Study of methane and carbon dioxide adsorption-desorption hysteresis in coals from Sydney Basin:A theoretical and experimental approach

Methane(CH_(4))and carbon dioxide(CO_(2))are primary components of coal seam gas(CSG).Understanding their adsorption-desorption hysteresis characteristics,along with the fundamental mechanism,is crucial for CSG exploitation and related hazards mitigation.This research focused on the representative Bulli coal seam in the Sydney Basin,Australia.Through the purpose-built indirect gravimetric high-pressure isothermal adsorption-desorption hysteresis experiment,a novel Langmuir-based desorption model,incorporating hysteresis effect and residual gas,was proposed.Quantitative characterization of the adsorption-desorption hysteresis degrees of CO_(2)and CH_(4)i n coal particles of various sizes and inΦ50mm 100 mm intact coal samples were achieved using the improved hysteresis index(IHI).The experimental findings validated that the proposed desorption model accurately describes the desorption behavior of CO_(2)and CH_(4)in coal(R^(2)>0.99).Based on the adsorption-desorption properties of inkbottle-shaped micropores and pore deformation caused by gas adsorption-induced coal expansion,the occurrence mechanism of adsorption–desorption hysteresis and the fundamental reasons for the presence of residual gas were elucidated.Furthermore,the study explored the impact of CO_(2)and CH_(4)adsorption-desorption hysteresis effects on coal and gas outbursts,suggesting that coal seams rich in CO_(2)do not have a higher propensity for outbursts than those rich in CH_(4).

Realized stable BP-N at ambient pressure by phosphorus doping

Black-phosphorus-structured nitrogen(BP-N)is an attractive high-energy-density material.However,high-pressure-synthesized BP-N will decompose at low pressure and cannot be quenched to ambient conditions.Finding a method to stabilize it at 0 GPa is of great significance for its practical applications.However,unlike cubic gauche,layered polymeric,and hexagonal layered polymeric nitrogen(cg-N,LP-N,and HLP-N),it is always a metastable phase at high pressures up to 260 GPa,and decomposes into chains at 23 GPa.Here,on the basis of firstprinciples simulations,we find that P-atom doping can effectively reduce the synthesis pressure of BP-N and maintain its stability at 0 GPa.Uniform distribution of P-atom dopants within BP-N layers helps maintain the structural stability of these layers at 0 GPa,while interlayer electrostatic interaction induced by N-P dipoles enhances dynamic stability by eliminating interlayer slipping.Furthermore,pressure is conducive to enhancing the stability of BP-N and its doped forms by suppressing N-chain dissociation.For a configuration with 12.5%doping concentration,a gravimetric energy density of 8.07 kJ/g can be realized,which is nearly twice that of trinitrotoluene.

An association analysis of lipidome and transcriptome highlights the involvement of MmGDPD1 in regulating low phosphorus tolerance in Malus mandshurica

Phosphorus(Pi)plays a crucial role in the growth and development of plants.Membrane lipid regulation is one of the main mechanisms underlying plant adaptation to Pi deficiency.Previously,the high tolerance to low-Pi stress was justified in an elite line,MSDZ 109,which was obtained from Malus mandshurica.To better understand the mechanism underlying high adaptation to low-Pi stress,currently,lipidomic and transcriptomic analysis,as well as CRISPR/Cas9 and MmGDPD1-overexpressing methodologies were comprehensively integrated into a strategy for elucidating the high tolerance to low-Pi stress.Totally,770 differential metabolites were identified from the roots between the low-Pi and stress-free,belonging to 21 sub-classes of lipid compounds.Fatty acids(FA)constituted the predominant lipid component,accounting for approximately 50%-60%of the total lipids,and triglycerides(TAG)ranked the second,comprising around 12%of the total,consecutively followed by phosphatidylcholine(PC)and diacylglycerol(DAG)with approximately 10%and 8%of the total,respectively.The synchronous transcriptomic analysis revealed a significant up-regulation of genes related to glycerophospholipid and glycerolipid metabolism,specifically those(e.g.,MmGDPD1,MmDGDG1,MmMGDG1,MmSQDG,etc.)involved in phospholipid and galactosyl synthesis in response to low-Pi stress.GUS fusing reporter assay showed that MmGDPD1 promoter induced GUS gene expression and demonstrated initiation activity.Based on expression analysis,a dual-luciferase reporter assay,as well as yeast one-hybrid(Y1H)identification,MmPHR1 was justified to bind with the MmGDPD1 promoter and positively regulate plant tolerance to low-Pi stress.To further elucidate the role of MmGDPD1,CRISPR/Cas9 and MmGDPD1-overexpressing vectors were successfully introduced into apple(‘Royal Gala')calli.Interestingly,the MmGDPD1-KO line calli exhibited the remarkable decreases in the contents of phosphodiesterase(PDE),activity,as well as the contents of total Pi,and Pi in comparison with those of the wild type.Conversely,MmGDPD1-OE ones demonstrated the significant elevation in Pi accumulations,further justifying its potential role in Pi remobilization in apple.Therefore,MmGDPD1 substantially involves elevating low-Pi tolerance via promoting Pi release in M.mandshurica.

Effects of Phosphate Adsorption on Adsorption-Desorption and Availability of Cu and Zn Ions in Ultisols and Alfisols

Surface charge, secondary adsorption- desorption and form distribution of Cu2+ and Zn2+ in Ultisols and Alfisols having adsorbed phosphate were studied by potentiometric titration, adsorption equilibrium and sequential extraction method, respectively. The soil surface negative charges increased whereas the amount of positive charges decreased with increase of P adsorbed. The soil secondary adsorption capacity for Cu2+ and Zn2+ was positively significantly correlated with the amount of P adsorbed by the soils, which could be described by the Langmuir equation. The amounts of Cu2+ and Zn2+ desorption from soils were decreased after P adsorption by the soils and the relationship between them was linear. After the soils adsorbed P, form distribution of Cu2+ and Zn2+ in soils changed remarforbly.

Interaction Between Charge Characteristics and Cu^(2+) Adsorption-Desorption of Soils with Variable or Permanent Charge

Charge characteristics and Cu2+ adsorption-desorption of soils with variable charge (latosol) and permanent charge (brown soil) and the relationship between them were studied by means of back-titration and adsorption equilibrium respectively. The amount of variable negative charge was much less in variable-charge soil than in permanent-charge soil and increased with the pH in the system, but the opposite trend occurred in the points of zero charge (PZCs). The amount of Cu2+ ions sorbed by permanent-charge soil was more than that by variable-charge soil and increased with the increase of Cu2+ concentration within a certain range in the equilibrium solution. The amount of Cu2+ ions desorbed with KC1 from permanent-charge soil was more than that from variable-charge soil, but the amount of Cu2+ ions desorbed with de-ionized water from permanent-charge soil was extremely low whereas there was still a certain amount of desorption from variable-charge soil. The increase of PZC of soils with variable or permanent charge varied with the increment of Cu2+ ions added. When the same amount of Cu2+ ions was added, the increments of PZC and variable negative surface charge of permanent-charge soil were different from those of variable-charge soil.

An Experimental Study on the Conductivity Changes in Coal during Methane Adsorption-Desorption and their Influencing Factors

During the processes of methane adsorption and desorption,the internal structure of coal changes,accordingly leading to changes in electrical conductivity.In this paper,using low rank coal seams of the Yan'an Formation in the Dafbsi field as the research subject,the relationship between coal resistivity,methane adsorption quantity,and equilibrium pressure is analyzed through proximate analysis,mercury injection tests,low temperature liquid nitrogen adsorption tests,and coal resistivity measurements during methane adsorption and desorption.The results show that during the process of pressure rise and methane adsorption,the conductivity of coal increases,resulting from heat release from methane adsorption,coal matrix swelling and adsorbed water molecules replaced by methane,but the resistivity reduction gradually decreases.The relationship between coal resistivity and methane adsorption quantity and equilibrium pressure can be described by a quadratic function.During the processes of depressurization and desorption,the resistivity of coal rebounds slightly,due to decalescence of methane desorption,coal matrix shrinkage and water-gas displacement,and the relationship coincides with a linear function.Methane adsorption leads to irreversible changes in coal internal structure and enhances the coal conductivity,and resistivity can not be restored to the initial level even after methane desorption.The resistivity and reduction rate of durain are higher than those of vitrain,with relatively greater homogeneous pore throat structure and fewer charged particles in the double electric layer.In addition,moisture can enhance the conductivity of coal and makes it change more complexly during methane adsorption and desorption.

Adsorption-Desorption Characteristics of Chlorimuron-Ethyl in Soils

The adsorption-desorption characteristics of chlorimuron-ethyl in soils were investigated to provide the basic data for evaluating the safety in field and the risk to water resource. The adsorption-desorption experiment was conducted by the batch equilibration and HPLC techniques; furthermore, data were analyzed with 5 mathematic models to describe the characteristics and mechanism of adsorption-desorption and translocation of the herbicide in soils. The results showed that the adsorption-desorption isotherms of chlorimuron-ethyl fitted for the Freundlich model well, and the physical reaction presents the main contribution during the adsorption-desorption process. The adsorption values （Kads-f） of chlorimuron-ethyl in 8 types of soil ranged from 0.798 to 6.891. The isotherms of 2# （Jiangxi clay） and 3# （Jiangxi sand loam） soils belong to the S-type curve, while the isotherms of another 6 type soils belong to the L-type isotherm. The results of desorption indicated that the hysteresis phenomena appeared during the desorption process, and the hysteresis coefficients （H） of the herbicides in 8 soils varied from 0.259-0.980. Furthermore, Kads-f and desorption values （Kads-f） increased with the OM （%） and the clay content increasing, while the values decreased with the soils pH increasing. The H values decreased with the OM and the clay content increasing, and increased with the soils pH increasing. It can be concluded that the low adsorption abilities of chlorimuron-ethyl in test soils and un-reversible adsorption existed in the process, which will induce the great translocation of the herbicide after application in field. It can be transported to ground or groundwater causing risk to environments. The physical and chemical properties of soils, including the OM, the clay content, and the pH of soil were the dominating factors during the adsorption-desorption.

Temperature Effect on Boron Adsorption-Desorption Kinetics in Soils

The effect of temperature on the properties of boron adsorption-desorption in brown-red soil, yellowbrown soil and calcareous alluvial soil of Hubei Province was investigated with the mobile displacement technique. The experimental data of B adsorption-desorption amounts and reaction t line at 25 and 40℃ were fitted by the zero-order, first-order and parabolic diffusion kinetic equations. The adsorption process was in conformity with the parabolic diffusion law at both the temperatures, and the values of rate constant of the parabolic diffusion equation in B adsorption were 0.138, 0.124 and 0.105 mg kg-1 min-1/2 at 25℃, and 0.147, 0.146 and 0.135 mg kg-1 min-1/2 at 40℃ for the brown-red soil, yellow-brown soil, and calcareous alluvial soil, respectively. The relationship between amount of B desorption and reaction time could be well described by the first-order kinetic equation, and the corresponding values of rate constant were 0.0422, 0.0563 and 0.0384 min-1 at 25℃, and 0.0408, 0.042 3 and 0.0401 min-1 at 40℃ for the brown-red soil, the yellow-brown soil and the calcareous alluvial soil, respectively. Therefore, the desorption process of B might be related to the amount of B adsorbed in soil. The higher the temperature, the lower the amount of B adsorption for the same soil in the same reaction time. The values of the apparent activation energy of B adsorption in the three soils calculated with the rate constants of parabolic diffusion equation were 3.27, 8.44 and 12.99 kJ mol-1, respectively, based on the experimental data of B adsorption amounts and reaction time at 25 and 40℃.

Optoelectronic Synapses Based on MXene/Violet Phosphorus van der Waals Heterojunctions for Visual‑Olfactory Crossmodal Perception

The crossmodal interaction of different senses,which is an important basis for learning and memory in the human brain,is highly desired to be mimicked at the device level for developing neuromorphic crossmodal perception,but related researches are scarce.Here,we demonstrate an optoelectronic synapse for vision-olfactory crossmodal perception based on MXene/violet phosphorus(VP)van der Waals heterojunctions.Benefiting from the efficient separation and transport of photogenerated carriers facilitated by conductive MXene,the photoelectric responsivity of VP is dramatically enhanced by 7 orders of magnitude,reaching up to 7.7 A W^(−1).Excited by ultraviolet light,multiple synaptic functions,including excitatory postsynaptic currents,pairedpulse facilitation,short/long-term plasticity and“learning-experience”behavior,were demonstrated with a low power consumption.Furthermore,the proposed optoelectronic synapse exhibits distinct synaptic behaviors in different gas environments,enabling it to simulate the interaction of visual and olfactory information for crossmodal perception.This work demonstrates the great potential of VP in optoelectronics and provides a promising platform for applications such as virtual reality and neurorobotics.

Deterioration Reason and Improvement Measure of the Retarding Effect of Protein Retarder on Phosphorus Building Gypsum

The retarding effect of protein retarder on phosphorus building gypsum(PBG)and desulfurization building gypsum(DBG)was investigated,and the results show that protein retarder for DBG can effectively prolong the setting time and displays a better retarding effect,but for PBG shows a poor retarding effect.Furthermore,the deterioration reason of the retarding effect of protein retarder on PBG was investigated by measuring the pH value and the retarder concentration of the liquid phase from vacuum filtration of PBG slurry at different hydration time,and the measure to improve the retarding effect of protein retarding on PBG was suggested.The pH value of PBG slurry(<5.0)is lower than that of DBG slurry(7.8-8.5).After hydration for 5 min,the concentration of retarder in liquid phase of DBG slurry gradually decreases,but in liquid phase of PBG slurry continually increases,which results in the worse retarding effect of protein retarder on PBG.The liquid phase pH value of PBG slurry can be adjusted higher by sodium silicate,which is beneficial to improvement in the retarding effect of the retarder.By adding 1.0%of sodium silicate,the initial setting time of PBG was efficiently prolonged from 17 to 210 min,but little effect on the absolute dry flexural strength was observed.

MOLECULAR BEAM STUDIES ON ADSORPTION-DESORPTION KINETICS OF CO AND H_2 ON Ni SURFACE

Adsorption-desorption kinetics of CO and H_2 on Ni surface were studied with molecular beam relaxation spectrometry. It is found that there are two adsorbed states in the substrate temperature range 330K<T<480K and 720K<T<900K respectively for CO/Ni system. These results can be explained by a precursor state model. Their kinetic parameters: E_(aα)=14.6kJ/mol, E_(dx)=49.3kJ/mol; E_(aβ)= 68.6kJ/mol, E_(dβ)=200.6kJ/mol. It is shown that there are two adsorbed states in the low (350K<T<430K) and high (550K<T<625K) temperature range respectively for H_2/Ni system. These results can be explained by a direct dissociative model. Their kinetic parameters:E_(dl)=26.3kJ/mol, E_(dh)=103.7kJ/mol.

Simultaneous removal of sulfur dioxide and nitrogen oxide from flue gas by phosphorus sludge:The performance and absorption mechanism

Developing low-cost and green simultaneous desulfurization and denitrification technologies is of great significance for sulfur dioxide(SO_(2))and nitrogen oxide(NO_(x))emission control at low temperatures,especially for small and medium-sized coal-fired boilers and furnaces.Herein,phosphorus sludge,an industrial waste from the production process of yellow phosphorus,has been developed to simultaneously eliminate SO_(2)and NO_(x)from coal-fired flue gas.The key factors affecting the experimental results indicate that desulfurization and denitrification efficiency of over 95%can be achieved at a low temperature of 55℃.Further,the absorption mechanism was investigated by characterizing the solid and liquid phases of the phosphorus sludge during the absorption process.The efficient removal of SO_(2)is attributed to the abundance of iron(Fe^(3+))and manganese(Mn^(2+))in the absorbent.SO_(2)can be rapidly catalyzed and converted to SO_(4)^(2-)by them.The key to NOx removal is the oxidation of NO toward watersoluble high-valent nitrogen oxides by oxidizing reactive substances induced via yellow phosphorus,which are then absorbed by water and converted to NO_(3)^(-).Meanwhile,yellow phosphorus is oxidized to phosphoric acid(H_(3)PO_(4)).The spent absorption slurry can be reused through wet process phosphoric acid production,as it contains sulfuric acid(H_(2)SO_(4)),nitric acid(HNO_(3)),and H_(3)PO_(4).Accordingly,this is a technology with broad application prospects.

Anisotropic Band Evolution of Bulk Black Phosphorus Induced by Uniaxial Tensile Strain

We investigate the anisotropic band structure and its evolution under tensile strains along different crystallographic directions in bulk black phosphorus(BP)using angle-resolved photoemission spectroscopy and density functional theory.The results show that there are band crossings in the Z-L(armchair)direction.

Environmental dynamics of nitrogen and phosphorus release from river sediments of arid areas

Human activities lead to the accumulation of a large amount of nitrogen and phosphorus in sediments in rivers.Simultaneously,nitrogen and phosphorus can be affected by environment and re-enter the upper water body,causing secondary pollution of the river water.In this study,laboratory simulation experiments were conducted initially to investigate the release of nitrogen and phosphorus from river sediments in Urumqi City and the surrounding areas in Xinjiang Uygur Autonomous Region of China and determine the factors that influence their release.The results of this study showed significant short-term differences in nitrogen and phosphorus release characteristics from sediments at different sampling points.The proposed secondary kinetics model(i.e.,pseudo-second-order kinetics model)better fitted the release process of sediment nitrogen and phosphorus.The release of nitrogen and phosphorus from sediments is a complex process driven by multiple factors,therefore,we tested the influence of three factors(pH,temperature,and disturbance intensity)on the release of nitrogen and phosphorus from sediments in this study.The most amount of nitrate nitrogen(NO_(3)^(–)-N)was released under neutral conditions,while the most significant release of ammonia nitrogen(NH_(4)^(+)-N)occurred under acidic and alkaline conditions.The release of nitrite nitrogen(NO_(2)^(-)-N)was less affected by pH.The dissolved total phosphorus(DTP)released significantly in the alkaline water environment,while the release of dissolved organic phosphorus(DOP)was more significant in acidic water.The release amount of soluble reactive phosphorus(SRP)increased with an increase in pH.The sediments released nitrogen and phosphorus at higher temperatures,particularly NH_(4)^(+)-N,NO_(3)^(–)-N,and SRP.The highest amount of DOP was released at 15.0℃.An increase in disturbance intensity exacerbated the release of nitrogen and phosphorus from sediments.NH_(4)^(+)-N,DTP,and SRP levels increased linearly with the intensity of disturbance,while NO_(3)^(–)-N and NO_(2)^(–)-N were more stable.This study provides valuable information for protecting and restoring the water environment in arid areas and has significant practical reference value.

Effects of phosphorus resorption on bioactive phosphorus of different-aged Pinus massoniana plantations

Phosphorus(P)is an important nutrient element in the photosynthesis process of plants.The effect of stand age on P nutrient dynamics in subtropical plantations is unclear.In this study,the mechanisms of above-and belowground P cycling in subtropical P.massoniana plantations of different stand ages(5,9,19,29 and 35 years)were investigated.The percentage of metabolic P in leaves exhibited an initial rise and subsequent decline with stand age of P.massoniana throughout the growing season,culminating in a metabolic P proportion of 34%–68% in litter.During the non-growing season,the main change in the P components of P.massoniana fine roots was a transition from metabolic P to residual P.Relative to during the growing season,soil ligand P fractions decreased by 7%–22% and exchangeable P fractions increased by 0–16%in the non-growing season.Organ P components tended to decrease with increasing stand age,mainly due to the gradual decrease in soil-bioavailable P,a trend alleviated by litter input.The generation of dissolved P by soil phosphatases would limit the reduction in soilbioavailable P caused by leaf P resorption to some extent.The differences in leaf organ P components between the growing and non-growing seasons are attributed to the allocation of P by the P.massoniana.Overall,the results of this study provide a basis for exploring the mechanisms of soil bioavailable P and soil P enzymemediated organ P component allocation in P.massoniana forests.These findings will help improve the management of P-limited P.massoniana plantations to enhance their productivity.

Soybean(Glycine max)rhizosphere organic phosphorus recycling relies on acid phosphatase activity and specific phosphorusmineralizing-related bacteria in phosphate deficient acidic soils

Bacteria play critical roles in regulating soil phosphorus(P) cycling. The effects of interactions between crops and soil P-availability on bacterial communities and the feedback regulation of soil P cycling by the bacterial community modifications are poorly understood. Here, six soybean(Glycine max) genotypes with differences in P efficiency were cultivated in acidic soils with long-term sufficient or deficient P-fertilizer treatments. The acid phosphatase(AcP) activities, organic-P concentrations and associated bacterial community compositions were determined in bulk and rhizosphere soils. The results showed that both soybean plant P content and the soil AcP activity were negatively correlated with soil organic-P concentration in P-deficient acidic soils. Soil P-availability affected the ɑ-diversity of bacteria in both bulk and rhizosphere soils. However, soybean had a stronger effect on the bacterial community composition, as reflected by the similar biomarker bacteria in the rhizosphere soils in both P-treatments. The relative abundance of biomarker bacteria Proteobacteria was strongly correlated with soil organic-P concentration and AcP activity in low-P treatments. Further high-throughput sequencing of the phoC gene revealed an obvious shift in Proteobacteria groups between bulk soils and rhizosphere soils, which was emphasized by the higher relative abundances of Cupriavidus and Klebsiella, and lower relative abundance of Xanthomonas in rhizosphere soils. Among them, Cupriavidus was the dominant phoC bacterial genus, and it was negatively correlated with the soil organic-P concentration. These findings suggest that soybean growth relies on organic-P mineralization in P-deficient acidic soils, which might be partially achieved by recruiting specific phoCharboring bacteria, such as Cupriavidus.

Combining field data and modeling to better understand maize growth response to phosphorus(P) fertilizer application and soil P dynamics in calcareous soils

We used field experimental data to evaluate the ability of the agricultural production system model (APSIM) to simulate soil P availability,maize biomass and grain yield in response to P fertilizer applications on a fluvo-aquic soil in the North China Plain.Crop and soil data from a 2-year experiment with three P fertilizer application rates(0,75 and 300 kg P_(2)O_(5) ha^(–1)) were used to calibrate the model.Sensitivity analysis was carried out to investigate the influence of APSIM SoilP parameters on the simulated P availability in soil and maize growth.Crop and soil P parameters were then derived by matching or relating the simulation results to observed crop biomass,yield,P uptake and Olsen-P in soil.The re-parameterized model was further validated against 2 years of independent data at the same sites.The re-parameterized model enabled good simulation of the maize leaf area index (LAI),biomass,grain yield,P uptake,and grain P content in response to different levels of P additions against both the calibration and validation datasets.Our results showed that APSIM needs to be re-parameterized for simulation of maize LAI dynamics through modification of leaf size curve and a reduction in the rate of leaf senescence for modern staygreen maize cultivars in China.The P concentration limits (maximum and minimum P concentrations in organs)at different stages also need to be adjusted.Our results further showed a curvilinear relationship between the measured Olsen-P concentration and simulated labile P content,which could facilitate the initialization of APSIM P pools in the NCP with Olsen-P measurements in future studies.It remains difficult to parameterize the APSIM SoilP module due to the conceptual nature of the pools and simplified conceptualization of key P transformation processes.A fundamental understanding still needs to be developed for modelling and predicting the fate of applied P fertilizers in soils with contrasting physical and chemical characteristics.

Natural variation in ZmGRF10 regulates tolerance to phosphate deficiency in maize by modulating phosphorus remobilization

Phosphorus is a limiting factor in agriculture due to restricted availability in soil and low utilization efficiency of crops.The identification of superior haplotypes of key genes responsible for low-phosphate(Pi)tolerance and their natural variation is important for molecular breeding.In this study,we conducted genome-wide association studies on low-phosphate tolerance coefficients using 152 maize inbred lines,and identified a significant association between SNPs on chromosome 7 and a low-phosphate tolerance coefficient.ZmGRF10 was identified as a candidate gene involved in adaptation of maize to Pi starvation.Expression of ZmGRF10 is induced by Pi starvation.A mutation in ZmGRF10 alleviated Pi starvation stress.RNA-seq analyses revealed significant upregulation of genes encoding various phosphatases in the zmgrf10-1 mutant,suggesting that ZmGRF10 negatively regulates expression of these genes,thereby affecting low-Pi tolerance by suppressing phosphorus remobilization.A superior haplotype with variations in the promoter region exhibited lower transcription activity of ZmGRF10.Our study unveiled a novel gene contributing to tolerance to low-Pi availability with potential to benefit molecular breeding for high Pi utilization.

Changes in Metabolites and Allelopathic Effects of Non-Pigmented and Black-Pigmented Lowland Indica Rice Varieties in Phosphorus Deficiency

Phosphorus(P) levels alter the allelopathic activity of rice seedlings against lettuce seeds. In this study, we investigated the effect of P deficiency on the allelopathic potential of non-pigmented and pigmented rice varieties. Rice seedlings of the white variety Khao Dawk Mali(KDML105, non-pigmented) and the black varieties Jao Hom Nin(JHN, pigmented) and Riceberry(RB, pigmented) were cultivated under high P(HP) and low P(LP) conditions. Morphological and metabolic responses to P deficiency were investigated. P deficiency inhibited shoot growth but promoted root growth of rice seedlings in all three varieties. Moreover, P deficiency led to decreased cytosolic phosphate(Pi) and total P concentrations in both shoot and root tissues. The subsequent reduction in internal P concentration enhanced the accumulation of phenolic compounds in both shoot and root tissues of the seedlings. Subsequently, allelopathy-based inter-and intra-specific interactions were assessed using water extracts from seedlings of the three varieties grown under HP and LP conditions. These extracts were tested on seeds of lettuce, the weed Dactyloctenium aegyptium, and the same rice variety. The shoot and root extracts from P-deficient seedlings reduced the germination of all recipient plants. Specifically, the shoot extract from P-deficient KDML105 seedlings reduced the germination index(GI) of lettuce seeds to 1%, while those from P-deficient RB and JHN seedlings produced GIs of 32% and 42%, respectively. However, when rice seeds were exposed to their own LP shoot and root extracts, their GIs increased up to 4-fold, compared with the HP extracts. Additionally, the shoot extracts from P-deficient plants also stimulated the germination of D. aegyptium by about 2–3-fold, whereas the root extracts did not have this effect. Therefore, P starvation led to the accumulation and exudation of phenolics in the shoots and roots of rice seedlings, altering their allelopathic activities. To adapt to P deficiency, rice seedlings potentially release signaling chemicals to suppress nearby competing species while simultaneously promoting their own germination and growth.

Integrating phosphorus management and cropping technology for sustainable maize production

Achieving high maize yields and efficient phosphorus(P)use with limited environmental impacts is one of the greatest challenges in sustainable maize production.Increasing plant density is considered an effective approach for achieving high maize yields.However,the low mobility of P in soils and the scarcity of natural P resources have hindered the development of methods that can simultaneously optimize P use and mitigate the P-related environmental footprint at high plant densities.In this study,meta-analysis and substance flow analysis were conducted to evaluate the effects of different types of mineral P fertilizer on maize yield at varying plant densities and assess the flow of P from rock phosphate mining to P fertilizer use for maize production in China.A significantly higher yield was obtained at higher plant densities than at lower plant densities.The application of single superphosphate,triple super-phosphate,and calcium magnesium phosphate at high plant densities resulted in higher yields and a smaller environmental footprint than the application of diammonium phosphate and monoammonium phosphate.Our scenario analyses suggest that combining the optimal P type and application rate with a high plant density could increase maize yield by 22%.Further,the P resource use efficiency throughout the P supply chain increased by 39%,whereas the P-related environmental footprint decreased by 33%.Thus,simultaneously optimizing the P type and application rate at high plant densities achieved multiple objectives during maize production,indicating that combining P management with cropping techniques is a practical approach to sustainable maize production.These findings offer strategic,synergistic options for achieving sustainable agricultural development.