Application of Streptomyces mutabilis Derived Rhamnolipid to Enhance Microbial Activity and Nutrient Uptake in Barley Grown Under Saline Conditions

A 72-day greenhouse pot experiment was conducted with a sandy loam or a silt loam soil to examine the effects of farmyard manure (FYM), poultry litter (PL) and biogenic waste compost (BWC) at 10 g dw kg-1 soil on microbial biomass and activity and growth and nutrient uptake by wheat. Soil samples were collected at days 0, 14, 28, 42, 56 and 72 after planting. Growth and nutrient uptake by wheat were determined on day 72. All three amendments increased microbial biomass C, N and P, dehydrogenase activity, plant growth and nutrient uptake with a greater effect by FYM and PL than by BWC. All amendments increased microbial biomass C, N and P and enzyme activity particularly on day 0. These microbial parameters decreased after day 0 indicating microbial biomass turnover. All amendments increased plant growth and nutrient uptake. It is concluded that organicamendments can stimulate microbial growth and nutrient uptake as well as plant growth and nutrient uptake. Microbes can increase plant nutrient availability by nutrient mobilisation but also because nutrients taken up by the microbial biomass initially could become available to plants when the microbial biomass turns over as the easily available C is depleted.

Plant biostimulants can play significant roles in organic agriculture by stimulating natural processes that enhance nutrient availability and plant uptake, improve abiotic stress tolerance, and boost overall plant growth and development. Despite their roles, data on the efficacy of biostimulants in organic agriculture is limited, particularly in Scandinavian countries such as Denmark. We evaluated the efficacy of 10 different biostimulants on organic snack carrots and potatoes in Denmark for two years. A factorial experimental design was set up under field conditions for two years at two locations characterized by sandy clay (2021) and sandy (2022) soil textures at the experimental stations of Aarhus University in Denmark. The two factors were nitrogen levels (100% and 50% of recommended nitrogen) and biostimulants of different origins, namely, microbial origin (Proradix and Vesta), plant extracts (Crop-set and Combi-set), seaweed extract (Acadian), humic and fulvic acids (Humifirst). The biostimulants were applied at recommended rates, time, and application methods per the guidelines indicated on the product's label. Soil samples were collected to 0-25 cm depth a week before harvest and after removing the upper ground biomass. Two soil enzymes, dehydrogenase (DHA) and β-glucosidase (BGA), were selected as indicators of soil microbial activities. Macro (N, P, K, S, Ca, Mg) and micro (Fe, Mn, B, Cu and Zn) nutrients in the soil and the potato tubers were analyzed to evaluate the effects of biostimulants on nutrient use efficiency indices such as nutrient uptake. There was no significant interaction effect of the biostimulants and nitrogen levels on both enzymes and most of the plant nutrient uptakes at the two locations. The 100% nitrogen level resulted in a significantly (p<0.05) higher DHA than the 50% nitrogen level only in the sandy soil. The biostimulants did not significantly change the DHA and BGA in sandy clay and sandy soil. Some of the biostimulants significantly increased (p<0.05) nutrient uptake for all the nutrients except Fe in sandy soil. However, significant effects (p<0.10) of biostimulants were observed only in P and Mg uptake in the sandy clay texture soil. The results indicate that the effect of biostimulant application on microbial activities and plant nutrient uptake depends on the type of biostimulant and soil texture used in organic potato production in Denmark.

Summary1. We measured NH4+ and PO4−3 uptake length (Sw), uptake velocity (Vf), uptake rate (U), biofilm respiration and enzyme activity and channel geomorphology in streams draining forested catchments in the northwestern (Northern California Coast Range and Cascade Mountains) and southeastern (Appalachian and Ouachita mountains) regions of the United States. Our goal was to use measures of biofilm enzyme activity and nutrient uptake to assess nutrient limitation in forested streams across broad regional scales.2. Geomorphological attributes, biofilm enzyme activity and NH4+ uptake were significantly different among streams in the four study units. There was no study unit effect on PO4−3 uptake. The proportion of the stream channel in pools, % woody debris, % canopy closure, median substrate size (d50), stream width (w), stream velocity (v), discharge (Q), dispersion coefficient (D) and transient storage (As/A) were correlated with biofilm enzyme activity and nutrient uptake in some study units.3. Canonical correlation analyses across study units revealed significant correlations of NH4‐Vf and PO4‐Vf with geomorphological attributes (w, d50, D, % woody debris, channel slope and % pools) and biofilm phosphatase activity.4. The results did not support our expectation that carbon processing rates by biofilm microbial assemblages would be governed by stream nutrient availability or that resulting biofilm enzyme activity would be an indicator of nutrient uptake. However, the relative abundances of peptidases, phosphatase and glycosidases did yield insight into potential N‐, P‐ and C‐limitation of stream biofilm assemblages, and our use of biofilm enzyme activity represents a novel application for understanding nutrient limitations in forested streams.5. Regressions of Vf and U against ambient NH4+ and PO4−3 indicated that none of our study streams was either NH4+ or PO4−3 saturated. The Appalachian, Ouachita and Coastal streams showed evidence of NH4+ limitation; the Ouachita and Coastal streams were PO4−3 limited. As a correlate of nutrient limitation and saturation in streams, ratios of total aminopeptidase and phosphatase activities and the ratio of NH4‐U to PO4‐U indicate these forested streams are predominantly N‐limited, with only the streams draining Ouachita and Coastal catchments demonstrating appreciable levels of P‐limitation.6. Our results comparing the stoichiometry of microbial enzyme activity with nutrient uptake ratios and with the molar ratios N and P in stream waters suggest that biological limitations are not strictly the result of stream chemistry and that the assessments of nutrient limitations in stream ecosystems should not be based on chemistry alone.7. Our present study, along with previous work in streams, rivers and wetlands, suggests that microbial enzyme activities, especially the ratios of total peptidases to phosphatase, are useful indicators of nutrient limitations in aquatic ecosystems.

A field experiment was undertaken during kharif 2012 to study effect of biofertilizers and foliar application of organic acids on yield, nutrient uptake and microbial activity of soybean at MARS, Dharwad under rainfed condition. The experiment was laid out in RCBD factorial having twenty treatment combinations and replicated thrice. The treatments comprised of four P-Solubilizers (PSB, VAM, PSB + VAM and Control) and five foliar spray of organic acids (Humic acid, Lecithin, Citric acid, Maleic acid and control). The results revealed that higher seed yield of soybean (35.96 q ha-1) was obtained with the treatment combination of dual inoculation of PSB+VAM with foliar spray of 0.1% humic acid at flower initiation and was higher to an extent 22.5 per cent compared to control (27.90 q ha-1). Similar trend was observed on microbial activity and nutrient uptake (N, P2O5 and K2O) of the soybean crop.

Background: Salinity is one of the environmental stress factors that restrict the crop production by endangering agricultural areas. Nitric oxide (NO) protects plants from damage caused by oxidative stress conditions in various biological ways. Methods: In this greenhouse investigation during 2018, pea plants were irrigated with three levels of NaCl (0, 50 and 100 mM) solutions. NO solutions were prepared with three different doses (0, 75 and 100 µM SNP). These solutions were applied to the seeds before sowing and then to the leaves of the pea cultivars. The study was conducted to analyze the impact of NO on growth, malondialdehyde (MDA), hydrogen peroxide (H2O2), antioxidant enzyme activity and nutrient uptake in two pea cultivars under salinity conditions. Result: Salinity reduced fresh-dry weight, relative water content (RWC), and chlorophyll a and b content of pea. However, NO enhanced these parameters under salt stress. Salinity increased tissue electrical conductance (TEC), H2O2 and MDA content, which were decreased by combined application of NaCl and NO. Salinity caused an increase in antioxidant enzyme activity in pea and NO made a significant improvement in their activities under salinity conditions. Salinity treatments decreased the ratio of K+/Na+ and Ca2+/Na+ in both cultivars, and application of NO elevated them as compared to the control under salt stress. In conclude, exogenous NO treatment could help pea to tolerate salinity stress by increasing the chlorophyll content and regulating antioxidant enzyme activity and nutrient uptake.

Brinjal is an important vegetable crop in the coastal districts of Odisha. To enhance yields, farmers often depend heavily on chemical fertilizers, which may not always deliver the desired results. To address this, a field experiment was conducted across seven farmer fields to evaluate the effectiveness of integrated nutrient management (INM), combining chemical fertilizers, organic manure, biofertilizers, and micronutrients, in improving brinjal productivity and farmer's income. The experiment followed a Randomized Block Design (RBD) with three treatments and seven replications. The treatments comprising Application of NPK: 120:60:60 kg/ha along with FYM-20t/ha and Biofertilizers like Azospirillum, PSB @ 5kg/ha and micronutrient application: Zn and B @ 0.1% twice before flowering (T3) indicated there is significant increase in yield and yield attributing characters over control. The influence of biofertilizer along with optimum dose of fertilizer increased microbial activity and uptake of nutrients which triggered the flowering behaviour and fruit yield in combination with Boron and Zn like micronutrients. The results revealed that Treatment T3 significantly improved yield and yield-attributing characters over the control. The synergistic effect of biofertilizers with the optimum fertilizer dose enhanced microbial activity and nutrient uptake, which in turn improved flowering, fruit set, and yield, further supported by the role of micronutrients such as boron and zinc. T3 recorded the highest fruit yield (428 q/ha) along with the maximum benefit-cost ratio (2.78), followed by T2 (382.2 q/ha; B:C ratio 2.50) and T1 (270 q/ha; B:C ratio 2.09). A similar trend was observed for other growth and yield parameters. Based on the findings, it can be concluded that the integrated application of NPK (120:60:60 kg/ha), FYM (20 t/ha), biofertilizers (Azospirillum and PSB @ 5 kg/ha) and foliar sprays of Zn and B (0.1%) significantly enhances brinjal productivity and farmers' income in a sustainable manner.

Partial substitution of NO 3− by NH 4+ fertilization increases ammonium assimilating enzyme activities and reduces the deleterious effects of salinity on the growth of barley

Effects of hardened wood ash on microbial activity, plant growth and nutrient uptake by ectomycorrhizal spruce seedlings

Plant growth, nutrient uptake, microbial biomass and activity were studied in pot systems containing spruce seedlings colonised with different ectomycorrhizal fungi from an ash-fertilised forest. The seedling root systems were enclosed in mesh bags inside an outer compartment containing crushed, hardened wood ash. Three different species of mycorrhizal fungi and a non-mycorrhizal control were exposed to factorial combinations of ash and N addition. Ash treatment had a highly significant, positive effect on plant growth and on shoot and root concentrations of K, Ca and P, irrespective of mycorrhizal status. Mycorrhizal inoculation had a significant effect on plant growth, which was proportionally greater in the absence of ash. N addition had a significant positive effect on plant biomass in mycorrhizal treatments with ash, but no effect in non-mycorrhizal treatments or most of the mycorrhizal treatments without ash. Piloderma sp. 1, which was earlier found to colonise wood ash granules in field studies, appeared to accumulate Ca from ash in the mycorrhizal roots. 5-6.7% of the total P in the ash was solubilised, with 0.9-1.5% in solution, 3.6-4.6% in the plants and 0.5-1.5% in microbial biomass. Bacterial activity as determined by [(3)H]-thymidine and [(14)C]-leucine incorporation was significantly greater in ash treatments than in controls with no ash addition. Principal component analysis (PCA) of phospholipid fatty acids (PLFAs) showed a clear difference in bacterial community structure between samples collected from ash-treated pots and controls without ash.

A pot experiment was conducted to study the performance of faba bean and barley growing under saline conditions, in terms of dry matter yield, total N, and percentages and amount of N derived from the soil, fertilizer and atmosphere using a 15N isotope dilution method. Three saline treatments were employed: 1) plants were grown on saline soil and irrigated with saline water (SsWs); 2) plants were grown on saline soil and irrigated with non-saline water (SsWn); and 3) plants were grown on non-saline soil and irrigated with saline water (SnWs). Furthermore, a control treatment was employed by growing the plants on non-saline soil and irrigating them with non-saline water (SnWn). The different salinity treatments reduced plant growth and the reduction was more pronounced in faba bean than in barley. However, the relative growth reduction of plants grown only on saline soil, using non-saline water, did not exceed 50% of the control, whereas the reduction exceeded 50% when plants were grown under completely saline conditions. The percentage of N2fixed (%Ndfa) was not affected negatively by saline conditions.the results clearly demonstrated that the effect of salinity on faba bean was more evident on plant growth than on N2-fixing activity. Further studies are needed to obtain more salt-tolerant faba bean genotypes that possess a higher growth rate. This could simultaneously improve yield and N2fixation under severely saline conditions.

Soil application of humic acid (HA), generally derived from leonardite shale, is a common practice in California vegetable production. Five commercial HA formulations were evaluated for their effects on soil microbial activity, seedling emergence, crop productivity, and nutrient uptake when applied to representative agricultural soils. Two soils differing in organic matter content (8 and 25 g·kg −1 ) were wetted to field capacity moisture content with solutions of water, nitrogen and phosphorus (P) fertilizer, HA, or fertilizer + HA and incubated aerobically at 25 °C. In the lower organic matter soil, a synergistic effect of fertilizer and HA was observed after 7 days of incubation on both microbial respiration and the amount of phospholipid fatty acids detected; these stimulatory effects were not observed in the higher organic matter soil. In a greenhouse pot study, the effects of HA on seedling emergence, dry mass accumulation, and P uptake of romaine lettuce ( Lactuca sativae L.) were evaluated in four soils of low P availability; HA was applied to the soil at a rate simulating a field application of 2.2 kg·ha −1 a.i. HA had no significant effect on emergence rate or percentage, or P uptake, in any soil; plant dry mass was increased in one soil. Field trials were conducted in 2008 and 2009 evaluating the effects of pre-transplant soil application of HA at 1.1 or 3.4 kg·ha −1 a.i. on growth, nutrient uptake, and fruit yield of processing tomato ( Lycopersicon esculentum Mill.). In neither year was macro- or micronutrient uptake increased with HA. Similarly, there was no significant HA effect on plant dry mass accumulation or fruit yield. We conclude that, at typical commercial application rates in representative field soils, HA is unlikely to significantly improve vegetable crop nutrient uptake or productivity.

Salinity is the most common problem in arid and semi-arid regions hindering nutrient accumulation in plants. A field trial (2017-18) was carried out to study the effect of sewage sludge (SS) and saline water irrigation on nutrient uptake under the pearl millet-wheat system and soluble ions in the soil. The experiment consisted of three irrigation levels (canal water, 8 and 10 dS/m ECiw saline water) and five fertilizer treatments i.e., control, sewage sludge (SS)- 5 t/ha, SS (5 t/ha) + 50% recommended dose of fertilizer (RDF), SS (5 t/ha) + 75% RDF and 100% RDF where sewage sludge was applied in rabi season only. The results indicated that the saline water irrigation significantly increased the concentrations of soluble ions (Na+, K+, Ca2++Mg2+, HCO3-, SO42- and Cl-) in the soil, and also the increase was non-significant under sewage sludge application. Na+ and Cl- ions were dominated under saline conditions among the soluble ions in the soil. The nutrient (N, P and K) uptake by grain and stover/straw of pearl millet and wheat crops were significantly reduced under saline environment. However, the maximum uptake in both crops was obtained under canal water irrigation (0.35 dS/m). Among fertilizer treatments, the maximum uptake (NPK) in both crops was attained under RDF being at par with SS (5 t/ha) + 75 RDF except K uptake in pearl millet crop, where the highest K uptake was obtained with SS (5 t/ha) + 75 RDF which was remained statistically at par with RDF treatment. The interactive effect was however non-significant. It is concluded that incorporating SS would enhance nutrient uptake in crops under saline conditions besides solving its dumping problem.

Leachate from litter and vegetation penetrates permafrost surface soils during thaw before being exported to aquatic systems. We know this leachate is critical to ecosystem function downstream and hypothesized that thaw leachate inputs would also drive terrestrial microbial activity and nutrient uptake. However, we recognized two potential endpoint scenarios: vegetation leachate is an important source of C for microbes in thawing soil; or vegetation leachate is irrelevant next to the large background C, N, and P pools in thaw soil solution. We assessed these potential outcomes by making vegetation leachate from frozen vegetation and litter in four Arctic ecosystems that have a variety of litter quality and soil C, N, and P contents; one of these ecosystems included a disturbance recovery chronosequence that allowed us to test our second hypothesis that thaw leachate response would be enhanced in disturbed ecosystems. We added water or vegetation leachate to intact, frozen, winter soil cores and incubated the cores through thaw. We measured soil respiration throughout, and soil solution and microbial biomass C, N, and P pools and gross N mineralization immediately after a thaw incubation (−10 to 2°C) lasting 6 days. Vegetation leachate varied strongly by ecosystem in C, N, and P quantity and stoichiometry. Regardless, all vegetated ecosystems responded to leachate additions at thaw with an increase in the microbial biomass phosphate flush and an increase in soil solution carbon and nitrogen, implying a selective microbial uptake of phosphate from plant and litter leachate at thaw. This response to leachate additions was absent in recently disturbed, exposed mineral soil but otherwise did not differ between disturbed and undisturbed ecosystems. The selective uptake of P by microbes implies either thaw microbial P limitation or thaw microbial P uptake opportunism, and that spring thaw is an important time for P retention in several Arctic ecosystems.

In this work, the effects of salicylic acid pretreatment on the seed germination, seedling growth (coleoptile percentage, radicle length, coleoptile length, radicle number and fresh weight) and leaf anatomy of barley under saline conditions were studied. In parallel with concentration rise, salt stress inhibited the germination and seedling growth of barley seeds. The inhibitive effect of salt on seed germination and seedling growth was alleviated in varying degrees, and dramatically, by salicylic acid pretreatment. On the other hand, it was determined that the mentioned plant growth regulator affected in different degrees on the various parameters of leaf anatomy of barley seedlings, and this difference was statistically important.

Effects of Ginkgo biloba L. extract on the seed germination, seedling growth and leaf anatomy of barley under saline conditions were studied. In parallel with concentration rise, salt stress inhibited the seed germination and seedling growth of barley. The inhibitive effect of salt on the germination and coleoptile percentage was alleviated in varying degrees, and dramatically, by Ginkgo biloba application. However, it became ineffective in alleviating of salt inhibition on the radicle, coleoptile length, radicle number and fresh weight of barley seedlings. On the other hand, it was observed that Ginkgo biloba extract affected in different degrees the various parameters of leaf anatomy of barley seedlings, and this difference was statistically important. DOI: http://dx.doi.org/10.3329/bjb.v44i1.22733 Bangladesh J. Bot. 44(1): 117-123, 2015 (March)