Phosphorus Content Research Articles

The influence of potassium nanoparticles as a foliar fertilizer on onion growth, production, chemical content, and DNA fingerprint

Potassium is an important macro-fertilizer for plant growth but can be lost from the soil after application via irrigation. Slow-release nano-fertilizers can achieve sustainable crop cultivation and production, so this study evaluated the influence of potassium nanoparticles (K-NPs) with various concentrations (0, 50, 100, and 200 mg/l) on onion development, production, pigments, chemical content, and DNA fingerprint during two sequential agriculture seasons in 2021 and 2022 at a private farm in Zagazig, Sharkia Governorate, Egypt. Spraying onion plants with K-NPs (200 mg/l) significantly improved the vegetative characteristics of onion plant growth and production, as well as increasing the plant pigments and the content of carbohydrate, oil, total indole, and phosphorus in onion bulbs. Similarly, 50 mg/l of K-NPs considerably increased the content of nitrogen, potassium, protein, antioxidant activity, and phenols in the onion bulbs. The content of total flavonoids and anthocyanin was increased with 100 mg/l of K-NPs. In conclusion, the foliar application of K-NPs improves the onion plant yield and quality and can achieve agricultural sustainability.

Influences of pretreatment methods on the mechanical and environmental behaviors of PG-GGBS-LM ternary stabilizer.

Phosphogypsum is a kind of acidic industrial byproducts with high content of soluble phosphorus and fluorine pollutants, which requires to be pretreated when used as cementitious material to (partial) replace traditional Portland cement. In this study, five different pretreatment methods were proposed for comparative analysis to examine the pretreatment effect on the mechanical and environmental behaviors of ternary phosphogypsum (PG), ground granulated blast-furnace slag (GGBS), and lime (LM) mixed stabilizer. Series laboratory tests, including unconfined compressive strength (UCS), pH, phosphorus (P)/fluorine (F) leaching, scanning electron microscopy (SEM), and X-ray diffraction (XRD) tests, were conducted to comprehend the macro- and microscopic mechanism. The results show that it is essential to grind raw PG to finer powdered state, so that it reacts more easily and quickly with LM and water. In addition, it was noticed that the UCS and P/F leaching concentration are not only affected by the mixing proportion of the PG-GGBS-LM ternary stabilizer, but also by the curing duration. The UCS increases rapidly from initial curing period and then grows slowly after 28days of curing. From the perspective of strength evolution, mixing proportion of PG: GGBS: LM = 15:80:5 is optimal, but considering the economy and environmental related issues, PG: GGBS: LM = 30:65:5 was regarded as a more attractive choice. The findings can provide a reference for the selection of pretreatment methods and design of PG-based cementitious materials suited for stabilized soils.

Abiotic processes control carbon dioxide dynamics in temperate karst lakes.

Inland waters are crucial in the carbon cycle, contributing significantly to the global CO2 fluxes. Carbonate lakes may act as both sources and sinks of CO2 depending on the interactions between the amount of dissolved inorganic carbon (DIC) inputs, lake metabolisms, and geochemical processes. It is often difficult to distinguish the dominant mechanisms driving CO2 dynamics and their effects on CO2 emissions. This study was undertaken in three groundwater-fed carbonate-rich lakes in central Spain (Ruidera Lakes), severely polluted with nitrates from agricultural overfertilization. Diel and seasonal (summer and winter) changes in CO2 concentration (CCO2) DIC, and CO2 emissions-(FCO2)-, as well as physical and chemical variables, including primary production and phytoplanktonic chlorophyll-a were measured. In addition, δ13C-DIC, δ13C-CO2 in lake waters, and δ13C of the sedimentary organic matter were measured seasonally to identify the primary CO2 sources and processes. While the lakes were consistently CCO2 supersaturated and FCO2 was released to the atmosphere during both seasons, the highest CCO2 and DIC were in summer (0.36-2.26 µmol L-1). Our results support a strong phosphorus limitation for primary production in these lakes, which impinges on CO2 dynamics. External DIC inputs to the lake waters primarily drive the CCO2 and, therefore, the FCO2. The δ13C-DIC signatures below -12‰ confirmed the primary geogenic influence on DIC. As also suggested by the high values on the calcite saturation index, the Miller-Tans plot revealed that the CO2 source in the lakes was close to the signature provided by the fractionation of δ13C-CO2 from calcite precipitation. Therefore, the main contribution behind the CCO2 values found in these karst lakes should be attributed to the calcite precipitation process, which is temperature-dependent according to the seasonal change observed in δ13C-DIC values. Finally, co-precipitation of phosphate with calcite could partly explain the observed low phytoplankton production in these lakes and the impact on the contribution to increasing greenhouse gas emissions. However, as eutrophication increases and the soluble reactive phosphorus (SRP) content increases, the co-precipitation of phosphate is expected to be progressively inhibited. These thresholds must be assessed to understand how the CO32- ions drive lake co-precipitation dynamics. Carbonate regions extend over 15% of the Earth's surface but seem essential in the CO2 dynamics at a global scale.

Variation of carbon, nitrogen and phosphorus content in fungi reflects their ecology and phylogeny

Fungi are an integral part of the nitrogen and phosphorus cycling in trophic networks, as they participate in biomass decomposition and facilitate plant nutrition through root symbioses. Nutrient content varies considerably between the main fungal habitats, such as soil, plant litter or decomposing dead wood, but there are also large differences within habitats. While some soils are heavily loaded with N, others are limited by N or P. One way in which nutrient availability can be reflected in fungi is their content in biomass. In this study, we determined the C, N, and P content (in dry mass) of fruiting bodies of 214 fungal species to inspect how phylogeny and membership in ecological guilds (soil saprotrophs, wood saprotrophs, and ectomycorrhizal fungi) affect the nutrient content of fungal biomass. The C content of fruiting bodies (415 ± 25 mg g–1) showed little variation (324–494 mg g–1), while the range of N (46 ± 20 mg g–1) and P (5.5 ± 3.0 mg g–1) contents was within one order of magnitude (8–103 mg g–1 and 1.0–18.9 mg g–1, respectively). Importantly, the N and P contents were significantly higher in the biomass of soil saprotrophic fungi compared to wood saprotrophic and ectomycorrhizal fungi. While the average C/N ratio in fungal biomass was 11.2, values exceeding 40 were recorded for some fungi living on dead wood, typically characterized by low N content. The N and P content of fungal mycelium also showed a significant phylogenetic signal, with differences in nutrient content being relatively low within species and genera of fungi. A strong correlation was found between N and P content in fungal biomass, while the correlation of N content and the N-containing fungal cell wall biopolymer—chitin showed only weak significance. The content of macronutrients in fungal biomass is influenced by the fungal life style and nutrient availability and is also limited by phylogeny.

Application of Phototrophic Microorganisms as Biofertilizer Isolated from South Gujarat, India

Chemical fertilizers have impact on soil texture and also affects the plant growth upto certain level. Due to overuse of chemicals, soil profile has major changes in Gujarat. South Gujarat having major agricultural practices in vegetables, fruits and Sugarcane. The phtotrophic microorganisms isolated from wetland of Nanikakrad situated near to Navasari. The impact of algal biofertilizers on the growth of Solanum melongena, Solanum lycopersicum, and Capsicum annum was researched through a pot study. Plant height, width, and the number of leaves at different time intervals were measured, and soil nutrient levels were analysed by measuring Carbon, Nitrogen, Phosphorus and Sulphur content. A total of 30 pots (10 for each plant species) were used, and eight different isolates were applied across treatment. Two pots of plants were maintained as controls; one including chemical fertilizers. Plant growth was significantly promoted by isolates I1 and I2 in Solanum melongena, while in Solanum lycopersicum and Capsicum annum, all treatments improved growth compared with controls. Chlorophyll content was significantly increased in chemical fertilized Solanum melongena, whereas in Solanum lycopersicum and Capsicum annum, I1 significantly increased Chlorophyll content. These findings underline the potential of algal biofertilizers as a smarter, safer alternative to chemical fertilizers that promise to drive sustainable growth in agriculture.

Phosphorus mass flows and economic benefits of food waste management: the case study of selected retail and wholesale fresh markets in Thailand

AbstractThis study aims to investigate the mass flow and the phosphorus flow of food waste in order to propose a viable technique for its recovery from food waste in retail and wholesale fresh markets. These markets are significant food waste sources, including valuable elements such as organic carbon, nitrogen, and phosphorus. This research provides critical data that can inform and guide the development of sustainable and cost-effective waste management strategies. The results indicate that retail markets generate 13.47 tons/d of food waste, while wholesale markets produce a staggering 192.62 tons/d. For phosphorus flow analysis, the data show that retail markets produce 12.80 kg P/d, while wholesale markets produce 40.79 kg P/d. Uncooked food waste is a major cause of phosphorus loss in retail and wholesale markets. An estimated 3.65 kg P/d is lost from retail and 20.72 kg P/d from wholesale. Separating food waste from general waste and recovering the phosphorus content is essential to reduce P loss. According to this study, separating food waste and selling it as animal feed (Scenario 1) or using it to create organic fertilizer (Scenario 2) are more profitable than the current waste management practice. These options can generate around 180,000 and 960,000 USD/year, respectively. Currently, it is not cost-effective to produce concentrated P fertilizer (scenario 3) due to the high energy and technology required. The study’s results can guide policymakers toward comprehensive food waste management in fresh markets and sustainable phosphorus recovery for food and agricultural production. Graphical abstract

Wear Resistance Behavior of Low-, Mid-, and High-Phosphorus Electroless Ni-P Coatings Heat-Treated in the Air Environment

The high-temperature heat treatment of electroless nickel–phosphorus (Ni-P) coatings in an air environment, and its consequences have scarcely been investigated. This work investigated tribological characteristics of the high-temperature, heat-treated, electroless Ni-P coatings on steel substrates with low-, mid-, and high-phosphorus content for which the average phosphorus content was 2.4 wt.%, 7.1 wt.%, and 10.3 wt.%, respectively. X-ray fluorescence and energy dispersive spectroscopy were implemented to determine the phosphorus content of the coatings. The oxidation of Ni and the formation of the NiO layer on the coating surface was confirmed by the X-ray diffraction technique. A reciprocating sliding method on a ball-on-flat system was utilized to evaluate the coating’s friction and wear behavior. Among the coatings with varying phosphorus content, a high hardness of 1086 HV was found for high-phosphorus coating when heat-treated at 400 °C in an air environment, and that was decreased to 691 HV when heat-treated at 650 °C. The oxidation of nickel in the electroless Ni-P coating occurred when heat-treated at 400 °C in an air environment, and this phenomenon was increased more when the temperature was increased to 650 °C. The characteristics of the NiO layer that formed on the surface of the heat-treated electroless Ni-P coating were influenced by the concentration of phosphorus, which caused different colors of NiO to be seen on the Ni-P coating surface. A greenish black NiO layer on the low-phosphorus and black NiO layer on the mid- and high-phosphorus Ni-P coating was developed during heat treatment at 650 °C in an air atmosphere. The adhesion and tribological characteristics of the Ni-P coatings were affected by the NiO layer developed on the heat-treated Ni-P coating surfaces. The Ni-P coatings with mid- and high-phosphorus content showed enhanced wear-resistance characteristics when they underwent heat treatment in an air atmosphere at the high temperature of 650 °C. The wear volume obtained for as-plated mid-phosphorus and high-phosphorus Ni-P coatings was 0.111 mm3 and 0.128 mm3, respectively, and that was reduced to 0.031 mm3 and 0.051 mm3, respectively, after the high-temperature heat treatment.

Efficiency of cavitary varnishes containing experimental bioglass particles in the occlusion of dentinal tubules.

This research aims to evaluate the efficiency of cavitary varnishes containing experimental bioglasses in the occlusion of dentinal tubules. One hundred and sixty-eight cervical buccal dentin samples were obtained from bovine teeth. Samples were randomized into the following groups: I. Distilled Water (DW); II. Cavity Varnish (CV); III. Colgate® Sensitive Pro-Relief™ (CS); IV. 45S5 Bioglass (45S5); V. KSr Bioglass strontium potassium (KSr); VI. P Bioglass phosphorus (P); and VII. PSi Bioglass phosphorus silica (PSi). The treatments were applied to the surfaces of the samples, which were then subjected to simulated brushing. The samples were analyzed for a) characterization of bioactive glasses; b) surface roughness; c) descriptive analysis of the dentin surface; d) total versus occluded number of dentinal tubules; e) diameter of the dentinal tubules; f) chemical composition of the dentin surfaces, and g) dentin permeability. All groups treated with biomaterials without the brushing challenge showed an increase in roughness and (total or partial) occlusion of the dentinal tubules. The PSi group had the best values for occlusion, while the KSr group had the highest calcium and phosphorus concentrations. After the brushing challenge the roughness was controlled by the presence of biomaterials; 45S5, KSr, and PSi showed occlusion of the dentin tubules. All bioactive glasses showed reduced tooth permeability compared to distilled water. The PSi group had the smallest tubule diameter and highest phosphorus concentration. KSr and PSi bioglasses are promising materials for dentin occlusion and remineralization and are promising new biomaterials for the treatment of dentin hypersensitivity.

Soil Quality Testing and Counseling Coastal Agricultural Communities in Taiwan

The Mailiao Town is a traditional agricultural community, located in the south-central region of Taiwan. In this region, the northeast monsoon is entrained with salt for seven months a year. Soil fertility test results between 2011 and 2021 showed that the tillage soil was alkaline and salinized. The content of total nitrogen, phosphorus, calcium, magnesium, potassium, and sodium in the soil were mostly excessive. In the region, open-air continuous farming with heavy fertilizer has been performed. Based on the 10 years of data from the test of soil fertility, we counseled farmers to understand the significance of the values in the reports and the impact on crop growth. We promoted rational fertilization with a series of agricultural counseling actions. The results of the continuous counseling showed that the dependence on nitrogenous fertilizer gradually decreased with the continuous increase of the application of organic fertilizers. The total nitrogen and exchangeable sodium content in soil decreased significantly, and the carbon-nitrogen ratio (C/N) increased every year. The soil environment became close to equilibrium gradually. As a result, the yield and quality of local crops have gradually improved.

Biochar effects on soil aggregation, phosphorus distribution, and colloidal phosphorus content in paddy soils: a comparative study

Biochar effects on soil aggregation, phosphorus distribution, and colloidal phosphorus content in paddy soils: a comparative study

Collaborative Impact of Inorganic and Organic Fertilizers Coupled with Kappaphycus alvarezii Bio-stimulant on the Quality Characteristics of Wheat (Triticum aestivum L.)

The study investigates the influence of different factors on the nutritional content of wheat grains, focusing on crude protein, nitrogen, phosphorus, and potassium contents in grain. Results indicate that varying combinations of factors such as NPK fertilization, farmyard manure (FYM) application, and bio-stimulant usage significantly affect nutrient concentrations in grain. Crude protein content, a vital indicator of grain quality, showed variability across the different treatments, with the highest levels observed in plots receiving RDF @100% + FYM@16.5 t ha-1 + SWBS@1250 ml ha-1. The crude protein content primarily relies on the nitrogen levels. In the research, the findings indicated that the nitrogen content was significant, which, in turn, led to a significant crude protein content. The levels of nitrogen, phosphorus, and potassium content also exhibited fluctuations, with significant interactions observed among various factors. These fluctuations are attributed to differences in nutrient uptake and utilization during the different growth stages of the wheat plant. All three factors can enhance the nutrient uptake facilities through soil as well as plant body, therefore, notably, interactions between NPK, FYM, and bio-stimulants exhibited significant effects on nutrient content, particularly at the 0.05 significance level. The findings underscore the importance of holistic agricultural management in enhancing the nutritional value of wheat grains, with implications for food security and agricultural sustainability.

An investigation of cyanobacteria, cyanotoxins and environmental variables in selected drinking water treatment plants in New Jersey

Harmful Algal Blooms (HAB) have the potential to impact human health primarily through their possible cyanotoxins production. While conventional water treatments can result in the removal of unlysed cyanobacterial cells and low levels of cyanotoxins, during severe HAB events, cyanotoxins can break through and can be present in the treated water due to a lack of adequate toxin treatment. The objectives of this study were to assess the HAB conditions in drinking water sources in New Jersey and investigate relationships between environmental variables and cyanobacterial communities in these drinking water sources. Source water samples were collected monthly from May to October 2019 and analyzed for phytoplankton and cyanobacterial cell densities, microcystins, cylindrospermopsin, Microcystis 16S rRNA gene, microcystin-producing mcyB gene, Raphidiopsis raciborskii-specific rpoC1 gene, and cylindrospermopsin-producing pks gene. Water quality parameters included water temperature, pH, dissolved oxygen, specific conductance, fluorescence of phycocyanin and chlorophyll, chlorophyll-a, total suspended solids, total dissolved solids, dissolved organic carbon, total nitrogen, ammonia, and total phosphorus. In addition to source waters, microcystins and cylindrospermopsin were analyzed for treated waters. The results showed all five selected New Jersey source waters had high total phosphorus concentrations that exceeded the established New Jersey Surface Water Quality Standards for lakes and rivers. Commonly found cyanobacteria were identified, such as Microcystis and Dolichospermum. Site E was the site most susceptible to HABs with significantly greater HAB variables, such as extracted phycocyanin, fluorescence of phycocyanin, cyanobacterial cell density, microcystins, and Microcystis 16S rRNA gene. All treated waters were undetected with microcystins, indicating treatment processes were effective at removing toxins from source waters. Results also showed that phycocyanin values had a significantly positive relationship with microcystin concentration, copies of Microcystis 16S rRNA and microcystin-producing mcyB genes, suggesting these values can be used as a proxy for HAB monitoring. This study suggests that drinking water sources in New Jersey are vulnerable to forthcoming HAB. Monitoring and management of source waters is crucial to help safeguard public health.

Grazing exclusion is more effective for vegetation restoration and nutrient transfer in the heavily degraded desert steppe

BackgroundGrazing exclusion is an efficient practice to restore degraded grassland ecosystems by eliminating external disturbances and improving ecosystems’ self-healing capacities, which affects the ecological processes of soil-plant systems. Grassland degradation levels play a critical role in regulating these ecological processes. However, the effects of vegetation and soil states at different degradation stages on grassland ecosystem restoration are not fully understood. To better understand this, desert steppe at three levels of degradation (light, moderate, and heavy degradation) was fenced for 6 years in Inner Mongolia, China. Community characteristics were investigated, and nutrient concentrations of the soil (0–10 cm depth) and dominant plants were measured.ResultsWe found that grazing exclusion increased shoots’ carbon (C) concentrations, C/N, and C/P, but significantly decreased shoots’ nitrogen (N) and phosphorus (P) concentrations for Stipa breviflora and Cleistogenes songorica. Interestingly, there were no significant differences in nutrient concentrations of these two species among the three degraded desert steppes after grazing exclusion. After grazing exclusion, annual accumulation rates of aboveground C, N, and P pools in the heavily degraded area were the highest, but the aboveground nutrient pools were the lowest among the three degraded grasslands. Similarly, the annual recovery rates of community height, cover, and aboveground biomass in the heavily degraded desert steppe were the highest among the three degraded steppes after grazing exclusion. These results indicate that grazing exclusion is more effective for vegetation restoration in the heavily degraded desert steppe. The soil total carbon, total nitrogen, total phosphorus, available nitrogen, and available phosphorus concentrations in the moderately and heavily degraded desert steppes were significantly decreased after six years of grazing exclusion, whereas these were no changes in the lightly degraded desert steppe. Structural equation model analysis showed that the grassland degradation level mainly altered the community aboveground biomass and aboveground nutrient pool, driving the decrease in soil nutrient concentrations and accelerating nutrient transfer from soil to plant community, especially in the heavily degraded grassland.ConclusionsOur study emphasizes the importance of grassland degradation level in ecosystem restoration and provides theoretical guidance for scientific formulation of containment policies.

Temporal variations of biological nitrogen fixation and diazotrophic communities associated with artificial seaweed farms

Diazotrophic communities contribute inorganic nitrogen for the primary productivity of the marine environment by biological nitrogen fixation (BNF). They play a vital role in the biogeochemical cycle of nitrogen in the marine ecological environment. However, there is still an incomplete understanding of BNF and diazotrophs in artificial seaweed farms. Therefore, this study comprehensively investigated the temporal variations of BNF associated with Gracilariopsis lemaneiformis, as well as the diazotrophic communities associated with macroalgae and its surrounding seawater. Our results revealed that a total of 13 strains belonging to Proteobacteria and Bacteroidetes were identified as N2-fixing bacteria using azotobacter selective solid medium and nifH gene cloning. Subsequently, BNF and diazotrophic communities were characterized using the acetylene reduction method and high-throughput sequencing of the nifH gene, respectively. The results showed that nitrogenase activity and nifH gene abundance of epiphytic bacteria on G. lemaneiformis varied significantly among four different cultivation periods, i.e., Cultivation Jan. (CJ), Cultivation Feb. (CF), Cultivation Mar. (CM), Cultivation Apr. (CA). Among them, the nitrogenase activity and nifH gene abundance of epiphytic bacteria on G. lemaneiformis in CM were significantly higher than those in CJ, CF, and CA, indicating that the BNF of eiphytic bacteria on G. lemaneiformis was markedly enhanced. Combined with the data on environmental factors, it was found that the low concentration of nitrogen and phosphorus in CM might considerably boost the BNF of epiphytic bacteria in G. lemaneiformis. The sequencing results of the nifH gene showed that the α-diversity of diazotrophic communities associated with G. lemaneiformis and seawater in CM was higher than that in other cultivation periods. In addition, the diazotrophic communities on G. lemaneiformis were significantly different in CJ, CF, CM, and CA, and they were significantly diverse from diazotrophic communities in seawater. LEfSe analysis indicated that Rhodobacterales, Hyphomonadaceae, Robiginitomaculum, and Robiginitomaculum antarcticum within α-proteobacteria played a remarkable role in BNF in response to nitrogen nutrient deficiency. Taken together, these results provide a unique insight into the interaction between macroalgae and its epiphytic bacteria and lay a foundation for further research on the mechanism of action of nitrogen-cycling microorganisms associated with macroalgae.

Effect of Fluorine and Phosphorus Impurities in Phosphogypsum on Microstructure and Mechanism of α‐Type Hemihydrate Gypsum Crystals

AbstractIn this study, phosphogypsum (PG) is simulated by doping fluorine and phosphorus ions in an analytically pure reagent of gypsum dihydrate. The influence of fluorine and phosphorus impurity and content on the dehydration reaction process of phosphogypsum and its crystalline micromorphology is assessed during the preparation of α‐type gypsum hemihydrate in the reversed‐phase microemulsion system and its mechanism. The results show that when the fluorine content increases from 0 to 1.0 mol L−1 (ωNaF = 1.0 mol L−1), the dehydration process of dihydrate gypsum will be greatly slowed down. Scanning electron microscopy (SEM) analysis showed that even a small amount of F− (ωNaF = 0.2 mol L−1) can significantly inhibit the formation of α‐type hemi‐hydrated gypsum. When ωH3PO4 = 0.10 mol L−1, the water of crystallization content in the solid phase of the sample decreased to 5.24% after 90 min, which is significantly lower than during the same period of the benchmark group. However, there is a threshold value for the effect of phosphorus on the microscopic morphology of the α‐type gypsum hemihydrate crystals, when ωH3PO4 ≤ 0.04 mol L−1, the crystal morphology is basically unaffected. Moreover, when ωH3PO4 continued to increase, the defects on the crystal surface increased.

Temporal Assessment of Phosphorus Speciation in a Model Ramsar Lake System in Asia

This study focused on monitoring phosphorus (P) concentrations in the water of the Ramsar site, Lake Vembanad, with a special focus on the mouths of the river bodies draining into the lake, a known hotspot for eutrophication. Four phosphorus fractions—total reactive phosphorus (TRP), total acid hydrolysable phosphorus (TAHP), total organic phosphorus (TOP), and total phosphorus (TP)—were monitored during the pre-monsoon and post-monsoon seasons. The results revealed high levels of all monitored phosphorus fractions, with an average concentration exceeding 300 ppb P across both seasons, indicating a highly eutrophic state. Notably, TRP, TOP, and TP showed high concentrations in both the pre-monsoon and post-monsoon periods. These data suggest significant phosphorus input into the lake’s surface water, potentially triggering excessive algal growth and threatening the biodiversity of this rich wetland ecosystem.

Multi-year crop rotation and quicklime application promote stable peanut yield and high nutrient-use efficiency by regulating soil nutrient availability and bacterial/fungal community

Diversifying cultivation management, including different crop rotation patterns and soil amendment, are effective strategies for alleviating the obstacles of continuous cropping in peanut (Arachis hypogaea L.). However, the peanut yield enhancement effect and temporal changes in soil chemical properties and microbial activities in response to differential multi-year crop rotation patterns and soil amendment remain unclear. In the present study, a multi-year localization experiment with the consecutive application of five different cultivation managements (including rotation with different crops under the presence or absence of external quicklime as soil amendment) was conducted to investigate the dynamic changes in peanut nutrient uptake and yield status, soil chemical property, microbial community composition and function. Peanut continuous cropping led to a reduction in peanut yield, while green manure-peanut rotation and wheat-maize-peanut rotation increased peanut yield by 40.59 and 81.95%, respectively. A combination of quicklime application increased yield by a further 28.76 and 24.34%. Alterations in cultivation management also strongly affected the soil pH, nutrient content, and composition and function of the microbial community. The fungal community was more sensitive than the bacterial community to cultivation pattern shift. Variation in bacterial community was mainly attributed to soil organic carbon, pH and calcium content, while variation in fungal community was more closely related to soil phosphorus content. Wheat-maize-peanut rotation combined with quicklime application effectively modifies the soil acidification environment, improves the soil fertility, reshapes the composition of beneficial and harmful microbial communities, thereby improving soil health, promoting peanut development, and alleviating peanut continuous cropping obstacles. We concluded that wheat-maize-peanut rotation in combination with quicklime application was the effective practice to improve the soil fertility and change the composition of potentially beneficial and pathogenic microbial communities in the soil, which is strongly beneficial for building a healthy soil micro-ecology, promoting the growth and development of peanut, and reducing the harm caused by continuous cropping obstacles to peanut.

Interspecific Differences in the Effects of Calcium and Phosphorus Coprecipitation Induced by Submerged Plants on the Water-to-Phosphorus Cycle

The effects of submerged plant-induced calcium and phosphorus coprecipitation on the phosphorus cycle in aquatic environments and interspecific differences are still unclear. Herein, we selected Ceratophyllum demersum L. and Potamogeton crispus L. to construct a sediment–water-submerged plant system. We examined how phosphorus concentrations in the water, sediment, and plant ash changed over time with different phosphorus and calcium treatments and explored the effects of photosynthesis-induced calcium and phosphorus coprecipitation on water’s phosphorus cycle and variations between different submerged plant species. The main results were as follows: (1) The phosphorus reduction in the P. crispus system was less than that in the C. demersum system. (2) P. crispus had higher total ash phosphorus (TAP) values than C. demersum. (3) The sediment total phosphorus (STP) and its fractions with P. crispus were most affected by phosphorus concentration while those with C. demersum were most affected by time. Overall, the two submerged species exhibited different calcium and phosphorus coprecipitation levels and had distinct effects on the water-to-phosphorus cycle. When submerged plants are introduced to reduce and stabilize the phosphorus levels, plant interspecific differences in their induced calcium and phosphorus coprecipitation on water and phosphorus cycling must be fully assessed.

Soil C:N:P stoichiometric signatures of grasslands differ between tropical and warm temperate climatic zones

AbstractClimate and land management affect nutrient cycling in grassland ecosystems. We aimed to understand whether temperate and tropical grasslands differ in terms of soil organic carbon (SOC), nitrogen (N), and phosphorus (P) concentrations, and their C:N:P stoichiometric ratios in grazed and ungrazed natural grasslands and pastures. For this, we used a meta-analysis approach (1296 records, 241 papers), and regression models to explain the observed patterns in terms of mean annual precipitation (MAP), mean annual temperature (MAT), altitude, and latitude. SOC, N, and P concentrations were higher in temperate regions than in tropical ones, and they negatively correlated with MAT and MAP. The grassland type effect was more significant for tropical regions. In tropical regions, soil C:N ratios were higher in ungrazed than in grazed pastures, and soil N:P ratios in ungrazed sites were higher in pastures than in natural grasslands. Grazing increases soil N and SOC for natural grasslands in temperate regions. Our findings suggest that soil stoichiometric C:N:P stoichiometric signatures in grasslands differed between tropical and temperate regions on a global scale. P is a key element in regulation and restriction on soil C and N cycling in tropical regions but less in the temperate ones. Our findings suggest the direction of effects of grazing or grassland type on C:N:P stoichiometric signature. Since imbalances in soil stoichiometric ratios may have implications for ecosystem functioning, the assessment of these patterns could serve as a valuable tool for management and conservation of grasslands and pastures in both tropical and temperate regions.

Enhancing flame retardancy and dielectric performance of epoxy resins through benzoxazine-phosphorus modification

A P/N-containing flame retardant, DOPOBH, was synthesized with salicylaldehyde, p-aminophenol, 9,10-dihydro-9-oxa-10-phosphophenanthrene-10-oxide (DOPO) and formaldehyde. The performance of DOPOBH in flame retardant modification of 4,4′-diaminodiphenyl sulfone(DDS)/diglycidyl ether of bisphenol A (DGEBA, E−44) system was studied in terms of limiting oxygen index (LOI), vertical burning testing (UL-94) and cone calorimeter test (CCT). When the phosphorus content was 1.5 wt% of the whole system, DOPOBH modified epoxy resin (EP/P1.5) exhibited excellent flame retardancy (achieving a UL-94 V-0 rating and the LOI value of 35.2 %). Compared with pure EP, a 54.3 % decrease of peak heat release rate (PHRR) and ca. 5 times of residue (with an intumescent structure) was obtained with EP/P1.5 in CCT. Based on the results of CCT, scanning electron microscope (SEM), thermal gravimetric analysis (TGA) and thermogravimetry-infrared spectroscopy (TG-IR), DOPOBH was verified to play important roles in both gas phase and solid phase. In addition, the addition of DOPOBH could improve the dielectric properties of epoxy resin and provide new strategies for high-performance applications in electronic packaging.