Total Nitrogen Accumulation Research Articles

Effects of amino acid value-added urea on rice growth and nitrogen utilization.

To investigate the impact of amino acid value-added urea on rice growth and nitrogen utilization, this study aimed to provide insights into enhancing the quality and efficiency of traditional nitrogen fertilizers using small molecule active substances. Amino acids were added at 5‰ and 5% levels to create different levels of amino acid value-added urea (AU0.5 and AU5) by blending with urea as test materials. Pot experiments were conducted using 'Liangyouhua 6' rice as the test crop, with four treatment groups: non-urea (CK), regular urea (U), and amino acid value-added urea (AU0.5, AU5) at two different addition ratios. All treatments, except the control, had the same application rates of nitrogen, phosphorus, and potassium. After harvesting the rice, plant and soil samples were collected from various depths to analyze the nutrient composition of rice, nitrogen content of fertilizer in different soil layers, and 15N abundance. The results showed that amino acid-added urea significantly enhanced biomass accumulation in different parts of rice. Compared to U, rice straw and grain biomass increased by 25.27% to 32.74% and 21.71% to 27.77% under AU0.5 and AU5 treatments, respectively. In terms of nitrogen application, effective panicle and grain numbers per panicle in AU0.5 and AU5 rice were 17.37% to 21.05% and 8.76% to 15.33% higher than in U, with a significant difference between AU0.5 and U. Furthermore, total aboveground nitrogen and fertilizer nitrogen accumulation in rice treated with AU0.5 and AU5 increased by 3.59% to 5.09% and 3.31% to 8.49%, respectively, compared to U. The accumulation of fertilizer nitrogen in grains and leaves also showed increases of 2.86% to 6.32% and 4.38% to 16.25%, respectively, compared to U. This study found that the application of amino acid value-added urea had a significant impact on the accumulation of fertilizer nitrogen in straw. Further analysis showed that it improved both the apparent nitrogen utilization efficiency and fertilizer nitrogen utilization efficiency. Compared to ordinary urea, the apparent nitrogen utilization efficiency of AU0.5 and AU5 increased by 23.71% and 33.93%, respectively, while the utilization efficiency of 15N increased by 15.66% and 6.78%, respectively. The residual fertilizer nitrogen in soil treated with amino acid value-added urea was mainly found in the 0-30cm soil layer, reducing nitrogen leaching downwards. Additionally, the nitrogen loss rate was significantly lower (reduced by 12.39%-12.97%) compared to regular urea. The difference between AU0.5 and AU5 was not significant, but AU5 showed an 18.80% higher fertilizer nitrogen residual rate than U. Overall, the study concluded that amino acid value-added urea promoted rice growth by enhancing nitrogen absorption, improving transport to grains, increasing nitrogen fertilizer efficiency, reducing nitrogen leaching, and lowering nitrogen loss rate. The best results were observed with the addition of 5‰ amino acid.

Warming exacerbates global inequality in forest carbon and nitrogen cycles

Forests are invaluable natural resources that provide essential services to humanity. However, the effects of global warming on forest carbon and nitrogen cycling remain uncertain. Here we project a decrease in total nitrogen input and accumulation by 7 ± 2 and 28 ± 9 million tonnes (Tg), respectively, and an increase in reactive nitrogen losses to the environment by 9 ± 3 Tg for 2100 due to warming in a fossil-fueled society. This would compromise the global carbon sink capacity by 0.45 ± 0.14 billion tonnes annually. Furthermore, warming-induced inequality in forest carbon and nitrogen cycles could widen the economic gap between the Global South and Global North. High-income countries are estimated to gain US$179 billion in benefits from forest assets under warming, while other regions could face net damages of US$31 billion. Implementing climate-smart forest management, such as comprehensive restoration and optimizing tree species composition, is imperative in the face of future climate change.

Heavy Nitrogen Application Rate and Long-Term Duration Decrease the Soil Organic Carbon and Nitrogen Sequestration Rates in Forest Ecosystems

Nitrogen addition alters soil organic carbon (SOC) and total nitrogen (TN) accumulation in forest ecosystems, but the responses of SOC and TN sequestration rates and dynamics to nitrogen addition in forest ecosystems worldwide remain unclear. This study conducted a global analysis to evaluate the effects of the nitrogen application rate, nitrogen addition duration (time), and humidity on the SOC and TN accumulation rates from 257 data points (63 articles). Nitrogen addition increased SOC and TN by 4.48% and 10.18%, respectively. The SOC and TN accumulation rates were 0.65 and 0.11 g kg−1 yr−1, respectively. Moreover, the percentage changes of SOC and TN overall increased with the nitrogen application rate and duration of nitrogen addition; however, the accumulation rates of SOC and TN overall decreased with the nitrogen application rate and the duration of nitrogen addition. In addition, the percentage changes and change rates of SOC and TN increased overall with the humidity index. In conclusion, nitrogen addition promoted SOC and TN accumulation in forest soil, and the nitrogen application rate and nitrogen addition duration increased the percentage changes in SOC and TN; however, they decreased the accumulation rate, whereas humidity increased the accumulation rates of SOC and TN. These results enhance our understanding of soil carbon and nitrogen cycling in forest soils in the context of global nitrogen deposition.

Cascading valorization of defatted rice bran for lactic acid fermentation and biogas production

This study investigated the integrated valorization of defatted rice bran (DRB) by converting it into lactic acid (LA) and subsequently utilizing the residues from LA production for biomethane generation through anaerobic digestion (AD). Processing 480 kg of DRB resulted in the production of 70 L of pure LA and generated significant waste streams, primarily consisting of 572 kg of decanted hydrolysate pellet (Pellet DEC) and 220 kg of microfiltration retentate (Retentate MF). Exceptionally high methane yields of 374‒434 LN kgVS-1 were observed for residues from LA fermentation in biochemical methane potential tests, indicating their high potential for biogas production. During long-term semi-continuous AD, varying organic loading rates (OLRs) from 0.5‒2.5 kgVS m-3 d⁻¹ demonstrated feedstock- and OLR-dependent methane production. Reactor failure at higher OLRs was attributed to the accumulation of total ammoniacal nitrogen (TAN). The co-digestion of Pellet DEC and Retentate MF proved to be more resilient, with OLRs up to 2 kgVS m-3 d-1, mitigating TAN inhibition. Methane yields, ranging from 265‒334 LN kgVS-1 before reaching inhibitory OLR levels, were higher than those found in the literature. Process integration has emerged as a promising approach because the biogas generated from residues could effectively offset the energy demands of LA production. Supported by life cycle assessment, the integrated processes showed a 67% lower environmental impact at the midpoint and a 71% lower environmental impact at the endpoint, along with an 80% reduction in energy costs compared to the standalone LA production. Results proved a significant enhancement of the sustainability and economic viability of this integrated biorefinery approach.

Effects of leguminous green manure-crop rotation on soil enzyme activities and stoichiometry

Abstract As a crucial strategy for sustainable agricultural production, green manure-crop rotation can regulate soil nutrient cycling and decrease the reliance on nitrogen fertilizers. However, we still lack a comprehensive understanding of the changes in soil eco-enzyme activities, microbial metabolism, and nutrient limitations caused by leguminous green manure crop rotation. Here, we conducted field experiments of leguminous green manure-crop rotation across China to analyze soil extracellular enzyme activities, specifically β-glucosidase (BG), N-acetyl-β-D-glucosaminidase (NAG), leucine aminopeptidase (LAP), and acid phosphatase (AP). The study revealed that long-term green manure-crop rotation increased carbon and nitrogen accumulation in farmland, with a significant average increase of 20.1% and 36.4% in BG, AP enzyme activities in topsoil, while showing a decrease in ln(NAG+LAP):ln(AP) ratios. The ratios of ln(BG):ln(NAG+LAP) and ln(NAG+LAP):ln(AP) in soil across various regions were typically below 1:1, indicating that soil microbial activity is more constrained by nitrogen and phosphorus nutrients rather than by carbon. Precipitation, temperature, soil total carbon, and total nitrogen were identified as key environmental factors for extracellular enzyme activities and stoichiometric ratios. Our study highlights that the green manure-crop rotation alleviates nitrogen limitation while enhancing phosphorus limitation, and is closely related to the accumulation of total carbon and nitrogen in the soil.

Effect of Fertilizers, Seeding Rates of the Legume Component and Weather Conditions on Yield and Accumulation of Plant Residues of LupineCereal Mixtures on Grain in the Center of the NonChernozem Region

On mediumcultivated mediumloamy sod-podzolic soils of the Central NonChernozem region, well provided with mobile phosphorus and potassium (IV–V class), the cultivation of lupine–cereal mixtures for grain with the participation of narrowleaved lupine varieties Ladny, spring wheat, barley and oats varieties of Nemchin breeding after grain precursors in a changing climate ensured grain production in an average of 5 up to 3.0–3.7 t/ha with a share of the legume component of 29–57% and the remaining dry mass of plant residues in the soil up to 6–8 t/ha with the accumulation of total nitrogen in it up to 40–60 kg/ha and biological – 12–17 kg/ha. In arid conditions (GTK = 0.80–0.92), a mixture of lupine and barley was distinguished for the better in terms of yield and weight of plant residues, and in case of waterlogging (GTK = 2.47) – mixtures with oats and spring wheat. The inclusion of liquid micronutrients of organic nature in the technological process with a stimulating effect for non-root top dressing eliminated the need for pre-sowing application of nitrogen fertilizer and, in conditions of moderate aridity, increased grain yield, depending on the composition of the mixture, to 3.9–4.9 t/ha (by 53–59%), the yield of plant residues – up to 7–11 t/ha (by 54–139%) and in them there is an accumulation of symbiotically bound nitrogen – up to 15–25 kg/ha or 5–8 times more than without their use.

Increasing dissolved oxygen concentration of irrigation water is beneficial to nitrogen uptake of cotton under mulched drip irrigation

ContextEnhancing crop nitrogen absorption is crucial for improving nitrogen fertilizer utilization efficiency. Soil oxygen conditions play a vital role in influencing crop nutrient uptake. However, the impact of dissolved oxygen concentration in irrigation water on cotton’s nitrogen absorption remains unknow under mulched drip irrigation conditions. RESEARCH QUESTION: This study aimed to investigate whether the dissolved oxygen concentration in irrigation water affects cotton’s nitrogen uptake. METHODS: Urea was utilized as the nitrogen fertilizer, and 5 dissolved oxygen concentration of irrigation water were set in the experiment by adding sodium percarbonate (CK: 3.9 mg L−1, CO1: 9.2 mg L−1, CO2: 13.3 mg L−1, CO3: 17.3 mg L−1, CO4: 25.5 mg L−1). RESULTS: The results showed that increasing the dissolved oxygen concentration in irrigation water could increase the soil urease activity and bacterial operational taxonomic units (OTU), which may be beneficial to the urea decomposition and nitrogen cycling function. Towards the end of the cotton growth period, oxygenation irrigation led to an increase in nitrate nitrogen and ammonium nitrogen content in the soil. The average nitrate nitrogen content in the 0–60 cm soil layer of CO1, CO2, CO3 and CO4 increased by 12.4 %, 14.7 %, 15.9 % and 17.3 % respectively compared with CK. Similarly, the average ammonium nitrogen content of CO1, CO2, CO3 and CO4 in the 0–40 cm soil layer increased by 8.9 %, 11.7 %, 12.0 % and 11.6 % respectively compared with CK. Increasing the dissolved oxygen concentration in irrigation water resulted in elevated dry matter accumulation in cotton. The total dry matter of CO1, CO2, CO3 and CO4 increased by 9.5 %, 12.6 %, 14.6 % and 16.8 % respectively compared with CK. Additionally, the nitrogen concentration in each cotton organ also exhibited an increase. The total nitrogen accumulation of CO1, CO2, CO3 and CO4 increased by 26.1 %, 36.2 %, 48.2 % and 53.1 % respectively compared with CK. Furthermore, increasing the dissolved oxygen concentration in irrigation water also facilitated nitrogen migration to cotton bolls (boll shell + seed + fiber). The cotton boll nitrogen accumulation of CO1, CO2, CO3 and CO4 increased by 1.8 %, 3.4 %, 4.2 % and 4.2 % (absolute value) compared with CK (reached significant level). Finally, the lint yield and fiber quality parameters (micronaire, fiber elongation, fiber breaking strength) exhibited further improvement with the increase in dissolved oxygen concentration in irrigation water. CONCLUSIONS: Increasing the dissolved oxygen concentration in irrigation water promotes nitrogen absorption in cotton, facilitates nitrogen accumulation in cotton bolls, and enhances nitrogen fertilizer utilization efficiency. Moreover, it positively impacts cotton lint yield and fiber quality.

Afforestation improves soil organic carbon and total nitrogen stocks mainly through increasing > 2 mm aggregate fractions and stimulating carbon and nitrogen transformations within aggregates in subtropical karst region

Vegetation restoration can significantly increase soil organic carbon (SOC) and total nitrogen (TN) stocks, however, the response of SOC and TN stocks, as well as their distribution, transformation, and stability within aggregates, to afforestation in fragile karst ecosystems remains unclear. In this study, soil samples were collected from orchards, 10-, 20-, and 40-year Dodonaea viscosa plantations after afforestation following orchard abandonment in a karst rocky desertification area. A natural succession shrubland soil served as the control. Aggregate size distribution, SOC and TN contents, and δ13C and δ15N values in bulk soils and aggregate fractions were determined. The results showed that 0.25–2 mm aggregates were the main contributors to SOC and TN stocks, amounting to 47.7 %-55.6 % and 43.0 %-51.7 %, respectively. Compared to orchards, D. viscosa afforestation significantly increased SOC and TN stocks by 160 %-393 % and 184 %-416 %, respectively, more obviously with prolonged afforestation. This effect was mainly attributed to the increases in > 2 mm aggregate fractions and their associated SOC and TN contents. In addition, δ13C and δ15N values decreased with decreasing aggregate size in afforested and shrubland soils. The C flow pathways followed the trend from < 0.053 mm to 4–8 mm following afforestation, but this was not the case for orchard soils exhibiting pathways from 2-4 mm to < 0.053 mm progressively. These results indicated that large aggregates showed a faster turnover rate and contributed to higher SOC and TN contents following afforestation. The significant and positive relationships between SOC and TN contents and magnesium, aluminium and iron oxides suggested the stimulatory effect on SOC and TN accumulation. Noticeably, although SOC and TN stocks in bulk soils following 40-year afforestation reached the level of shrubland, the proportion of > 2 mm aggregates and the geometric mean diameter remained significantly lower than those of shrubland soils. Soil aggregate stability following D. viscosa afforestation may take longer to reach natural restoration levels.

Clay minerals accelerate the formation of indoor biocrusts: Effects and mechanism

The rapid formation or restoration of biocrusts by human intervention, such as constructing artificial biocrusts, is considered a promising technology for desertification control. To date, most of the studies mainly focused on the role of cyanobacteria and their excreted exopolysaccharides (EPSs) in the process of biocrusts formation and development, while few studies have been concerned about clay minerals, which play an important role in soil development as the abiotic factor. In this study, two clay minerals (montmorillonite and kaolinite) were added to crushed natural biocrusts at different ratios(0.5 %, 1 %, 2 %, 5 %, 10 %; w/w), aiming to explore the effects and mechanism of clay minerals on the formation of biocrusts. The results showed that low-level montmorillonite (0.5–2 %; w/w) addition significantly increased the photosynthetic biomass by about 50 % (indicated by Chlorophyll-a and gene copies) and promoted the accumulation of total nitrogen, nitrate nitrogen, ammonia nitrogen, and total organic carbon. The results of the structural equation model showed that the enhancement effect of clay minerals on the formation of biocrusts is mainly ascribed to its direct positive effect on biocrust physical stability and indirect positive effects through increasing both the cyanobacterial biomass and EPS excretion. Notably, the addition of montmorillonite increased the physical stability of the biocrusts by 18 %-53 %, while kaolinite did not play a positive role in the formation of biocrusts. Moreover, excessive montmorillonite (more than 2 %) and kaolinite caused the significant shift of dominance from Cyanobacteria to Proteobacteria, and a sharp decrease in EPS excretion, posing a high risk of biocrust disintegration. Overall, our findings demonstrate the stimulation mechanism of clay addition on restoring natural biocrusts, providing new insight for constructing artificial biocrusts and restoring degraded biocrusts in dryland.

Influence of Intercropping Arisaema amurense with Acanthopanax senticosus on Soil Microbial Community and the Effective Ingredients of A. senticosus

Intercropping is an effective cultivation strategy for promoting soil health, changing microbial community, reducing fertiliser application and enhancing the quality of medicinal plants. Nevertheless, the interaction effect of intercropping between Arisaema amurense and Acanthopanax senticosus remains unknown. Herein, we investigated the difference in soil properties, soil enzyme activities, microbial community diversity and active ingredients of A. senticosus in monoculturing versus intercropping of A. senticosus/A. amurense in a field experiment. High-throughput sequencing and liquid chromatography–mass spectrometry were employed to explore the growth promotion effect in the intercropping mode. Results revealed that intercropping benefitted the accumulation of ammonium nitrogen and total nitrogen in soil; total nitrogen and ammonium nitrogen increased by 33% (rhizosphere) and 65% (inter-row) and by 123% (rhizosphere) and 124% (inter-row) at 0–20 cm soil depths, respectively. Furthermore, intercropping increased the soil carbon/nitrogen ratio at the soil from 20 to 40 cm and promoted the growth of the root system of the deep-rooted plant A. senticosus. However, it exerted a certain inhibitory effect on the activities of urease, sucrase and neutral phosphatase on the soil surface. Intercropping increased bacterial diversity and inhibited fungal diversity in soil, potentially preventing the soil microflora changed from bacterial type to fungal type. In terms of community composition, intercropping exhibited a greater effect on bacteria than on fungi. At the phylum level, the relative abundance of microorganisms associated with nutrient cycling and increased ecosystem resistance increased in intercropped soils, such as those of Proteobacteria, Actinobacteriota and Bacteroidota. At the genus level, the bacterial genera that showed significantly increased relative abundance in intercropping soil included unclassified_Acidobacteriales, Sphingomonas, Gemmatimonas and Candidatus_Solibacter. Furthermore, the relative abundance of Cladosporium, a potential plant pathogen in intercropped rhizosphere soil, was 42% lower than that in monocultured rhizosphere soil. Additionally, intercropping can promote the accumulation of eleutheroside B, eleutheroside E, quercetin, protocatechuic acid and polysaccharide, which increased by 551%, 53%, 10%, 28% and 26%, respectively, compared with that after monoculturing. According to the Pearson correlation heat map, rapidly available phosphorus, rapidly available potassium, ammonium nitrogen, nitrate nitrogen, total nitrogen and urease exhibited the greatest impact on the soil microbial community and on the active ingredients of A. senticosus. In conclusion, intercropping altered the composition of the soil microbial community and increased the content of the active ingredients of A. senticosus, consequently begetting economic and ecological benefits.

Effect of auxiliary materials on the formation of humic acid carbon and nitrogen and bacterial dynamics in kitchen waste composting

This study investigated the impacts of different types of auxiliary materials on the humification process and bacterial dynamics during kitchen waste composting. Five types of auxiliary materials, including sawdust (SD), garden waste (GW), aquatic plants (AP), rice straw (RS), and rice husk (RH), were compared. The relationship between humic acid carbon and nitrogen components as well as bacterial community was analyzed by structural equation model and redundancy analysis. The results dindicated that SD and RS exhibited better thermophilic stage duration, germination index, and organic fractions degradation than other groups, which had higher degree of polymerization and the humification index of kitchen waste composting. AP, SD and RS had higher total nitrogen (TN) content and ammonia nitrogen accumulation, and RS had more humic acid nitrogen in TN with more amino acids and polyphenols precursors compared to other groups. High-throughput sequencing indicated that sawdust affected the variation of community structure and bacterial genera associated with lignocellulose degradation more than others. Redundancy analysis showed that Pseudoxanthomonas helped to the NH4+-N conversion to humic acid nitrogen for TN preservation. Structural equation modelling suggested that the conversion and utilization efficiency of microbes directly influenced the accumulation of humic acid carbon and nitrogen based on the types of intermediate metabolites. This study highlighted the role of auxiliary materials on improving the humification process of rapid kitchen waste composting.

Optimizing Irrigation and Fertilization to Simultaneously Improve Potato Tuber Yield, Water and Fertilizer Use Efficiency and Net Income in Northwest China

Irrigation, fertilization, and variety are important factors affecting potato production in northwest China. Field experiments (2021 and 2022) were performed to investigate the effects of irrigation and fertilization on the plant growth and soil microbial population of different potato varieties. Three irrigation levels were used, i.e., 100% ETc (W1), 80% ETc (W2), and 60% ETc (W3), with ETc standing for crop evapotranspiration. Three fertilization levels were used (N-P-K), i.e., 240-120-300 kg ha−1 (F1), 180-90-225 kg ha−1 (F2), and 120-60-150 kg ha−1 (F3). Three variety types were used, i.e., Feiurita (V1), Longshu 7 (V2), and Qingshu 9 (V3). These factors significantly influenced tuber yield (TY), net income (NI), and water productivity (WP). TY, NI, WP, total nitrogen accumulation (TNA), and nitrogen use efficiency (NUE) peaked at F2. Fertilization significantly impacted soil bacteria quantity (SBQ), fungi quantity (SFQ), and actinomycetes quantity (SAQ). TY, NI, SBQ, SFQ, and SAQ were highest at W2. Soil microbial population was strongly correlated with TY, NI, WP, TNA, and NUE. Comprehensively, this study suggests that irrigation that is varied from 248 to 266 mm, and fertilization (N-P-K) that is varied from 149.09-74.55-186.36 to 212.73-106.36-265.91 kg ha−1 can promote the potato industry’s sustainable development and provide important references for the optimal field management of potato cultivation in northwest China.

Effects of cold plasma and ultra-high-pressure sterilization on the quality, flavor, and safety of semi-dried golden pompano

This investigation aimed to assess the impact of cold plasma (CP) and ultra-high-pressure (UHP) treatment on the quality, flavor, and safety of semi-dried golden pompanos during the storage period. The results showed the highest severity of lipid oxidation in the CP group, whereas alternation in protein structure and protein oxidation were the most apparent in the UHP group. Compared with CP, UHP better inhibited the accumulation of total volatile basic nitrogen and biogenic amines. The shelf life of samples was prolonged by 10–12 and 12–17 days upon treatment with CP and UHP, respectively. Furthermore, the freshness preservation effect of UHP was superior. Compared with CP, UHP better mitigated the loss of free amino acids and showed the best inhibitory effect on the production of bad odor-producing compounds, such as 3-methyl-butanal, 2,3-butanediol, acetic acid, and trimethylamine.

A novel multitrophic biofloc technology for duckweed and Megalobrama amblycephala integrated culture: Improving nutrient utilization and animal welfare

Biofloc technology (BFT) is an eco-friendly aquaculture model that utilizes zero-exchange water. In this study, we investigated the integration of duckweed into BFT in an effort to enhance nitrogen, phosphorus, and carbon utilization and to improve animal welfare for cultivating Megalobrama amblycephala. The experiment spanned 75 days, comparing a group of M. amblycephala supplemented with duckweed (DM) to a control group (CG) with no supplementation, where duckweed consumption relied solely on the feeding behavior of the fish. The concentrations of nitrate, total nitrogen, and phosphorus accumulation were lower in the DM than in the CG from day 45 onwards, with differences of 16.19, 26.90, and 1.45 mg/L, respectively, at the end of the experiment. The DM showed simultaneous increases of 5.77, 11.20, and 5.07 % in the absolute utilization of nitrogen, phosphorus, and carbon, respectively. The abundance of TM7a (10.27 %), linked to nitrate absorption, became the dominant genus in the water of the DM. Additionally, the abundance of Cetobacterium, associated with carbohydrate digestion, was significantly higher in gut of the DM (23.83 %) than in the gut of CG (1.24 %, P < 0.05). Supplementing the diet of M. amblycephala with duckweed improved digestion and antioxidant enzyme activity. Transcriptome data showed that duckweed supplementation resulted in an increase in the expression of genes related to protein digestion and absorption and carbohydrate metabolism in M. amblycephala, and analysis of the significantly enriched pathways further supported improved antioxidant capacity. Based on the above results, we concluded that as M. amblycephala consumes more duckweed, the differences in nitrogen and phosphorus levels between the DM and CG would continue to increase, along with a simultaneous increase in fixed carbon. Thus, this study achieved the goal of recycling BFT resources and improving animal welfare by integrating duckweed.

Performance of pilot-scale gravel and sponge bed hydroponic systems vegetated with Duranta erecta treating wastewater in a developing country, Ethiopia, Africa

This study aimed to assess the performance of hydroponics vegetated with Duranta erecta in removing nutrients from domestic wastewater in a pilot-scale study. Domestic wastewater was fed to four lines of hydroponic-constructed filter systems (HCFS). The lines 1 and 3 were filled with gravel, but the lines 2 and 4 were filled with polyester sponges. The experimental biofilters (lines 1 and 2) were planted with Duranta erecta, and the control biofilters (lines 3 and 4) were unplanted. This experiment was operated at hydraulic retention times (HRT) of 1, 3, 5, and 7 days which were conducted sequentially. Results indicated that the planted biofilters in gravel media removed nutrients better than the other planted biofilters in sponge media. Better removal efficiencies of 55 and 47% for total nitrogen (TN) and of 32 and 26% for total phosphorus (TP) removal by planted and control lines, respectively, were obtained at 7 days HRT. At the end of the experiment, TN and TP accumulation in the plant biomass sample increased from 132 to 216 g TN/Kg of dry weight, and from 53to 86 g TP/Kg of dry weight, respectively at 7 days HRT. Hence, it can be concluded that nature-based hydroponic filters planted with Duranta erecta might have a promising potential, mainly with gravel media. HCFS represents a very welcome technology to treat domestic wastewater at a decentralized level in developing countries, including Ethiopia.

Mitigating quality deterioration in chilled pork by combining cinnamaldehyde nanoemulsions and a high-voltage electrostatic field

Cinnamaldehyde nanoemulsion (CNE) was obtained through ultrasonication, using Tween 80 as an emulsifier. The CNE was then applied to chilled pork in conjunction with a high-voltage electrostatic field (HVEF) to mitigate quality deterioration during refrigerated storage. The particle size of CNE ranged from 60 to 150 nm and was positively correlated with the amount of added cinnamaldehyde. The polydispersity index and zeta potential of CNE ranged from 0.25 to 0.30 and − 12 to −11 mV, respectively, indicating a narrow size distribution and stability. The CNE released the odor specific to cinnamaldehyde to pork in the first 4 days of chilling; however, it had little effect on the taste. HVEF pretreatment reduced the initial total viable count (TVC) in pork by 1.14 log cycle. The combination of CNE with HVEF successfully slowed down the loss of moisture, decrease in pH, and accumulation of total volatile basic nitrogen in pork during refrigeration. Furthermore, it mitigated the increase in TVC of pork. Therefore, this integrated method appears to be suitable for extending the shelf life of chilled pork.

Enhanced methane recovery from anaerobic membrane bioreactor coupled with cold plasma pretreatment for rapid hydrolysis and nitrogen removal

Research to increase biomethane recovery efficiency from thickened sewage sludge (TSWS) using sustainable anaerobic digestion (AD) in municipal wastewater treatment plants is ongoing. Pretreating substrates is known to increase organic biodegradation and biomethane conversion rates in AD. Cold plasma (CP), a recently adopted advanced oxidation processes (AOP) has emerged as an alternative to accelerate pretreatment times under different operation variables. This study assessed raw and CP-pretreated TSWS in an anaerobic sequencing batch reactor (ASBR) and anaerobic membrane bioreactor (AnMBR). The effects of incremental organic loading rates (OLR) and nitrogenous compounds concentration on enhanced CH4 bioconversion efficiency were evaluated. We found that the AnMBR outperformed the ASBR, with an overall chemical oxygen demand (COD) conversion rate of 67%, lower total nitrogen (T–N) accumulation (594 mg L−1), and an overall methane yield of 0.24 L CH4 g−1 COD. CP pretreatment improved TSWS AD, resulting in more efficient COD removal and methane recovery. This study suggests that CP technology is a promising pretreatment to improve AD when treating TSWS.

Rh proteins and H+ transporters involved in ammonia excretion in Amur Ide (Leuciscus waleckii) under high alkali exposure

High alkaline environment can lead to respiratory alkalosis and ammonia toxification to freshwater fish. However, the Amur ide (Leuciscus waleckii), which inhabits an extremely alkaline lake in China with titratable alkalinity up to 53.57 mM (pH 9.6) has developed special physiological and molecular mechanisms to adapt to such an environment. Nevertheless, how the Amur ide can maintain acid-base balance and perform ammonia detoxification effectively remains unclear. Therefore, this study was designed to study the ammonia excretion rate (Tamm), total nitrogen accumulation in blood and tissues, including identification, expression, and localization of ammonia-related transporters in gills of both the alkali and freshwater forms of the Amur ide. The results showed that the freshwater form Amur ide does not have a perfect ammonia excretion mechanism exposed to high-alkaline condition. Nevertheless, the alkali form of Amur ide was able to excrete ammonia better than freshwater from Amur ide, which was facilitated by the ionocytes transporters (Rhbg, Rhcg1, Na+/H+ exchanger 2 (NHE2), and V-type H+ ATPase (VHA)) in the gills. Converting ammonia into urea served as an ammonia detoxication strategy to reduced endogenous ammonia accumulation under high-alkaline environment.

Quantifying source–sink relationships in leaf-color modified rice genotypes during grain filling

Leaf-color modification can affect canopy photosynthesis, with potential effects on rice yield and yield components. Modulating source–sink relationships through crop management is often used to improve crop productivity. This study investigated whether and how modifying leaf color alters source–sink relationships and whether current crop cultivation practices remain applicable for leaf-color modified genotypes. Periodically collected data of total biomass and nitrogen (N) accumulation in rice genotypes of four genetic backgrounds and their leaf-color modified variants (greener or yellower) were analyzed, using a recently established modelling method to quantify the source–sink (im)balance during grain filling. Among all leaf-color variants, only one yellower-leaf variant showed a higher source capacity than its normal genotype. This was associated with greater post-flowering N-uptake that prolonged the functional leaf-N duration, and this greater post-flowering N-uptake was possible because of reduced pre-flowering N-uptake. A density experiment showed that current management practices (insufficient planting density accompanied by abundant N application) are unsuitable for the yellower-leaf genotype, ultimately limiting its yield potential. Leaf-color modification affects source–sink relationships by regulating the N trade-off between pre-and post-flowering uptake, as well as N translocation between source and sink organs. To best exploit leaf-color modification for improving crop productivity, adjustments of crop management practices are required.

Increased light intensity enhances photosynthesis and biochemical components of red macroalga of commercial importance, Kappaphycus alvarezii, in response to ocean acidification

The concentration of atmospheric carbon dioxide (CO2) has increased drastically over the past several decades, resulting in the pH of the ocean decreasing by 0.44 ± 0.005 units, known as ocean acidification (OA). The Kappaphycus alvarezii (Rhodophyta, Solieriaceae), is a commercially and ecologically important red macroalga with significant CO2 absorption potential from seawater. The K. alvarezii also experienced light variations from self-shading and varied cultivation depths. Thus, the aim of present study was to investigate the effects of two pCO2 levels (450 and 1200 ppmv) and three light intensities (50, 100, and 150 μmol photons·m−2·s−1) on photosynthesis and the biochemical components in K. alvarezii. The results of the present study showed that a light intensity of 50 μmol photons·m−2·s−1 was optimal for K. alvarezii photosynthesis with 0.663 ± 0.030 of Fv/Fm and 0.672 ± 0.025 of Fv’/Fm’. Phycoerythrin contents at two pCO2 levels decreased significantly with an increase in light intensity by 57.14–87.76%, while phycocyanin contents only decreased from 0.0069 ± 0.001 mg g−1 FW to 0.0047 ± 0.001 mg g−1 FW with an increase in light intensity at 1200 ppmv of pCO2. Moreover, moderate increases in light intensity and pCO2 had certain positive effects on the physiological performance of K. alvarezii, specifically in terms of increasing soluble carbohydrate production. Although OA and high light levels promoted total organic carbon accumulation (21.730 ± 0.205% DW) in K. alvarezii, they had a negative impact on total nitrogen accumulation (0.600 ± 0.017% DW).