High Rate Applications Research Articles

Phosphorus High-rate application through band placement improved cotton productivity under arid climate

The plant-available soil phosphorus rate and methods for applying phosphatic fertilizer and soil P-fixation capacity are critical factors for lower cotton productivity in Southern Punjab, Pakistan. Hence, a two-year study was conducted in Central Cotton Research Institute (CCRI), Multan, Pakistan, to examine the effects of various P rates and application methods on cotton crop output during the growing seasons of 2014 and 2015. Phosphorus was applied in four rates (0, 40, 80, and 120 kg ha−1 P2O5) using broadcast, band application, and fertigation methods. Results indicated that the impact of P rates was statistically significant on plant height, the number of nodes, monopodial and sympodial branches, leaf area index, harvest index, and seed cotton yield. The greater P application (120 kg P2O5 ha−1) had a better effect on cotton productivity than the lower application rates (0, 40, and 80 kg P2O5 ha−1). The band application responded better on nodes plant−1, sympodial branches plant−1, boll weight, leaf area index, lint yield, and harvest during the growing season 2015. Therefore, by adopting the band application coupled with 120 kg P2O5 ha−1 rather than the conventional method of broadcast, productivity of cotton crops could be increased.

Biochar and soil contributions to crop lodging and yield performance - A meta-analysis

Applying biochar has beneficial effects on regulating plant growth by providing water and nutrient availability for plants due to its physicochemical characteristics. Nevertheless, it is still unclear how soil and biochar interactions strengthen crop lodging resistance. The objective of the current study was to find out how soil physicochemical conditions and alterations in biochar affect lodging resistance and crop productivity in cereals. To do this, a meta-analysis was carried out using nine groups of effective variables including type of feedstock, pyrolysis temperature, application rate, soil pH, total nitrogen, available phosphorus, potassium, organic matter (OM), and soil texture. Results showed that straw-derived biochar caused the highest positive effect size in the dry weight of biomass (20.5%) and grain yield (19.9%). Also, the lowest lodging index was observed from straw (−8.3%) and wood-based (−5.6%) biochars. Besides, the high application rate of biochar results in the highest positive effect sizes of plant cellulose (8.1%) and lignin content (7.6%). Soils that contain >20 g kg−1 OM, resulted in the highest positive effect size in dry biomass (27.9%), grain yield (30.2%), and plant height (4.7%). Also, fine-textured soil plays an important role in increasing polymers in the anatomical structure of plants. Overall, the strong connection between biochar and soil processes, particularly the availability of OM, could strengthen plants' ability to tolerate lodging stress and contribute to high nutrient efficiency in terms of crop output and cell wall thickening.

Model Predictive Control for Level Control of a Conical Tank

Conical tanks have a high application rate in industrial processes, especially in colloidal mills, chemical processes, and food processing. The use of conical tanks presents significant benefits because they contribute to sedimentation and reduce the accumulation of impurities compared to conventional cylindrical tanks. However, level control of a conical tank due to its shape requires advanced strategies to guarantee efficient control. In this research, a model predictive control (MPC) method was designed and implemented for the level control of a conical tank on a laboratory scale. To evaluate the performance of the controller, it was compared with a traditional proportional–integral (PI) controller, and the rise time, settling time, overshoot, and error in the steady state were analyzed when different set point changes were tested. In addition, the system was subjected to disturbances, and the MPC demonstrated better performance in a transient state, as well as smooth and stable action controls that allowed for an increase in the useful life of the actuator. In addition, an interactive graphical interface was developed that allowed a dynamic response in a real plant to be experienced; this provides an academic tool for designing control strategies before implementation in a real process.

Sulfoxaflor residues and exposure risk assessment in grape under Egyptian field conditions.

Grapes are among the most popular fruits globally, and insecticides are commonly used on grape farms. Sulfoxaflor, a novel sulfoximine insecticide that works against various insect pests, is extensively used in Egypt. Our field trials assessed the dynamics and final residues of sulfoxaflor in grapes and grape leaves grown in Egyptian environments with different application rates, including worst-case scenarios. A QuEChERS-based method with LC-MS/MS was used to analyze residues of sulfoxaflor in grapes and grape leaves. The limit of quantification (LOQ) was validated at 0.01 mg‧kg-1. Sulfoxaflor residues are degraded in grapes and grape leaves according to a first-order kinetic model, with an estimated half-life (t1/2) of 7.04 and 7.7 days, respectively, and considerable degradation (74.68 and 72.16%, respectively) after 14 days. The final residues in grapes and grape leaves were below the Codex or EU maximum residue limit (MRL) (2 mg‧kg-1) after 3 days of the recommended and high application rates. The findings showed that grapes and leaves treated with sulfoxaflor at the recommended rate are safe for humans 3 days after two or three consecutive treatments with intervals of 14 days. The current study should pave the way for implementing safe and appropriate sulfoxaflor use in grapes and grape leaves in Egypt.

Polyaniline-Coated Na3V2(PO4)2F3 Cathode Enables Fast Sodium Ion Diffusion and Structural Stability in Rechargeable Batteries.

Na3V2(PO4)2F3 (NVPF), a typical sodium superionic conductor (NASICON) type structure, has attracted much interest as a potential positive electrode in sodium-ion battery. However, the inherently poor electronic conductivity of phosphates compromises the electrochemical properties of this material. Here, we develop a general strategy to improve the electrochemical performance by preparing a new composite material "polyaniline (PANI)@NVPF" using a Pickering emulsion method. The X-ray diffraction and Raman results indicated a successful PANI coating without affecting the NASICON-type structure of NVPF, and they enhanced the interfacial bonding between the two components. Also, thermogravimetric analysis and scanning electron microscopy analyses revealed that the PANI content influenced the thermal stability and morphology of the nanocomposites. As a result, the sodium test cells exhibited multielectron reactions and a better rate performance for PANI@NVPF nanocomposites as compared to NVPF. Specifically, 2%PANI@NVPF maintained 70% of its initial capacity at 5C. Ex-situ electron paramagnetic resonance revealed the existence of mixed valence states of vanadium (V4+/V3+) in both discharge and charge processes. Consequently, the successful PANI coating into the sodium superionic conductor framework improved the sodium diffusion channels with a measurable increase of diffusion coefficients with cycling (ca. 3.25 × 10-11 cm2 s-1). Therefore, PANI@NVPF nanocomposites are promising cathode candidates for high-rate sodium-ion battery applications.

Liquid-Phase Exfoliation of Arsenic Trisulfide (As2S3) Nanosheets and Their Use as Anodes in Potassium-Ion Batteries.

Here, we demonstrate the production of 2D nanosheets of arsenic disulfide (As2S3) via liquid-phase exfoliation of the naturally occurring mineral, orpiment. The resultant nanosheets had mean lateral dimensions and thicknesses of 400 and 10 nm, and had structures indistinguishable from the bulk. The nanosheets were solution mixed with carbon nanotubes and cast into nanocomposite films for use as anodes in potassium-ion batteries. These anodes exhibited outstanding electrochemical performance, demonstrating an impressive discharge capacity of 619 mAh/g at a current density of 50 mA/g. Even after 1000 cycles at 500 mA/g, the anodes retained an impressive 94% of their capacity. Quantitative analysis of the rate performance yielded a capacity at a very low rate of 838 mAh/g, about two-thirds of the theoretical capacity of As2S3 (1305 mAh/g). However, this analysis also implied As2S3 to have a very small solid-state diffusion coefficient (∼10-17 m2/s), somewhat limiting its potential for high-rate applications.

Optimizing application of dairy effluent with synthetic N fertilizer reduced nitrogen leaching in clay loam soil

High application rates of dairy effluent and manure are often associated with nitrogen (N) leaching, which can affect groundwater quality. Here, we used a lysimeter to examine N leaching losses and biomass yield following application of dairy effluent and manure under wheat-maize cropping. The field experiment included seven treatments: no N fertilizer (Control); 200/300 kg N ha−1 synthetic N fertilizer only (wheat/maize) (CN); 100/150 kg N ha−1 synthetic N fertilizer plus 100/150 (DE1), 150/200 (DE2) and 250/350 (DE3) kg N ha−1 dairy effluent; 100/150 kg N ha−1 synthetic fertilizer plus 100/150 kg N ha−1 dairy manure (SM1); and 150/225 kg N ha−1 synthetic fertilizer plus 50/75 kg N ha−1 dairy manure (SM2). Compared with CN, DE1 treatment increased maize yield by 10.0 %, wheat N use efficiency (NUE) by 26.5 %, and wheat and maize N uptake by 7.7–16.3 %, while reduced N leaching by 22.4 % in wheat season and by 40.4 % in the maize season. In contrast, DE2 and DE3 treatment increased N leaching by 27.2–241 % and reduced NUE by 26.2–55.2 %. SM2 treatment increased yield and NUE by 8.8 % and 7.8 %, respectively, and reduced N leaching by 42.9 % during the wheat but not the maize season. Annual N leaching losses were 37.6 kg N ha−1 under CN treatment, but decreased to 27.4 kg N ha−1 under DE1. In contrast, N leaching increased to 52.8 and 84.1 kg N ha−1 under DE2 and DE3 treatment, respectively (P < 0.05). Meanwhile, under SM1 and SM2 treatment, N leaching decreased by 71.2 % and 32.0 %, respectively, compared with CN. These results suggest that replacing 50 % and 25 % synthetic N fertilizer with dairy farm effluent and manure could reduce N leaching losses but had varied effects on crop productivity under wheat-maize cropping.

Effect of Ridge–Furrow with Plastic Film Mulching System and Different Nitrogen Fertilization Rates on Lodging Resistance of Spring Maize in Loess Plateau China

The ridge–furrow with plastic film mulching (RF) system has been widely adopted in rain-fed crop planting due to its potential to enhance crop yield and water use efficiency. However, the impact of the RF system on maize lodging resistance, particularly when nitrogen fertilizer is applied, remains uncertain. Therefore, a two-year field experiment was carried out with two planting systems (FP: flat planting and RF) and two nitrogen application rates (N180: 180 kg·N ha−1 and N300: 300 kg·N ha−1) to assess the risk of lodging in maize. The results showed that compared to FP, RF resulted in a significant increase of 78.7% in lodging rate. In addition, the lodging rate increased by 22.6% with increasing nitrogen fertilizer application. The lignin content increased by 43.4%, while the stalk bending strength rose by 42.5%, under RF compared to the FP system. These improvements in the mechanical properties of maize stalks contributed to the improved lodging resistance index of RF, which was found to be approximately 21.3% higher than that of FP. In addition, high nitrogen application rates increased the risk of lodging for different planting patterns over two years. In conclusion, fertilization of spring maize with 300 kg·N ha−1 under the RF system led to higher yields but increased lodging rates. The risk of lodging should be considered when planting maize under the RF system. The results of this study can provide scientific basis and technical support for the optimization of rain-fed maize cultivation measures in the Loess Plateau.

Optimal design of LiMn2O4 for high-rate applications by means of citric acid aided route and microwave heating

Due to shortening the duration of the process and possibility to obtain crystals of smaller and uniform size, microwave heating is considered an effective and promising tool for the synthesis of LiMn2O4, a valuable cathode material for lithium-ion batteries. However, electrochemical characteristics of LiMn2O4 obtained with its help are almost completely absent and do not allow for drawing a sound conclusion regarding advantages and drawbacks of microwave processing. Here we present a description of the microwave-assisted citric acid aided synthesis, characterization and electrochemical performance of LiMn2O4. The disclosure of detailed working protocols enabling one to manufacture samples tolerant to extremely high currents is the main novelty of this paper. Specifically, our material sustains current loads up to 40 C (5920 mA g-1) and completely recovers after cycling at harsh conditions.

Holistic analysis of cropping diversity and intensity implications for productive, environmental, and nutritional performance of smallholder farms in Bihar, India

The agricultural productivity and sustainability in Eastern Gangetic Plain Zones of India are threatened because of the inefficiency of current production practices, shortage of resources, and socioeconomic constraints. We hypothesized the potential impact of intensified cereal systems with mung bean as a third crop within the annual cropping cycle. We assessed economic, social, and environmental indicators for intensified and current cropping system management practiced by different farm types in the region using the FarmDESIGN model. Building on a farm typology constructed for the region in our past research, we used five types of farmers: part-time (PT), well-endowed (WE), small-scale (SS) crop and livestock mix, medium-scale (MS), and resource-poor farmers (RP) in this study. The performance indicators of the 229 original cropping systems cultivated within the 43 farms varied strongly in the eight performance indicators. This variability of cropping systems performance within the farm types resulted in the absence of significant differences between the types. Compared to the original cropping systems, the intensified cropping systems with mung bean not only performed high in dietary energy (DE) production and organic matter (OM) inputs into the soil but also had high application rates of biocides and minimized losses of nitrogen (N). The intervention systems were low in labor requirement and scored at an intermediate level for crop gross margin, water use, and greenhouse gas (GHG) emissions. The ranges of areas of maize- and rice-based systems that could be replaced by intensified systems were largest for the WE and RP farm types. This was reflected in large ranges of change in the performance indicators, but no significant differences in response were found between the farm types. The intensification of maize- and rice-based systems with the proposed intervention cropping systems involving mung bean would result in increased profitability, higher DE yield, and lower requirements for labor and water as the proportion of the farms being converted increases. However, the use of biocides would increase, while the intervention cropping systems would have no significant effect on OM input, GHG emissions, and soil N losses.

Biochar-Poultry Manure Compost Alters Temperature and Nitrogen Dynamics during Composting and Improves Potato Growth Following Field Application

Composting is an aerobic process that transforms organic wastes into valuable agricultural product, but the composting process frequently results in losses of nitrogen (N) through NH3 volatilization. We evaluated the potential for high-temperature, wood-based biochar to reduce N loss when included as a compost feedstock. Biochar was composted with wood shavings and poultry manure (4:1 v/v) at rates of 0, 20 and 40% (v/v) in replicated, actively aerated 1.43 m3 in-vessel compost piles. Biochar addition caused more rapid temperature increase and truncated thermophilic phase. N loss from the entire compost mass was reduced with 40% and 20% biochar addition compared to the control (29.9, 32.3, and 35.6% N loss, respectively; P value = 0.027). However, assuming no N was lost from the added biochar, difference in N loss was less significant (P value = 0.100). With 40% biochar addition, finished compost had greater NO3 --N concentration, lower electrical conductivity, greater carbon to nitrogen ratio, and greater total carbon content. Compost products were amended to soil at rates of 7 or 15 Mg C ha−1 in potato production. Relative to an unamended control, the high application rates tended to decrease bulk density and increase total N in soil, but no differences were detected between the compost or composted biochar treatments. Tuber weights were increased 40% with application of composted biochar (biochar 40% v/v). Biochar is a promising bulking agent for composting which may reduce N loss and increase nitrification. Future studies should examine how specific biochar products affect the compost process, nutrient retention, and crop production.

Performance of thin-RPC detectors for high rate applications with eco-friendly gas mixtures

In the last few years, an intense R &D activity on particle detectors for future HEP applications has been carried on with the aim of developing new techniques as well as studying the performance of already existing detectors when operated in a high rate environment. As for Resistive Plate Chamber detectors, the main challenges to face are the improvement of their detection capabilities and longevity at very high-rates, and the search for new eco-friendly gasmixtures free from greenhouse components. Results obtained in the framework of the RPC ECOGas@GIF++ Collaboration on a thin-Resistive Plate Chamber exposed at the CERN Gamma Irradiation Facility and operated with eco-friendly gas mixtures based on Tetrafluoropropene and Carbon dioxide will be discussed in this paper.

A bibliometric perspective on the occurrence and migration of microplastics in soils amended with sewage sludge.

The land application of sewage sludge from wastewater treatment plants has been recognized as a major source of microplastic contamination in soil. Nevertheless, the fate and behavior of microplastics in soil remain uncertain, particularly their distribution and transport, which are poorly understood. This study does a bibliometric analysis and visualization of relevant research publications using the CiteSpace software. It explores the limited research available on the topic, highlighting the potential for it to emerge as a research hotspot in the future. Chinese researchers and institutions are paying great attention to this field and are promoting close academic cooperation among international organizations. Current research hot topics mainly involve microplastic pollution caused by the land application of sewage sludge, as well as the detection, environmental fate, and removal of microplastics in soil. The presence of microplastics in sludge, typically ranging from tens of thousands to hundreds of thousands of particles (p)/kg, inevitably leads to their introduction into soil upon land application. In China, the estimated annual accumulation of microplastics in the soil due to sludge use is approximately 1.7 × 1013 p. In European countries, the accumulation ranges from 8.6 to 71 × 1013 p. Sludge application has significantly elevated soil microplastic concentrations, with higher application rates and frequencies resulting in up to several-fold increases. The primary forms of microplastics found in soils treated with sludge are fragments and fibers, primarily in white color. These microplastics consist primarily of components such as polyamide, polyethylene, and polypropylene. The vertical transport behavior of microplastics is influenced by factors such as tillage, wind, rainfall, bioturbation, microplastic characteristics (e.g., fraction, particle size, and shape), and soil physicochemical properties (e.g., organic matter, porosity, electrical conductivity, and pH). Research indicates that microplastics can penetrate up to 90 cm into the soil profile and persist for decades. Microplastics in sewage sludge-amended soils pose potential long-term threats to soil ecosystems and even human health. Future research should focus on expanding the theoretical understanding of microplastic behavior in these soils, enabling the development of comprehensive risk assessments and informed decision-making for sludge management practices. PRACTITIONER POINTS: Microplastics in sewage sludge range from tens to hundreds of thousands per kilogram. Sludge land application contributes significantly to soil microplastic pollution. The main forms of microplastics in sludge-amended soils are fragments and fibers. Microplastics are mainly composed of polyamide, polyethylene, and polypropylene. Microplastics can penetrate up to 90 cm into the soil profile and persist for decades.

Two-stage injection of polymer and microsand during ballasted flocculation for treating kaolin waters with or without humic acid: Floc evolutional characteristics, performance and mechanisms

Ballasted flocculation is regarded as a most promising water treatment technology in aspects of retrofit and high-rate applications. To deep understand the incorporation behaviors of ballasting agent into ballasted floc growth, two distinct injection modes (namely a two-stage injection of polyacrylamide (PAM) alone, and a two-stage injection of both PAM and microsand) were developed in this study. Then, ballasted flocculation tests of kaolin and kaolin-HA (humic acid) waters were conducted at varying split ratios for fixed total dosages of both PAM and microsand. The experimental results showed that for either two-stage injection mode, the higher the second percentage of each split ratio, the greater the average size of maturated flocs at the second sub-stage of maturation. Meanwhile, the turbidity and UV254 values of settled water became lower at 30 and 180 s of sedimentation, suggesting that varying split ratios significantly affected the kinetics of ballasted floc growth. Moreover, it was suggested that the selection of either two-stage injection mode or corresponding split ratios played a more pronounced role in the HA removal than the total dosage of PAM. This suggestion was supported by SEM, FTIR and XPS analyses for surface morphological details, functional groups and chemical states of maturated flocs eventually formed in the kaolin-HA water through both two-stage injection modes. Accordingly, newly-established conceptual models of ballasted floc growth were proposed to explore the potential influencing mechanisms of varying split ratios on the ballasted flocculation performance. At each sub-stage of maturation, an appropriate dosage ratio between PAM and microsand was of great importance to effectively incorporate microsand particles into ballasted floc formation, besides the hydrolyzed produces of AS coagulant formed at the coagulation stage of ballasted flocculation. This study is expected to provide valuable insights for making ballasted flocculation more effective, economical and sustainable in water treatment engineering.

Rock Phosphate and Biochar Effects on Greenhouse Gas Emissions and Soil Fertility in Southern Alberta Potato Field

The application of biochar soil amendment and rock phosphate fertilizer to the soil could lead to achieving net zero emissions and food security; however, the effectiveness of using biochar and rock phosphate in southern Alberta brown chernozemic soil is not yet assessed. In the first trial of this study, varying levels of urea (N), with varying levels of biochar (B) were applied. The same level of rock phosphate (RP) and triple super phosphate (TSP) were applied to compare efficiency of the two fertilizers. The second trial involved applying the same nutrients, but with higher levels than the first trial. The results indicated that the fertilizer application rates did not affect the growth and yield of potatoes because of the application rates of the fertilizer and fertility status of the soil, whereas in the second trial, TSP and RP treatments had the same growth and yield. Furthermore, the high application rate of nitrogen fertilizer and RP with or without biochar in the potato plot emitted high nitrous oxide gas emissions while the low application rate of nitrogen fertilizer and RP kept the carbon dioxide in the soil. Nevertheless, in the second experiment, the application of biochar and rock phosphate reduced nitrous oxide and carbon dioxide emissions. We observed high residual nitrogen and manganese nutrients after harvest in the plot treated to rock phosphate and biochar. Therefore, rock phosphate and biochar have the potential to increase food production and mitigate climate change.

An experimental investigation of forced convective liquid immersion cooling of a 12-cell li-ion battery module

This study details an experimental investigation of forced convective liquid immersion cooling of lithium-ion batteries. Twelve Samsung INR 18650 20S cylindrical cells, each with a nominal voltage of 4.2 V and nominal capacity of 2 Ah, are placed in a 4-in-series, 3-in-parallel arrangement inside a polycarbonate chamber. The cells are immersed in the dielectric fluid SF-33 and are discharged at C rates in the range of 1C to 4C. Temperature sensors placed along the body of each cell near the electrodes monitor their thermal behaviour during experiments. Results show that liquid immersion cooling is an effective method to maintain all cell temperatures within the desired temperature range of 15°C to 35°C for all cases tested, maintaining temperature differences within individual cells to ≤1.5°C, and those between cells to ≤3°C. This research contributes to the understanding of thermal management strategies for lithium-ion batteries, particularly in scenarios involving high discharge rate applications.

Active Soil Organic Carbon Pools Decrease with Increased Time since Land-Use Transition from Rice Paddy Cultivation to Areca Nut Plantations under the Long-Term Application of Inorganic Fertilizer

Many croplands in the tropics of China have been converted over the last decades into areca nut plantations due to their high economic returns. This land-use transition was accompanied by changes in agricultural practices such as soil moisture regimes and fertilizer inputs, which may affect soil organic carbon (SOC) and its fractions, especially in tropical soils with low fertility and high nitrogen loss. Yet, how the time since land-use transition from rice paddy cultivation to areca nut plantations affects soil carbon dynamics and their underlying mechanisms in the tropics of China remains elusive. Here, areca nut plantation soils with different ages (2, 5, 10, 14, and 17 years) and paddy fields in the tropical region of China were investigated. The study result indicates that the contents of dissolved organic carbon (DOC), particulate organic carbon (POC), easily oxidized organic carbon (EOC), light organic carbon (LFOC), and microbial biomass carbon (MBC) decreased significantly with increased time since land-use transition from rice paddy cultivation to areca nut plantations. Similarly, the ratios of DOC/SOC, MBC/SOC, POC/SOC, LFOC/SOC, and EOC/SOC decreased significantly with increased time since land-use transition. Compared with the paddy soil, the carbon pool management index decreased by 36.6–76.7% under the areca nut plantations, concluding that increasing the time since land-use transition from rice paddy cultivation to areca nut plantations with high application rates of chemical fertilizers resulted in reduced soil active carbon fractions and SOC supply capacity. Therefore, agricultural practices such as the use of organic fertilizers should be applied to improve the soil’s ability to supply organic carbon in managed plantation ecosystems in the tropics of China.

A rigid microfluidic chip for high-throughput fluorescence-activated cell sorting

Fluorescence-activated cell sorting (FACS) holds great promise for the separation of single cells or cell populations according to specific light scattering and fluorescent characteristics. Here, we present a new perspective on microfluidic FACS (μFACS) with predictable geometry, which meets the requirements of high-throughput analysis and sorting. Instead of the widely applied elastic polydimethylsiloxane (PDMS), a rigid epoxy resin chip was rapidly fabricated and irreversibly encapsulated to eliminate channel deformation (tenfold reduction) and enhance performance while meeting high pressure (>600 kPa) and high flow rate application scenarios. Fluorescence discrimination and particle differentiation were additionally validated in a self-contained μFACS system using calibration microspheres and mammalian cells. The μFACS chip and system were integrally optimized to achieve a minimum interval (0.58 ms) with a mean flow rate of 1.5 m/s. Ultimately, event recording and automated sorting were accomplished in real time while achieving a sorting efficiency of 87% at cell throughput of 8,000 events/s. This rigid chip for high-throughput μFACS, which is independent of the physical properties of cells could pave the way for cell screening in plasma samples for personalized medicine.

Long-term effects of biochar one-off application on soil physicochemical properties, salt concentration, nutrient availability, enzyme activity, and rice yield of highly saline-alkali paddy soils: based on a 6-year field experiment

Biochar application can alleviate the adverse effects of saline-alkali stress on crops. However, the long-term effects of one-off biochar application on soil physicochemical properties, salt concentration, nutrient availability, soil enzyme activities, and rice yield under highly saline-alkali paddy soils remain unclear. Here, a 6-year paddy field study was conducted in a saline-alkali paddy field using two nitrogen application levels (0 and 225 kg ha−1) and four biochar application rates [0 (T0), 1.5% (T1.5), 3.0% (T3.0), and 4.5% (T4.5) biochar, w/w]. The results showed that compared with T0, the bulk density (BD) under T1.5, T3.0, and T4.5 treatments significantly decreased by 11.21%, 16.33%, and 25.57%, while total porosity (Tp) and saturated hydraulic conductivity (Ks) increased by 19.15–27.34% and 3217.78–5539.83%, respectively. Biochar consistently improved soil macro-aggregates, mean weight diameter (MWD), and the percentage of water-stable aggregates (PWSA) over the years. Additionally, one-off application of biochar continuously reduced the soil Na+ concentration, Na+/K+ ratio, Na+/Ca2+ ratio, saturated paste extract (ECe), exchangeable sodium percentage (ESP), and sodium adsorption ratio (SARe). However, it reduced the pH in 2021 and 2022 only. It enhanced the concentration of K+, Ca2+, Mg2+, and cation exchange capacity (CEC) over the 6-year study, indicating its longer-term positive impact. Furthermore, the one-off biochar application, especially under high application rate treatments (T3.0 and T4.5), significantly and continuously improved nutrient availability and soil enzyme activities. However, alkali-hydrolysable nitrogen (AN) decreased in the initial year of biochar application. The grain yield of T1.5, T3.0, and T4.5 surpassed that of T0 by 116.38%, 141.24%, and 145.20%, respectively. Notably, the rice yield reached its peak with the treatment of 3.0% (w/w) in all 6 years of study period. These findings offered new perspectives on repairing and improving soil quality and production ability of highly saline-alkali paddy soils.Graphical

Effects of phosphorus application rate on distribution of 13C assimilates and spike formation in different til-lers of wheat with supplementary irrigation

To clarify the appropriate rate of phosphorus application and physiological mechanism for promoting wheat tillering and efficient utilization of phosphorus fertilizer with supplementary irrigation, we used 'Jimai 22' wheat variety as the test material, to set up three phosphorus application treatments, including low (90 kg P2O5·hm-2, P1), medium (135 kg P2O5·hm-2, P2), and high (180 kg P2O5·hm-2, P3) application rates, with no phosphorus application as the control (P0). We increased the relative soil water content of each treatment at join-ting stage and anthesis stage to 70%, and measured the area of tiller node, the content of endogenous hormones, the number of tillers in each tiller position, photosynthetic parameters, the distribution of 13C assimilates in each stem and tiller, as well as the grain yield and partial productivity of phosphate fertilizer. The results showed that compared with P0 and P1 treatments, P2 significantly increased the area of tiller node and the trans-zeatin (tZ), the photosynthetic parameters of the uppermost expanded leaves of the main stem, the total tillers per plant, and the distribution of 13C assimilates in each tiller. The number of ears per plant was increased by 0.51 and 0.36, and grain yield was increased by 40.3% and 13.2%, respectively. In P3 treatment, the number of tillers increased, but the panicles per plant, and the grain yield and phosphate fertilizer partial productivity decreased. Our results suggested that the moderate phosphorus treatment (135 kg·hm-2) under supplementary irrigation was suitable for high yield and high efficiency of wheat.