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Understanding the effect of different C. citriodora removal management in a Conservation Unit (CU) aimed at forest restoration on the dynamics of the labile and stable fractions of the SOM and to quantify the stoichiometric relationships of these fractions. Soil samples were collected in four areas in the União Biological Reserve (REBIO), Rio de Janeiro, Brazil, namely: forest (FF); C. citriodora trees submitted to girdling (GR); C. citriodora trees submitted to the practice of clear cutting and subsequent planting of native species (PL); abandoned C. citriodora trees without management practice (EU). In these samples, the total content of carbon (C), nitrogen (N) and phosphorus (P) in the air-dried fine earth (ADFE) were determined; in light-fraction organic matter (LFOM) and in the particle size fractions of SOM. It was observed that the C:N and C:P ratios were higher in the EU area and lower in PL in both ADFE and LFOM samples. In EU, lower levels of C, N and P were observed in the SOM particulate fraction. GR favors the production of less recalcitrant and more labile material when compared to EU. The short time (4 years) of implementation of the system in PL directly affects the low production of LFOM; however, this material has high levels of N and P, favoring the low C:N and C:P ratio. EU intensifies the concentration of nutrients in stable fractions in the soil, which can favor the preservation of the soil structure, mitigating its losses. [ABSTRACT FROM AUTHOR]

Green manure legumes represent an important nitrogen (N) source potentially reducing the need for fertilizer inputs. Organic vegetable production systems, which aim to reduce reliance on external N sources, require enhanced control over legume-derived N and high transfer efficiency, with which this N contributes to the N supply for vegetable crops. The primary objective of the study was to quantify the N fertilizer value of cut green manure herbage transferred to vegetable crops and to evaluate residual effects on subsequent cereal crops. During four field experiments, the apparent net N mineralization of soil incorporated and surface mulched cut-and-carry biomass differing in nutrient composition and application rate ranged from 6 to 39% and from 4 and 27% within the year of their application, respectively. Despite a positive response of mulch N mineralization to application rate, the highest short-term N release was observed for soil incorporated herbage with low C:N ratio, being potentially comparable to that of organic N fertilizers. Net residual N effects on subsequent cereal crops averaged 5.2 and 5.3% for soil incorporated and mulched herbage biomass respectively, and did not compensate for low N mineralization rates in the year of application. Ensiled herbage exhibited low short-term N mineralization rates not exceeding 9%, limiting its potential to replace organic N fertilizers for early-season vegetable crops. Thus, a significant challenge arises from the lack of timely synchronicity between biomass availability and vegetable cropping periods, constraining efforts to reduce reliance on external N sources. [ABSTRACT FROM AUTHOR]

Changes in vegetation and land use alter the biogeochemical cycles of soil C and N, as a result of agricultural practices that alter soil quality and function. Adopting sustainable agricultural practices improves soil health by increasing its capacity to store C in the long term. The objective of this study was to evaluate the content and stocks of C and N and the C:N ratio, under different land uses in an Andosol. Four composite soil samples were collected in a pine-oak forest, conventional avocado, organic avocado and organic macadamia soil uses at 0-20 and 20-40 cm soil depths (n=32). The total C content was determined by the Walkley and Black method (Woerner, 1989), the total N by the Kjeldahl method with the Velp Scientifica's UDK159 model equipment (Bremner and Mulvaney 1982). In order to detect significant differences, a two factor analysis of variance (ANOVA) was applied C (%), N (%), SOC (Mg ha-1 ), Nt (Mg ha-1 ) and C:N ratio variables. When applied, a Tukey comparison of means (p≤0.05) was performed. The results indicate that conventional avocado land use presented the highest C and N content at both soil depths (C: 9.22 and 7.32%, N: 0.70 and 0.40%), while the C:N ratio was higher in the forest land use in the first depth (14.5) and higher in the organic avocado land use in the second soil depth (25.8). The stock of SOC varied from 65.27 to 267.30 (Mg ha-1 ) and the Nitrogen from 4.61 to 14.61 (Mg ha-1 ). The C:N ratio showed significant variations between land uses, specifically in the first depth it ranged from 10.33 (O. Macadamia) to 14.51 (Forest), while in the second depth it varied from 13.09 (Conventional) to 25.83 (O avocado). The pine-oak forest, organic avocado and organic macadamia systems, with the smallest reseivors, were statistically similar only in C content, while the conventional system, with the largest stocks, was differente in C and N content. The change in land use from forest to agricultural caused a significant effect on the carbon and nitrogen content and the stocks in the Andosol soil, which may be attributes to the different agricultural applied practices such as pruning, pesticides and fertilization used in the organic and conventional regimes, respectively. The C:N ratio indicates that mineralization rates decrease as depth increases because the quantity and quality of soil organic matter also decreases. Specifically, the conventional avocado practice compared to organic avocado and macadamia practices maximized crop yields. [ABSTRACT FROM AUTHOR]

Biofloc technology (BFT) is an environmentally friendly fish production system as a way to reduce the negative impacts of aquaculture. Numerous types of investigations have been conducted on various aspects of BFT. The focal point of this review is to visualize the insights of the biofloc system's performance in context to stocking density, yield, carbonaceous sources, and carbon-nitrogen ratio (C:N), BFT role in aquaculture and flocponics. Hybrid biofloc-RAS system highlights the existing challenges and suggests the right approach for future research. The published data bank includes papers containing the keywords like biofloc, flocponics, hybrid biofloc-RAS system and fish production. The insights of this review are useful for the efficient development of biofloc and focuses on further research to establish commercially viable biofloc technology; and thus, contributing to sustainable aquaculture production. [ABSTRACT FROM AUTHOR]

We investigated the distribution, C:N elemental ratio, and δ¹³C of suspended particulate carbon in the surface and upper 100 m of the water column during three seasons in areas of the Western Tropical North Atlantic influenced by the Amazon River Plume: the Spring high flow period (KN197 Cruise, May-June), the late Summer period of reduced flow (AT2104 cruise, July), and the low flow period in the Fall (MV1110 cruise, Sept-Oct). We used a habitat delineation method to examine spatial and temporal variability in our biogeochemical parameters. We found the highest biomass concentration ([PC]=259.7 µM), high C:N ratio (13.6), and the most negative δ¹³C (-26.8 ‰) in the area proximate to the river mouth during the late summer cruise. We measured elevated [PC] (64.5 µM), C:N ratios (14.1), and δ¹³C (max -15.7 ‰) in the plume core habitats during the peak flow season, reflecting the impact of both the outflow and in situ phytoplankton production. We found that the western margin of the plume had relatively higher biomass, C:N ratios, and organic matter more enriched in 13C than the east margins. In our work area, oceanic waters had the lowest [PC] (1.3 µM), a C:N ratio higher than the Redfield ratio (6.6), and an average δ¹³C of -22 ‰. We explored the relationships between PC and Chla, and δ¹³C and C:N ratio to estimate the contribution of phytoplankton production and terrigenous sources to the suspended particulate carbon pool. We found terrestrial and detrital sources contributing more to the organic matter of the river mouth area. However, the contribution of phytoplankton and living sources dominate most of our study area in all seasons. Our findings emphasize the role of the Amazon River Plume in enhancing biomass and productivity of the WTNA and the biogeochemical dynamic of the carbon cycle.

We examined the feeding ecology of planktonic crustaceans at three waterbodies situated across a latitudinal gradient in Europe (Croatia, Poland, Lithuania) using stable isotope measurements (δ13C, δ15N) in animal tissues. Relative, lake-specific values of δ15N showed that in all lakes, calanoid copepods occupied the highest trophic position, while Daphnia sp. and Diaphanosoma sp. were located closer to primary producers with Cyclopoid copepods located between these groups. We found a negative correlation between C:N ratio (proxy for lipid content) and δ15N, which indicates lipid content declined with the trophic level of the animals. Employment of stable isotope-based approach allows better recognition of trophic linkages than could be inferred from classical methods, and therefore our results contribute improvement of management strategies developed for aquatic ecosystems.

Context: The goal of increasing sequestration of carbon (C) in soil assumes that management factors can be as influential as intrinsic factors such as climate and parent material. Aim: The hypotheses tested in this study were (i) that soil C would increase more in limed than in unlimed pasture treatments, and (ii) that well-managed perennial pasture treatments would accumulate soil C to a greater depth than annual pasture treatments. Method: An 18-year field experiment was conducted on a duplex soil in the mixed farming zone of south-eastern Australia. The experiment contained four treatment contrasts: limed and unlimed perennial and annual pasture systems. Soils samples to 120 cm were taken annually and analysed for C and nitrogen (N) concentrations. Soil C and N stocks were calculated. Key results: The four treatments produced a similar annual rate of increase in soil C concentration and C stocks. The increase in C stock was confined to the surface 30 cm of soil in all four treatments, leading to the rejection of both hypotheses. Nitrogen concentration and N stocks to 30 cm depth increased significantly over the 18 years, with no difference among treatments. Conclusion: Pasture land use increased soil C storage by ~700 kg ha−1 year−1; however, the increase was confined to the surface soil. Implication: The soil C sequestered in this duplex soil is vulnerable to erosion. The co-retained N might have more value from both production and environmental perspectives. Accumulation of soil organic carbon is considered beneficial to both farm productivity and the environment. Although conservation farming might make little direct contribution to soil carbon stocks, it is likely to be essential for the retention of soil carbon stores in duplex soils. Conversely, the co-retained nitrogen might have more value than the carbon stocks. [ABSTRACT FROM AUTHOR]

The efficient monitoring of foliar nutrient such as the C:N ratio is important for sustainable rangeland productivity. Recent advances in Earth observation technology provide multispectral sensors with high spatial, spectral and temporal resolution suitable for modelling foliar nutrients. This study explored the fusion of Sentinel-2 and PlanetScope datasets using the pixel fusion technique and the random forest algorithm. The result in this study is vital in understanding the value of image fusion in enhancing rangeland nutrient estimation for optimal productivity. The study concludes that the fusion of optical sensors requires further investigation. [ABSTRACT FROM AUTHOR]

Inappropriate waste disposal imposes significant health risks in densely populated urban environments and schools, necessitating sustainable waste management. Therefore, a study was carried out at Al-Jazaer School, Kuwait, to evaluate rotary drum composting (RDC) of organic school waste comprising used paper, dry leaves, and vegetable food wastes in a 1:4:20 ratio. Feedstock comprising 42% organic school wastes, 42% horse manure, and 16% sawdust produced mature compost with a C:N ratio of 20.55 on the 43rd day of composting. Distinct mesophilic, thermophilic, cooling, and curing phases were observed during composting. Mature compost recorded a moisture content of 54.3%, pH 8.56, EC of 2.71 mS/cm, total nitrogen of 0.77%, total organic carbon of 18.25%, carbon content of 15.86%, and sulfur content of 0.14%. Soilless growing media comprising peat moss, perlite, and rotary drum compost in three proportions (1:1:1, 1:1:2, and 1:1:3), and peat moss, perlite, and commercial organic compost in a 1:1:3 ratio were evaluated for greenhouse vegetable production. The performance of cucumbers (Cucumis sativus cv. Ramos) raised in the lowest proportion of in-house prepared rotary drum compost (1:1:1 ratio) was comparable with that raised in the highest proportion of commercial compost (1:1:3). The study revealed the potential of RDC for decentralized sustainable waste management at the small-community scale and the suitability of compost from school wastes for soilless culture. [ABSTRACT FROM AUTHOR]

Biofloc technology (BFT) is gaining popularity in the aquaculture sector. In this study, the effects of different carbon-to-nitrogen (C:N) ratios in jaggery-supplemented BFT systems on water quality, microbial diversities, feed performance, and growth, welfare, and proximate composition of Nile tilapia (Oreochromis niloticus) were investigated. The study had a completely randomized design (312.5 g/m3 in water tanks containing 4000 L water) and was carried out in triplicate, with a control group without biofloc and three groups of BFT-treated Nile tilapia (0.50 ± 0.05 g) reared in different C:N ratios, i.e., 15:1 (CN15), 20:1 (CN20), and 25:1 (CN25), for 120 days. The fish were fed a commercial diet at 2–5% of their body weight daily. The BFT performed significantly (P < 0.05) better in all measured aspects. Lower dissolved oxygen, pH, ammonia, abundance of beneficial microbes like Firmicutes and Actinobacteria, higher floc volume, and total heterotrophic counts were observed with increasing C:N ratios. The highest survivability, highest body weight, lowest feed conversion ratio, and better stress and liver biomarkers, hematology, innate immunity and antioxidant properties were recorded in the BFT system with the lower C:N ratios. The best histological status of the liver and intestines was found in fish cultured in the CN15 group, followed by fish cultured in the CN20 and CN25 groups. Considering all aspects, the C:N ratio of 15:1 was the most suitable for the biofloc culture of Oreochromis niloticus. [ABSTRACT FROM AUTHOR]

Little is known about how the degree of mixing various forest-forming species affects forest floor hydrology. We evaluated the water storage capacity of the resulting litter layer by mixing the litterfall of Scots pine and sessile oak and studying their decomposition time. We prepared 90 artificial samples containing pure pine litter, pure oak litter, and mixed pine–oak litter with varying shares of pine needles. These samples were subjected to 15 months of decomposition in soil. After every three months of decay, some samples were removed from the soil, and their water storage capacity, bulk density, and C:N ratio were evaluated. Our findings indicate that samples with the greatest water storage capacity had a low C:N ratio and a predominant share of oak leaves. Conversely, samples with a high C:N ratio and a predominant share of pine needles had the lowest water storage capacity. After 12 and 15 months of decomposition, the water storage capacity increased by more than 52% compared to the initial water capacity of the samples. The highest increase in water storage capacity (>40%) was observed in samples with a predominant share of oak leaves, while the lowest (approximately 28%) was recorded in samples with 80 and 100% of pine needles. Our findings suggest that introducing mixed-species stands, with deciduous species as the predominant component, can yield several ecological benefits, such as an increased ability to store water in forest floor. [ABSTRACT FROM AUTHOR]

Domesticated rice Oryza sativa L. is a major staple food worldwide, and the cereal most sensitive to salinity. It originated from the wild ancestor Oryza rufipogon Griff., which was reported to possess superior salinity tolerance. Here, we examined the morpho-physiological responses to salinity stress (80 mM NaCl for 7 days) in seedlings of an O. rufipogon accession and two Italian O. sativa genotypes, Baldo (mildly tolerant) and Vialone Nano (sensitive). Under salt treatment, O. rufipogon showed the highest percentage of plants with no to moderate stress symptoms, displaying an unchanged shoot/root biomass ratio, the highest Na+ accumulation in roots, the lowest root and leaf Na+/K+ ratio, and highest leaf relative water content, leading to a better preservation of the plant architecture, ion homeostasis, and water status. Moreover, O. rufipogon preserved the overall leaf carbon to nitrogen balance and photosynthetic apparatus integrity. Conversely, Vialone Nano showed the lowest percentage of plants surviving after treatment, and displayed a higher reduction in the growth of shoots rather than roots, with leaves compromised in water and ionic balance, negatively affecting the photosynthetic performance (lowest performance index by JIP-test) and apparatus integrity. Baldo showed intermediate salt tolerance. Being O. rufipogon interfertile with O. sativa, it resulted a good candidate for pre-breeding towards salt-tolerant lines. [ABSTRACT FROM AUTHOR]

To understand the long-term effects of combined organic and chemical nitrogen fertilization on soil organic C (SOC) and total N (TN), we conducted a 30-year field experiment with a wheat–maize rotation system on the Huang-Huai-Hai Plain during 1990–2019. The experimental treatments consisted of five fertilizer regimes: no fertilizer (control), chemical fertilizer only (NPK), chemical fertilizer with straw (NPKS), chemical fertilizer with manure (NPKM), and 1.5 times the rate of NPKM (1.5NPKM). The NPK, NPKS, and NPKM treatments had equal N inputs. The crop yields were measured over the whole experimental duration. Soil samples were collected from the topsoil (0–10 and 10–20 cm) and subsoil (20–40 cm) layers for assessing soil aggregates and taking SOC and TN measurements. Compared with the NPK treatment, the SOC and TN contents increased significantly in both the topsoil (24.1–44.4% for SOC and 22.8–47.7% for TN) and subsoil layers (22.0–47.9% for SOC and 19.8–41.8% for TN) for the organically amended treatments (NPKS, NPKM and 1.5NPKM) after 30 years, while no significant differences were found for the average annual crop yields over the 30 years of the experiment. The 0–10 cm layer of the NPKS treatment and the 20–40 cm layer of the NPKM treatment had significantly higher macroaggregate fraction mass proportions (19.8 and 27.0%) than the NPK treatment. However, the 0–10 and 20–40 cm layers of the 1.5NPKM treatment had significantly lower macroaggregate fraction mass proportions (–19.2 and –29.1%) than the control. The analysis showed that the higher SOC and TN in the soil of organically amended treatments compared to the NPK treatment were related to the increases in SOC and TN protected in the stable fractions (i.e., free microaggregates and microaggregates within macroaggregates), in which the contributions of the stable fractions were 81.1–91.7% of the increase in SOC and 83.3–94.0% of the increase in TN, respectively. The relationships between average C inputs and both stable SOC and TN stocks were significantly positive with R2 values of 0.74 and 0.72 (P

Purpose Nitrogen loss as ammonia (NH3) in a waste cocoa pod co-composting process was determined following the addition of three potential chemical amendments that could lower NH3 loss. Further, amended compost products were assessed for quality and possible phytotoxicity in a pot experiment. Method Pod borer damaged cocoa pods were co-composted in lab-scale vessels under ambient conditions with double superphosphate, phosphoric acid, and gypsum at 2%, 5% and 1% of fresh weight, respectively. NH3 emitted during composting was trapped in standard H2SO4 and determined titrimetrically. Composting mixtures were sampled on days 0, 7, 56 and 90 to monitor pH, total C, total N, and C:N ratio. Mature co-composts were incorporated to the soil at 20 t haâ1 and growth response of Chinese cabbage plants (Brassica rapa chinensis) assessed for the phytotoxicity. Results The chemical amendments were ineffective (pâ>â0.05) in preventing loss of NH3 but the quality of composting mixtures were significantly (pâ

The aim of this study was to better understand how soil carbon (C) and nitrogen (N) contents and the C:N ratio are related to soil texture, pH, and exchangeable aluminum and calcium in forest soils.For this purpose, we studied 1992 temperate and boreal forest soils located all over Sweden. We measured organic C and N as well exchangeable aluminum, calcium, and pH in the organic layer and three depth increments in the mineral soil (down to 65 cm), and analyzed the relationship between element contents, soil texture, and soil pH as well as their interactions.Soil C concentration and the C:N ratio were negatively related to soil pH. The C concentration was on average 2.6 times higher in very acidic soils (pH ≤ 4.0) than in soils with pH > 5.0, in the uppermost 10 cm of the mineral soil. In contrast, N varied much less with pH, particularly in the organic layer, but was related to soil texture. The N concentration was 2.3 times higher in clayey and fine silty soils than in sandy soils, while the C concentration was only 1.85 times higher in clayey and fine silty soils than in sandy soils (in the uppermost 10 cm). Differences in C and N concentrations between clayey and fine silty soils compared to sandy soils were largest in the class of soils with pH > 5.0 and smallest in the class of soils with pH ≤ 4.0. Furthermore, C and N concentrations were both positively correlated with the concentration of exchangeable aluminum in the mineral soil, and these correlations were stronger in coarse-textured than in fine-textured soils. In addition, the C concentration was positively correlated with the concentration of exchangeable calcium in the organic layer.In conclusion, our results show that C concentration varied much more strongly with pH than N concentration, likely due to effects of pH on microbial respiration. The N concentration was more strongly related to soil texture than the C concentration, which is very likely due to the high charge density of organic N, which gives organic N a high affinity to adsorb to mineral surfaces. Furthermore, exchangeable aluminum seems to play an important role in the sorptive stabilization of organic matter in the mineral soil.

Little is known about the rate of mineralisation of chicory (Cichorium intybus) residues and how this may influence the availability of nitrogen (N) for subsequent crops. An incubation study was conducted to compare the relative rates of N mineralisation and carbon dioxide production from different plant fractions of chicory and lucerne (Medicago sativa) over 112 days. Plants were separated into leaves, stems, fibrous roots (<1 mm), and taproots (>4 mm), which were either ground or segmented, and then mixed with soil in sealed jars. Results showed that net N mineralisation occurred from day 7 for lucerne leaves, but not until day 56 for chicory leaves. By day 112, chicory leaves only produced approximately 25% of the N mineralised by lucerne leaves. Segmented chicory taproots released 32% and 24% more of the plant N and carbon (C), respectively, than any other chicory and lucerne plant fractions despite having a C:N ratio greater than 30. The presence of a common fungal saprophyte (Rhizopus spp.) in the segmented chicory taproot treatments appeared to accelerate the net N mineralisation rate. Whilst coarse chicory roots released mineral N relatively rapidly, the lower N content observed in the chicory plant residues limited the capacity of chicory to release the same quantity of mineral N compared to lucerne. Chicory needs to be grown with a companion legume so that N mineralisation of the residues better matches the demands of N requirement for the following non‐legume cropping phase. [ABSTRACT FROM AUTHOR]

Although ectomycorrhizal (ECM) contribution to soil organic matter processes receives increased attention, little is known about fundamental differences in chemical composition among species, and how that may be affected by carbon (C) availability. Here, we study how 16 species (incl. 19 isolates) grown in pure culture at three different C:N ratios (10:1, 20:1, and 40:1) vary in chemical structure, using Fourier transform infrared (FTIR) spectroscopy. We hypothesized that C availability impacts directly on chemical composition, expecting increased C availability to lead to more carbohydrates and less proteins in the mycelia. There were strong and significant effects of ECM species (R2 = 0.873 and P = 0.001) and large species-specific differences in chemical composition. Chemical composition also changed significantly with C availability, and increased C led to more polysaccharides and less proteins for many species, but not all. Understanding how chemical composition change with altered C availability is a first step towards understanding their role in organic matter accumulation and decomposition. [ABSTRACT FROM AUTHOR]

Algal carbon‐to‐nitrogen (C:N) and carbon‐to‐phosphorus (C:P) ratios are fundamental for understanding many oceanic biogeochemical processes, such as nutrient flux and climate regulation. We synthesized literature data (444 species, >400 locations) and collected original samples from Tasmania, Australia (51 species, 10 locations) to update the global ratios of seaweed carbon‐to‐nitrogen (C:N) and carbon‐to‐phosphorus (C:P). The updated global mean molar ratio for seaweed C:N is 20 (ranging from 6 to 123) and for C:P is 801 (ranging from 76 to 4102). The C:N and C:P ratios were significantly influenced by seawater inorganic nutrient concentrations and seasonality. Additionally, C:N ratios varied by phyla. Brown seaweeds (Ochrophyta, Phaeophyceae) had the highest mean C:N of 27.5 (range: 7.6–122.5), followed by green seaweeds (Chlorophyta) of 17.8 (6.2–54.3) and red seaweeds (Rhodophyta) of 14.8 (5.6–77.6). We used the updated C:N and C:P values to compare seaweed tissue stoichiometry with the most recently reported values for plankton community stoichiometry. Our results show that seaweeds have on average 2.8 and 4.0 times higher C:N and C:P than phytoplankton, indicating seaweeds can assimilate more carbon in their biomass for a given amount of nutrient resource. The stoichiometric comparison presented herein is central to the discourse on ocean afforestation (the deliberate replacement of phytoplankton with seaweeds to enhance the ocean biological carbon sink) by contributing to the understanding of the impact of nutrient reallocation from phytoplankton to seaweeds under large‐scale seaweed cultivation. [ABSTRACT FROM AUTHOR]

Background and aims: Understanding the fate and residence time of organic matter added to soils, and its effect on native soil organic carbon (SOC) mineralisation is key for developing efficient SOC sequestration strategies. Here, the effect of litter quality, particularly the carbon-to-nitrogen (C:N) ratio, on the dynamics of particulate (POC) and mineral-associated organic carbon (MAOC) were studied. Methods: In a two-year incubation experiment, root litter samples of the C4-grass Miscanthus with four different C:N ratios ranging from 50 to 124 were added to a loamy agricultural topsoil. In an additional treatment, ammonium nitrate was added to the C:N 124 litter to match the C:N 50 litter input ratio. Soils were size-fractionated after 6, 12 and 24 months and δ13C was measured to determine the proportion of new and native POC and MAOC. Litter quality was further assessed by mid-infrared spectroscopy and compound peak analysis. Results: Litter quality strongly affected SOC dynamics, with total SOC losses of 42.5 ± 3.0% in the C:N 50 treatment and 48.9 ± 3.0% in the C:N 124 treatment after 24 months. Largest treatment effects occurred in mineralisation of native MAOC, which was strongly primed by litter addition. The N amendment in the C:N 124 treatment did not alleviate this potential N mining flux. Conclusion: Litter quality plays a major role in overall SOC dynamics, and priming for N mining from the MAOC pool could be a dominant mechanism. However, adding N did not compensate for poor litter quality, highlighting the role of litter quality beyond stoichiometric imbalances. [ABSTRACT FROM AUTHOR]

Assessment on how current standard tomato production impacts plant and soil C and N dynamics is necessary to improve sustainable nutrient management strategies for the intensive production of vegetables in warm climates. Carbon (C), nitrogen (N) and C:N ratios were determined for tomato variety 'BHN 602' (Solanum lycopersicum) in spring and fall season at harvest, in north Florida. A replicated field study was conducted where tomatoes were grown in sandy soils with fertilizers injected through the drip irrigation lines under a plastic-mulched bed system. Ammonium nitrate as the N source was applied at four different rates (0, 168, 224, and 280 kg ha−1). Soluble N fertilizer was applied weekly in 13 equal doses through the drip system for both seasons. Whole plant C:N ratios were similar among N rates in both spring and fall applications showing that the lowest applied N rate (168 kg ha−1) was sufficient in supplying N to the crop. Therefore, fertilized whole plant C:N ratios of 15.2 (spring) and 13.8 (fall) indicated optimal N uptake capability by the tomato crop. Soil TC and TN concentrations were maintained in the top 0-45 cm increments of the soil profile in both seasons, where concentrations did not differ among the rates of N fertilizer applied. Due to the lack of fertilizer input response, the reduction of N fertilizer rates would improve the sustainability of conventional vegetable production systems that are grown in sandy soil under a warm climate. Soil C was commensurate with soil N levels with regard to stabilizing the C:N ratio below 20, thus promoting mineralization in the soil for the subsequent crop. [ABSTRACT FROM AUTHOR]

The objective was to study the impact of ten year's manuring and fertilization on chemical stability of clay-organic complex (COC) in rice−potato−wheat (R–P–W) and maize−potato−onion (M–P–O) cropping systems. Soil samples were collected from the control, 100% NPK–Fertilizer, 100% N–Vermicompost (VC), 50% NPK–Fertilizer + 50% N–VC, 100% NPK–Fertilizer + crop residue (CR), 100% N–VC + CR. The stability (1/k) of humus C i.e. inverse of humus desorption rate constant (k) in hours (h), in COC was higher in 100% N–VC an1d 00% N–VC + CR in both the cropping systems. The C:N ratio of humic acid (HA) was also higher in the treatments receiving full organics (100% N–VC and 100% N–VC + CR) and showed positive correlation (p < 0.05) with the humus C stability in COC. Long-term manuring treatments created C = N and C–O stretching of aromatic ether in HA extracted from 100% NPK–VC and other selected treatments in both the cropping systems. 100% N–VC and 100%N–VC + CR produced higher stability of humus-C in Inceptisol. The R–P–W imparted higher stability of humus C than M–P–O cropping system. [ABSTRACT FROM AUTHOR]

Semi-arid forests of the Aravalli hills are rich in tree diversity, but plant invasions during the last several decades, especially by Prosopis juliflora (Sw.) DC. have affected the vegetation structure and biogeochemical cycles of these forests. We compared carbon (C), and nitrogen (N) concentrations in the fine root, leaf, and soil physicochemical properties under the invasive tree species, P. juliflora, and native, Acacia nilotica (L.) Willd. ex Delile, to evaluate the effect of invasive tree species on total soil C, N concentrations, and C:N ratios. We also analyzed the soil samples for soil organic C (SOC), total N (TN), soil microbial biomass C (MBC), and soil microbial biomass N (MBN) and stocks. Soil physical and chemical properties under the invasive P. juliflora and native A. nilotica trees varied significantly (p < 0.05). The C and N concentrations in the fine root, leaf, soil SOC, TN and MBC, and MBN concentrations were significantly (p < 0.05) higher in P. juliflora than A. nilotica while C:N ratio, and bulk density, exhibited the opposite trends. The C concentrations followed the order fine root > leaf > soil > microbial biomass while for N concentration and C:N ratios, it was leaf > fine root > soil > microbial biomass. The invasive P. juliflora had a lower C:N ratio in leaf, fine root, and soil than the native A. nilotica. The average rhizosphere soil, fine root, and leaf C concentration for P. juliflora were 36.72 ± 0.84 g kg−1, 547.84 ± 18.56 g kg−1, and 534.77 ± 5.12 g kg−1, respectively and were 1.42, 1.16 and 1.04 times higher than for A. nilotica. Similarly, P. juliflora average rhizosphere soil, fine root, and leaf N concentrations were 4.37 ± 0.11 g kg−1, 19.96 ± 0.94 g kg−1, and 23.18 ± 0.84 g kg−1, respectively, and 2.0, 1.27, and 1.85 times, respectively, higher than for A. nilotica. Further, the MBC:SOC or MBN:TN ratios were higher in native A. nilotica, likely indicating higher efficiency of microbes in soil C decomposition. Together, our results indicate that invasive P. juliflora altered the ecosystem processes and increased the soil and microbial C, and N stocks compared to native A. nilotica in the semi-arid forests of the Aravalli hills. [ABSTRACT FROM AUTHOR]

Straw return is the simplest and the most economic method to improve soil structure. Slow decomposition rate limits straw return in sandy fields, which has becoming one of the obstacles in sandy land reclamation. Ammonification of straw before return accelerates straw decomposition, but it requires the use of extra N fertilizer, however, little is known about N fertilizer management in fields with ammoniated straw incorporation. So, a 3‐year field experiment was conducted with different proportions of N fertilizer aimed to maize straw ammonification and field broadcasting, and evaluated straw decomposition proportion, straw N release, soil organic carbon content, soil aggregates, soil water and N availability, and grain yield. Total N application rate was 300 kg per hectare, with five N input amounts for straw per hectare ammonification: 0 (SN0), 40 (SN40), 80 (SN80), 120 (SN120), and 160 (SN160) kg, and the rest of N broadcasted in soil during maize growing season. Ammonification accelerated straw decomposition and N release, and these effects showed no significant difference between SN80, SN120, and SN160. After straw decomposition for 150 days, the decomposition proportion was 62.1%, 53.0%, and 39.2% in SN80, SN40, and SN0, respectively. After 3 years of straw return, SN80 exhibited a significantly higher mean weight diameter of soil aggregates (35.6% higher), organic carbon content (18.4% higher), water‐holding capacity (17.4% higher), and soil water storage (17.2% higher) than SN0. Additionally, SN80 and SN120 showed the most significant effect on "N slow‐release" in soil. The above effects resulted with more available soil water and N used for crop growth, and increased grain yields (18.1% higher) and water use efficiency (18.6% higher) in SN80, compared with SN0. Hence, we conclude that a proper N allocation between straw and soil can synergistically enhance soil structure and crop productivity in sandy farmlands. This founding would provide scientific and technological support for straw return in sandy fields and is beneficial to sustainable development of oasis. [ABSTRACT FROM AUTHOR]

Soil salinization is a critical environmental issue restricting agricultural production. Deep return of straw to the soil as an interlayer (at 40 cm depth) has been a popular practice to alleviate salt stress. However, the legacy effects of straw added as an interlayer at different rates on soil organic carbon (SOC) and total nitrogen (TN) in saline soils still remain inconclusive. Therefore, a four-year (2015–2018) field experiment was conducted with four levels (i.e., 0, 6, 12 and 18 Mg ha–1) of straw returned as an interlayer. Compared with no straw interlayer (CK), straw addition increased SOC concentration by 14–32 and 11–57% in the 20–40 and 40–60 cm soil layers, respectively. The increases in soil TN concentration (8–22 and 6–34% in the 20–40 and 40–60 cm soil layers, respectively) were lower than that for SOC concentration, which led to increased soil C:N ratio in the 20–60 cm soil depth. Increases in SOC and TN concentrations in the 20–60 cm soil layer with straw addition led to a decrease in stratification ratios (0–20 cm:20–60 cm), which promoted uniform distributions of SOC and TN in the soil profile. Increases in SOC and TN concentrations were associated with soil salinity and moisture regulation and improved sunflower yield. Generally, compared with other treatments, the application of 12 Mg ha–1 straw had higher SOC, TN and C:N ratio, and lower soil stratification ratio in the 2015–2017 period. The results highlighted that legacy effects of straw application as an interlayer were maintained for at least four years, and demonstrated that deep soil straw application had a great potential for improving subsoil fertility in salt-affected soils.

Density effects are a fundamental ecological question, but their impacts on the individual growth of insects are highly variable. Scarab larvae in soils often occur at high density, but density effects of their population are rarely reported. We examined how the density of the first instar larvae of the soil-dwelling omnivore Anomala cuprea Hope (Coleoptera: Scarabaeidae) affected their growth when fed two diet types in which carbon to nitrogen ratio (C:N ratio) differs. The C:N ratio was used as a parameter of diet quality in the context of ecological stoichiometry. The larvae were grown for 34 days at three population densities (one, three, or five larvae per cup) and fed two diet types (humus as a low C:N ratio diet or wood flakes as a high C:N ratio diet). An increase in population density reduced larval growth under the low C:N ratio diet, but it enhanced larval growth under the high C:N ratio diet. Larval mortality was always low, but it was observed only at a population density of three or five larvae. Compensatory growth, gut symbionts, and hormesis are discussed as possible mechanisms of these results. In nature, larvae occur at high density and the C:N ratio of their diets is low. Therefore, our results suggest that high population density will have positive effects under natural conditions.

Rising global temperatures have the potential to increase soil nitrogen (N) mineralization from soil organic matter (SOM). By increasing SOM over time, management practices that increase SOM through the addition of soil amendments, such as compost, have been recognized as effective strategies for mitigating the effects of climate change and building resilience in agricultural ecosystems. However, the effects of these strategies on temperature-induced changes to soil N cycling are unclear, particularly when soils are managed to increase SOM. To determine how agricultural management history and compost amendments affect net N mineralization, net nitrification, and nitrous oxide (N2O) production, we performed a laboratory incubation of soils with two distinct agricultural management histories under three incubation temperatures. Three compost treatments (green-waste compost, food-waste compost, and no compost) were applied, each with and without the addition of synthetic urea fertilizer. We found that organically managed soil exhibited higher rates of net N mineralization and nitrification than conventionally managed soil, leading to greater nitrate production. The rate of N mineralization in organically managed soil was also more sensitive to temperature increases. Although compost addition stimulated microbial activity, it did not affect the N-cycling processes measured in this study at any temperature. Therefore, the implementation of climate change resilience and mitigation strategies aimed at augmenting stocks of soil carbon may render agricultural soils more susceptible to increased N mineralization and subsequent losses under warming, particularly if plant uptake of the mineralized N does not occur concurrently. Moreover, the effects of compost application to stimulate the immobilization of excess N is likely limited in soils with low background C.

Forest mycorrhizal type is getting more attention as a potentially significant factor controlling carbon (C) and nitrogen (N) cycling. Ectomycorrhizal (ECM) forests are frequently reported to have lower N availability and higher soil C storage than arbuscular mycorrhizal (AM) forests. However, it is still unclear whether such characteristics stem from the low organic matter quality inherent in the ECM forest or other biotic and abiotic factors, such as competition for N between ECM fungi and free-living microbes. We conducted soil and litter reciprocal transplant experiments between AM-symbiotic black locust and ECM-symbiotic oak forests to separate the effects of organic matter quality and forest type (i.e., factors including ECM fungal presence and soil physicochemical properties) on decomposition rates and N availability. We hypothesized that the forest type, rather than organic matter quality, is a more determinant factor for available N content but not organic matter decomposition rate. Forest type had a more substantial effect not only on nitrate content but also on decomposition rate than organic matter quality. Since the litter decomposition rate was higher when placed in the oak forest, the higher soil C accumulation in the oak than in the black locust forests may be caused by greater C input rather than the slower decomposition in the oak than black locust forest. In addition, nitrate content was determined by forest type, suggesting the suppression of nitrate content by ECM fungal presence. This study suggests that the forest type with different mycorrhizal associations can affect biogeochemical cycling independent of organic matter quality. [ABSTRACT FROM AUTHOR]

Under Indian scenario poultry birds are mainly reared as broiler and layer for the production of meat and egg respectively. With the increase in poultry population in the country, the production of waste also increases. This waste was difficult to handle as it was having lower c:n ratio. C:N ratio is crucial factor in order to improve the utilization of waste or process it through any value-added technique. In the present study, different locally available carbonaceous materials were studied for adjusting the C:N ratio of poultry waste. Poultry waste was collected in the form of broiler litter and layer excreta from poultry farm, ICAR-Central Avian Research Institute. The composition of these wastes was determined and the carbon deficit was calculated. This carbon deficit was fulfilled with carbonaceous materials, which incudes wheat straw, rice husk, rice paddy, fallen dry leaves and wooden straw. The quantity of carbonaceous material required to adjust c:n ratio at 25:1 per 100 kg of broiler litter and layer excreta were ranging between 26.38 to 30.52 kg and 17.57 to 20.32 kg, respectively. [ABSTRACT FROM AUTHOR]

Current understanding of nitrogen (N) mineralization from organic soil inputs considers three alternative processes: immediate net mineralization of N, net immobilization followed by net mineralization, or exclusively net immobilization. The three processes are compatible and linked with the C:N ratio rule. However, research evidence from a number of incubation studies incorporating processed materials like manures, composts, manure composts, or already decomposed plant residues suggest the presence of a second N immobilization phase. The mechanisms and conditions of this process, which is against the prevailing theory of soil N cycling, have not been ascertained, but they should most likely be attributed to impeded dead microbial biomass turnover. The transfer of mineral forms of N to the organic N pool may reasonably be explained by the chemical stabilization of nitrogenous compounds with secondary products of lignin degradation, which occurs late after incorporation of an organic input in soil. Secondary immobilization questions the reliability of the C:N ratio and most likely of other quality indices if proved to be real, even to some extent, while it may also have significant consequences on the management of soil organic additives applied as fertilizers.

Chemical preservatives can alter stable isotope ratios in animal tissues. The effects of preservation on δ13C and δ15N values have been investigated in a variety of species, but not on δ2H values or on the freshwater pearl mussel (FPM, Margaritifera margaritifera) tissues. We evaluated the effect of ethanol preservation (unpreserved vs preserved tissues) over 6 months on the δ13C, δ15N and δ2H values of FPM foot and gonad tissues. Ethanol preservation significantly increased δ13C values (foot 0.4 ‰; gonad 0.3 ‰), whereas it did not significantly affect δ15N values (foot 0.2 ‰; gonad − 0.1 ‰). The positive effect of ethanol preservation on δ2H values (foot 7.1 ‰; gonad 14.5 ‰) and the negative effect on C:N ratios (foot − 0.1; gonad − 0.5) depended on the tissue type, with larger effects found on the lipid-rich gonad. Overall, ethanol preservation affected δ2H values more than the δ13C, δ15N or C:N ratios of FPM tissues. After 1 month of preservation, the isotope values remained rather stable, and significant changes were only observed in δ15N values. The results imply that ethanol-preserved FPM samples can be used if potential shifts in isotopic and elemental ratios are accounted for prior running mixing models for estimating dietary proportions. [ABSTRACT FROM AUTHOR]

The increase in the concentration of CO2 in the atmosphere is currently causing metabolomic and physiological changes in living beings and especially in plants. Future climate change may affect crop productivity by limiting the uptake of soil resources such as nitrogen (N) and water. The contribution of legume–rhizobia symbioses to N2 fixation increases the available biological N reserve. Elevated CO2 (eCO2) has been shown to enhance the amount of fixed N2 primarily by increasing biomass. Greater leaf biomass under eCO2 levels increases N demand, which can stimulate and increase N2 fixation. For this reason, bean plants (Phaseolus vulgaris L.) were used in this work to investigate how, in a CO2-enriched atmosphere, inoculation with rhizobia (Rhizobium leguminosarum) affects different growth parameters and metabolites of carbon and nitrogen metabolism, as well as enzymatic activities of nitrogen metabolism and the oxidative state of the plant, with a view to future scenarios, where the concentration of CO2 in the atmosphere will increase. The results showed that bean symbiosis with R. leguminosarum improved N2 fixation, while also decreasing the plant's oxidative stress, and provided the plant with a greater defense system against eCO2 conditions. In conclusion, the nodulation with rhizobia potentially replaced the chemical fertilization of bean plants (P. vulgaris L.), resulting in more environmentally friendly agricultural practices. However, further optimization of symbiotic activities is needed to improve the efficiency and to also develop strategies to improve the response of legume yields to eCO2, particularly due to the climate change scenario in which there is predicted to be a large increase in the atmospheric CO2 concentration. [ABSTRACT FROM AUTHOR]

In India, 700 million tons of agricultural waste generated annually is burned by farmers in the fields, which decreases biological activity in soil. The issue of handling the enormous amounts of crop residues that emerge from increased crop output might be resolved by composting. However, different crop residues improve soil physico-chemical and biological properties in different ways. Crop residue incorporation and fertilization (NPK) impact crop productivity due to changes in soil microbial biomass carbon, nitrogen, phosphorous, and the soil enzymatic activity. A field experiment was conducted for two years (2020–2021 and 2021–2022), which comprises five partially composted crop residues treatments viz., control, clusterbean straw, groundnut shell, pearlmillet husk, and sesame stover (added at rate of 5 t ha−1), and four fertilization (NPK) treatments viz., control, 75% RDF, 100% RDF, and 125% RDF. The microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), microbial biomass phosphorus (MBP), enzymatic activities in soil and wheat yield were studied under a semi-arid environment (India). Data showed that the continuous application of crop residues and fertilizer significantly affected MBC, MBN, MBP, and soil enzymatic activity after two years of experimentation in a semi-arid region environment. The highest levels of microbial biomass (viz, MBC, MBN, MBP) and enzyme activities were noticed in the sesame stover and 125% recommended dose of fertilizer (RDF) treatments. Therefore, this study highlights the need for restoring crop residue for effective soil management. The crop residue and NPK fertilization are more efficient in improving the soil's microbial properties and the yield of wheat. [ABSTRACT FROM AUTHOR]

Domesticated rice Oryza sativa L. is a major staple food worldwide, and the cereal most sensitive to salinity. It originated from the wild ancestor Oryza rufipogon Griff., which was reported to possess superior salinity tolerance. Here, we examined the morpho-physiological responses to salinity stress (80 mM NaCl for 7 days) in seedlings of an O. rufipogon accession and two Italian O. sativa genotypes, Baldo (mildly tolerant) and Vialone Nano (sensitive). Under salt treatment, O. rufipogon showed the highest percentage of plants with no to moderate stress symptoms, displaying an unchanged shoot/root biomass ratio, the highest Na+ accumulation in roots, the lowest root and leaf Na+/K+ ratio, and highest leaf relative water content, leading to a better preservation of the plant architecture, ion homeostasis, and water status. Moreover, O. rufipogon preserved the overall leaf carbon to nitrogen balance and photosynthetic apparatus integrity. Conversely, Vialone Nano showed the lowest percentage of plants surviving after treatment, and displayed a higher reduction in the growth of shoots rather than roots, with leaves compromised in water and ionic balance, negatively affecting the photosynthetic performance (lowest performance index by JIP-test) and apparatus integrity. Baldo showed intermediate salt tolerance. Being O. rufipogon interfertile with O. sativa, it resulted a good candidate for pre-breeding towards salt-tolerant lines.

Introduction: The decomposition of plant litter mass is responsible for substantial carbon fluxes and remains a key process regulating nutrient cycling in natural and managed ecosystems. Litter decomposition has been addressed in agricultural monoculture systems, but not in intercropping systems, which produce species-diverse litter mass mixtures. The aim here is to quantify how straw type, the soil environment and their combined effects may influence straw decomposition in widely practiced maize/legume intercropping systems. Methods: Three decomposition experiments were conducted over 341 days within a long-term intercropping field experiment which included two nitrogen (N) addition levels (i.e. no-N and N-addition) and five cropping systems (maize, soybean and peanut monocultures and maize/soybean and maize/peanut intercropping). Experiment I was used to quantify litter quality effects on decomposition; five types of straw (maize, soybean, peanut, maize-soybean and maize-peanut) from two N treatments decomposed in the same maize plot. Experiment II addressed soil environment effects on root decomposition; soybean straw decomposed in different plots (five cropping systems and two N levels). Experiment III addressed 'home' decomposition effects whereby litter mass (straw) was remained to decompose in the plot of origin. The contribution of litter and soil effects to the home-field advantages was compared between experiment III ('home' plot) and I-II ('away' plot). Results and discussions: Straw type affected litter mass loss in the same soil environment (experiment I) and the mass loss values of maize, soybean, peanut, maize-soybean, and maize-peanut straw were 59, 77, 87, 76, and 78%, respectively. Straw type also affected decomposition in the 'home' plot environment (experiment III), with mass loss values of maize, soybean, peanut, maize-soybean and maize-peanut straw of 66, 74, 80, 72, and 76%, respectively. Cropping system did not affect the mass loss of soybean straw (experiment II). Nitrogen-addition significantly increased straw mass loss in experiment III. Decomposition of maize-peanut straw mixtures was enhanced more by 'homefield advantage' effects than that of maize-soybean straw mixtures. There was a synergistic mixing effect of maize-peanut and maize-soybean straw mixture decomposition in both 'home' (experiment III) and 'away' plots (experiment I). Maize-peanut showed greater synergistic effects than maize-soybean in straw mixture decomposition in their 'home' plot (experiment III). These findings are discussed in terms of their important implications for the management of species-diverse straw in food-production intercropping systems. [ABSTRACT FROM AUTHOR]

Yeasts are considered potential lipid producers to substitute oil-producing plants. Previous study succeeded in isolating Zygosaccharomyces siamensis AP1 from Indonesia which was able to accumulate 19% lipid. The strain, however, was not optimized for high cell density growth which is required for industry-level. In this study, efforts were made to increase cell density and lipid production of Z. siamensis AP1 using molasses as carbon source and implementing sequencing batch method. The yeast was grown in various combinations of carbon and nitrogen sources. The C:N ratio of the best substrate combination is then optimized. Afterwards, batch and sequencing batch methods were applied in fermentation with various concentrations (20–480 g/L) of molasses. The results show that lipid produced using molasses was slightly higher compared to using glucose, 0.21 g/L and 0.19 g/L respectively, with the same nitrogen source. Combination of molasses and ammonium sulfate with C:N ratio 70:1 gave the highest lipid (0.28 g/L). Sequencing batch able to increase cell density 2.4-fold compared to batch method. This study was the first to report that sequencing batch application with molasses as carbon source can increase lipid production from Z. siamensis. Further study to optimize medium composition for sequencing batch is suggested. [ABSTRACT FROM AUTHOR]

Plant functional traits play important roles in determining plant responses to environmental change and further shaping community composition, but the role of plant stoichiometry remains poorly understood in regulating community responses to continually increased nitrogen (N) deposition.In this paper, we used a 5‐year manipulative experiment with six N addition rates (Nrate) to explore how the N response of different plant functional groups including forbs, grasses, sedges and legumes links to above‐ground plant carbon‐to‐N ratio (C:N, related to N use strategies) in an alpine meadow.We found that plant C:N explained 45.8% and 42.6% of N response variation among functional groups in plant above‐ground net primary productivity (ANPP) and abundance. Over increasing Nrate, functional groups with higher C:N (grasses and sedges) tended to grow better and have greater abundance, yet those with lower C:N (forbs and legumes) were at risk of loss, subsequently mitigating the N‐caused decline in community‐level plant C:N. This was mainly due to that functional groups with higher C:N not only possessed higher N use efficiency but also had greater competitiveness for above‐ground light due to higher plant height. In addition, we also found that plant C:N differences among functional groups remained relatively constant over Nrate, suggesting that the ability of this trait to indicate functional group‐specific N responses was stable.Synthesis. Our results show that the N responses of different herbaceous plants can be well explained by plant C:N. Thus, we suggest the prediction of plant community composition changes under N deposition would be greatly improved by considering this easily measured stoichiometric trait. [ABSTRACT FROM AUTHOR]

Biofloc culture system is an eco-friendly method, because it limits the water usage and effluent discharge to the surrounding environment. The present study aimed to investigate immune potential, growth, and survival of Indian white shrimp Penaeus indicus, post larvae in the biofloc technology (BFT) with C:N ratio of 15:1 during nursery phase in different salinities (5‰, 15‰, 25‰, 30‰, and 35‰). Experiments were conducted in triplicate in 100-L-reinforced fiber plastic (FRP) tanks, and P. indicus (post larvae 10) were stocked at the density of 120 numbers/tank (1.2post larvae/L). The total suspended solid (TSS) level in each biofloc group was maintained at 200–300 mg/L. The results showed that the final biomass and survival in each treatment were significantly higher in biofloc-reared shrimps when compared to clear water culture (p < 0.05). Among the salinity and BFT treatments, shrimps reared in 15‰ with BFT condition showed better growth and survival than other treatments and achieved a significantly higher final body weight (1.67 g ± 0.067 g). Net shrimp production in terms of growth and survival was 50% higher in the BFT tanks (average body weight = 0.85 ± 0.082 g to 1.67 ± 067 g) than in the control tanks (ABW = 0.61 ± 0.07 g to 0.98 ± 0.07 g). The final survival observed in different biofloc system with varying salinity was significantly higher than respective clear water (CW) system. Total serum protein showed significantly higher levels (120.32 ± 3.68 mg/ml) in 15‰ with BFT treatments than the other. The 15‰ with BFT (0.14 ± 0.011OD/min) and 5‰ with BFT showed more pro-phenol oxidase levels (0.11 ± 0.009 OD/min) of activity than other treatments. Total haemocyte count (THC) was calculated and the highest value of 6.33 ± 0.33 × 106 showed in 15‰ BFT. In conclusion, the lower salinity rearing with biofloc did not show significantly lower growth than optimum range of salinity in case of Penaeus indicus post larvae. [ABSTRACT FROM AUTHOR]

Nitrate (NO3−) leaching losses from lysimeters on a dairy farm were measured using an automated monitoring system designed to reduce labour and analysis costs. Nitrate leaching losses were measured under two soil types on farm (moderately deep and moderately shallow, stony silt loam) and under both urine patches and non-urine areas. The moderately deep soil leached significantly less NO3−-N than the relatively shallow soil in the 2016–17, 2017–18 and 2019–20 seasons. The NO3−-N leaching losses, under urine patches, were higher in autumn (168.5–190.1 kg NO3−-N ha−1) than in spring (3.7–4.9 kg NO3−-N ha−1) and summer (28.2–35.1 kg NO3−-N ha−1). Paddock scale NO3− leaching losses were calculated using a semi-empirical model. The calculated NO3−-N leaching losses ranged from 18.3 to 47.3 kg NO3−-N ha−1 year−1, with a mean loss of 30.7 kg NO3−-N ha−1 year−1. These relatively low leaching losses from free-draining dairy pasture soils may be due to the recent conversion from forestry to dairy, with the soil having a high soil C:N ratio that may have caused increased immobilisation and subsequently lower NO3−-N leaching loss. [ABSTRACT FROM AUTHOR]

Background: Organic vegetable production has a demand for alternative fertilizers to replace fertilizers from sources that are not organic, that is, typically animal‐based ones from conventional farming. Aims: The aim of this study was to develop production strategies of plant‐based fertilizers to maximize cumulative nitrogen (N) production (equal to N yield by green manure crops), while maintaining a low carbon‐to‐nitrogen (C:N) ratio, and to test the fertilizer value in organic vegetable production. Methods: The plant‐based fertilizers consisted of the perennial green manure crops—alfalfa, white clover, red clover, and a mixture of red clover and ryegrass—and the annual green‐manure crops—broad bean, lupine, and pea. The crops were cut several times at different developmental stages. The harvested crops were used fresh or pelleted as fertilizers for field‐grown white cabbage and leek. The fertilizer value was tested with respect to biomass, N offtake, N recovery, and soil mineral N (Nmin). Poultry manure and an unfertilized treatment were used as controls. Results: The cumulative N production of the perennial green manure crops ranged from 300 to 640 kg N ha–1 year–1 when cut two to five times. The highest productions occurred at early and intermediate developmental stages, when cut three to four times. Annual green manure crops produced 110–320 kg N ha–1 year–1, since repeated cutting was restricted. The C:N ratio of the green manure crops was 8.5–20.5, and increased with developmental stage. The fertilizer value of green manure, as measured in white cabbage and leek, was comparable to animal‐based manure on the condition that the C:N ratio was low (<18). N recovery was 20%–49% for green manure and 29%–42% for poultry manure. A positive correlation was detected between soil Nmin and vegetable N offtake shortly after incorporating the green manure crops, indicating synchrony between N release and crop demand. Conclusions: Plant‐based fertilizers represent highly productive and efficient fertilizers that can substitute conventional animal‐based fertilizers in organic vegetable production. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate the potential nitrogen (N) mineralization of contrasting soils after the addition of different sunflower seed hulls (CG) (Helianthus annuus L.) doses, an abundant residue of the southwest of Buenos Aires Province (SOB). Long-term aerobic incubations (37 weeks) were performed, using three different soils (0-20 cm) and various CG levels based on their organic N content: 100 (D1), 200 (D2) and 400 (D3) kg N ha-1. Soils differs in granulometric fractions (S1: sand 509 g kg-1; silt 320 g kg-1 and clay 171 g kg-1; S2: sand 351 g kg-1; silt 448 g kg-1 and clay 201 g kg-1; S3: sand 827 g kg-1, silt 107 g kg-1 and clay 66 g kg-1). The CG chemical characteristics: electrical conductivity= 1.6 dS m-1; pH= 5.6; organic matter (MO) = 958 g kg-1; total N= 7.8 g kg-1, C:N ratio = 79. Significant differences were found in potentially mineralizable N (N0) for three soils, whose values were S1>S2>S3; as well as in the mineralization rate (k) (S1 and S3= 0.0036 week-1, S2=0.0056 week-1). Significant interaction was found with the CG contribution and soils, so the contribution was analyzed for each soil. When GC was applied, a positive response was observed on S3 with D1 and D2. For S1 and S2, the application of GC did not increase the potential for N mineralization, however, it had not a detrimental effect on the potential. Dynamics of accumulated N mineralization showed different effects of CG addition with respect to soil type. The CG addition to soil increased the potential N mineralization in the sandy-loam soil, without reducing the potential in the remaining soils, which is why it could be used as an organic amendment under these conditions. [ABSTRACT FROM AUTHOR]

Although most studies have indicated that biochar can boost rice (Oryza sativa) growth, the material may also suppress it, depending on ratios of carbon (C) to nitrogen (N) and available N to available phosphorous (P). The current study sought to examine the impacts of biochar on rice growth and to identify underlying mechanisms. A pot experiment was conducted using two soils of high (3.05%) and low (0.54%) organic carbon (OC) content, mixed with 0, 1.5, 3, 6, and 12% biochar and planted with rice. Rice growth components, five rice tissue nutrients, and nine soil properties were measured. The results showed that the response of rice growth to biochar rates could be described using an exponential‐growth function in high‐OC soil but an inverted U‐shaped curve in low‐OC soil. In high‐OC soil, the 12% biochar rate led to the greatest total biomass, increased by 47%, whereas in low‐OC soil, the 3 and 6% rates exhibited the highest total biomass, increased by 44%, compared to the no‐biochar added soils. Biochar elevated the C:N ratio from 11.5 to 39.1, with an optimal range of 20–30 corresponding to the highest rice growth. Biochar declined the ratio of NH4‐N to Mehlich‐1 P, causing N deficiency. In brief, high biochar rates may suppress rice growth when the soil C:N ratio exceeds 30. The applied biochar rate should be considered based on soil properties typically OC and N content to obtain the C:N ratio between 20 and 30 for optimal rice growth. [ABSTRACT FROM AUTHOR]

Research on mitigating the effects of water scarcity by applying silicon to perennial grasses is still insufficient. This study was conducted to investigate the effect of spring and summer droughts and silicon applications on gas exchange parameters; the morphometric characteristics of root systems; and the biomass distribution of Festulolium braunii, Festuca arundinacea, and Lolium perenne cultivars. Plants were treated with a drought during the tillering phase once a year (during spring or summer regrowth) for 21 days. Foliar nutrition with silicon was applied twice under the drought conditions. Grasses in a pot experiment were cut three times during vegetation. The plants that were exposed to the drought had lower values of the gas exchange parameters than those that were well watered. The beneficial effect of silicon was related to the reduction of excessive water loss through transpiration during the spring drought. Under the drought and silicon applications, the water use efficiency, root dry mass, and length increased compared to the control. Moreover, silicon increased the proportion of both the finer and thicker roots in F. braunii and L. perenne, while the distribution of the root diameter changed least in the more resistant F. arundinacea. Silicon also reduced the carbon content in the roots and increased root carbon accumulation. Our results indicated that Si may help perennial forage grasses cope better with drought stress. This was due to the allocation of carbon to the roots to develop the fine root network, increasing the length and root biomass and improving the water use efficiency. [ABSTRACT FROM AUTHOR]

Abstract Background Phaeodactylum tricornutum accumulates lipids while the growth also increases under high CO2, shedding light on its potential application in the reduction of CO2 emissions and at the same time acquiring biodiesel raw materials. However, the sensing and transducing of high C:N signals and the related response mechanism(s) remained unknown. Results In this study, a multiple omics analysis was performed with P. tricornutum under low nitrogen (LN) and high CO2 (HC) conditions. The results indicated that 2-oxoglutarate was significantly increased under both LN and HC. Meanwhile, proteins involved in carbon concentration mechanism decreased, indicated that 2-oxoglutarate might regulate C:N balance through suppressing carbon fixation. Lactate, which acts in energy metabolism, signal transduction and ‘LactoylLys’ modification on proteins, was the most upregulated metabolite under both LN and HC conditions. Meanwhile, proteins involved in carbon, nitrogen and energy metabolisms were significantly regulated. Western blotting analysis suggested that non-histone L-lactylation modification was enhanced under LN and HC. Moreover, lactylated proteins were enriched in photosynthesis, central carbon metabolism, nitrogen metabolism, fatty acid synthesis and oxidative phosphorylation. Conclusion It is suggested that lactate might play important roles in energy homeostatic maintenance and C:N balance regulation in P. tricornutum through protein lactylation modification.

Increasing the soil organic carbon (SOC) content is gaining growing attention nowadays due to its double function of restoring soil fertility and mitigating climate change. This study aims to investigate the effect of different residue management including residue removal, residue incorporation, and residue incorporation + 1 t ha−1 poultry manure, on SOC, soil inorganic carbon (SIC), total soil carbon (TSC), total Kjeldahl nitrogen (TN) and C:N ratio on a long-term experiment located in North-East Italy. After 55 years of residue retention, SOC content increased by ∼12 % in the tilled topsoil and 6 % in the subsoil. Among the 0–60 cm soil profile, this corresponded to a SOC storage of ∼6 t ha−1 that was achieved in response to ∼127 t ha−1 residue-derived C input. Therefore, assuming that C sequestration was linear during the experimentation, an average annual conversion rate from residue-derived C to SOC can be estimated as 4.7 % which is comparable to what is usually reported in the literature. The addition of poultry manure only marginally affected the SOC stock while increasing the 0–30 cm TN stock of 0.5 t TN ha−1, demonstrating how it acts more as a mineral source of N rather than affecting the soil organic matter (OM) dynamics. Any significant effect of treatments was instead found on SIC, TSC, and C:N. Crop residue incorporation increased the SOC stock, but its low conversion efficiency might suggest a different use (e.g., bioenergy production). Despite not improving the OM dynamics, poultry manure can be used as an alternative to mineral fertilizers, reducing fossil fuel consumption and giving new insight into the circular economy. • A long-term experiment starting in 1966 on a silt loam soil was investigated. • Crop residue allowed ∼6 t ha-1 C storage in the 0–60 cm profile. • Residues resulted in a 4.7 % yearly conversion rate into SOC. • The addition of poultry manure only marginally affected the SOC stock. [ABSTRACT FROM AUTHOR]

The West Siberian Plain holds special ecological significance as the largest peatland region of the world, which is expected to be affected by the climate change. We analysed water chemistry, chemical composition of Sphagnum tissues (total C, total N, K, P, and a range of trace elements) and biodiversity (abundance, species richness, community composition) of free-living mites (Oribatida and Mesostigmata) in twelve Sphagnum peatlands along the 1600 km transect (54°46′N to 67°29′N) on the West Siberian Plain. Mites were classified into two functional groups – "limnic" (Oribatida species which inhabit aquatic habitats), and "terrestrial" (all other species). The results showed a latitudinal productivity gradient, with a consistent increase in nutrient content of Sphagnum and water pH from North to South; the northern-most site had lowest N and highest C:N ratio, indicating potential N limitation. There was an increase in levels of Cr, Zn, Ni and Sr in the Sphagnum tissues in proportion to the abundance of lithophile Ti on the southern end of the transect; however, in absolute terms, the concentrations of these elements were low. The abundance patterns of terrestrial and limnic mites reflected increasing nutrient load in Sphagnum bogs from North to South, as well as increasingly xeric conditions. Latitude and nutrients (P and C:N ratio) together explained 67.2 % variability in community composition of Oribatida and Mesostigmata. We found no effect of latitude or productivity on species richness; the main driver for species richness appeared to be the local micro-topography, with dryer areas colonised by a wider range of species. Our data help to elucidate landscape-scale patterns of productivity and biodiversity in West Siberian peatlands and provide a checkpoint in the timeline of global change. As sensitive intrazonal ecosystems, peatlands can act as useful early warning systems, offering insights about the effects of human activities on a large scale. [Display omitted] • Latitude and productivity in Sphagnum bogs are linked, with nutrients and water pH increasing North to South • Trace elements were low but Cr increased North to South and southern sites enriched in Zn, Ni and Sr • Terrestrial mites increase North to South; their species richness linked not with latitude but with micro-topography • Limnic Oribatida decrease North to South as conditions increasingly xeric; locally their abundance linked with higher P [ABSTRACT FROM AUTHOR]