Nutrient Addition Research Articles

Characterization of Prokaryotic Community Dynamics and Functional Profiles in Soils Contaminated Long Term with Petroleum Hydrocarbons in Response to the Addition of Soil Bioremediation Nutrients

Characterization of Prokaryotic Community Dynamics and Functional Profiles in Soils Contaminated Long Term with Petroleum Hydrocarbons in Response to the Addition of Soil Bioremediation Nutrients

Order of arrival and nutrient supply alter outcomes of co-infection with two fungal pathogens.

A pathogen arriving on a host typically encounters a diverse community of microbes that can shape priority effects, other within-host interactions and infection outcomes. In plants, environmental nutrients can drive trade-offs between host growth and defence and can mediate interactions between co-infecting pathogens. Nutrients may thus alter the outcome of pathogen priority effects for the host, but this possibility has received little experimental investigation. To disentangle the relationship between nutrient availability and co-infection dynamics, we factorially manipulated the nutrient availability and order of arrival of two foliar fungal pathogens (Rhizoctonia solani and Colletotrichum cereale) on the grass tall fescue (Lolium arundinaceum) and tracked disease outcomes. Nutrient addition did not influence infection rates, infection severity or plant biomass. Colletotrichum cereale facilitated R. solani, increasing its infection rate regardless of their order of inoculation. Additionally, simultaneous and C. cereale-first inoculations decreased plant growth and-in plants that did not receive nutrient addition-increased leaf nitrogen concentrations compared to uninoculated plants. These effects were partially, but not completely, explained by the duration and severity of pathogen infections. This study highlights the importance of understanding the intricate associations between the order of pathogen arrival, host nutrient availability and host defence to better predict infection outcomes.

What would happen in the United States if there were no cow milk-based preterm infant nutritional products: historical perspective and evaluation of nutrient-related challenges

Recent litigation has led to a situation where preterm cow milk-based infant nutritional products (PCMBPs) may soon have limited or no availability in the United States. Given their limited availability, similar products based only on human milk are unlikely to meet the needs of most preterm infants requiring such products, especially those born >1500 g or very preterm infants born at <1500 g after they reach 34–35 wk postmenstrual age. Alternative nutritional strategies, used before the introduction of specialized preterm products, would require modular nutrient additions to a formula designed for full-term infants and donor or maternal milk. The addition of modular products would require careful calibration to provide needed macro and micronutrients which would expose infants to risks of contamination, poor growth, and limited bioavailability of some of these modulars. Substantial risks of metabolic derangements, and ultimately, poor outcomes would occur. In the long-term greater availability and support for the use of human milk-based products is needed. However, policymakers cannot assume that PCMBPs will not be critically needed and should identify strategies for their continued marketplace availability.

How do additions of submerged macrophytes, large-bodied cladocerans and nutrients impact tropical plankton communities? A mesocosm experiment

AbstractWe investigated the individual and combined impacts of manipulation of submerged macrophytes, large-bodied cladocerans, and nutrients on plankton communities in a tropical hypereutrophic shallow reservoir. We tested how the addition of the macrophyte Ceratophyllum demersum, the cladoceran Sarsilatona serricauda, and nutrients affected phytoplankton and zooplankton diversity, composition, and structure using mesocosms and a factorial design (3 × 3) with eight treatments. During the experiment, the reservoir experienced an intense bloom of algae (207 mg l−1 of biomass), mainly composed of cyanobacteria (&gt; 98%). The submerged macrophytes were found to significantly reduce the biomass of cyanobacteria (by 85%), diatoms (80%), and green algae (78%), while the addition of zooplankton and nutrients led to a 96% reduction for diatoms. While both submerged macrophytes and the added cladocerans impacted the native zooplankton community, the macrophytes exerted stronger effects on phytoplankton and zooplankton diversity, composition, and structure. Intriguingly, nutrient addition did not alter the main effects of macrophytes and large cladocerans. Our findings reveal the positive potential of introducing submerged macrophytes in tropical shallow lakes, even at a low to moderate percentage of the volume inhabited, to control toxic cyanobacterial blooms. Under our experimental conditions, the method was effective even without extra zooplankton grazing and at increased nutrient input.

Rethinking environmental sustainability in rainfed cropping systems

Activity data from a 30-year on-farm experiment with six soil-management treatments were used to develop inventory data for environmental partial life-cycle assessment (LCA). The purpose was to compare the treatments based on environmental outcomes and evaluate conservation agriculture (CA) in Australia's dryland cropping zone. Multiple trade-offs were revealed that highlight the need for a nuanced approach to sustainable intensification and show that rules-based CA is not sufficient to guarantee low greenhouse gas (GHG) emissions, nor low overall environmental impact. Nutrient mining in dryland cropping even under CA can lead to losses in soil carbon that can double GHG intensity. In these systems, additional nutrient inputs can reduce the loss of soil carbon as well as net GHG emissions, demonstrating the critical need to include the effects of soil carbon change in LCA to prevent perverse outcomes.The treatment involving strategic tillage and nutrient balancing, along with stubble retention, had the lowest GHG intensity, but there was a trade-off with the higher embedded impacts across several other environmental categories. Higher fertiliser input could lead to toxicity impacts, due to heavy-metal content, that contribute significantly to the Human health endpoint. However, limitations in modelling such local, site-specific impacts were considerable and more research is needed to address this.In general, trade-offs were found to exist between impacts from on-farm activities versus upstream manufacture of inputs; between GHG emissions and land use (yield) versus other environmental categories; and between different on-farm GHG emission sources. Despite these trade-offs, the treatments all had similar overall scores in the Human health and Ecosystems damage categories. There was no single treatment with low, or high, impact scores across all environmental indicators, indicating that trade-offs need to be carefully considered when making farm-management decisions in the context of net-zero or carbon-neutral farming.

Phosphorus controls symbiotic nitrogen fixation in fire‐dependent longleaf pine savannas

Abstract Symbiotic nitrogen (N) fixation has the potential to replenish fire‐induced N losses in frequently burned ecosystems. A strong relationship between fire and fixation may exist because fire volatilizes N and mineralizes phosphorus (P), creating N‐poor, P‐rich soils that favour plants capable of N‐fixation. However, human activities have enriched ecosystems with N, which may complicate the interplay among fire, fixation and soil P. We evaluated how N and P modulate the relationship between fire and symbiotic N fixation in longleaf pine savannas, where it was previously documented that N fixation fails to replenish N losses from fire. Across gradients of stand age and fire frequency, we investigated how N and P availability influence fixation, and we established a nutrient addition experiment to evaluate the effects of N and P on legume growth, fixation and mycorrhizal investment. We uncovered a clear signal of P limitation of herbaceous legumes. Legume growth and fixation were linked to the availability of soil mineral P and were further stimulated by P additions. In contrast, neither soil N availability nor N additions affected legume growth or fixation. Synthesis. Our findings suggest that symbiotic N fixation in sandhill longleaf pine savannas is controlled by soil P availability, which varies according to soil age and parent material. Therefore, fixation may only counterbalance N losses from fire if there is enough P in the soil to support this process. Nonetheless, recent N enrichment in contemporary longleaf pine ecosystems may have reduced the importance of N fixation as a post‐fire recovery mechanism.

PENCEGAHAN ANEMIA PADA IBU HAMIL MELAUI “PEDIKUR“ (PENDEKATAN EDUKASI DAN PUDING KURMA) DI DESA WONOSARI – NGORO

Anemia in pregnancy is still a major problem experienced by almost half of pregnant women in all countries in the world including Indonesia. Many pregnant women refuse and do not comply with taking FE tablets for various reasons so that the prevalence of anemia in pregnant women is still high. A mother is said to be compliant with taking FE tablets if ≥ 90 % of the amount should have been taken. Anemia in pregnancy is a national problem because it reflects the value of the socio-economic welfare of the community, and has a very large impact on the quality of human resources, which is called "potential danger to mother and child". The purpose of the service is to provide education on the addition of nutrients to reduce anemia. Based on the results of the activity, the delivery of material. The results of this activity are the participation of pregnant women during educational and simulation activities running smoothly, indicated by the activeness of pregnant women and attended by all pregnant women class participants and there is an increase in understanding of anemia by 50 %. The service was carried out on 23 June 2023 at Waonosari Polindes in the class of pregnant women. The method used was education and simulation in making soy milk and date pudding. Indonesia itself has an anemia prevention program for pregnant women by providing a minimum FE supplement of 90 tablets during pregnancy.

CRP improves the survival and competitive fitness of Salmonella Typhimurium under starvation by controlling the cellular maintenance rate.

Catabolite repression is a mechanism of selectively utilizing preferred nutrient sources by redirecting the metabolic pathways. Therefore, it prevents non-essential energy expenditure by repressing the genes and proteins involved in the metabolism of other less favored nutrient sources. Catabolite repressor protein (CRP) is a chief mediator of catabolite repression in microorganisms. In this context, we investigated the role of CRP in starvation tolerance, at both cell physiology and molecular level, by comparing the growth, survival, competitive fitness, maintenance rate, and gene and protein expression of wild type (WT) and ∆crp of Salmonella Typhimurium, under nutrient-rich and minimal medium condition. The ∆crp shows slow growth upon the arrival of nutrient-limiting conditions, poor survival under prolong-starvation, and inability to compete with its counterpart WT strain in nutrient-rich [Luria broth (LB)] and glucose-supplemented M9 minimal medium. Surprisingly, we observed that the survival and competitive fitness of ∆crp are influenced by the composition of the growth medium. Consequently, compared to the glucose-supplemented M9 medium, ∆crp shows faster death and a higher maintenance rate in the LB medium. The comparative gene and protein expression studies of WT and ∆crp in LB medium show that ∆crp has partial or complete loss of repression from CRP-controlled genes, resulting in a high abundance of hundreds of proteins in ∆crp compared to WT. Subsequently, the addition of metabolizable sugar or fresh nutrients to the competing culture showed extended survival of ∆crp. Therefore, our results suggest that CRP-mediated gene repression improves starvation tolerance and competitive fitness of Salmonella Typhimurium by adapting its cellular maintenance rate to environmental conditions.IMPORTANCESalmonella Typhimurium is a master at adapting to chronic starvation conditions. However, the molecular mechanisms to adapt to such conditions are still unknown. In this context, we have evaluated the role of catabolite repressor protein (CRP), a dual transcriptional regulator, in providing survival and competitive fitness under starvation conditions. Also, it showed an association between CRP and nutrient composition. We observed that Δcrp growing on alternate carbon sources has lower survival and competitive fitness than Δcrp growing on glucose as a carbon source. We observed that this is due to the loss of repression from the glucose and CRP-controlled genes, resulting in elevated cellular metabolism (a high maintenance rate) of the Δcrp during growth in a medium having a carbon source other than glucose (e.g., Luria broth medium).

Efficient PAHs removal and CO2 fixation by marine microalgae in wastewater using an airlift photobioreactor for biofuel production

Microalgae cultures have emerged as a promising strategy in diverse areas, ranging from wastewater treatment to biofuel production, thus contributing to the search for carbon neutrality. These photosynthetic organisms can utilize the resources present in wastewater and fix atmospheric CO2 to produce biomass with high energy potential. In this study, the removal efficiency of Polycyclic Aromatic Hydrocarbons (PAHs), CO2 fixation and lipid content in the biomass produced from microalgae grown in airlift photobioreactor were evaluated. Four mesoscale cultures were carried out: Control (Seawater + Conway medium), Treatment A (Oil Produced Water + Poultry Effluent Water), Treatment B (Poultry Effluent Water + Seawater) and Treatment C (Oil Produced Water, Seawater and nutrients). The impact of biostimulation, through the addition of nutrients, on PAHs removal efficiency (up to 90%), CO2 fixation rate (up to 0.20 g L−1 d−1) and the composition of the generated biomass was observed. Primarily, the addition of nitrates to the culture medium impacted CO2 fixation rate of the microalgae. In addition, a direct correlation was observed between PAHs removal and lipid accumulation in the biomass, up to 36% in dry weight, demonstrating microalgae's ability to take advantage of the organic carbon (PAHs) present in the culture medium to generate lipid-rich biomass. The concentration of polysaccharides in the biomass obtained did not exceed 12% on a dry weight basis, and the Higher Heating Value (HHV) ranged between 17 and 21 MJ kg−1. Finally, the potential of generating hydrogen through pyrolysis was highlighted, taking advantage of the characteristics of biomass as a conversion route to produce biofuels. These results show that microalgae are effective in wastewater treatment and have great potential in producing biofuels, thus contributing to the transition towards more sustainable energy sources and climate change mitigation.

CELLULASE PRODUCTION BY TRICHODERMA REESEI AND ITS APPLICATION IN HYDROLYZING OIL PALM EMPTY FRUIT BUNCHES

This study aimed to optimize cellulase production from Trichoderma reesei and apply it for the hydrolysis of oil palm empty fruit bunches (OPEFB). The effects of substrate, pH, nutrient, incubation period, and temperature on cellulase production were investigated using the solid-state fermentation method. OPEFB hydrolysis involved varying enzyme loadings (5, 10, 15, and 20 U/g substrate). The results indicated that the highest CMCase activity (1.02±0.008 U/mL) was achieved under optimal conditions, which included using rice bran as the substrate at 30 °C, pH 6.5, without nutrient addition, and an incubation period of 6 days. In OPEFB hydrolysis, the highest concentration of reducing sugars, 2.395 mg/mL, was observed with a 10 U/g enzyme loading after 48 hours of hydrolysis. FTIR results revealed that the characteristic absorption band at 1205 cm-1, representing the C1-O-C4 glycosidic bond of cellulose, was not observed in the sample hydrolyzed at the 10 U/g enzyme loading. This suggests the capability of the enzyme to hydrolyze OPEFB.

Once in Three-Year Deep-Banding and Annual Shallow-Banding of P, K and Cu Fertilizer Effects on Crops and Soil Nutrients

Deep-banding of the immobile nutrients (P, K, and Cu) is considered one technique that may improve crop production under temperate dryland systems, where moister soil conditions prevail at seeding followed by relatively drier soil during the growing period. The objectives were to compare growth and yield of canola (Brassica napus L.), field pea&amp;rsquo;s (Pisum sativum L.) and wheat (Triticum aestivum L.); and nutrient concentrations in crops and soil from once in three-year deep-banding (12.5-15 cm) and annual shallow-banding (3.75 to 5 cm diagonally deeper than seeding depth) of P, K and Cu under direct seeding systems. Small plot trials were conducted at the three sites; representing Brown (Dark Brown Chernozem), Black (Black Chernozem), and Grey (Dark Grey Luvisol) soil zones in Alberta, Canada; which represent crop growing conditions for most areas of western Canada. The nine treatments were annual shallow-banding and once in three year deep-banding of P, K, Cu and PKCU nutrients plus a control (no P, K, or Cu fertilizer). Applied thrice the recommended rate for deep-banding (in 2018) treatments and the recommended rate for the annual shallow-banding treatments in 2018, 2019 and 2020. All three phases of pea&amp;rsquo;s-wheat-canola rotation were grown at each site to generate nine years of data for each crop. The density, height, NDVI (normalized difference vegetation index) and biomass of plants, yield for crops and nutrient concentrations in seed and biomass of crops and soil showed significantly positive responses to P, K, and PKCu additions in some cases; generally not linked to the deep or shallow placement of tested nutrients. Changes in nutrient concentrations in seed and biomass of crops in response to nutrient additions were not consistent. Treatments with P showed response more often than with the K and Cu. The soil P and Cu concentrations increased in response to their additions in some cases, but no change was observed from the K addition. Once in three-year deep-banding or annual shallow-banding methods were equally effective. The findings provide another option (once in three year deep-banding) for applying the P, K and Cu fertilizers.

Long-term effects of nitrogen and phosphorus fertilization on profile distribution and characteristics of dissolved organic matter in fluvo-aquic soil

Dissolved organic matter (DOM) drives numerous biogeochemical processes (e.g. carbon cycling) in agro-ecosystems and is sensitive to fertilization management. Nevertheless, changes in the quantity and quality of DOM in the vertical soil profile following long-term continuous nitrogen (N) and phosphorus (P) inputs remain unclear. In this study, the contents and optical characteristics of DOM along a 2-m soil profile were investigated using a 40-year wheat/maize rotation combined with experiments using different N and P fertilization rates in the North China Plain. The results revealed that the dissolved organic carbon (DOC) content decreased with an increase in soil depths. Compared with that in the control (no fertilization), 40-year N, P, and N + P additions increased the soil DOC content by 26%–69%, except for 270-kg N, and 67.5-kg P treatments. N + P application resulted in higher DOC contents than N-alone and P-alone applications. N, P, and N + P inputs increased or did not affect the aromaticity and hydrophobicity of DOM at 0–40 cm but reduced them from 40 to 200 cm. Compared with that in the control, N, P, and N + P inputs enhanced the content of humic acid-like substances (C1+C2+C3+C4) and decreased the content of protein-like substance (C5). C1 was the dominant component among the five DOM, representing the microbial humic component. Optical indices also indicated that soil DOM primarily originated from microbial sources. Nutrient addition accelerated transformation between complex C1 and simple C5 via promoting microbial activities. These results imply that N and P fertilizers increased the DOM content and altered its composition, thereby potentially affecting the stability of soil organic matter in the agroe-cosystems.

Dual isotopic (33P and 18O) tracing and solution 31P NMR spectroscopy to reveal organic phosphorus synthesis in organic soil horizons

Soil microorganisms can do both, mineralize and synthesize organic and condensed phosphate (P) species. Whereas P mineralization has been extensively studied, few studies have assessed the biological synthesis of organic P species, which can potentially accumulate in soil. The goal of this study was to investigate biotic and abiotic P transformations, particularly the synthesis of organic P species, upon water-soluble P addition in the organic (O) horizons of two beech forest sites with contrasting P availability.The two O horizons (low-P and high-P) were subjected to four different nutrient addition treatments (Control without addition, CN, P, and CNP additions) in an incubation experiment of up to 104 days. We combined isotopic tracing (33P-labelled P addition and 18O-enriched soil water) into sequentially extracted P pools with the characterization of organic P species (solution 31P nuclear magnetic resonance (NMR) spectroscopy) and soil respiration measurements.The P availability of the two O horizons shaped the microbial response to the nutrient additions. In the low-P O horizon, P addition stimulated microbial activity together with the increase of organic (phosphodiesters and phosphonates) and condensed (polyphosphates) P species, most likely from microbial origin. In the high-P O horizon, microbes were unaffected by the added P and abiotic processes controlled its fate. CN addition had no effect on P fate in the high-P O horizon but reduced the transformation of added P into organic P and increased soil-derived P in the resin P pool in the low-P O horizon. The 18O isotopic values in phosphate of the resin P pool suggest that the released P was biologically cycled.Our study confirms with a unique multi-analytical approach the microbial synthesis of phosphodiesters, phosphonates, and polyphosphates upon inorganic P addition under low P availability.

The experimental implications of the rate of temperature change and timing of nutrient availability on growth and stoichiometry of a natural marine phytoplankton community

AbstractClimate change increases the need to understand the effect of predicted future temperature and nutrient scenarios on marine phytoplankton. However, experimental studies addressing the effects of both drivers use a variety of design approaches regarding their temperature change rate and nutrient supply regimes. This study combines a systematic literature map to identify the existing bias in the experimental design of studies evaluating the phytoplankton response to temperature change, with a laboratory experiment. The experiment was designed to quantify how different temperature levels (6°C, 12°C, and 18°C), temperature regimes (abrupt vs. gradual increase), timings of nutrient addition (before or after the temperature change) and nutrient regimes (limiting vs. balanced) alter the growth and stoichiometry of a natural marine phytoplankton community. The systematic map revealed three key biases in marine global change experiments: (1) 66% of the studies do not explicitly describe the experimental temperature change or nutrient regime, (2) 84% applied an abrupt temperature exposure, and (3) only 15% experimentally manipulated the nutrient regime. Our experiment demonstrated that the identified biases in experimental design toward abrupt temperature exposure induced a short‐term growth overshoot compared to gradually increasing temperatures. Additionally, the timing of nutrient availability strongly modulated the direction of the temperature effect and strength of growth enhancement along balanced N : P supply ratios. Our study stresses that the rate of temperature change, the timing of nutrient addition and the N : P supply ratio should be considered in experimental planning to produce ecologically relevant results as different setups lead to contrasting directions of outcome.

Modulating metabolism through synthetic biology: Opportunities for two-stage fermentation.

Bio-based production of fuels, chemicals and materials is needed to replace current fossil fuel based production. However, bio-based production processes are very costly, so the process needs to be as efficient as possible. Developments in synthetic biology tools has made it possible to dynamically modulate cellular metabolism during a fermentation. This can be used towards two-stage fermentations, where the process is separated into a growth and a production phase, leading to more efficient feedstock utilization and thus potentially lower costs. This article reviews the current status and some recent results in application of synthetic biology tools towards two-stage fermentations, and compares this approach to pre-existing ones, such as nutrient limitation and addition of toxins/inhibitors.

Valorization of Fecal Sludge Stabilization via Vermicomposting in Microcosm-Enriched Substrates Using Organic Plant-Derived Materials and Agricultural Soil for Compost Production

The enormous generation of fecal sludge without proper treatment is a major sanitation problem. Vermicomposting of fecal sludge is an innovative way of producing value added compost called vermicompost. A vermicomposting technique that involves augmenting vermibed substrates with organic rich materials to provide additional nutrients and underlying layers needed for microcosm development to produce desirable vermicompost is mostly referred to as substrate enrichment. This study investigated the substrate enrichment of using plant-derived materials, which include coconut coir, palm coir and saw dust, combined with agricultural soil for the production of vermicompost from fecal sludge. Enriched substrates were prepared with 80 g of agricultural soil as amending material, 120 g of fecal matter (65-70% dry matter) and 160 g of the plant-derived materials. The treatments were labeled T1-T3, thus, T1 contained coconut coir, T2 contained palm coir and T3 contained saw dust, followed by a control treatment (T4) that had no plant-derived material. Treatments were triplicated and about 3-week-old 20 clitellated, E. fetida (live weight ∼255–275 mg) were used in the vermicomposting for 12 wk. Physicochemical parameters such as pH, Organic Carbon (Corg), Total Nitrogen (Ntot), Available Phosphorus (Pavail), Exchangeable Calcium (Caexch), Iron (Fe), Lead (Pb) and Aluminum (Al) test were performed. Vermicompost at T1 had the most Corg mineralization, most enhancement in Ntot, Pavail, Caexch, and least concentration of Fe, Pb and Al. Less than 20% earthworm mortality was recorded in all treatments except T4 (28.38 ± 8.71%). The enriched substrates were suitable for vermiculture with a worm weight ranged from 593.77 to 569.39 ± 2.30 mg and the vermicompost recorded high nutrient contents. The nutritious nature and the reduced metal concentration of the produced vermicompost might be safe and productive for agricultural use. However, further studies on the effectiveness of the vermicompost on plants growth and yield needs to be investigated.

Pertumbuhan dan Produksi Jagung pada Berbagai Varietas dan Dosis Trichokompos

The productivity of maize as a staple food needs continuous enhancement through various methods, one of which is fertilization. The exploration of diverse fertilizers is expected to help reducing the reliance on increasingly expensive synthetic fertilizers. Fertilization is a crucial practice to improve soil fertility on marginal lands. It refers to land with productivity limitations due to factors such as low soil fertility, poor soil texture, or environmental conditions that do not support optimal plant growth. By providing additional nutrients through trichocompost fertilizer, plants are expected to grow better even under suboptimal soil conditions. This study aims to investigate the effect of trichocompost fertilizer dosage on various maize varieties grown on marginal land. The research was conducted using an experimental design with plot sizes of 3 x 5 meters. The method employed was a factorial Randomized Block Design (RBD) with two factors. The first factor was the dosage of trichocompost (control, 3 tons/ha, and 6 tons/ha), and the second factor was maize varieties (Sinhas1, Nasa29, JH36, Bisi18, and Pioneer27), with each treatment repeated three times, resulting in a total of 45 experimental plots. The parameters tested included plant height, number of leaves, ear height, days to flowering, and fresh ear weight. The results showed that trichocompost had a significant effect on two parameters: the increase in plant height and the number of leaves at 49 days after planting (DAP), as well as the fresh ear weight. The maize variety significantly affected almost all tested parameters.

Greenhouse gas emissions and nutrient use efficiency assessment of six New York organic dairies

Improving nutrient use efficiency and reducing greenhouse gas (GHG) emissions are important environmental priorities for organic-certified dairy operations. The objectives of this research were to quantify annual nutrient use and GHG emissions in 6 organic New York dairy farms. Farm-gate nutrient mass balances (NMB) were estimated with the Cornell NMB calculator. Whole-farm GHG emissions were estimated using Cool Farm Tool (CFT) and COMET. Farm-gate NMBs were low, ranging from -6.5 to 19 kg N ha-1 for N1 (without legume N fixation), 26 to 71 kg N ha-1 for N2 (including N fixation), -2.4 to 8.2 kg P ha-1 for P, and 1.1 to 19.8 kg K ha-1 for K. Additional nutrient imports, coupled with nutrient management planning, adequate legume stands and diet balancing may help improve P balances, and ensure no N deficiencies in the system. Estimates of annual GHG emission intensity ranged from 0.98 to 2.10 kg CO2-eq per kg of fat and protein corrected milk (FPCM) estimated by CFT, and from 0.69 to 2.48 kg CO2-eq kg FPCM-1 estimated by COMET. Enteric fermentation, feed production and fuel and energy use represented the largest sources of GHGs. For farms with liquid manure storages, manure management was also a significant source. Estimates of soil carbon (C) stock changes from CFT were in agreement or smaller than previous studies, and estimates from COMET were in agreement or greater. Variability and uncertainty in the results for soil C stock change indicate more research and new protocols are needed. Impact of individual management changes on GHG emissions intensity were small, ranging from -8 to +7% in CFT, and -8% to +8% in COMET. The management changes that resulted in the largest reductions in GHG emissions intensity included increasing individual cow productivity and milk to total feed ratio, and implementation of manure treatment systems.

Microbial electrochemical Cr(VI) reduction in a soil continuous flow system.

Microbial electrochemical technologies represent innovative approaches to contaminated soil and groundwater remediation and provide a flexible framework for removing organic and inorganic contaminants by integrating electrochemical and biological techniques. To simulate in situ microbial electrochemical treatment of groundwater plumes, this study investigates Cr(VI) reduction within a bioelectrochemical continuous flow (BECF) system equipped with soil-buried electrodes, comparing it to abiotic and open-circuit controls. Continuous-flow systems were tested with two chromium-contaminated solutions (20-50 mg Cr(VI)/L). Additional nutrients, buffers, or organic substrates were introduced during the tests in the systems. With an initial Cr(VI) concentration of 20 mg/L, 1.00 mg Cr(VI)/(L day) bioelectrochemical removal rate in the BECF system was observed, corresponding to 99.5% removal within nine days. At the end of the test with 50 mg Cr(VI)/L (156 days), the residual Cr(VI) dissolved concentration was two orders of magnitude lower than that in the open circuit control, achieving 99.9% bioelectrochemical removal in the BECF. Bacteria belonging to the orders Solirubrobacteriales, Gaiellales, Bacillales, Gemmatimonadales, and Propionibacteriales characterized the bacterial communities identified in soil samples; differently, Burkholderiales, Mycobacteriales, Cytophagales, Rhizobiales, and Caulobacterales characterized the planktonic bacterial communities. The complexity of the microbial community structure suggests the involvement of different microorganisms and strategies in the bioelectrochemical removal of chromium. In the absence of organic carbon, microbial electrochemical removal of hexavalent chromium was found to be the most efficient way to remove Cr(VI), and it may represent an innovative and sustainable approach for soil and groundwater remediation. Integr Environ Assess Manag 2024;20:2033-2049.© 2024 The Author(s). Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Enhancing soil petrochemical contaminant remediation through nutrient addition and exogenous bacterial introduction

Biostimulation (providing favorable environmental conditions for microbial growth) and bioaugmentation (introducing exogenous microorganisms) are effective approaches in the bioremediation of petroleum-contaminated soil. However, uncertainty remains in the effectiveness of these two approaches in practical application. In this study, we constructed mesocosms using petroleum hydrocarbon-contaminated soil. We compared the effects of adding nutrients, introducing exogenous bacterial degraders, and their combination on remediating petroleum contamination in the soil. Adding nutrients more effectively accelerated total petroleum hydrocarbon (TPH) degradation than other treatments in the initial 60 days’ incubation. Despite both approaches stimulating bacterial richness, the community turnover caused by nutrient addition was gentler than bacterial degrader introduction. As TPH concentrations decreased, we observed a succession in microbial communities characterized by a decline in copiotrophic, fast-growing bacterial r-strategists with high rRNA operon (rrn) copy numbers. Ecological network analysis indicated that both nutrient addition and bacterial degrader introduction enhanced the complexity and stability of bacterial networks. Compared to the other treatment, the bacterial network with nutrient addition had more keystone species and a higher proportion of negative associations, factors that may enhance microbial community stability. Our study demonstrated that nutrient addition effectively regulates community succession and ecological interaction to accelerate the soil TPH degradation.