel inoculants for cucumber.

Exploring Crop–Microbiome Interactions Towards Improving Symbiotic Performance of Chickpea (Cicer arietinum) Cultivars Using Cyanobacterial Inoculants

The significance of integrated nutrient management practices is well established in improving the productivity of chickpea (Cicer arietinum); however, the effects of the inoculation of cyanobacterial inoculants on nodule metabolism, microbiome and associated genes are less explored. In the present investigation, cyanobacterium Anabaena laxa (A. laxa) and biofilm developed using Anabaena torulosa, with Mesorhizobium ciceri as a partner (An-M. ciceri), were evaluated along with Mesorhizobium ciceri (M. ciceri) alone, in three chickpea cultivars. Microbial inoculation led to 40–70% enhancement in nitrogen fixation, leghaemoglobin and ureide content, and two- to threefold increment in nitrate reductase and phosphoenolpyruvate carboxylase activity of the nodules. An enhancement of 30–50% in the soil available macro- and micronutrients and plant growth attributes was also observed. A significant correlation between the soil microbiological and plant parameters was recorded, particularly in relation to the nitrogen dynamics. Increases in the leghaemoglobin content in nodules due to An-M. ciceri, A. laxa and M. ciceri ranged from 18 to 40%, particularly in chickpea cv. BG372 in which 60–80% enhancement was recorded. Whereas the nifH gene copies in the nodule tissues ranged from 5.00 × 106 to 3.35 × 107 g−1, the application of A. laxa led to higher abundances of nifH gene copies in desi chickpea cv. BG372 and kabuli BG1053 cultivars. An-M. ciceri, followed closely by A. laxa, was the top-ranking treatment, and chickpea cv. BG372 was the best performing cultivar; An-M. ciceri—chickpea cv. BG372 proved to be the superior combination for higher plant growth and soil nutrient-related traits.

Humus Forms and Soil Microbiological Parameters in a Mountain Forest: Upscaling to the Slope Scale

Humus forms are the morphological results of organic matter decay and distribution in the topsoil, and thus important indicators for decomposer activities in forest ecosystems. The first aim was to examine if humus forms are suitable indicators of microbiological properties of the topsoil in a high mountain forest (Val di Rabbi, Trentino, Italian Alps). The second aim was to predict microbiological parameters based on the topsoil pH value on two slopes of the study area (ca. 1200-2200 m a.s.l.). We investigated humus forms and determined pH values and microbiological parameters (enzymatic activities, carbon/nitrogen (C/N) ratio and the ratio of bacterial/archaeal abundance) of the uppermost mineral horizon. The results reveal significant correlations between pH value and microbiological parameters (except for bacterial/archaeal abundance), which enable upscaling to the landscape scale using linear models. Based on a random forest with kriging of model residuals, predictive maps of humus form, pH value and microbiological parameters show that decomposition processes in our study area correspond with the topography. As compared to locations on south-facing slopes or close to the valley bottom, locations on north-facing slopes or close to the upper treeline exhibit Moder (scarcely Mull or Amphimull), more acidic topsoil (around pH 4), a lower activity of leucine-aminopeptidase, a lower ratio of alkaline/acid phosphomonoesterase activity and a higher soil C/N ratio (above 20). Our results suggest a high potential of humus forms to indicate soil microbiological properties in a high mountain forest. Together with the pH values of the topsoil, humus forms proved to be a useful tool as a basis for predictive maps of leucine-aminopeptidase activity, ratio of alkaline/acid phosphomonoesterase activity and C/N ratio of the mineral topsoil.