Universality of Tip Singularity Formation in Freezing Water Drops

A drop of water deposited on a cold plate freezes into an ice drop with a pointy tip. While this phenomenon clearly finds its origin in the expansion of water upon freezing, a quantitative description of the tip singularity has remained elusive. Here we demonstrate how the geometry of the freezing front, determined by heat transfer considerations, is crucial for the tip formation. We perform systematic measurements of the angles of the conical tip, and reveal the dynamics of the solidification front in a Hele-Shaw geometry. It is found that the cone angle is independent of substrate temperature and wetting angle, suggesting a universal, self-similar mechanism that does not depend on the rate of solidification. We propose a model for the freezing front and derive resulting tip angles analytically, in good agreement with observations.Comment: Letter format, 5 pages, 3 figures. Note: authors AGM and ORE contributed equally to the pape

SOC sequestration affected by fertilization in rice-based cropping systems over the last four decades

Enhancing soil organic carbon (SOC) stocks through fertilization and crop rotation will contribute to sustaining crop productivity and mitigating global warming. In this study, we analyzed the differences in total SOC stocks and their driving factors in the topsoil (0–20 cm) with various fertilization measures in two puddled lowland rice-based cropping systems (i.e., rice-wheat rotation and double rice rotation systems) over the last four decades from seven long-term experiments in the Yangtze River catchment. The soil types include Cambisol, Luvisol, and Anthrosol. The treatments include no fertilizer application (CK), application of chemical nitrogen, phosphorus and potassium fertilizers (NPK) and a combination of NPK and manure applications (NPKM). Every year, field was ploughed to a depth of 15–20 cm before wheat sowing and rice transplanting. Residue was removed after plant harvesting. Results showed that during the last four decades, the average crop grain yield ranged from 1,151 ± 504 kg ha−1 yr−1 under CK treatment to 7,553 ± 1,373 kg ha−1 yr−1 under NPKM treatment. The topsoil SOC stock significantly increased by 8.6 t ha−1 on average under NPKM treatment in rice-wheat system and by 2.5–6.4 t ha−1 on average under NPK and NPKM treatments in double rice system as compared with CK. A higher SOC sequestration rate and a longer SOC sequestration duration were found in NPKM treatment than that in NPK treatment in both cropping systems. The highest SOC stock ratio (SOC stock in fertilizer treatments to CK) was observed under the NPKM treatment in both cropping systems, though no significant difference was found between these two cropping systems. However, the fertilization-induced relative increase of the SOC stock was 109.5% and 45.8% under the NPK and NPKM treatments, respectively in the rice-wheat system than that in the double rice system. This indicates that the rice-wheat system is more conducive for SOC sequestration. RF and SEM analyses revealed that the magnitude and influencing factors driving SOC sequestration varied between two systems. In the double rice system, continuous flooding weakens the influence of precipitation on SOC sequestration and highlights the importance of soil properties and C input. In contrast, soil properties, C input and climate factors all have important impacts on SOC sequestration in rice-wheat system. This study reveals that the rice-wheat system is more favorable for SOC sequestration despite its lower C input compared to the double rice system in China’s paddies

Manure amendment acts as a recommended fertilization for improving carbon sequestration efficiency in soils of typical drylands of China

It is generally known that soil organic carbon (SOC) stocks tend to increase with increasing C input, whereas the C sequestration efficiency (CSE), i.e. the conversion ratio of C input to SOC, differs depending on the amount and type of C input. However, there still exists the need to better understand the impact of various fertilization practices on CSE. We studied the data from 8 long-term experiments located in the main dryland region of China in order to comprehensively assess the key drivers of CSE in the plough layer considering nearly four decades of various fertilizer treatments, i.e. no fertilizer (CK), chemical nitrogen, phosphorus and potassium (NPK/NP), chemical fertilizers plus manure (NPKM/NPM/NM) and straw (NPKS/NPS/NS). Our results showed that manure amendment had the most significant fertilization effect on SOC sequestration with the average CSE of 14.9%, which was significantly higher than that of chemical fertilizations (9.0%) and straw return treatments (7.9%). And manure amendment also had the highest average SOC increase rate of 684 kg C ha-1 yr-1. Variance partitioning analysis (VPA) illustrated that CSE of the main dryland region of China was mostly controlled by edaphic characteristics (32.2%), especially the soil C/N ratio and clay content. The VPA and structural equation modeling (SEM) revealed that the magnitude and influencing factors driving CSE varied among different fertilizer treatments. Soil total N was the limiting factor for CSE in the CK treatment, whereas the soil C/N ratio and pH were the main explanatory factors for CSE in the long-term chemical NPK fertilizer treatment. The negative impact of C input from straw was the main driver of CSE under straw return treatments, though C input had a positive effect on soil physical properties improvement. However, when considering manure amendments, the improvement of soil nutrients and clay content controlled CSE, underlining the main positive direct effect of soil chemical properties. In a nutshell, our results recommend manure plus chemical fertilizers as a sustainable practice for improving C sequestration rate and efficiency in dryland cropping systems

First-principles study of ternary fcc solution phases from special quasirandom structures

In the present work, ternary Special Quasirandom Structures (SQSs) for a fcc solid solution phase are generated at different compositions, $x_A=x_B=x_C=\tfrac{1}{3}$ and $x_A=\tfrac{1}{2}$, $x_B=x_C=\tfrac{1}{4}$, whose correlation functions are satisfactorily close to those of a random fcc solution. The generated SQSs are used to calculate the mixing enthalpy of the fcc phase in the Ca-Sr-Yb system. It is observed that first-principles calculations of all the binary and ternary SQSs in the Ca-Sr-Yb system exhibit very small local relaxation. It is concluded that the fcc ternary SQSs can provide valuable information about the mixing behavior of the fcc ternary solid solution phase. The SQSs presented in this work can be widely used to study the behavior of ternary fcc solid solutions.Comment: 20 pages, 7 figure

Detection Of Apple Stem Grooving Virus In Dormant Apple Trees With Crude Extracts As Templates For One-Step Rt-Pcr

peer reviewe

Pour un échantillonnage et un conseil agronomique raisonné, les outils d'aide à la décision

To a sampling and personal fertility advice, the tools for decision support. Environmental and agronomic issues require always more well thought and suited farmer management of agricultural inputs; soil analysis is therefore an essential tool to support decision. However, for a soil analysis to provide valuable information, it is essential for the sample to be representative of the studied field. Without this representativeness, an analytical result, as accurate as it could be, would not be of interest if it could mislead the farmer. In practice, the main difficulty for the sampler is the recognition of soil criteria which are essential to provide a fertility advice, especially in Wallonia (Belgium) where soil variability is very important. With the Digital Soil Map of Wallonia (DSMW), drowned at the scale 1/5,000, it seems appropriate to give these information to the samplers in an useful form for routine works. That is why a mapping tool for decision support, named REQUACARTO, was designed to be used for soil analysis by provincial laboratories, members of the REQUASUD laboratories network. This tool responds to a real requirement in Wallonia: achieving a quality sampling for the development of personalized soil fertility advice

L'intérêt de la spectroscopie proche infrarouge en analyse de terre (synthèse bibliographique)

Use of near-infrared reflectance spectroscopy in soil analysis. A review. This paper presents a literature review on the development of near infrared reflectance spectroscopy for soil analysis and the contribution of this technique to the evaluation of soil fertility analysis. This technique is used to estimate the chemical composition of soil samples on the basis of their absorption properties. It is therefore an indirect method of measurement, which requires a calibration phase for the prediction of these properties. NIR spectroscopy offers many advantages compared to reference analysis: it is known to be a physical, non-destructive, rapid, reproducible and low cost method. Often employed in other analytical domains, such as agro-food, NIR spectroscopy has, however, seldom been used in soil characterization, due to the complexity of the soil matrix. Thanks to the development of chemometric methods, numerous studies have recently been conducted to evaluate the feasibility of the application of the technique in soil analysis. Most authors conclude that NIR spectroscopy is promising; however, to date, use of the technique has not spread to routine laboratories. The paper is organized as follows. Firstly, we provide an overview of the NIR spectroscopy technique and related chemometric methods. Secondly, we describe the soil characteristics that can be predicted using this technique. Finally, we detail examples of results that have been obtained through the use of the technique, mainly in the determination of clay and organic carbon content, and of cation exchange capacity

Charge Distributions in Metallic Alloys: a Charge Excess Functional theory approach

Charge Distributions in Metallic Alloys: a Charge Excess Functional theory approachComment: 13 pages, 5 figure

Both yields of maize and soybean and soil carbon sequestration in typical Mollisols cropland decrease under future climate change SPACSYS simulation

Although Mollisols are renowned for their fertility and high-productivity, high carbon (C) losses pose a substantial challenge to the sustainable provision of ecosystem services, including food security and climate regulation. Protecting these soils with a specific focus on revitalizing their C sequestration potential emerges as a crucial measure to address various threats associated with climate change. In this study, we employed a modeling approach to assess the impact of different fertilization strategies on crop yield, soil organic carbon (SOC) stock, and C sequestration efficiency (CSE) under various climate change scenarios (baseline, RCP 2.6, RCP 4.5, and RCP 8.5). The process-based SPACSYS model was calibrated and validated using data from two representative Mollisol long-term experiments in Northeast China, including three crops (wheat, maize and soyabean) and four fertilizations (no-fertilizer (CK), mineral nitrogen, phosphorus and potassium (NPK), manure only (M), and chemical fertilizers plus M (NPKM or NM)). SPACSYS effectively simulated crop yields and the dynamics of SOC stock. According to SPACSYS projections, climate change, especially the increased temperature, is anticipated to reduce maize yield by an average of 14.5% in Harbin and 13.3% in Gongzhuling, and soybean yield by an average of 10.6%, across all the treatments and climatic scenarios. Conversely, a slight but not statistically significant average yield increase of 2.5% was predicted for spring wheat. SOC stock showed a decrease of 8.2% for Harbin and 7.6% for Gonghzuling by 2,100 under the RCP scenarios. Future climates also led to a reduction in CSE by an average of 6.0% in Harbin (except NPK) and 13.4% in Gongzhuling. In addition, the higher average crop yields, annual SOC stocks, and annual CSE (10.15–15.16%) were found when manure amendments were performed under all climate scenarios compared with the chemical fertilization. Soil CSE displayed an exponential decrease with the C accumulated input, asymptotically approaching a constant. Importantly, the CSE asymptote associated with manure application was higher than that of other treatments. Our findings emphasize the consequences of climate change on crop yields, SOC stock, and CSE in the Mollisol regions, identifying manure application as a targeted fertilizer practice for effective climate change mitigation