Nitrogen Fractions Research Articles

Effect of long term conservation agriculture and nitrogen management on soil nitrogen, phosphorus and sulfur fractions under maize–wheat–mungbean cropping system

Conservation agriculture (CA) covers nearly 3.5 mha in Indian. And there is lack of studies on the CA effects soil nutrient dynamics. So, this study examines the effects of nine years of conservation agriculture on soil nitrogen (N), phosphorus (P), and sulfur (S) fractions in an Inceptisol under maize–wheat–mungbean cropping system. Different tillage and nitrogen management practices were evaluated to understand how nutrient management in CA, contrasts with conventional methods. The CA practices and N fertilizer addition significantly enhanced the soil mineral N, alkali-permanganate N, potentially mineralizable N and microbial biomass N. The CA and N fertilization enhanced soluble and loosely bound P by dissolving the iron-bound, aluminum-bound, reductant soluble and calcium-bound P. All the soil S fractions i.e. available S, total water-soluble S, heat soluble S, sodium bicarbonate extractable S, inorganic sulfur, organic sulfur and total sulfur was positively affected by CA and N fertilization practices over conventional tillage and control plots, respectively. It is important to note that the green seeker-based N management options especially with urea super granules showed tendency in enhancing the available nutrient pools of N, P and S compared to recommended dose of N (RDN) applied and control plots indicating that in due course of time it may reduce the amount of RDN without hindering any soil nutrient dynamics. These findings contribute crucial knowledge for sustainable development by offering valuable perspectives on N, P and S management strategies.

Regulation of wheat yield by soil multifunctionality and metagenomic-based microbial degradation potentials under crop rotations

Crop rotation benefits soil fertility and crop yield by providing organic components including cellulose, lignin, chitin, and glucans that are mainly degraded by soil microbial carbohydrate-active enzymes (CAZymes). However, the impacts of crop rotation on soil microbial CAZyme genes are not well understood. Hence, CAZyme genes and families involved in the degradation of differentially originated organic components were investigated using metagenomics among distinct crop rotations. Crop rotation had a more significant effect on soil nitrogen than on carbon fractions with higher content in the complex rotation referring to alfalfa (Medicago sativa L.; 4 year)-potato (Solanum tuberosum L.; 1 year)-winter wheat (3 year; A4PoW3). The composition of soil microbial CAZyme genes related to the degradation of fungi-derived components was more affected by crop rotation compared with the degradation of plant- and bacteria-derived components. The total abundance of CAZyme genes and families was significantly higher in the complex rotation. Notably, CAZyme genes belonging to glycoside hydrolase and glycosyl transferase families had more connections in their network. Moreover, key genes including CE4, GH20, and GH23 assembled toward the middle of the network, and were significantly regulated by dominant soil nitrogen fractions including soil potential nitrogen mineralization and microbial biomass nitrogen. Soil multifunctionality was mostly explained by the composition and total abundance of CAZyme genes, but wheat grain yield was profoundly regulated by fungi-derived components degradation genes under effects of dominant nitrogen fractions. Overall, the findings provide deep insight into the degradation potentials of soil microbial CAZyme genes for developing sustainable crop rotational agroecosystems.

Leaf nutrient basis for the differentiation of photosynthetic traits between subtropical evergreen and deciduous trees.

Compared to evergreens, deciduous tree species usually have higher photosynthetic efficiency to complete vegetative and reproductive growth in a shorter growing season. However, the nutrient basis for the differentiation of photosynthesis functional traits between evergreen and deciduous tree species has not yet been clarified. Thirty evergreen and twenty deciduous angiosperm tree species from a subtropical common garden were compared in terms of photosynthetic traits and leaf nutrients. Generally, their differences in area-based photosynthetic capacity were uncorrelated with area-based leaf nutrient content but were caused by the fraction of nitrogen allocated to photosynthetic components. By comparison, the differences in mass-based photosynthetic capacity were more correlated with leaf nitrogen content than leaf phosphorus and potassium content. Convergence in phosphorus and potassium constraints to photosynthesis occurred in deciduous tree species but not in evergreen tree species. Furthermore, leaf C/N ratio played a more significant role than leaf mass per area in determining the differentiation of photosynthetic traits between evergreen and deciduous groups. Our findings provide insight into the nutrient basis for photosynthetic carbon gain and functional strategies across trees species.

Effects of Cover Measures on Soil Organic Nitrogen Fractions and Total Soluble Nitrogen Pools in Citrus Orchards of the Red Soil Hilly Region of Southern China

Effects of Cover Measures on Soil Organic Nitrogen Fractions and Total Soluble Nitrogen Pools in Citrus Orchards of the Red Soil Hilly Region of Southern China

Qualitative indicators of milk and fermented milk products when activated zeolite and probiotics are included in the diet of cows

Relevance. The quality of milk depends on the season of the year, the breed of animals, the state of metabolism, and the characteristics of feeding and maintenance technology. The quality of milk determines its technological properties and the quality of its processed products.Methods. The content of somatic cells in milk, the acidity of milk, cottage cheese, yogurt, and syneresis of yogurt were determined. In milk processing products, the content of the mass fraction of nitrogen and crude protein, crude ash, calcium, and phosphorus was determined.Results. When feeding cows with the yeast probiotic activated zeolite and the phytoprobiotic “Provitol”, a significant decrease in the content of somatic cells in freshly milked milk of cows was established by 13.02% (p < 0.05). Significantly lower milk acidity values were established (by 6.00% (p < 0.001) and 12.79% (p < 0.001), respectively), significantly higher yogurt acidity values (by 6.00% (p < 0.001) and 12.79% (p < 0.001), respectively, significantly lower yogurt syneresis (by 4.70% (p < 0.001) and 3.10% (p < 0.01), respectively). The use of activated zeolite and yeast probiotic “Kluver Pro” in the diets leads to a significantly higher content (compared with the control) of the mass fraction of fat in cottage cheese and yogurt — by 10.47 abs. % (p < 0.001) and 4.58 abs. % (p < 0.001).

Effect of 67-years of manuring, fertilization and amendments on fractions of soil organic carbon, nutrient dynamics and yield sustainability in an acidic Alfisol

Amending a problem soil in addition to nutrient input is crucial for maintaining a healthy and productive soil in the long run. The study aimed at evaluating the long-term impact of manuring and fertilization with or without liming on different soil attributes and crop yield in an acidic Alfisol. Surface soil samples (0–15 cm) were collected from selected 7 treatments, viz. Control; N; FYM; ½(N+FYM)+PX/2+KY/2; NPK; NPK+L; and P(A-X)K(B-Y)+FYM+L of the Permanent Manurial Trial (PMT) of Birsa Agricultural University, Ranchi, after the harvesting of rainy (kharif) maize (Zea mays L.) at the 67th crop cycle (2023 and 2024) and assessed for various fractions of soil organic carbon (SOC), available nutrients and yield attributes. The experiment was laid out in a randomized block design (RBD) and replicated thrice. The treatments which received manures either alone or in combination with chemical fertilizers recorded significantly higher amount of all the fractions of SOC, available nitrogen and lower bulk density as compare to the unfertilized plot or treatment with inorganic alone. The study also revealed that, addition of lime helped maintaining an optimum pH level, enhanced microbial activities and nutrient availability in the soil leading to a higher crop yield. Therefore, integrated use of manures and fertilizers in addition to lime for a prolonged period would have significant positive impact on soil health and sustaining its productivity.

Effects of manure and nitrogen fertilization on soil microbial carbon fixation genes and associated communities in the Loess Plateau of China

The effects of long-term fertilization on soil carbon (C) cycling have been a key focus of agricultural sustainable development research. However, the influences of different fertilization treatments on soil microbial C fixation profiles are still unclear. Metagenomics technology and multivariate analysis were employed to inquire changes in soil properties, soil microbial C fixation genes and associated bacterial communities, and the influence of dominant soil properties on C fixation genes. The contents of soil C and nitrogen fractions were signicficantly higher in manure or combined with nitrogen fertilization (NM) than other treatments. The composition of soil microbial C fixation genes and associated bacterial communities varied among different fertilization treatments. Compared with other treatments, the total abundance of microbial C fixation genes and the abundance of Proteobacteria were significantly higher in NM than in other treatments, as well as the abundances of C fixation genes involved in dicarboxylate/4-hydroxybutyrate cycle and reductive citrate cycle. Key functional genes and main bacterial communities presented in the middle of the co-occurrence network. Soil organic carbon, total nitrogen, and microbial biomass nitrogen were the dominant soil properties influencing microbial C fixation genes and associated bacterial communitis. Fertilization increased the abundance of C fixation genes by affecting the changes in bacterial communities abundance mediated by soil properties. Overall, elucidating the responses of soil microbial C fixation genes and associated communities to different fertilization will enhance our understanding of the processes of soil C fixation in farmland.

Rice straw biochar and NPK minerals for sustainable crop production in arid soils: a case study on maize-wheat cropping system

Maize and wheat are the main cereals grown in Egypt. However, the country relies on grain imports to meet its local demands. In order to improve their production, appropriate fertilization programs are needed. The present study investigates the effects of amending a clayey soil of an arid region with rice straw biochar and NPK mineral fertilizers, individually or in combination, for increasing growth and productivity of maize and wheat crops. Additionally, impacts of these additives on soil biological activities and carbon (C) transformations in soil were a matter of concern herein. To achieve this objective, a field research of a randomized block design was conducted during the summer (maize) and winter (wheat) seasons of 2020/2021. The following treatments were considered: unmodified control (CK), 100% N inputs in the form of biochar (reference organic treatment, RSB) (T1), 100% mineral treatment (reference inorganic treatment, T2), 75% RSB + 25% NPK minerals (T3), 50% RSB + 50% NPK minerals (T4) and 25% RSB + 75% NPK minerals (T5). Additional doses of mineral fertilizers were added to treatments from T3 to T5 to maintain NPK inputs within the recommended doses. Key results showed that all additives significantly enhanced plant growth parameters and productivity. They also increased soil organic carbon level by the end of the growing season hence reduced soil bulk density, even for the treatment that received only mineral NPK applications (T2). All additives also upraised soil cation exchange capacity (CEC), soil available nitrogen (N), and soil salinity. However, sole application of biochar recorded the least increase in soil salinity. Combined mineral-organic treatments not only recorded the highest increases in soluble and microbial fractions of organic carbon and nitrogen in soil; but also noted the greatest improvements in growth and grain productivity of maize and wheat versus sole applications of mineral fertilizers or biochar. The alkaline nature of biochar was buffered by soil while no significant differences were observed in harvest index among treatments. In conclusion, combined use of biochar and mineral fertilizers, especially T5 is recommended for increasing soil fertility and wheat and maize grain productvity.

Soil profile distribution of organic, inorganic, and labile carbon and nitrogen fractions vary in semi‐arid drylands under long‐term conservation tillage systems

AbstractChanges in soil carbon (C) and nutrients considerably influence soil health and agricultural sustainability. However, how agricultural management affects C and N allocation among various soil organic matter pools and their linkages with soil health are not clear for arid and semi‐arid regions. This study aimed to evaluate the soil profile distribution of selected C and N fractions and associated soil health properties in conventional tillage (CT), no‐tillage (NT), and strip tillage (ST) fields and quantify the relationship of labile and inorganic C and N fractions to soil organic carbon (SOC) sequestration in semi‐arid dryland cropping systems. Crop rotation was a 4‐year cycle of corn (Zea mays L.)—sorghum (Sorghum bicolor L. Moench)—winter wheat (Triticum aestivum L.)—fallow across all tillage systems. Soil samples were collected from 0–20, 20–40, and 40–60 cm depths of each plot in July 2022, after 9 years of plot establishment, and analysed for potentially mineralizable carbon (PMC), microbial biomass carbon (MBC), SOC, soil inorganic (SIC), soil total carbon (STC), soil inorganic nitrogen (SIN), total labile nitrogen (TLN), total organic nitrogen (SON), and labile organic nitrogen (LON) and other soil health indicators. The results indicate that PMC was 31% more and LON was 23% more in NT than in CT, whilst ST resulted in lower pH and had only 10%, 9%, and 24% more SON, STN, and LON, respectively, than CT in 0–60 cm profile. The SIC stock was negatively correlated with MBC, PMC, SON, STN, LON, TLN, and SIN, whilst positively correlated with depth, STC, and pH. After 9 years of conservation tillage, whilst depth‐wise distribution varied among tillage systems, soil C sequestration rate was negative in the 0–60 cm profile under both NT and ST compared with CT, mainly owing to more SIC accumulation in deeper depth of conventional system. These results show the complexity of soil C and N allocation under different tillage systems, with NT and ST supporting greater C and N storage in the surface soil and CT supporting more C and N storage in the deeper depth. Soil biological activity indicators appear to drive surface SOC accumulation, whilst soil pH and N availability influenced SIC accumulation in lower depths.

TECHNOLOGICAL SOLUTION FOR COMBATING HYDROGEN SULFIDE AT THE FIELD

One of the urgent problems in the production of hydrogen sulfide-containing oils is the problem of increasing the efficiency of hydrogen sulfide removal. Optimization of costs associated with the production, transportation and preparation of oil is very important at the present time. In order to reduce the costs of oil preparation, the use of a differentiated approach to solving the problem of its purification from hydrogen sulfide at the Kashagan field depends on the volumes of oil preparation, the mass fraction of hydrogen sulfide in the oil, the presence of gas near the high-sulfur oil preparation unit (UPVSN) that does not contain hydrogen sulfide, the presence of a gas collection system and the possibility of transporting increased volumes of hydrogen sulfide-containing gas to the sulfur purification unit. Taking these factors into account, it is necessary to identify the maximum values ​​​​of the volume fractions of methane, ethane, nitrogen and carbon dioxide in the composition of the stripping gas, at which the mass of oil will be preserved, as well as the conditions under which it will be purified from hydrogen sulfide in the conditions of the Kashagan field. Studies have shown that with an increase in the oil heating temperature and a decrease in the pressure in the desorption column, the maximum total volume fraction of methane and nitrogen in the mixture in the composition of the stripping gas decreases. A decrease in the mass fraction of hydrogen sulfide in oil below 100 ppm and maintaining the mass yield of oil depending on the proportion of these components in the composition of the stripping gas is possible if the oil temperature and pressure in the column are optimized. An increase in the total volume fraction of methane and nitrogen in the composition of the stripping gas leads to a decrease in its required consumption to achieve a certain efficiency of oil purification from hydrogen sulfide at specified operating parameters of the column.

The use of protein hydrolysate from fish waste as part of microbiological culture media

The need to involve in the processing of significant amount of secondary protein-containing raw materials formed during fish cutting, on the one hand, and on the other hand, the shortage of a source of the protein component of microbiological nutrient media determines the relevance of the work. The goal was to study the possibility of using fish protein hydrolyzate obtained by enzymatic hydrolysis from secondary fish raw materials in microbiological nutrient media. Microbiological and physicochemical methods were used to conduct research. When optimizing the developed algorithm for the fermentation process, a mathematical model of the experiment was used with a minimum number of experiments. An algorithm has been developed for obtaining fish protein hydrolyzate from meat and bone waste from cutting pelagic fish (cod). The hydrolysis parameters were optimized: the concentration of the enzyme preparation is 1.33 % of the total mass of waste, the duration of the fermentation process – 3 hours. The characteristics of the resulting fish hydrolyzate are determined: the mass fraction of total nitrogen – 13 %, amine – 3.6 %, water – 4.6 %, sodium chloride – 2.7 %, fat – 0.3 %. An experimental fish hydrolyzate has been studied as a source of protein nitrogen in accordance with the formulation of a microbiological medium used for counting when growing colonies of microorganisms. The effectiveness of the prepared nutrient media was assessed by comparing the performance coefficients of the experimental and control nutrient media, as well as by identifying test microorganisms grown on the experimental medium. It was established that the growth pattern of test cultures both on the studied nutrient medium and on the control medium was almost the same. Test microorganisms retained their biochemical, morphological and cultural characteristics. The research results showed the possibility of using fish protein hydrolyzate obtained by enzymatic hydrolysis from secondary fish raw materials in microbiological nutrient media.

Blood Urea Nitrogen to Left Ventricular Ejection Ratio as a Predictor of Short-Term Outcome in Acute Myocardial Infarction Complicated by Cardiogenic Shock

Introduction: Cardiogenic shock (CS) is the most critical complication after acute myocardial infarction (AMI) with mortality above 50%. Both blood urea nitrogen and left ventricular ejection fraction were important prognostic indicators. We aimed to evaluate the prognostic value of admission blood urea nitrogen to left ventricular ejection fraction ratio (BUNLVEFr) in patients with AMI complicated by CS (AMI-CS). Methods: 268 consecutive patients with AMI-CS were divided into two groups according to the admission BUNLVEFr cut-off value determined by Youden index. The primary endpoint was 30-day all-cause mortality and the secondary endpoint was the composite events of major adverse cardiovascular events (MACEs). Cox proportional hazard models were performed to analyze the association of BUNLVEFr with the outcome. Results: The optimal cut-off value of BUNLVEFr is 16.63. The 30-day all-cause mortality and MACEs in patients with BUNLVEFr≥16.63 was significantly higher than in patients with BUNLVEFr<16.63 (30-day all-cause mortality: 66.2% vs. 17.1%, p < 0.001; 30-day MACEs: 80.0% vs. 48.0%, p < 0.001). After multivariable adjustment, BUNLVEFr≥16.63 remained an independent predictor for higher risk of 30-day all-cause mortality (HR = 3.553, 95% CI: 2.125–5.941, p < 0.001) and MACEs (HR = 2.026, 95% CI: 1.456–2.820, p < 0.001). Subgroup analyses found that the effect of BUNLVEFr was consistent in different subgroups (all p-interaction>0.05). Conclusion: The admission BUNLVEFr provided important prognostic information for AMI-CS patients.

Dynamic Changes of Soil Nitrogen Fractions at Aggregate Scales in a Chronosequence of Chinese Fir Plantations

Dynamic Changes of Soil Nitrogen Fractions at Aggregate Scales in a Chronosequence of Chinese Fir Plantations

Distribution of the electrical resistivity of a n-type 4H-SiC crystal

Nitrogen is commonly doped to obtain n-type 4H-SiC crystals, which have been commercialized for the development of power electronics in recent years. Now the uniformity of electrical resistivity becomes an important issue for the growth of n-type 4H-SiC crystals. In this work, the effects of the radial thermal gradient and growth facet on the distribution of the electrical resistivity were investigated for a n-type 4H-SiC crystal with a diameter of 150 mm during its physical-vapor-transport growth. It is found that the resistivity at the center of the crystal is low in the early growth stage. As the crystal grows, the growth facet expands, accompanied by a reduction in the resistivity of this facet. The change in the distribution of the resistivity in the crystal is initially governed by the radial thermal gradient and then influenced by the spiral growth mode of the growth facet. In the non-facet region of the crystal step-flow growth occurs, where the doping of nitrogen is primarily affected by the temperature and C/Si ratio. In the facet region, the volume fraction of nitrogen in the mixture of argon and nitrogen input into the growth system mainly governs the doping of nitrogen during the spiral growth. The insights gained in the current work may help the fabrication of n-type 4H-SiC crystals with uniform resistivity.

Carbon and Nitrogen Stocks in Soil under Native Pastures in the Pantanal Wetland Biome, Brazil

The Pantanal has a high diversity of native pastures that provide food for many wild and domestic animals. Pantanal cattle raising is practiced in an extensive grazing-based system that varies according to the flood levels in the area. This study aimed to evaluate the fractions of soil organic matter in areas of native pastures under different uses and to quantify C and N stocks in sandy soils of the Pantanal. Soil samples from three native pastures differentiated by the predominance of Hymenachne amplexicaulis, Axonopus purpusii, and Mesosetum chaseae under different land use systems (continuous grazing and no grazing for five years) were collected and used to quantify the contents of carbon, nitrogen, and humic fractions. The dynamics of SOM are modified in grazed areas of the Pantanal, with influence on C and N, including their stocks. Native pastures of Axonopus purpusii and Hymenachne amplexicaulis showed an increase in organic matter after five years without grazing, while Mesosetum chaseae showed lower soil density and nitrogen levels. The highest C stock was observed in ungrazed areas of H. amplexicaulis (127.41 Mg ha−1 in the 0–40 cm layer). The dynamics of nitrogen in Pantanal pastures are influenced by the type of vegetation and land management, with higher nitrogen content in the surface layer (0–10 cm) and an increasing C/N ratio with soil depth, indicating lower nitrogen availability.

Fractionation of Sediment-Bound Nitrogen: Bioavailability and Contamination Status of the Nutrient in Thrissur Kole Wetlands, Southwest India

ABSTRACT Fractionation of sediment-bound nitrogen (N) in Thrissur Kole wetland was carried out to assess the mobility, bioavailability, and nutrient contamination status. Various N fractions were extracted using KCl equilibrium extraction method, and the concentration of each N fraction was analyzed by spectrophotometric method. Dominance of ammonia during all seasons was due to dissimilatory NO3 − reduction to NH4 + and direct inputs from agriculture fields. Enrichment of urea during post-monsoon (181.78 ± 8.47 ppm) was attributed to fertilizer sources. NO3 −-N deficit at central zone of the study area (monsoon and post-monsoon) was due to the anoxia. Comparatively higher values of NO2 −-N during monsoon (0.07 ± 0.02 ppm) was due to the land run-off, leaching of fertilizers from agriculture fields, and higher rate of denitrification. Elevated content of total N [1819.94 ± 40.20 ppm (pre-monsoon); 3061.62 ± 13.21 ppm (monsoon); 2763.44 ± 9.65 ppm (post-monsoon)] reflected the inputs from in-situ production, agriculture, terrestrial run-off, waste disposal, and guano as well as carcass of birds. Average contribution of bioavailable N to total N was higher (36.16%) indicated the possibility for eutrophication risk during pre-monsoon. Agriculture dominated regions recorded severe contamination and eutrophication risk as indicated by organic pollution index, organic nitrogen index, and phosphorous pollution index.

Modified rapid small-scale fractionation method for quantitatively separating pyrrolic nitrogen compounds, phenols-ketones and carboxylic acids fractions from petroleum

This research outlines a fast and efficient technique for separating the pyrrolic, phenolic-ketonic, and carboxylic acid fractions from oils in a small-scale setting. This approach enables the separation and analysis of neutral nitrogen fractions that contain indoles, carbazoles, and benzocarbazoles, as well as ketonic-phenolic fractions that contain phenols and ketones. The study showcases the potential for accurately measuring petroleum composition. The reliability of the fractions’ concentration results is determined by the mass of the separated fraction, with completely reliable results achievable for masses exceeding 1.4 mg. The fraction’s mass can also be used to evaluate the relative expanded uncertainty of a single separation procedure. As the mass and concentration of the fraction increase, the relative expanded uncertainty of the concentration decreases, and this can be modelled using a power function.

Polarity Switching As a Technique for Enhanced Electrochemical Treatment of Waste Activated Sludge for Nutrient Recovery

Traditionally, fertilizers have been produced with ammonia (which is produced from the Haber-Bosch process) as the main feedstock. The Haber-Bosch process which requires the reaction of atmospheric nitrogen with hydrogen at high temperature and pressure is energy and cost intensive [1]. Only about half fraction of reactive nitrogen in the produced ammonia fertilizers is used by the plants with the rest remaining in the soil as waste [2]. These ‘excess’ nutrients find a way into water bodies and wastewater treatment plants (WWTP) as run-offs and this poses a big threat to the nitrogen balance in the environment. This research aims to recover these nutrients primarily nitrogen and phosphorous to produce a low-cost fertilizer of at least compatible potency as commercial fertilizers.Waste Activated Sludge (WAS), the solids obtained from the primary and secondary clarifiers in WWTPs contain a wide range of organic compounds as well as valuable nutrients such as phosphorus and nitrogen which can account for up to 4% and 9% of dry sludge, respectively [3]. The leachate from landfills can release these nutrients into the environment, raising serious environmental pollution concerns. Therefore, recovering nutrients from WAS presents a significant opportunity towards a nitrogen circular economy.Most of the research in sludge treatment are exclusively focused on improving biological treatment processes like anaerobic digestion and composting which can take anywhere from a month to three months and thermal treatments such as pyrolysis and hydrothermal treatments [4] which are energy intensive and expensive. This work provides a novel approach to recover nutrients at low energy consumption with nickel based electrocatalysts [5].The hypothesis here is that the alkaline medium will help break the floc structure of the sludge to release the proteins and other organic compounds which will then be hydrolyzed by the nickel oxyhydroxide (NiOOH) group formed on the electrode surface by application of a small voltage sufficient to form NiOOH. The NiOOH is consumed quickly on the surface of the electrode by the organic nitrogen present in solution [6]. Hence, alternating the polarity between two identical nickel electrodes will ensure that NiOOH is always present on the electrode surface. The approach square wave potential pulses also enhance the desorption of species and clean the surface of the electrodes, especially when dealing with a complex mixture of organics that can polymerize in the surface of electrodes during the oxidation/reduction process. The effect of frequency of polarity oscillation, electrode surface area, pH and conductivity on nutrient recovery are being studied and results will be reported at the conference. Since sludge treatment accounts for a sizable portion i.e., close to 60% of wastewater treatment plant operational costs [7], WAS nutrient recovery could also provide economic benefits. This research highlights the potential for electrochemical approaches to address environmental concerns, improve resource efficiency and provide a sustainable solution for sludge management. Acknowledgement This work is funded by the National Science Foundation, EEC Division of Engineering Education and Centers, NSF Engineering Research Center for Advancing Sustainable and Distributed Fertilizer production (CASFER), NSF 20-553 Gen-4 Engineering Research Centers award # 2133576. References Appl M. The Haber-Bosch heritage: The ammonia production technology. In 50th Anniversary of the IFA Technical Conference 1997 Sep 25 (Vol. 25). Spain: Seville.Galloway JN, Aber JD, Erisman JW, Seitzinger SP, Howarth RW, Cowling EB, Cosby BJ. The nitrogen cascade. Bioscience. 2003 Apr 1;53(4):341-56.Bi W, Li Y, Hu Y. Recovery of phosphorus and nitrogen from alkaline hydrolysis supernatant of excess sludge by magnesium ammonium phosphate. Bioresource technology. 2014 Aug 1;166:1-8.Wu B, Dai X, Chai X. Critical review on dewatering of sewage sludge: Influential mechanism, conditioning technologies and implications to sludge re-utilizations. Water research. 2020 Aug 1;180:115912. Jafari, M., Botte, G.G. Electrochemical treatment of sewage sludge and pathogen inactivation. Appl. Electrochem. 51, 119–130 (2021). https://doi.org/10.1007/s10800-020-01481-6Wang D, Botte GG. In situ X-ray diffraction study of urea electrolysis on nickel catalysts. ECS Electrochemistry Letters. 2014;3(9):H29.Andreoli CV, Von Sperling M, Fernandes F. Sludge treatment and disposal. IWA publishing; 2007.

Distributions and controlling factors of soil total nitrogen and nitrogen fractions along an altitude gradient in Qinghai-Tibet Plateau

Distributions and controlling factors of soil total nitrogen and nitrogen fractions along an altitude gradient in Qinghai-Tibet Plateau

Organic substitution contrasting direct fertilizer reduction increases wheat productivity, soil quality, microbial diversity and network complexity

Excessive use of chemical fertilizers negatively impacts crop productivity and farmland ecosystem, impeding sustainable agricultural progress. Consequently, there is an immediate need for a chemical fertilizer reduction strategy that ensures crop productivity and improves soil quality and the ecological environment of farmland. This study implemented a three-year (2018–2020) field experiment with two chemical fertilizer reduction methods (direct fertilizer reduction and organic substitution) to investigate their effects on wheat productivity, soil quality, heavy metal pollution risk and microbial characteristics. The results showed that organic substitution treatments (OF1, OF2 and OF3) improved most wheat plant (nutrient uptake and yield and its components) and soil properties (soil nutrients and carbon and nitrogen fractions), leading to increased crop productivity index (CPI, by 9.18 %-16.39 % and 14.14 %-23.36 %) and soil quality index (SQI, by 84.67 %-138.86 % and 104.11 %-175.91 %) compared to conventional fertilization (CF) and direct fertilizer reduction treatments (RF1, RF2 and RF3) in 2019 and 2020. Additionally, organic substitution enhanced the diversity and network complexity of bacterial community, while raising the soil pollution index (SPI, by 9.30 %-12.84 % and 12.20 %-18.49 %) without causing soil heavy metal pollution. Thus, it is recommended to adopt organic fertilizer substitution as the primary chemical fertilizer reduction strategy for wheat production. This approach will ensure crop yield, and improve soil quality and microbial characteristics, but its long-term application requires monitoring changes in soil heavy metals. Overall, this study provides guidelines for implementing scientific fertilization in agricultural practices, thus contributing to the health and sustainability of farmland ecosystems.