Nitrogen Phosphorus Research Articles

Comparative Analysis of Nitrogen Use Efficiency in Boro Rice under Long-term Inorganic and Organic Fertilization Practices

An experiment was conducted during Boro rice in the permanent experimental field of the Department of Soil Science, Bangladesh Agricultural University (BAU), Mymensingh to investigae the long term outcome of manure and fertilizers on the yield and Nitrogen Use Efficiency (NUE) of BRRI dhan29 in floodplain (Subtropical) soil (Aeric Haplaquepts). The experiment was designed in a randomized complete block design with three replications. There were ten treatment combinations viz, control; Nitrogen (N); (Nitrogen Phosphorus) NP; Nitrogen Potassium (NK); Nitrogen Phosphorus Potassium (NPK); Nitrogen Zinc (NZn); Nitrogen Sulphur (NS); Nitrogen Sulphur Zinc (NSZn), Nitrogen Phosphorus Potassium Sulphur Zinc (NPKSZn) and NPK+FYM. The yield contributing characters and yield of BRRI dhan29 significantly increased due to different treatments. Grain and straw yields were highly influenced by the application of nutrients in various combinations. The longest panicle length (25.3 cm), the highest 1000 grain weight (22.7 g), the maximum grain yield (6.29 t ha-1), the highest nitrogen uptake in grain (70.4 kg ha-1) were found for the NPKSZn treatment. Grain yield increased by 24.8%, 85.8%, 40.7%, 68.9%, 29.2%, 33.2%, 107.1%, 28.9% and 78.9% due to N, NP, NK, NPK, NS, NSZn, NPKSZn, NZn and NPK+FYM treatments respectively and the corresponding straw yields attainment by 49.6%, 51.1%, 82.0%, 95.3%, 37.8%, 34.4%, 82.7%, 41.8% and 90.2%. The maximum value of apparent nitrogen use efficiency was obtained with NPKSZn (54.06%) treatment which evidently suggested its resultness for the long term fertilized soil.

Slaughterhouse wastewater remediation using carbonized sawdust followed by textile filtration

Slaughterhouse wastewater (SWW) is considered an industrial wastewater, which seriously harms the environment due to the high concentration of contaminants such as biochemical oxygen demand (BOD), chemical oxygen demand (COD), and total suspended solids (TSS). Additionally, the wastewater from slaughterhouses contains harmful bacteria. This study used a lap-scale model to treat SWW from a local private slaughterhouse. The treatment process involves three stages: adsorption using activated carbon, which is derived from sawdust, followed by sedimentation, and finally, a slow sand filter with a modified layer of woven textile cotton. The first two steps were tested to obtain the ideal operation condition of the treatment system. After the final step of treatment, we evaluated the overall process using a modified slow sand filter (MSSF). We used a Jar test to determine the optimal dosage of activated carbon from sawdust (ACS). The monitored parameters were physicochemical, such as turbidity, total suspended solids (TSS), total dissolved solids (TDS), biochemical oxygen demand (BOD), chemical oxygen demand (COD), total phosphorus (TP), and total nitrogen (TN). The bacteriological examination included both total coliform count (TCC) and fecal coliform count (FCC). The results of the jar test revealed that the optimal ACS dose was 2.0 g/l. After adjusting the contact time and pH levels for the adsorption process, we discovered that the ideal contact time was 100 min and the ideal pH level was 4.0. Finally, we evaluated the entire treatment system by applying the MSSF after the sedimentation process, and found that the removal efficiencies of turbidity, BOD, COD, TSS, TDS, TP, and TN were 97.14, 94.80, 91.80, 98.96, 81.17, 81.12, and 82.50%, respectively. This is in addition to the filter's ability to remove bacteria counts at a rate of up to 98.93 and 99.13% of TCC and FCC, respectively.

Native Gramineae outperform Leguminosae in enhancing ecosystem multifunctionality during semiarid desert steppe restoration

The effects of reseeded native Gramineae and Leguminosae species on the multifunctionality of desert steppe have remained unclear. Therefore, we examined a semiarid desert steppe that was reseeded 5 years earlier with a dominant native Gramineae species, Agropyron mongolicum; a dominant native Leguminosae species, Lespedeza potaninii; and a 1:1 reseeded mixture of A. mongolicum × L. potaninii. We evaluated the changes in plant communities and soil properties and then quantified aboveground ecosystem multifunctionality (AEMF), belowground ecosystem multifunctionality (BEMF), and overall ecosystem multifunctionality (EMF) using an averaging approach. Compared with the native steppe without reseeding, both reseeded A. mongolicum and A. mongolicum × L. potaninii increased fine root volume, plant height, plant cover, aboveground biomass (AGB), belowground biomass (BGB), soil water storage (SWS), soil organic carbon, light fraction organic carbon, labile organic carbon, total nitrogen (TN), nitrate nitrogen, and total phosphorus (P), but decreased soil bulk density. However, reseeded L. potaninii increased coarse root volume, plant height, plant cover, AGB, BGB, and SWS but decreased plant richness, plant diversity, TN, and total P. In addition, reseeded A. mongolicum and A. mongolicum × L. potaninii increased AEMF, BEMF, and overall EMF, but reseeded L. potaninii only increased AEMF. Further analysis indicated that the fine roots played a crucial role in improving individual ecosystem functions and eventually in determining EMF. Therefore, the reseeding of a desert steppe with Gramineae species has greater potential than with Leguminosae species for improving EMF, since Gramineae species have greater fine roots volume than Leguminosae species.

Mathematical model of dissolved microbial products in sewage treatment system

Water is the source of life, but all kinds of water resources in the world are suffering from different degrees of pollution. Water pollution leads to a serious shortage of available fresh water resources, and sewage treatment is the main way to solve water pollution. For the sewage after biological treatment of activated sludge, the organic matter contained in the effluent is mainly the dissolved microbial products (SMPs) produced in the process of microbial metabolism. The composition of SMPs is complex, mainly including macromolecular substances such as protein, polysaccharide, humic acid and DNA and cell fragments. The mathematical model of activated sludge is a quantitative description of the mathematical relationship between substrate degradation parameters and microbial growth. Starting from the Monod equation representing the relationship between substrate consumption and microbial growth, it combines the reactor theory and microbiology theory in the chemical field. Based on the principle of conservation of materials and Monod equation, the mathematical expression of organic degradation model was determined according to the collected data and empirical values of parameters. The general idea of activated sludge model No.1 (ASM1) for activated sludge process simulation was introduced, and the influence of sludge concentration on SBR process water treatment was explored. It was found that the removal rate of COD, ammonia nitrogen, total nitrogen and total phosphorus increases with the increase of sludge concentration. When C/N=8, the removal rate of ammonia nitrogen increased from 62% to 81%, and the removal rate of total nitrogen increased from 64% to 82%, with the most obvious effect.

Changes in Soil Physicochemical Properties and Fungal Communities Following a Forest Fire in the Pine Forest of Uljin, Republic of Korea

Soil samples from the rhizosphere of pine (Pinus densiflora) stands in the fire-disturbed Uljin forest were collected to analyze their physicochemical properties and fungal communities. In the burned area, soil pH decreased by 0.56, and organic matter content decreased by 0.32%p compared to the undisturbed area. Fungal community analysis revealed that all alpha diversity indices decreased in the burned area, but there were no differences according to fire severity. Soil pH, available phosphorus, and total nitrogen showed a positive correlation with the alpha diversity. Additionally, beta diversity analysis also indicated significant differences in the fungal communities between the burned area and the control sites (p value = 0.031). The changes in fungal communities were considered to be influenced by the decline in the order Atheliales, genus Russula, and genus Trechispora. A prediction analysis of the functional traits of fungi showed that the number of fungi involved in nutrient absorption and decomposition decreased in the burned area. It seems that the soil restoration of pine forests is progressing very slowly, as the soil fungi related to nutrient absorption by pine trees have not recovered even 18 months after the forest fire. Therefore, it is necessary to monitor continuous fungal communities in pine forest restoration after a forest fire to determine forest ecosystem restoration success and stabilization.

Straw return can increase maize yield by regulating soil bacteria and improving soil properties in arid and semi-arid areas

Straw return has been found to benefit soil fertility and crop yield, however, by which it affects microbial communities to mediate soil factors driving crop yields under maize continuous cropping systems in dryland areas is still unclear. To fill this gap, a 6-year field experiment was established with five straw return amounts (T0, T1, T2, T3, and T4, representing 0, 3,000, 6,000, 9,000, and 12,000kgha-1 of straw, respectively), and investigated the effects of on soil properties, enzymes, bacterial community composition and diversity, and crop yields. Our analysis showed that soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP) contents significantly increased by 1-8%, 5-25%, and 2-9% under straw return treatments, respectively, compared to the T0, and soil catalase, urease, and alkaline phosphatase activities increased by at least 34.00%. Additionally, crop yield significantly increased by 4.23-12.00% under T1-T4 treatments, and showed highly significant relationships with SOC, TN, and TP. Importantly, we found straw return significantly altered the community of bacteria involved in the carbon and nitrogen cycle, and their abundance of strong responses depending on the amounts of straw return. For example, straw input increased the abundance of Proteobacteria (+2.64–5.57%), Acidobacteria (+3.82–13.83%), and Bacteroidetes (+15.37–30.49%). Similarly, the amount of straw application increased the bacterial diversity indexes (Shannon, 2.65–10.93%; Chao1, 13.47–18.50%), and had significant positive correlations with SOC, TN, and TP contents. Structural equation models (SEM) revealed that straw return management practice had positive and indirect effects on crop yields by influencing soil properties or the bacteria community. In conclusion, our findings revealed common associations and variations of bacterial community diversity with soil factors and crop yields at different straw return rates, and these findings provide insights and options for the development of better straw return strategies and sustainable agriculture in semi-arid regions.

The detrimental effect of rainforest conversion to rubber plantations on soil dissolved organic carbon and C: N stoichiometry, mediated by altered soil biogeochemistry

Rainforest conversion into rubber (Hevea brasiliensis) plantations (RP) alters global carbon cycling and contributes to climate change. However, the impact of this widespread tropical land use change on various elements of the carbon cycle is poorly understood. Here, we aimed to investigate the impact of rainforest conversion into RP on soil-dissolved organic carbon (DOC), one of the most mobile organic matter (OM) in the terrestrial ecosystem that causes the transformation and migration of C. We also explored the underlying edaphic factors regulating soil DOC changes. Our study sites were rubber monoculture, mixed-rubber plantations (H. brasiliensis, Ficus langkokensis, and Actinodaphne henryi), and a reference rainforest. We found that soil DOC concentration was 150-200% higher in RP than in rainforests, with an unchanged pattern across the seasons (dry and rainy) and plantation type. These results were concomitant with degradation in main soil properties, markedly including lower pH, electrical conductivity, SOC, available nitrogen, available phosphorus, total nitrogen (TN), and total phosphorus (TP), following the RP establishment and explicitly having a significant negative correlation with DOC. Our fitted structure equation model (SEM) highlights that RP caused accelerated DOC production and a higher DOC/DN ratio by decreasing SOC (38.5%) and nutrients (TN and TP). Further, the SEM revealed a significant negative correlation between microbial biomass C (MBC) and N (MBN) and the DOC/DN ratio, implying limited microbial degradation of DOC under RP. This is further supported by our findings of 81.1% lower MBC per unit DOC and 37.1% lower MBN per unit DN under RP compared to rainforests, indicating poor transformation of DOC to microbial biomass under RP. Collectively, our findings suggest that RP with high nutrient demands and altered soil properties lead to increased leaching of DOC due to its limited utilization by microbes. These findings underscore the importance of robust and sustainable soil management (such as optimizing plant density and legume intercropping) in RP to improve soil health and minimize DOC leaching and its potential environmental consequences.

Quantitatively unveiling the role of coastal wetlands in regulating eutrophication and enhancing water environmental capacity

Human activities have intensified the global challenge of coastal eutrophication. Recently, water resource managers have encountered difficulties in formulating precise pollutant reduction strategies to mitigate coastal eutrophication. Despite the recognized importance of coastal wetlands and pollution sources in influencing coastal nutrient levels, accurately quantifying their impact remains difficult. To address this challenge, this study introduces a novel approach for optimizing water environmental capacity. A coupled model integrating hydrodynamics, water quality, and wetland nutrient mechanisms was developed to simulate the spatio-seasonal distribution of water, sediment, and vegetation nutrients in a semi-enclosed bay (Liaodong Bay, China) and a large-scale coastal wetland (Liaohe estuary wetland, China). Model parameters and simulation results were calibrated and validated using extensive long-term field investigations and laboratory experiments. The average root mean square errors between simulated and observed values for all validation points were as follows: 0.80mgL-1, 0.53mgL-1, 0.08mgL-1, 6.70μgL-1, and 0.50μgL-1 for dissolved oxygen, chemical oxygen demand, dissolved inorganic nitrogen, dissolved inorganic phosphorus, and chlorophyll-a, respectively. The total nitrogen (TN) and total phosphorus (TP) in the sediment were 0.10gkg-1 and 0.05gkg-1, respectively. For Suaeda salsa, the TN and TP were 2.91gkg -1 and 0.08gkg -1, respectively. For Phragmites australis, the TN and TP were 114.22gkg -1 and 6.21gkg -1, respectively. The results suggest that excessive river discharge and a stable residual circulation structure contribute to the persistent eutrophication in Liaodong Bay. The Liaohe estuary wetland enhances the environmental capacity of dissolved inorganic nitrogen and dissolved inorganic phosphorus in Liaodong Bay to 271±31tyr-1 and 8±1tyr-1, respectively, accounting for 1.8±0.2% and 1.3±0.2% of their respective environmental capacities. The reduction in dissolved inorganic nitrogen concentration is significant, with a maximum decrease of 0.17mgL-1. The maximum contributions of atmospheric deposition and aquaculture wastewater to dissolved inorganic nitrogen concentration are 0.08mgL-1 and 0.03mgL-1, respectively, with higher contributions in spring and summer than in fall and winter. These findings highlight the critical role of coastal wetlands in mitigating eutrophication and underscore the need for spatio-seasonal water management programs. This work serves as a model for effectively reducing global coastal pollution emissions.

Insights into multivalent metal removal-assistant anaerobic fermentation of waste activated sludge: Impact factor identification and mechanism clarification of metal removal

The study investigated the impact factors of metal removal and their role in enhancing anaerobic fermentation of waste activated sludge (WAS), aiming to identify key mechanisms. By optimizing the sludge concentration, it found that a sludge suspension solid range of 10–30 g/L significantly improved the efficiency of anaerobic fermentation, and yielded SCOD of 93.8–177.1 mg/g volatile suspension solid after 8 h, respectively, which was 3.67–4.77 times higher than the control. Correspondingly, the production of short-chain fatty acids (SCFAs) was significantly enhanced. At the optimal sludge suspension solid of 10–30 g/L, the SCFAs were 1.28–1.51 times higher than that of the control. Furthermore, the study evaluated the performance of different metal removal reagents and discovered that microporous COOH reagent outperformed gel SO3H and macroporous SO3H reagent. The macroporous COOH reagent achieved 1.54 and 1.22 times higher SCOD values and significantly enhanced the production of SCFAs, demonstrating its superiority in metal removal and fermentation enhancement. Moreover, the research revealed that sludge concentration and metal removal agent types influenced the activities of key enzymes involved in anaerobic fermentation. Additionally, the macroporous COOH reagent showed the most efficient ability to remove metal ions, contributing to increased nutrient recovery in terms of nitrogen (NH4+-N) and total phosphorus (TP) release during the acidification process. In summary, the enhancing mechanism of metal removal-assistant anaerobic fermentation was discussed from the sludge floc concentration, the skeleton structure and the ion exchange group type. The identified mechanism significantly improves fermentation efficiency and facilitate the organic recovery, representing an innovative approach for wide application in WAS management and resource recovery.

Bioremediation of soils contaminated with nicosulfuron by the bacterial complex ES58

Nicosulfuron residues in soil can be harmful to the environment. In this study, acid-producing Klebsiella oxytoca ES5 and Klebsiella grimontii ES8 were isolated to construct the ES58 bacterial complex. The culture medium was optimized using response surface methodology, nicosulfuron degradation by ES58 reached 97.21% in 96h. The optimal degradation conditions were: temperature: 25℃, pH 6, initial nicosulfuron concentration: 50mgL-1 and inoculum volume: 2%. The two individual strains and the bacterial complex were tested for the ability of nitrogen fixation, phosphorus solubilization, potassium decomposition and iron carrier production. The results revealed that both strains and the bacterial complex had the ability to promote the growth, with bacterial complex being more capable than the two individual bacterial strains. After 28 d of bioremediation of nicosulfuron-contaminated soil by ES58, degradation rate of nicosulfuron was 90.84% in the unsterilized soil. Furthermore, the remediation process restored the activities of catalase, invertase, dehydrogenase and urease in the soil. The ES5-specific gene budA and ES8-specific gene ldh were detected in the soil at the 28th day. ES58 exhibited different effects on the growth indexes of nicosulfuron-sensitive crops. The study provides a novel strategy for nicosulfuron degradation effective by constructing and utilizing bacterial complex.

Wastewater Treatment through Sequencing Batch Reactor: Adaptation of a Hydro-cyclone Decanter to Enhance Particle Segregation

Objectives:This study investigates the integration of a hydro-cyclone decanter into Sequencing Batch Reactor (SBR) systems to enhance particle segregation during the decanting phase, aiming to improve removal efficiencies of suspended particles in SBR. Methods:A hydro-cyclone separator was designed for the SBR reactor, optimizing particles separation using centrifugal forces without extensive process modifications. Experiments were conducted to evaluate the performance with synthetic and actual wastewater at different concentrations and flow rates.Results and Discussion:The hydro-cyclone decanter achieved removal efficiencies of up to 32.3% for synthetic wastewater and approximately 73.2% for actual wastewater, demonstrating significant particle segregation capabilities. However, its impact on dissolved pollutants like total nitrogen (T-N) and total phosphorus (T-P) was limited.Conclusion:Integrating a hydro-cyclone decanter in SBR systems significantly enhances particle segregation, particularly for larger particles, while moderately improving COD removal, suggesting its effective use in wastewater treatment processes.

Improving the water quality in the Zandvlei Estuary, Cape Town, by retrofitting sustainable drainage systems in the Diep River catchment

The Zandvlei Estuary is the only functioning estuary along the False Bay coastline of Cape Town and is therefore of extreme local ecological importance. The most significant problems are eutrophication and siltation caused by the increased total inorganic nitrogen (TIN) and soluble ready phosphorus (SRP) levels due to urban development and the associated increased impervious surface area in the catchment that drains into it. In South Africa, stormwater drainage systems conventionally channel everything they collect into receiving water bodies without significant treatment. Sustainable drainage systems (SuDS) provide an alternative approach to managing stormwater runoff. They are designed to manage both stormwater quality and quantity while potentially improving biodiversity and amenity. This project modelled the potential improvement in the quality of the water entering Zandvlei Estuary resulting from the implementation of selected SuDS control measures in Zandvlei’s Diep River catchment using the software program, PCSWMM. SRP, TIN, total phosphorus (TP) and total suspended solids (TSS) were selected as pollutant indicators. Treatment trains that included a large, constructed wetland at the bottom of the catchment will likely provide the greatest improvements to the water quality entering Zandvlei – potentially reducing SRP, TIN, TP and TSS by approximately 59%, 53%, 53%, and 66%, respectively – as well as potentially reducing the runoff by 48%.

Phosphorus–Nitrogen Interaction in Fire Retardants and Its Impact on the Chemistry of Treated Wood

This work focuses on the changes in the chemical composition of wood caused by impregnation with fire retardants such as guanidine carbonate (GC), urea (U), diammonium phosphate (DAP) and their mixtures. The treated wood was tested using the oxygen index (LOI), Py–GC/MS analysis and FTIR Spectroscopy. The wood was vacuum treated at a pressure of 0.8 MPa for 20 min and then subjected to thermal degradation using the LOI. This way, degraded and nondegraded layers were obtained and ground (0.2 mm). All treatment variants achieved the class of non-flammable materials based on LOI tests; the exception was the 5% urea solution, defined as a flame-retardant material. Using the analytical methods, it was found that cellulose and hemicelluloses undergo the fastest thermal degradation. This study found that the variant protected with a 5% mixture of GC and DAP before and after the degradation process had the best fire-retardant properties regarding cellulose content in the wood. The highest content of anhydrosugars characterised the same variants, the amount of which indicates a slowdown in the degradation process and, consequently, a reduction in the release of levoglucosan during combustion, suggesting potential applications in fire safety.

The Impact of Beneficial Microorganisms on Soil Vitality: A Review

The paper summarizes the literature on the critical impact of beneficial microorganisms on soil vitality. Common soil microorganisms, including bacteria, fungi, algae, protozoa, and viruses contribute significantly to enhancing soil fertility through processes such as nitrogen fixation, phosphorus solubilization and mobilization, sulfur cycle, composting, and heavy metal remediation. Their abundance and biomass vary significantly across taxa within the uppermost 15 cm of soil, with bacteria dominating numerically and fungi contributing substantially to biomass. These microorganisms mediate essential biogeochemical cycles in soil, including carbon, nitrogen, and phosphorus cycles, by facilitating the decomposition of organic matter and recycling soil nutrients. Nitrogen-fixing bacteria like Rhizobium are prevalent symbionts capable of biologically fixing nitrogen. Additionally, bacteria such as Micrococcus spp., Enterobacter aerogens, Pseudomonas capacia, fungi including Aspergillus niger, A. flavus, A. japonicas, Penicillum spp., and actinomycetes like Streptomyces play crucial roles in phosphorus solubilization, making phosphorus available for plant uptake. This synthesis underscores the critical role of beneficial microorganisms in maintaining soil vitality. These organisms interact with plants through beneficial relationships, influencing soil fertility dynamics by enhancing nutrient availability, promoting plant growth, and controlling pathogens. The use of biofertilizers has emerged as a sustainable strategy to improve crop yields and restore soil fertility, reducing environmental impacts linked to chemical fertilizers. Understanding the intricate dynamics of soil-beneficial microorganism and their interactions with Plants are pivotal for optimizing agricultural practices, ensuring long-term soil health, and enhancing productivity in sustainable farming systems.

Soil bacterial community characteristics and influencing factors in different types of farmland shelterbelts in the Alaer reclamation area

To investigate the effects of various types of farmland shelterbelts on soil quality and soil bacterial community diversity, this study focused on soil samples from four different shelterbelt types in the Alaer reclamation area, including Populus euphratica Oliv.- Populus tomentosa Carrière (PP), Elaeagnus angustifolia L.- Populus euphratica Oliv. (EP), Populus alba var. pyramidalis Bunge (P), and Salix babylonica L. (S). We analyzed their physical, chemical, biological properties as well as the differences in bacterial community structure, and explored the influencing factors on soil microbial community characteristics through microbial correlation network analysis. The results showed that: (1) There were significant differences in soil properties among the four types of farmland shelterbelts (p < 0.05), with P soils exhibiting the highest levels of organic matter, total nitrogen, and total phosphorus contents. (2) The Alpha diversity indices of soil bacteria showed significant differences among the four types of farmland shelterbelts (p < 0.05), with the P soils displayed the highest Chao1 and Shannon indices. (3) There were differences in the composition and abundance of dominant soil bacterial communities among different farmland shelterbelts, notably, the abundances of Verrucomicrobia, Acidobacteria, and Planctomycetes were significantly higher in P soils compared to the other three types. (4) The complexity of the correlation network between microbial species and environmental factors was highest in EP soils, soil microbial biomass nitrogen and available phosphorus were the main influencing factors. These findings indicated that different types of farmland shelterbelts had significant impacts on soil properties and soil bacterial communities. Soil bacterial communities were regulated by soil properties, their changes reflected a combined effect of soil characteristics and tree species.

Removal of nutrients and bioelectricity generation from institutional wastewater using constructed wetland-microbial fuel cell

This study evaluated the removal of nutrients from institutional wastewater and the generation of bioelectric power using a microcosm-scale constructed wetland system integrated with a microbial fuel cell (CW-MFC). The research explored the impact of vegetation on both bioelectric production and wastewater treatment within the wetland matrix. Results indicated that the CW-MFC system with vegetation outperformed the unplanted system in terms of treatment efficiency. The planted modules achieved average total nitrogen (TN) and total phosphorus (TP) removal efficiencies of 94.6 % and 90.0 %, respectively, compared to 90.59 % and 83.5 % in the unplanted system. Notably, the CW-MFC planted with Scirpus atrovirens exhibited the highest average output voltage (0.648 V) and power density (232 mW/m³). In contrast, the unplanted CW-MFC produced a maximum voltage of 0.537 V and a power density of 220 mW/m³. These findings suggest that Scirpus atrovirens enhances both the treatment efficiency and bioelectricity generation by facilitating microbial activity involved in the biodegradation of organic compounds and improving electron flow from the anode to the cathode. The significant nutrient removal efficiencies and bioelectric power generation demonstrate the potential of using a vegetated CW-MFC system to achieve sustainable wastewater treatment while simultaneously producing renewable energy, thus contributing to more eco-friendly waste management practices

Study on phosphorus recovery from sludge-incinerated bottom ash to produce nitrogen–phosphorus compound fertilizer: Preparation method, transfer mechanism and practical application

Study on phosphorus recovery from sludge-incinerated bottom ash to produce nitrogen–phosphorus compound fertilizer: Preparation method, transfer mechanism and practical application

Effect of Different Irrigated Crop Successions on Soil Carbon and Nitrogen–Phosphorus–Potassium Budget Under Mediterranean Conditions

Sustainability in agroecosystems relies on the optimized use of resources to achieve consistent yields while maintaining or improving soil health. The monitoring of soil quality is crucial when changes from rainfall-fed to irrigated crop systems occur. The objective of this study was to assess the impact of different crop successions in the Mediterranean area under irrigation and different technical practices. The soil nitrogen–phosphorous–potassium (NPK) and soil organic carbon (SOC) balances were observed in four fields with irrigated annual crops in a two-year succession timeframe, namely, sunflower–maize (P1), sunflower–clover (P2), maize–sunflower (P3), and alfalfa–alfalfa (P4). The SOC and nutrient balance, integrating the total irrigation, mineral fertilizers, and exported yield, was calculated for each farm. Except for maize–sunflower succession (P3), all fields presented a negative SOC balance at the end of the two-year crop succession, indicating losses from 2.84 to 4.91 Mg SOC ha−1 y−1. While in N-fixing plants the soil N decreased, in the remaining crops a surplus was observed, possibly leading to future N losses. The continuous depletion of soil P revealed a potential underestimation of this nutrient. Soil K appears to be related to specific crop management practices, namely, crop residue incorporation after harvest. In annual irrigated crops under Mediterranean conditions, crop succession can induce soil fertility degradation if conservation practices are absent.

Effects of Recommended Fertilizer Application Strategies Based on Yield Goal and Nutrient Requirements on Drip-Irrigated Spring Wheat Yield and Nutrient Uptake

Excessive application of fertilizers in drip-irrigated wheat production can suppress yields, lower nutrient utilization efficiency, and lead to economic and environmental issues such as nitrogen residues in the soil. Based on a recommended fertilizer application (RF) strategy that takes into account target yield and nutrient requirements, this study explores the responses of wheat plant traits, changes in topsoil and subsoil nutrients, fertilizer utilization, and economic benefits under this strategy. From 2022 to 2023, a field experiment was conducted in a typical oasis spring wheat production area at the northern foot of the Tianshan Mountains in Xinjiang. The treatments included no fertilizer control (CK), the farmer’s conventional practice (FP), recommended fertilizer (RF), RF with nitrogen omission (RF-N), phosphorus omission (RF-P), and potassium omission (RF-K). The results showed that compared with FP, the RF reduced 91 kg N ha−1 (30.3%) and 33 kg P2O5 ha−1 (24.8%) in 2022, and 69 kg N ha−1 (23.0%) and 2 kg P2O5 ha−1 (1.5%) in 2023. The effect in 2023 was better; RF also decreased the NO3−1-N residue in the 0–100 cm soil layer by 40.1 kg N ha−1 compared with FP, with no significant difference in wheat grain yield (RF: 5382.9 kg ha−1) or economic benefit (RF: USD 1613.1 ha−1). Furthermore, there were no significant differences between RF and FP in pre-anthesis NP transport or post-anthesis NP accumulation; however, RF significantly increased pre-anthesis potassium transport volume (15.8%) and transport rate (12.5%). RF led to a 16.3% increase in nitrogen utilization efficiency (NUE), while there was no significant difference in phosphorus utilization efficiency (PUE) compared with FP. The fertilizer yield effect for RF was evaluated as N > P > K. Correlation analysis indicated that grain yield was significantly positively correlated with pre-anthesis NPK transport and post-anthesis NP accumulation. It was also positively correlated with organic matter, alkali-hydrolyzed nitrogen, and Olsen-P content in both the topsoil (0–20 cm) and subsoil (20–40 cm), but not with available potassium in the soil. Therefore, conducting soil tests and determining fertilizer recommendations based on the proposed RF method at harvest can reduce fertilizer usage and achieve a balance between the conflicting objectives of environmental protection, increased crop yields, nutrient utilization efficiency, and improved economic benefits in oasis agricultural areas facing excessive fertilizer application.

Correlation between Different Factors of Non-point Source Pollution in Yangtze River Basin

This research used the improved export coefficient model to estimate non-point source load in sub-watersheds and a self-organizing map model to identify the correlation relationship of factors, that can be affected by non-point source load in Yangtze River Basin. Research results indicate that total nitrogen load is 4.87 - 15.53 kg/ha; total phosphorus load is 0.18 - 0.51 kg/ha; Dong Ting Lake sub-basin has the lowest contribution value of total nitrogen and phosphorus; Tai Lake sub-basin has the highest contribution load of total nitrogen and total phosphorus; Jinsha River sub-basin reveals the highest value of total nitrogen and phosphorus contribution on grassy land and desert land; Tai Lake sub-basin has the highest total nitrogen and total phosphorus load on forest, agricultural land, and urban construction land. The correlation relationship of factors reveals a very close correlation with each other as precipitation, total nitrogen load, and total phosphorus load factors have correlation in the highest value, in which total nitrogen load and total phosphorus load factors have a close correlation with each other from the lowest value to highest value; wetland and barren land factors correlate with the lowest value and the highest value; agricultural land, forestland, and grassy land factors correlate with one another in the high value and the highest value. The forest cover rate factor, as well as the population factor, does not correlate with other factors.