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The accurate estimation and timely diagnosis of crop nitrogen (N) status can facilitate in-season fertilizer management. In order to evaluate the performance of three leaf and canopy optical sensors in non-destructively diagnosing winter wheat N status, three experiments using seven wheat cultivars and multi-N-treatments (0-360 kg N ha -1 ) were conducted in the Jiangsu province of China from 2015 to 2018. Two leaf sensors (SPAD 502, Dualex 4 Scientific+) and one canopy sensor (RapidSCAN CS-45) were used to obtain leaf and canopy spectral data, respectively, during the main growth period. Five N indicators (leaf N concentration (LNC), leaf N accumulation (LNA), plant N concentration (PNC), plant N accumulation (PNA), and N nutrition index (NNI)) were measured synchronously. The relationships between the six sensor-based indices (leaf level: SPAD, Chl, Flav, NBI, canopy level: NDRE, NDVI) and five N parameters were established at each growth stages. The results showed that the Dualex-based NBI performed relatively well among four leaf-sensor indices, while NDRE of RS sensor achieved a best performance due to larger sampling area of canopy sensor for five N indicators estimation across different growth stages. The areal agreement of the NNI diagnosis models ranged from 0.54 to 0.71 for SPAD, 0.66 to 0.84 for NBI, and 0.72 to 0.86 for NDRE, and the kappa coefficient ranged from 0.30 to 0.52 for SPAD, 0.42 to 0.72 for NBI, and 0.53 to 0.75 for NDRE across all growth stages. Overall, these results reveal the potential of sensor-based diagnosis models for the rapid and non-destructive diagnosis of N status.

Intensive management of C. oleifera has produced many pure C. oleifera plantations. The transmission of C. oleifera plantation will potentially affect soil C, N, and P pools as well as their stoichiometric characteristics both in top soil layer and vertical soil profile due to the intensive management. To understand changes in vertical pools and stoichiometric characteristics of soil C, N, and P as affected by intensive management of C. oleifera plantations, both mixed and pure C. oleifera plantations were studied. We conducted studies in five locations in Jiangxi, China with both pure and mixed C. oleifera plantations, to compare changes in vertical pools and stoichiometry of C, N, and P. Both C and N pools were significantly different between mixed and pure plantation types of C. oleifera. However, the ratio of C:N, C:P, and N:P was consistently higher in mixed plantations with C:P and N:P altered but C:N ratio did not change with soil depth. The intensive management significantly impact both C and N pools and the stoichiometry of C, N, and P. Intensive management of C. oleifera plantations decreased both C and N pools, especially at the depth of 30-50 cm soil layer. C. oleifera plantation alteration from mixed to pure should be considered in future forest management practice considering the substantial effects on soil element cycling and distribution along vertical soil profile., Competing Interests: The authors have declared that no competing interests exist.

Critical nitrogen (N) dilution curves (CNDCs) have been developed to describe the dilution dynamic of N and to diagnose N status in plants. In this study, to develop a convenient alternative CNDC determination method, four field experiments involving different N rates (0-360 kg N ha -1 ) and six wheat varieties were performed at different eco-sites from 2014 to 2019. The normalised difference red-edge (NDRE) index extracted from the RapidSCAN CS-45 (Holland Scientific Inc., Lincoln, NE, USA) sensor was used as a driving factor instead of plant dry matter (PDM) to establish a new alternative winter wheat CNDC. The newly developed CNDC was described by the equation Nc = 0.90NDRE -0.88 , when NDRE values were ≤ 0.19 and constant Nc = 3.81%, which was independent of the NDRE values. Compared to PDM-derived CNDC (R 2 = 0.73) developed with the same dataset, a comparable precision was obtained using NDRE-derived CNDC (R 2 = 0.76) and both CNDCs could accurately discriminate wheat N status. Moreover, the NDRE could be inexpensively and rapidly measured using the active sensor. The relationship between NDRE-derived CNDC and grain yield was also analysed to facilitate in-season N management, and the R 2 value reached 0.79 and 0.87 at jointing and booting stages, respectively. The NDRE-based CNDC can be used to effectively diagnose wheat N status and as an alternative approach for non-destructive determination of crop N levels.

Accurate estimation and monitoring of crop nitrogen can assist in timely diagnosis and facilitate necessary technical support for fertilizer management. Four experiments, involving three cultivars and six nitrogen (N) treatments, were conducted in southeast China to compare the two leaf-clip meters (Dualex 4 Scientific+, Force-A, Orasy, France; Soil and Plant Analyzer Development (SPAD) meter, Minolta Camera Co., Osaka, Japan) for their ability to measure nitrogen nutrient-related indicators. The results indicated that Chl had a better monitoring accuracy for chlorophyll in per unit leaf area as compared to SPAD value, and there was no saturation to appear under high leaf chlorophyll concentration status. Flavonoids (Flav) presented the advantage of early diagnosis of rice N nutrition status (about one day as compared to SPAD value). As a reliable N nutrient diagnosis indicator, it also improved the estimation accuracy compared with the classical SPAD-based method. The other Dualex value also obtained good monitoring results. Flav was positively correlated with N deficiency, and with higher R 2 in panicle initiation and booting stages with low RMSE, respectively; whereas SPAD value was negatively correlated with nitrogen deficiency. Therefore, the Flav-based nitrogen application model was found to provide an early rice nitrogen fertilizer application approach, especially in the panicle initiation and booting stages.

The critical nitrogen (N) dilution curve is a suitable analytical tool for in-season estimation of N status to implement precision N management. This study was undertaken for a comprehensive comparison of N dilution curves in Japonica and Indica rice to investigate, whether a single curve can be used for both rice ecotypes and to determine the most robust plant index for assessing N status in rice ecotypes. The different N dilution curves were developed based on plant dry matter (PDM), leaf area index (LAI), leaf dry matter (LDM) and stem dry matter (SDM) for N diagnosis in Japonica and Indica rice. The comparison of N dilution curves of two rice ecotypes showed non-significant differences, therefore a single/unified curve can be used to assess plant N status for precision N management in both rice ecotypes. The relationships between PDM based, with LAI, LDM, and SDM based N nutrition index, accumulated N deficit and N requirement, indicated that leaf based approaches could be used as substitutes for PDM approach. The lower coefficient b values of LDM based curve (due to efficient physiological N use in leaves) implied that LDM was the most appropriate approach for developing N curve as compared to other approaches.

Diagnosing the status of crop nitrogen (N) helps to optimize crop yield, improve N use efficiency, and reduce the risk of environmental pollution. The objectives of the present study were to develop a critical N (Nc) dilution curve for winter wheat (based on spike dry matter [SDM] during the reproductive growth period), to compare this curve with the existing Nc dilution curve (based on plant dry matter [DM] of winter wheat), and to explore its ability to reliably estimate the N status of winter wheat. Four field experiments, using varied N fertilizer rates (0-375 kg ha-1) and six cultivars (Yangmai16, Ningmai13, Ningmai9, Aikang58, Yangmai12, Huaimai 17), were conducted in the Jiangsu province of eastern China. Twenty plants from each plot were sampled to determine the SDM and spike N concentration (SNC) during the reproductive growth period. The spike Nc curve was described by Nc = 2.85×SDM-0.17, with SDM ranging from 0.752 to 7.233 t ha-1. The newly developed curve was lower than the Nc curve based on plant DM. The N nutrition index (NNI) for spike dry matter ranged from 0.62 to 1.1 during the reproductive growth period across the seasons. Relative yield (RY) increased with increasing NNI; however, when NNI was greater than 0.96, RY plateaued and remained stable. The spike Nc dilution curve can be used to correctly identify the N nutrition status of winter wheat to support N management during the reproductive growth period for winter wheat in eastern China., Competing Interests: The authors have declared that no competing interests exist.

Biomass-derived nitrogen self-doped porous carbon was synthesized by a facile procedure based on simple pyrolysis of water hyacinth (eichhornia crassipes) at controlled temperatures (600-800 °C) with ZnCl2 as an activation reagent. The obtained porous carbon exhibited a BET surface area up to 950.6 m(2) g(-1), and various forms of nitrogen (pyridinic, pyrrolic and graphitic) were found to be incorporated into the carbon molecular skeleton. Electrochemical measurements showed that the nitrogen self-doped carbons possessed a high electrocatalytic activity for ORR in alkaline media that was highly comparable to that of commercial 20% Pt/C catalysts. Experimentally, the best performance was identified with the sample prepared at 700 °C, with the onset potential at ca. +0.98 V vs. RHE, that possessed the highest concentrations of pyridinic and graphitic nitrogens among the series. Moreover, the porous carbon catalysts showed excellent long-term stability and much enhanced methanol tolerance, as compared to commercial Pt/C. The performance was also markedly better than or at least comparable to the leading results in the literature based on biomass-derived carbon catalysts for ORR. The results suggested a promising route based on economical and sustainable biomass towards the development and engineering of value-added carbon materials as effective metal-free cathode catalysts for alkaline fuel cells.

Plant analysis is a very promising diagnostic tool for assessment of crop nitrogen (N) requirements in perspectives of cost effective and environment friendly agriculture. Diagnosing N nutritional status of rice crop through plant analysis will give insights into optimizing N requirements of future crops. The present study was aimed to develop a new methodology for determining the critical nitrogen (Nc) dilution curve based on stem dry matter (SDM) and to assess its suitability to estimate the level of N nutrition for rice (Oryza sativa L.) in east China. Three field experiments with varied N rates (0-360 kg N ha(-1)) using three Japonica rice hybrids, Lingxiangyou-18, Wuxiangjing-14 and Wuyunjing were conducted in Jiangsu province of east China. SDM and stem N concentration (SNC) were determined during vegetative stage for growth analysis. A Nc dilution curve based on SDM was described by the equation (Nc = 2.17W(-0.27) with W being SDM in t ha(-1)), when SDM ranged from 0.88 to 7.94 t ha(-1). However, for SDM < 0.88 t ha(-1), the constant critical value Nc = 1.76% SDM was applied. The curve was dually validated for N-limiting and non-N-limiting growth conditions. The N nutrition index (NNI) and accumulated N deficit (Nand) of stem ranged from 0.57 to 1.06 and 51.1 to -7.07 kg N ha(-1), respectively, during key growth stages under varied N rates in 2010 and 2011. The values of ΔN derived from either NNI or Nand could be used as references for N dressing management during rice growth. Our results demonstrated that the present curve well differentiated the conditions of limiting and non-limiting N nutrition in rice crop. The SDM based Nc dilution curve can be adopted as an alternate and novel approach for evaluating plant N status to support N fertilization decision during the vegetative growth of Japonica rice in east China.

Leaf equivalent water thickness (LEWT) is an important indicator of crop water status. Effectively monitoring the water status of wheat under different nitrogen treatments is important for effective water management in precision agriculture. Trends in the variation of LEWT in wheat plants during plant growth were analyzed based on field experiments in which wheat plants under various water and nitrogen treatments in two consecutive growing seasons. Two-band spectral indices [normalized difference spectral indices (NDSI), ratio spectral indices (RSI), different spectral indices (DSI)], and then three-band spectral indices were established based on the best two-band spectral index within the range of 350-2500 nm to reduce the noise caused by nitrogen and saturation. Then, optimal spectral indices were selected to construct models of LEWT monitoring in wheat. The results showed that the two-band spectral index NDSI(R1204, R1318) could be used for LEWT monitoring throughout the wheat growth season, but the model performed differently before and after anthesis. Therefore, further two-band spectral indices NDSIb(R1445, R487), NDSIa(R1714, R1395), and NDSI(R1429, R416), were constructed for the two developmental phases, with NDSI(R1429, R416) considered to be the best index. Finally, a three-band index (R1429-R416-R1865)/(R1429+R416+R1865), which was superior for monitoring LEWT and reducing the noise caused by nitrogen, was formed on the best two-band spectral index NDSI(R1429, R416) by adding the 1,865 nm wavelenght as the third band. This produced more uniformity and stable performance compared with the two-band spectral indices in the LEWT model. The results are of technical significance for monitoring the water status of wheat under different nitrogen treatments in precision agriculture.

Nitrogen (N) fertilizer management plays a crucial role in high-yield rice production. To choose a well-performing rice N nutrient diagnosis indicator for developing rice production management strategies, this research conducted five field experiments under various N treatments. The results showed that machine learning and stepwise multiple linear regression suggested a strong relationship between vegetation indexes and agronomic indicators (0.70 > R2 > 0.51). A strong correlation was obtained between red-edge based vegetation indexes and agronomic indicators (R2 > 0.40). Additionally, the all-subset regression method results demonstrated that the red-edge basis vegetation indexes were generally applied during different vegetation index combinations. The red-edge basis vegetation indexes reached an approximately 40% contribution in nitrogen nutrient index prediction and an approximately 48% contribution in leaf area index monitoring. Furthermore, this study combined the normalized difference red-edge (NDRE) basis dynamic model to calculate the N dose, which ranged from 106 to 134 kg per hectare in large-scale N management according to the NDRE from Sentinel-2B images, a decrease of approximately 46 kg N ha−1 fertilizer compared with farmers' practices. Nevertheless, more refinements are needed to ensure that this strategy can be applied to farmers' yield- and income-enhancing production. [ABSTRACT FROM AUTHOR]

• Three CNFs with different defective degrees are synthesized and identified. • N-doping of CNFs is implemented using in-situ synthesis and post treatment methods. • Thermal treatment of N-doped CNFs is adopted for generating edge-like defects. • Pt catalysts supported over various CNFs display different catalytic activity in dehydrogenation. • Edges and edge-like defects in CNFs are proven to be the most efficient active sites in catalysis. Three kinds of carbon nanofibers (CNFs) with different microstructures: platelet CNFs (CNFs-P), fishbone CNFs (CNFs-F) and tubular CNFs (CNFs-T) were synthesized as Pt catalyst supports for decalin dehydrogenation to release hydrogen. Different types of defects including doped nitrogen and edge-like sites were purposefully introduced into three pristine CNFs by employing N-doping and thermal treatment methods. The defective properties of the CNFs were identified by combining the intensity ratio and full width at half maximum of D and G bands derived from Raman spectra of the CNFs. It was revealed together with XPS analysis of Pt 4f 7/2 binding energy that the electronic property of Pt nanoparticles is very sensitive to the surface defect density of CNF supports. Further catalytic performance evaluation showed that Pt supported on the CNFs-P which are featured of the largest quantity of exposed edge sites can provide the most proper electronic property of the catalyst due to suitable metal-support interaction, thereby affording the highest catalytic activity. Moreover, N-doping by both in-situ synthesis and post-treatment manner can favor the Pt catalysts on the tubular and fishbone CNFs to increase their activity, but do harm to the activity of the Pt/CNFs-P. Thermal treatment of N-doped CNFs can generate new edge-like defects by removing N-species, thus beneficial to the activity of Pt catalysts on either tubular or fishbone CNFs. Therefore, the edge sites and edge-like defects on the surface of CNFs are proven to be the best ones, which can promote the catalytic activity of the supported Pt nanoparticles for the dehydrogenation reaction efficiently. [ABSTRACT FROM AUTHOR]

Capacitive deionization (CDI) is a promising technique for water treatment and desalination. To enable high CDI performance, the electrode materials should possess high surface area, conductivity, hydrophilicity, and cycling stability. Here, we report the design and construction of a hierarchical porous composite of N-doped hollow mesoporous carbon sphere and holey graphene hydrogel with in-plane pores, i.e. , N-HMCS/HGH composite, for high-performance CDI. The N-HMCS/HGH composite shows a three-dimensional (3D), hierarchical porous structure with a specific surface area of 337.7 m2 g−1, high conductivity, and high hydrophilicity. With these structural characteristics, the optimized N-HMCS/HGH electrode exhibits a large specific capacitance (226.5 F g−1) in 0.5 M NaCl solution to ensure a large electrosorption capacity of 17.8 and 32 mg g−1 in a feeding NaCl solution with initial concentration of 500 and 2500 mg L−1, respectively. Upon 35 CDI-regeneration cycles, the electrosorption capacity of the N-HMCS/HGH electrode shows no obvious attenuation, exhibiting excellent cycling stability. These results indicate that the hierarchical N-HMCS/HGH composite shows great potential for practical application. Unlabelled Image • N-HMCS/HGH composite with a high specific surface area was prepared. • Its HGH matrix endows high conductivity avoiding the use of electrode binder. • N-doping further improves the hydrophilicity of the composite. • The composite delivers a large capacitance for remarkable electrosorption capacity. [ABSTRACT FROM AUTHOR]

Crop nitrogen (N) status during vegetative growth is an essential indicator of crop vigor and predictor of subsequent grain yield. The concept of the critical nitrogen (Nc) dilution curve has been used for in-season assessment of crop N status, yet it remains to be determined that how plant N status during vegetative growth can be related to grain yield at maturity in rice. The present study was endeavored to establish the relationships of relative grain yield (RY) to N nutrition index (NNI), accumulated N deficit (AND), and N requirement (NR) at different growth stages of Japonica and Indica rice on the basis Nc dilution curve of the rice plant. Four multi-N rate field experiments were conducted in Jiangsu province of east China using five rice hybrids. Growth analysis was carried out to determine the Nc dilution curve and related N parameters during vegetative growth period. The relationships between RY and NNI, AND, NR at different growth stages were highly significant with R 2 values all greater than 0.74 for both Japonica and Indica rice, with the strongest R 2 ranging from 0.94 to 0.99 for the relationships at panicle initiation (PI) and booting (BT) stages. Validation of the regression models with independent datasets exhibited a solid model performance at PI and BT stages with R 2 values greater than 0.92 and RMSE values lower than 10%, confirming the robustness of the relationships at PI and BT stages. The k coefficients at PI and BT stages for the observed and predicted RY were close to 1. Overall, the robust relationships of RY to NNI, AND and NR at PI and BT stages well explained the variation in RY under limiting and non-limiting N growth conditions, and gave a reliable estimation of rice grain yield in east China. [ABSTRACT FROM AUTHOR]

A synthetic method was developed for the preparation of N-doped porous carbon through hydrothermal treatment at controlled temperatures by using glucose and dicyandiamide as precursors and ZnCl2 as an activation reagent. Nitrogen doping was quantitatively determined by using XPS measurements and identified in the forms of pyridinic, pyrrolic, graphitic, and pyridinic N+O−nitrogen atoms. Further structural analysis by using SEM, TEM, XRD, Raman, FTIR, and BET measurements showed that the N-doped porous carbons exhibited a microcrystalline graphite structure and a high specific surface area up to 1000 m2 g−1. Electrochemical studies showed that the samples all exhibited a remarkable ORR catalytic activity in alkaline media, which was comparable to that of state-of-the-art Pt/C catalysts, and the one prepared at 800 °C was found to be the best among the series with an onset potential of +0.96 V, almost complete reduction of oxygen to OH−, and superior methanol tolerance and cycling stability. [ABSTRACT FROM AUTHOR]

Abstract: The common spectra wavebands and vegetation indices (VI) were identified for indicating leaf nitrogen accumulation (LNA), and the quantitative relationships of LNA to canopy reflectance spectra were determined in both wheat (Triticum aestivum L.) and rice (Oryza sativa L.). The 810 and 870nm are two common spectral wavebands indicating LNA in both wheat and rice. Among all ratio vegetation indices (RVI), difference vegetation indices (DVI) and normalized difference vegetation indices (NDVI) of 16 wavebands from the MSR16 radiometer, RVI (870, 660) and RVI (810, 660) were most highly correlated to LNA in both wheat and rice. In addition, the relations between VIs and LNA gave better results than relations between single wavebands and LNA in both wheat and rice. Thus LNA in both wheat and rice could be indicated with common VIs, but separate regression equations are better for LNA monitoring. [Copyright &y& Elsevier]

• Using different optical sensors indexes for developing nitrogen dilution curves. • Proving plant nitrogen accumulation is more reliable nitrogen status diagnosis indicator. • Comparing the performance of Greenseeker and SPAD meter in nitrogen nutrition diagnosis. Nitrogen (N) plays an essential role in the crop growing cycle. Canopy vegetation indexes and chlorophyll concentration were important tools in-crop N status diagnosis and provided a crucial guide for agricultural managers. This work focused on evaluating the performance of different chlorophyll-related indexes (canopy chlorophyll index, CCI) and Greenseeker RT 200 values (GS values, normalized difference vegetation index, NDVI & Ratio vegetation index, RVI) in crop N nutrient diagnosis. Four experiments were conducted with multiple N fertilizer rates (0 ∼ 390 kg N ha−1) and seven Japonica rice (Oryza sativa L.). Results suggested that the relationship between CCI value and tissue nitrogen accumulation [including leaf nitrogen accumulation (LNA) and plant N accumulation (PNA)] was more reliable than that of GS values. Compered GS values with CCI values-based N concentration dilution curves, CCI-based Nc curve showed better accuracy and lower bias than GS values-based curves. And this curve lower than the reference LAI basis Nc curve and higher than the dry matter-based curve. The N nutrition index (NNI), calculated by the CCI-based curve, ranged from 0.31 to 1.33 during the vegetative stage. A significant positive relationship between CCI values and accumulated N deficit (AND) applications over the rice developmental stages. This present study also proved that CCI could be used to predict grain yield in total growth periods. These developed canopy level vegetation indexes-based Nc curve as a novel tool to offer more choices for evaluating crop N nutrition status and precision N topdressing management in Japonica rice of China. [ABSTRACT FROM AUTHOR]

Accurate estimation and monitoring of crop nitrogen can assist in timely diagnosis and facilitate necessary technical support for fertilizer management. Four experiments, involving three cultivars and six nitrogen (N) treatments, were conducted in southeast China to compare the two leaf-clip meters (Dualex 4 Scientific+, Force-A, Orasy, France; Soil and Plant Analyzer Development (SPAD) meter, Minolta Camera Co., Osaka, Japan) for their ability to measure nitrogen nutrient-related indicators. The results indicated that Chl had a better monitoring accuracy for chlorophyll in per unit leaf area as compared to SPAD value, and there was no saturation to appear under high leaf chlorophyll concentration status. Flavonoids (Flav) presented the advantage of early diagnosis of rice N nutrition status (about one day as compared to SPAD value). As a reliable N nutrient diagnosis indicator, it also improved the estimation accuracy compared with the classical SPAD-based method. The other Dualex value also obtained good monitoring results. Flav was positively correlated with N deficiency, and with higher R2 in panicle initiation and booting stages with low RMSE, respectively; whereas SPAD value was negatively correlated with nitrogen deficiency. Therefore, the Flav-based nitrogen application model was found to provide an early rice nitrogen fertilizer application approach, especially in the panicle initiation and booting stages. [ABSTRACT FROM AUTHOR]

Lithium-sulfur batteries are considered as one of the most promising energy storage systems beyond commercial lithium-ion batteries, but the practical application of lithium-sulfur batteries is still hindered by the severe polysulfides dissolution and sluggish redox reaction kinetics with low areal capacity. Herein, ultrafine NbN decorated nitrogen-doped porous carbon nanosheets are reported via C 3 N 4 sacrifice template using phenolic resol as carbon precursor. The ultrafine NbN nanoparticles and nitrogen-doped carbons guarantee efficient polysulfides trapping and fast redox reaction kinetics even with a high sulfur content of 75 wt%. In addition, porous carbon nanosheets and NbN nanoparticles provide more active sites for Li 2 S nucleation and serve as a second host for the reuse of sulfur. Hence, the lithium-sulfur cells with NbN@CNS-5 modified multifunctional separator deliver a high initial capacity of 1252 mAh g−1 @ 0.2 C, 683 mAh g−1 @ 4 C, and high capacity retention of 84.5% after 200 cycles at 0.2 C. Furthermore, a high initial capacity of 4.95 mAh cm−2 and 4.01 mAh cm−2 @0.2 C after 200 cycles are achieved at a sulfur loading of 4.2 mg cm−2. These findings open up a new method for the practical application of lithium-sulfur batteries with superior sulfur utilization and a long lifespan. [Display omitted] • Ultrafine NbN decorated N-doped porous carbon nanosheets was successfully prepared. • NbN could enhance the adsorption and accelerate the conversion of polysulfides. • Nitrogen doped porous carbon nanosheets provide more sites for S/Li 2 S deposition. • Li–S battery performance is enhanced using NbN@CNSs decorated PP separator. [ABSTRACT FROM AUTHOR]

Wheat and rice are the main food crops in China. Appropriate nitrogen (N) fertilizer can effectively promote the crop growth, whereas excessive use has repercussions on yield formation and environmental preservation. Therefore, timely assessment of crop N status and precise N application management are of paramount importance. The study aims to assess the impacts of N fertilizer on N accumulation and spectral dynamics in wheat and rice, and investigate the feasibility of real-time crop N status diagnosis using unmanned aerial vehicle (UAV) spectra and devise subsequent managements. Ten experiments were conducted in Xinghua City and Lianyungang City from 2017 to 2020, involving different N fertilizer rates (0–405 kg N ha−1) and various cultivars. Field sampling was carried out simultaneously with UAV image acquisition, and the crop dry matter and N concentration were obtained by indoor analysis. Normalized difference red-edge index (NDRE) and N nutrition index (NNI) demonstrated a robust power function relationship (R2 > 0.70). The time series N diagnosis curves established by critical NDRE values achieved recognition accuracy of over 89%. The validation accuracy of critical NDRE values achieved 93.84%. The probability of the calculated topdressing rate (N) falling between the agronomic optimal N rate (AONR) and economic optimal N rate (EONR) is 86%. The time series N diagnosis curve offered possibility to real-time judgement of plant N status. In addition, the subsequent N topdressing design was proved through the improvement of existing sufficiency index (SI) algorithm. The time series N diagnosis curve will provide valuable decision support for the optimal N fertilizer management of wheat and rice. Moreover, the UAV platform holds promising potential for regional-scale application in the future. • N fertilizer significantly affected dynamics of N accumulation and canopy spectra. • NDRE had a good correlation with PNA and NNI of wheat and rice. • RAGDD-based time series N diagnosis curve was established and verified. • N diagnosis curve combined well with SINR to guide field topdressing in real time. [ABSTRACT FROM AUTHOR]

Accurate and transferable wheat nitrogen status estimation is very important to plant phenotyping and smart agricultural management. The goal of this study was to establish a wheat nitrogen status estimation model across all growth stages by combining proximal sensing and meteorological data. From 2010–2020, nine multi-nitrogen rates field trials were conducted at five sites involving different wheat varieties. Proximal sensing data were acquired from a Crop Circle sensor at key growth stages and meteorological data were aggregated from planting to the corresponding sensing date. Deep neural network (DNN) and long short-term memory (LSTM) were adopted to estimate above-ground biomass, plant nitrogen uptake, plant nitrogen concentration, and the nitrogen nutrition index. Random forest (RF) was used as a benchmark regression model. Multi-task learning (MTL) based on DNN was conducted to estimate the four nitrogen indicators simultaneously. A genetic algorithm (GA) was tested to optimize the hyperparameters, connection weights, and loss function weights (for MTL) of neural networks separately. The results revealed that DNN (R2 =0.83–0.96) and MTL (R2 =0.81–0.96) achieved an overall comparable high accuracy with RF (R2 =0.83–0.97), whereas LSTM (R2 =0.76–0.93) did not improve the nitrogen status estimation in our dataset. This study presented a concise and efficient framework dedicated to exploring the transferability of phenotypic predictions and provided insights into understanding crop growth and nitrogen dynamics in response to environmental conditions. • A framework combined deep learning and evolutionary algorithm was proposed. • The proposed model performed high transferability in different space and time. • Features with cumulative effect greatly impacted the wheat N status estimation. • Water-related features were essential for wheat nitrogen content estimation. [ABSTRACT FROM AUTHOR]

Precision fertilizer management has been well proved to allow farmers to synchronize nitrogen (N) fertilizer input with crop demand to improve grain yield and N use efficiency (NUE). However, the potential environmental benefits of precision fertilizer management have been less evaluated and appreciated. In this study, we selected five most commonly used optimized N fertilizer management strategies (OPM), which are Flav-basal strategy, site-specific N management strategy, optimization algorithm, N nutrient index-based fertilizer management strategy and normalized difference red-edge based fertilizer management strategy, and compared with farmer practices (FP) in yield, resource inputs (i.e., mineral, land, labor, etc.), energy use, NUE, greenhouse gases emissions (GHGs), NH 3 , NO X and SO 2 emissions, N leaching and runoff, and economic returns in Chinese southeast paddy fields. Our results showed that the OPM strategies could increase grain yield by 13.5 % at most, NUE by 3–10 % and harvest index by 1–7 kg kg−1 compared to the FP with the optimal total N application was approximately 270–290 kg N ha−1. Agronomic benefits generally increased by $ 145–620 ha−1, with the shoot biomass increasing by $ 90–185 ha−1 of adopting through OPM for rice production. Additional benefits from the mitigation of GHGs emissions could significantly increase the environmental benefits of precision N management. Altogether, the environmental benefits of OPM are considerable, and they are likely to be adopted by farmers if new incentives from the government. • This study firstly quantized the environmental effect of various optimizing nitrogen fertilizer management strategies (OPM). • This work explored a cap-and-trade scheme in China's rice field nitrogen loss firstly. • The OPM application can increase nitrogen use efficiency while reducing the Nitrogen loss. • Approximately 1300–1500 $·ha-1 increases in OPM plots compared with farmers' practices. [ABSTRACT FROM AUTHOR]

Various indices established on a portable SPAD-502 meter can serve as indicators of the nitrogen status of a plant. We compared di-positional SPAD readings and indices with several reliable nitrogen indicators during vegetative growth stage of rice ( Oryza sativa L.) and developed a prediction model for diagnosing nitrogen status. Three field experiments were conducted in Jiangsu province of east China during 2013 and 2014. Different nitrogen application rates were used to generate contrasting conditions of nitrogen availability in three Japonica, Wuyunjing 19, Yongyou 8, and Wuyunjing 24, and one Indica rice hybrid, Yliangyou 1. The SPAD values of the uppermost four fully expanded leaves were measured from tillering to heading stages, and these values were further used to calculate the normalized SPAD index (NSI), relative SPAD index (RSI), difference SPAD index (DSI), relative difference SPAD index (RDSI), and normalized difference SPAD index (NDSI). Five hills from each plot were simultaneously sampled, and four nitrogen indicators, including leaf nitrogen concentration (LNC), plant nitrogen concentration (PNC), plant nitrogen accumulation (NA), and nitrogen nutrition index (NNI), were measured. The results of linear correlations among the SPAD and nitrogen indicators indicated that NSI of the fourth fully expanded leaf from top (NSI4) was the most reliable and generally applicable SPAD indicator. In total, 24 potential single-stage and duration models were established, taking into consideration the fact that duration models covering the period from stem elongation to booting stages are more robust, two duration diagnostic models (Model 1: NA = 0.0279e 8.6957NSI4 , R 2 = 0.730**, n = 45; Model 2: NNI = 0.0163e 4.13NSI4 , R 2 = 0.767**, n = 45, NSI4 = 0.80–1.00) were developed and calibrated. Both models can provide accurate and appropriate N diagnosis from the stem elongation to booting growth stages for rice production. [ABSTRACT FROM AUTHOR]

Abstract: Real-time and nondestructive monitoring of crop nitrogen (N) status is of significant importance for precision N management in rice and wheat production. In eight field experiments with different N rates, water regimes and cultivars in rice and wheat crops, a new form of three-band vegetation indices was constructed to reduce saturation in two-band vegetation indices, and the optimal common three-band vegetation index was selected to establish models for canopy leaf N concentration (LNC) monitoring in rice and wheat. The results showed that the linear models for LNC monitoring with (R 924 − R 703 +2× R 423)/(R 924 + R 703 −2× R 423) were stable and accurate, with coefficient of determination (R 2) of 0.870 and 0.857, and SE of 0.052 and 0.148 in rice and wheat, respectively. Testing of the models with independent data gave R 2 of 0.866 and 0.883, RRMSE of 13.1% and 16.9%, and slope of 0.741 and 0.980 in rice and wheat, respectively. Further analysis of the influence of bandwidth change on LNC accuracy indicated that the allowable bandwidths for the central bands were 36nm for 924nm, 15nm for 703nm and 21nm for 423nm. The new three-band vegetation indices with narrow bands and broad bands in the present study are generally more effective for LNC monitoring compared with the other published vegetation indices. [Copyright &y& Elsevier]

Although lithium sulfur battery is considered as one of the promising energy storage systems beyond lithium ion battery, the severe polysulfides dissolution and sluggish reaction kinetics with low level sulfur loading still retard the practical application of lithium sulfur battery. Herein, an interconnected hollow carbon nanocages with tailored nitrogen-doping (CNCs) is reported via confined pyrolysis of Zn, Co zeolitic imidazolate framework within the resorcinol-melamine-formaldehyde shell. The interconnected cavity and the porous carbon skeletons guarantee the well-dispersion and immobilization of sulfur cathode even with high sulfur content of 80 wt %. In addition, developed microporosity and numerous nitrogen functional groups on the carbon surface favor for the chemisorption, conversion of polysulfide and uniform growth of Li 2 S. Hence, the resulting S/CNC-1 cathode delivers a high initial capacity of 1310 mAh g−1@0.2 C, excellent rate performance with 762 mAh g−1 at 8 C and ultra-long lifespan with a reversible capacity of 841 mAh g−1 after 800 cycles. More importantly, a high capacity of 4.8 mAh cm−2 is attained at high sulfur content of 80 wt% and areal sulfur loading of 4.2 mg cm−2. These findings provide an effective method for future development of practical lithium sulfur battery with superior rate performance and long lifespan. Image 1 • Interconnected hollow carbon nanocages with tailored nitrogen doping. • Interconnected cavity and the porous shells for sulfur with well immobilization. • Nitrogen doping for polysulfide conversion and Li 2 S deposition. • S/CNC-1 shows good electrochemical performance with high areal sulfur loading. [ABSTRACT FROM AUTHOR]