Effect of Different Rates of Nitrogen Fertilization on Crop Yield, Soil Properties and Leaf Physiological Attributes in Banana Under Subtropical Regions of China

Impact of nitrogen fertilization on soil microbial diversity, its mediated enzyme activities, and stem nematode population in sweet potato fields

Excessive nitrogen fertilization in sweet potato cultivation poses significant ecological and economic challenges in China, negatively impacting soil health by altering microbial community diversity, enzyme activities, and increasing the risk of stem nematode damage. In this study, we conducted a field trial in Northeast China, applying 0-72 kg of urea-N per hectare to brown soil under a five-year sweet potato cropping system. The results demonstrated that optimal nitrogen fertilization (64.8 kg ha-1) significantly promoted beneficial microbial populations, enhanced soil urease activity, and reduced the incidence of stem nematode disease while maintaining high sweet potato yields.

Impact of Steam-Exploded Feather Incorporation on the Biodegradation Performance of Renewable Biocomposites

The increasing environmental concerns regarding plastic waste, especially in agriculture, have driven the search for sustainable alternatives. Agricultural plastics, such as mulching films and greenhouse covers, are heavily reliant on petrochemical-derived materials, which persist in the environment and contribute to long-term pollution. This study explores the use of biodegradable biocomposites made from steam explosion-treated chicken feathers and various polymer matrices to address these issues. Chicken feathers, a waste by-product of the poultry industry, present an excellent biodegradability as a result of the steam explosion treatment and contain nitrogen, potentially enhancing soil fertility. The biocomposites were characterized by thermal stability, mechanical properties, and biodegradability, and ecotoxicity assessments were carried out studying the incorporation of feathers into the soil. Results showed that the incorporation of treated chicken feathers increased the water absorption capacity of the composites, promoting faster disintegration and biodegradation. In particular, biocomposites made with polyhydroxyalkanoates and Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) exhibited a significant increase in degradation rates, from 3-10% in the first month for pure matrices to 40-50% when reinforced with treated feathers. Meanwhile, those made from polylactic acid showed slower degradation. Furthermore, the addition of feathers positively influenced crop growth at low concentrations, acting as a slow-release fertilizer. However, high concentrations of feathers negatively affect plant growth due to excess nitrogen. These findings highlight the potential of poultry feathers as a valuable, sustainable filler for agricultural bioplastics, contributing to waste valorization and environmentally friendly farming practices.

Chemical Forms of Nitrogen Fertilizers Differentially Influence the Content and Composition of Aroma Volatiles and Phytonutrients in Strawberry Fruits

The amount of nitrogen (N) fertilization influences the content and composition of phytochemicals in plants. However, the influence of different chemical forms of N fertilizers on the phytochemical profiles of fruits remains less known. We investigated the effect of nitrate [NO3-; supplied as CaNO3], ammoniacal [NH4+; supplied as (NH4)2SO4], and organic-N (supplied as meat and bone meal [MBM]) fertilization on the profile of volatile compounds, primary, and secondary metabolites in the fruits of Alpine strawberries (Fragaria vesca "Reine des Vallées") using global metabolomic approaches. The form of plant-available soil N varied as a function of fertilization, with (NH4)2SO4 and MBM fertilization retaining a higher proportion of N as ammoniacal-N throughout the growing period. Leaf nitrate reductase activity was 5 times higher in CaNO3 treatments, suggesting NO3- as the major N form taken up by plants in this treatment. Although ammoniacal-N fertilization resulted in lower plant biomass, the fruit yield and tissue nutrient content were similar to those of nitrate-N treatments. The plant biomass of organic-N treatment was similar to that of nitrate-N fertilization, but the fruit yield was 30% lower. Compared to nitrate-N treatment, aroma-related volatile compounds increased under organic- and ammoniacal-N fertilization, including up to a 5-fold increase in esters, a 6-fold increase in alcohols, a 3-fold increase in volatile fatty acids, and a 60% increase in organic acids. The content of primary metabolites, especially sugar, sugar alcohol, and amino acids, exhibited an opposite trend and increased in nitrate-N than under ammoniacal- and organic-N fertilization. Compared to nitrate-N, the secondary metabolites generally were higher under ammoniacal- and organic-N fertilization, with an 80% increase in the activity of phenylalanine ammonia lyase, resulting in up to 38% increase in flavones, 28% increase in flavanols, and 33% increase in anthocyanins, except for dihydroflavonols and proanthocyanidins, which decreased by 6 and 13%, respectively. The hydrolyzable tannins, including galloyl glucosides, ellagitannins, and ellagic acids, were 25% abundant under organic-N fertilization. Our results indicate that while nitrate-N generally increased the primary metabolites, organic-N and ammoniacal-N fertilization enhanced the aroma-related volatiles and secondary metabolites in strawberry fruits. Thus, precise management of the chemical form of N fertilization can be a valuable tool to improve the phytonutrient content of strawberries.

Integrating Microalgal Chlorella Biomass and Biorefinery Residues into Sustainable Agriculture and Food Production: Insights from Lettuce Cultivation

Microalgal biomass offers a promising biofertilizer option due to its nutrient-rich composition, adaptability, and environmental benefits. This study evaluated the potential of microalgal-based biofertilizers-microalgal Chlorella biomass, de-oiled microalgal biomass (DMB), and de-oiled and de-aqueous extract microalgal biomass (DAEMB)-in enhancing lettuce growth, soil nutrient dynamics, and microbial community composition. Lettuce seedlings were cultivated with these biofertilizers, and plant growth parameters, photosynthetic pigments, and nitrogen uptake were assessed. Soil incubation experiments further examined nutrient mineralization rates, while DNA sequencing analyzed shifts in rhizosphere microbial communities. Lettuce grown with these biofertilizers exhibited improved growth parameters compared to controls, with Chlorella biomass achieving a 31.89% increase in shoot length, 27.98% in root length, and a 47.33% increase in fresh weight. Chlorophyll a and total chlorophyll levels increased significantly in all treatments, with the highest concentrations observed in the Chlorella biomass treatment. Soil mineralization studies revealed that DMB and DAEMB provided a gradual nitrogen release, while Chlorella biomass exhibited a rapid nutrient supply. Microbial community analyses revealed shifts in bacterial and fungal diversity, with increased abundance of nitrogen-fixing and nutrient-cycling taxa. Notably, fungal diversity was enriched in biomass and DAEMB treatments, enhancing soil health and reducing pathogenic fungi. These findings highlight microalgal biofertilizers' potential to enhance soil fertility, plant health, and sustainable resource use in agriculture.

Effects of different organic materials and reduced nitrogen fertilizer application on sorghum yield and soil nutrients

Rapeseed and sorghum, important economic crops in China, generate abundant straw resources. However, studies examining the effects of straw return combined with reduced nitrogen fertilization on soil quality are still insufficient to meet the precise fertilization needs, necessitating further research. This study employed two treatments: rapeseed straw plus sorghum straw (LT) and rapeseed green manure plus sorghum straw (YGT) returned to the soil. Nitrogen was applied at three rates: 0%, 70% of the conventional amount (0.7CK) and the conventional fertilization (CK). Meanwhile, conventional fertilization was used as a control. Over three consecutive years, this experiment investigated the impact of these treatments on sorghum yield and soil nutrient properties, evaluating overall soil quality and individual soil fertility components. Straw return significantly improved soil quality, with enhancements ranging from 6.5 to 61.4% compared to the CK. The LT + 0.7CK and YGT + 0.7CK produced relatively higher yields, increasing by 10.9% and 10.49% respectively over the CK. Moreover, the comprehensive soil quality of these two treatments is also relatively high, and the comprehensive soil quality of both is at the same level. However, the absence of rapeseed yield in the YGT + 0.7CK treatment during the rapeseed season suggests that LT + 0.7CK is a more economically viable fertilization approach. Soil fertility evaluations indicated that the LT + 0.7CK treatment did not meet the third-level farmland nutrient standards for available potassium, organic matter, total phosphorus, and total potassium. Future fertilization strategies should continue incorporating organic fertilizers and further research to enhance soil phosphorus and potassium contents, thus improving fertilization schemes. This study provides valuable insights for the sustainable utilization of straw resources and the reduction of chemical fertilizers in the Yangtze River Basin.

Metabolic and Nutritional Responses of Contrasting Aluminium-Tolerant Banana Genotypes Under Al Stress

Aluminum (Al) toxicity is a major constraint to crop productivity in acidic soils, frequently encountered in banana-growing regions. This study investigates physiological and biochemical responses to Al stress in two Cavendish banana genotypes, Baodao and Baxi (Musa acuminata L.), which exhibit contrasting levels of Al tolerance. Banana plantlets were grown hydroponically under three AlCl3 concentrations (0, 100, and 500 μM) for 24, 48, and 72 h. Root elongation was progressively inhibited with increasing Al concentrations, with Baodao showing greater inhibition than Baxi. Al primarily accumulated in roots and displayed genotype-specific distribution patterns: Baodao concentrated more Al in root tips, suggesting lower exclusion efficiency. In contrast, Baxi, the Al-tolerant genotype, translocated Al from roots to shoots more effectively, indicating potential sequestration mechanisms in less sensitive tissues. Al stress influenced enzyme activities, with Baxi exhibiting higher phosphoenolpyruvate carboxylase and citrate synthase activities at 100 µM Al, while both genotypes showed similar reductions at 500 µM. Baodao experienced more pronounced reductions in H+-ATPase activity. At 100 µM Al, Baxi retained higher levels of key nutrients (P, Zn, Mg, Mn, Fe, K, and B) in essential tissues than Baodao. However, nutrient levels were reduced in both genotypes at 500 µM Al. These findings highlight Baxi's superior resilience under Al stress, making it a suitable genotype for cultivation and breeding in acidic soils.

The impact of dissolved organic nitrogen (DON) retention in the vadose zone on nitrogen leaching losses

Leaching of dissolved organic nitrogen (DON) is a significant pathway for nitrogen (N) loss in agricultural ecosystems. The excessive application of N for enhanceing agricultural productivity often results in the leaching of N into groundwater. Yet not well understood, the extent of retention in the vadose zone has critical implications for risk management and remediation strategies. This study aims to advance simulation techniques for modelling the transport process of reactive DON within a heterogeneous vadose zone. Through a combination of laboratory experiments and numerical simulations, the study firstly examines the extent of DON retention in the vadose zone and quantitatively analyse groundwater contamination risk from this kind of accumulation. Our findings indicate that heavy N fertilizer application and high-intensity rainfall events led to elevated contents of DON in the vadose zone and increased DON leaching fluxes into groundwater. Besides, intensifier rainfall reduced the N storage more quickly in scenarios devoid of DON application with higher mineralization rate, while DON slowly mineralized to other forms, largely accumulated in the top layer and migrated deeper with intensifier rainfall after input of urea. In our scenarios, DON accounted for a substantial portion (33-68%) of the total dissolved nitrogen (TDN) leaching fluxes, with exogenous DON content contributing significantly (25-85%) to the overall DON leaching into the aquifer. These results underscore the need for effective strategies to mitigate groundwater contamination risks associated with agricultural N use.

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.

Ultra-high-resolution hyperspectral imagery datasets for precision agriculture applications

Technology infusion in agriculture has been progressing steadily, touching upon various spheres of agriculture such as crop identification, soil classification, yield prediction, disease detection, and weed-crop discrimination. On-demand crop type detection, often realized as crop mapping, is a primary requirement in agriculture. Alongside the topographic LiDAR and thermal imaging, hyperspectral remote sensing is a versatile technique for mapping and predicting various parameters of interest in agriculture. The ongoing developments in the methods and algorithms of remote sensing data analyses for crop mapping require the availability of curated, high-resolution hyperspectral datasets, varied by crop type, nutrient supply (nitrogen level), and ground truth data. Aimed at enabling the development and validation of approaches for crop mapping at the plant level, we present a high-resolution ground-based hyperspectral imaging dataset acquired over fields of two vegetable crops (cabbage, eggplant). These crops were grown on experimental plots of the University of Agricultural Sciences, Bengaluru, India, maintaining three different nitrogen levels (high, medium, and low). The datasets contain hyperspectral imagery of the vegetable crops grown under two configurations: (i) imagery, which contains only a single crop type in a scene, and (ii) imagery, which contains both crops in a single scene. In both configurations, each crop has plots representing three different nitrogen levels. Ultra-high spatial resolution hyperspectral imaging data were acquired in 400 to 900 nm with an effective spectral resolution of 3 nm and spatial resolution of 3 mm using a ground-based push-broom hyperspectral imaging system (Headwall Photonics, USA). Ground truth data were also presented. The datasets are valuable for developing and validating various methods and algorithms for precision agriculture applications, such as machine learning methods for crop mapping at plants and estimating crop growth responses to different nitrogen levels.

Effect of nitrogen, phosphorus and potassium fertilization management on soil properties and leaf traits and yield of Sapindus mukorossi

Rational fertilization is the main measure to improve crop yield, but there are differences in the optimal effects of nitrogen (N), phosphorus (P) and potassium (K) rationing exhibited by the same crop species in different regions and soil conditions. In order to determine the optimum fertilization ratio for high yield of Sapindus mukorossi in western Fujian to provide scientific basis. We carried out the experimental design with different ratios of N, P and K to investigate the effects of fertilization on the yield. and leaf physiology of Sapindus mukorossiand soil properties. Results showed that the yield of Sapindus mukorossi reached the highest value (1464.58 kg ha-1) at N2P2K2 treatment, which increased to 1056.25 kg ha-1 compared with the control. There were significant differences in the responses of soil properties and leaf physiological factors to fertilization treatments. Factor analysis showed that the integrated scores of soil factors and leaf physiological characteristic factors of Sapindus mukorossi under N2P2K2 fertilization treatment were the highest, which effectively improved the soil fertility and leaf physiological traits. The yield of Sapindus mukorossi showed a highly significant linear positive correlation with the integrated scores (r=0.70, p<0.01). Passage analysis showed that soil available nitrogen content, organic carbon content, and leaf area index were the key main factors to affect the yield. RDA showed that soil organic carbon and available phosphorus were the most important factors to affect leaf physiological traits. We recommend that the optimum fertilization ratio of Sapindus mukorossi was 0.96Kg N, 0.80Kg P and 0.64Kg K per plant. Reasonable fertilization can improve soil fertility and leaf physiological traits, while excessive fertilization has negative effects on soil fertility, leaf physiology and yield. This study provides theoretical support for scientific cultivation of woody oil seed species.

Effect of nitrogen reduction by chemical fertilization with green manure (Vicia sativa L.) on soil microbial community, nitrogen metabolism and and yield of Uncaria rhynchophylla by metagenomics

Uncaria rhynchophylla is an important herbal medicine, and the predominant issues affecting its cultivation include a single method of fertilizer application and inappropriate chemical fertilizer application. To reduce the use of inorganic nitrogen fertilization and increase the yield of Uncaria rhynchophylla, field experiments in 2020-2021 were conducted. The experimental treatments included the following categories: S1, no fertilization; S2, application of chemical NPK fertilizer; and S3-S6, application of chemical fertilizers and green manures, featuring nitrogen fertilizers reductions of 0%, 15%, 30%, and 45%, respectively. The results showed that a moderate application of nitrogen fertilizer when combined with green manure, can help alleviate soil acidification and increase urease activity. Specifically, the treatment with green manure provided in a 14.71-66.67% increase in urease activity compared to S2. Metagenomics sequencing results showed a decrease in diversity in S3, S4, S5, and S6 compared to S2, but the application of chemical fertilizer with green manure promoted an increase in the relative abundance of Acidobacteria and Chloroflexi. In addition, the nitrification pathway displayed a progressive augmentation in tandem with the reduction in nitrogen fertilizer and application of green manure, reaching its zenith at S5. Conversely, other nitrogen metabolism pathways showed a decline in correlation with diminishing nitrogen fertilizer dosages. The rest of the treatments showed an increase in yield in comparison to S1, S5 showing significant differences (p < 0.05). In summary, although S2 demonstrate the ability to enhance soil microbial diversity, it is important to consider the long-term ecological impacts, and S5 may be a better choice.

Short term effects of digestate and composted digestate on soil health and crop yield: Implications for sustainable biowaste management in the bioenergy sector

Composting mitigates environmental risks associated with using solid digestate as fertilizer. However, evidence is lacking on benefits of using composted digestate as fertilizer in enhancing soil health and increasing agronomic yield compared to non-composted digestate (hereafter, digestate). A field study was conducted consisting of digestate, composted digestate, co-composted digestate with biogas feedstocks (corn [Zea mays L.] silage, poultry litter, corn silage + poultry litter or food processing by-product), inorganic nitrogen fertilizer, and control (no treatment applied) on soil microbial biomass, enzyme activities (EA), soil organic carbon (SOC), bioavailable P (P), total nitrogen (TN), soil health index (SHI), and sunflower (Helianthus annuus L.) yield. The Partial Least Square Path Model (PLS-PM) was used to predict: 1) nutrient cycling in response to changes in microbial growth and EA and 2) agronomic yield in response to SHI and soil nutrients dynamics. Composted digestate had equivalent soil health benefits with most of co-composted materials and digestate, albeit agronomic yield was greatest with composted digestate, which was 40 % and 100 % greater than with inorganic nitrogen fertilizer and digestate, respectively, indicating composted digestate's potential to replace the synthetic N fertilizer. Moreover, composts from a sole digestate, rather than the ones from co-composted with fresh feedsstocks, can be promising organic amendments and fertilizers for growing sunflower. The PLS-PM model identified that triggered microbial biomass growth and EA, following digestate and composted digestate applications, catalyzed organic matter decomposition, resulting in enhanced nutrients contents and soil health. However, the model revealed that improved SHI did not predict agronomic yield, as opposed to P and TN, suggesting agronomic performance may have been more sensitive to changes in specific soil nutrients status than the overall soil health condition. We conclude that the benefits of composted digestate as fertilizer hint the significance of digestate valorization via post-digestate composting and compost utilization for sustainability of the bioenergy sector.

Impact of manures and fertilizers on yield and soil properties in a rice-wheat cropping system

The use of chemical fertilizers under a rice-wheat cropping system (RWCS) has led to the emergence of micronutrient deficiency and decreased crop productivity. Thus, the experiment was conducted with the aim that the use of organic amendments would sustain productivity and improve the soil nutrient status under RWCS. A three-year experiment was conducted with different organic manures i.e. no manure (M0), farmyard manure @ 15 t ha-1 (M1), poultry manure @ 6 t ha-1(M2), press mud @ 15 t ha-1(M3), rice straw compost @ 6 t ha-1(M4) along with different levels of the recommended dose of fertilizer (RDF) i.e. 0% (F1), 75% (F2 and 100% (F3 in a split-plot design with three replications and plot size of 6 m x 1.2 m. Laboratory-based analysis of different soil as well as plant parameters was done using standard methodologies. The use of manures considerably improved the crop yield, macronutrients viz. nitrogen, phosphorus, potassium and micronutrients such as zinc, iron, manganese and copper, uptake in both the crops because of nutrient release from decomposed organic matter. Additionally, the increase in fertilizer dose increased these parameters. The system productivity was maximum recorded under F3M1 (13,052 kg ha-1) and results were statistically identical with F3M2 and F3M3. The significant upsurge of macro and micro-nutrients in soil and its correlation with yield outcomes was also observed through the combined use of manures as well as fertilizers. This study concluded that the use of 100% RDF integrated with organic manures, particularly farmyard manure would be a beneficial resource for increased crop yield, soil nutrient status and system productivity in RWCS in different regions of India.

Global evaluation of key factors influencing nitrogen fertilization efficiency in wheat: a recent meta-analysis (2000-2022)

Improving nitrogen use efficiency (NUE) without compromising yield remains a crucial agroecological challenge in theory and practice. Some meta-analyses conducted in recent years investigated the impact of nitrogen (N) fertilizer on crop yield and gaseous emissions, but most are region-specific and focused on N sources and application methods. However, various factors affecting yield and N fertilizer efficiency in wheat crops on a global scale are not extensively studied, thus highlighting the need for a comprehensive meta-analysis. Using 109 peer-reviewed research studies (published between 2000 and 2022) from 156 experimental sites (covering 36.8, 38.6 and 24.6% of coarse, medium, and fine texture soils, respectively), we conducted a global meta-analysis to elucidate suitable N management practices and the key factors influencing N fertilization efficiency in wheat as a function of yield and recovery efficiency and also explained future perspectives for efficient N management in wheat crop. Overall, N fertilization had a significant impact on wheat yield. A curvilinear relationship was found between N rates and grain yield, whereas maximum yield improvement was illustrated at 150-300 kg N ha-1. In addition, N increased yield by 92.18% under direct soil incorporation, 87.55% under combined chemical and organic fertilizers application, and 72.86% under split application. Site-specific covariates (climatic conditions and soil properties) had a pronounced impact on N fertilization efficiency. A significantly higher yield response was observed in regions with MAP > 800 mm, and where MAT remained < 15 °C. Additionally, the highest yield response was observed with initial AN, AP and AK concentrations at < 20, < 10 and 100-150 mg kg-1, respectively, and yield response considerably declined with increasing these threshold values. Nevertheless, regression analysis revealed a declining trend in N recovery efficiency (REN) and the addition of N in already fertile soils may affect plant uptake and RE. Global REN in wheat remained at 49.78% and followed a negative trend with the further increase of N supply and improvement in soil properties. Finally, an advanced N management approach such as "root zone targeted fertilization" is suggested to reduce fertilizer application rate and save time and labor costs while achieving high yield and NUE.

A Controlled-Release Nanofertilizer Improves Tomato Growth and Minimizes Nitrogen Consumption

Minimizing the consumption of agrochemicals, particularly nitrogen, is the ultimate goal for achieving sustainable agricultural production with low cost and high economic and environmental returns. The use of biopolymers instead of petroleum-based synthetic polymers for CRFs can significantly improve the sustainability of crop production since biopolymers are biodegradable and not harmful to soil quality. Lignin is one of the most abundant biopolymers that naturally exist.In this study, controlled-release fertilizers were developed using a biobased nanocomposite of lignin and bentonite clay mineral as a coating material for urea to increase nitrogen use efficiency. Five types of controlled-release urea (CRU) were prepared using two ratios of modified bentonite as well as techniques. The efficiency of the five controlled-release nano-urea (CRU) fertilizers in improving the growth of tomato plants was studied under field conditions. The CRU was applied to the tomato plants at three N levels representing 100, 50, and 25% of the recommended dose of conventional urea. The results showed that all CRU treatments at the three N levels significantly enhanced plant growth parameters, including plant height, number of leaves, fresh weight, and dry weight, compared to the control. Additionally, most CRU fertilizers increased total yield and fruit characteristics (weight, length, and diameter) compared to the control. Additionally, marketable yield was improved by CRU fertilizers. Fruit firmness and acidity of CRU treatments at 25 and 50% N levels were much higher than both the 100% CRU treatment and the control. The vitamin C values of all CRU treatments were lower than the control. Nitrogen uptake efficiencies (NUpE) of CRU treatments were 47-88%, which is significantly higher than that of the control (33%). In conclusion, all CRU treatments at an N level of 25% of the recommended dose showed better plant growth, yield, and fruit quality of tomatoes than the conventional fertilizer.

Study on nitrogen demand model in pakchoi (Brassica campestris ssp. Chinensis L.) based on nitrogen contents and phenotypic characteristics

INTRODUCTION

In precision agriculture, the diagnosis of the nitrogen (N) nutrition status based on the plant phenotype, combined effects of soil types, various agricultural practices, and environmental factors which are essential for plant N accumulation. It helps to assess the N supply for plants at the right time and optimal amount to ensure high N use efficiency thereby reducing the N fertilizer applications to minimize environmental pollution. For this purpose, three different experiments were performed.

METHODS

A critical N content (Nc) model was constructed based on cumulative photothermal effect (LTF), Napplications, and cultivation systems on yield and N uptake in pakchoi.

RESULTS AND DISCUSSION

According to the model, aboveground dry biomass (DW) accumulation was found equal or below to 1.5 t/ha, and the Nc value was observed at a constant of 4.78%. However, when DW accumulation exceeded 1.5 t/ha, Nc declined with the increase in DW accumulation, and the relationship between Nc and DW accumulation developed with the function Nc %=4.78 x DW-0.33. An N demand model was established based on the multi-information fusion method, which integrated multiple factors, including Nc, phenotypical indexes, temperature during the growth period, photosynthetically active radiation, and N applications. Furthermore, the model's accuracy was verified, and the predicted N contents were found consistent with the measured values (R2 = 0.948 and RMSE = 1.96 mg/plant). At the same time, an N demand model based on N use efficiency was proposed.

CONCLUSIONS

This study can provide theoretical and technical support for precise N management in pakchoi production.

Nitrogen Supplementation Modulates Morphological, Biochemical, Yield and Quality Attributes of Peppermint

Due to the rising demand for essential oil in the world market, peppermint has gained an important status among aromatic and medicinal plants. It becomes imperative to optimize its performance in terms of the growth, physiological functioning and biosynthesis of specialized metabolites. A factorial randomized pot experiment was performed using three peppermint cultivars (Kukrail, Pranjal and Tushar) and five levels of leaf-applied nitrogen (N), viz. 0 (control), 0.5, 1.0, 1.5 and 2%. The phenological features, biochemical parameters, viability of root cells, stomatal and trichome behavior were assessed at 100 days after transplanting (DAT). The yield-related parameters, viz., herbage yield, essential oil content, menthol content and yield were studied at 120 DAT. The results revealed that increasing the N doses up to 1.5% enhanced all the studied parameters of peppermint, which thereafter (at the dose above 1.5% N) decreased. The variation pattern of the studied parameters was "low-high-low". Cultivar Kukrail surpassed the two other cultivars Tushar and Pranjal. Among the foliar sprays, the application of 1.5% N increased chlorophyll content and net photosynthetic rate in all three cultivars. Moreover, the essential oil (EO), EO yield and menthol yield of the plant were also increased linearly in all three cultivars as compared with their control plants. Nitrogen application enhanced the trichome size and density of the plants, as revealed through scanning electron microscopy. Furthermore, from the GC-MS studies, the EO content in the studied cultivars increased, particularly in the case of menthol, with the N application. It may be concluded that two sprays of N (1.5%) at appropriate growth stages could be beneficial for improving morphological, physio biochemical and yield attributes of peppermint.

Effects of nitrogen reduction combined with organic fertilizer on growth and nitrogen fate in banana at seedling stage

Nitrogen reduction combined with organic fertilizer is of considerable significance for the sustainable development of agriculture. A pot experiment using nitrogen reduction combined with organic fertilizer was conducted to explore the effects of different treatments on matter accumulation, physiological resistance, and fertilizer nitrogen fate in banana seedlings. Compared with conventional fertilization, a 20% reduction of nitrogen did not affect the dry weight, chlorophyll content, physiological resistance, and fertilizer utilization rate of banana seedlings, but significantly reduced the nitrogen leaching loss and increased the nitrogen soil residue. Compared with conventional fertilization, organic nitrogen substituting 20% or 30% of the nitrogen reduced by 20% significantly promoted dry matter accumulation and physiological resistance. Organic nitrogen substituting 30% of the 20% reduction of nitrogen increased the dry matter of the whole plant by 24.94%, the nitrogen uptake in the root by 30.87%, the chlorophyll content by 6.05%, the soluble sugar content by 16.88%, Peroxidase (POD) activity by 26.35%, Catalase (CAT) activity by 27.48%, and Super Oxide Dismutase (SOD) activity by 22.97%. Compared with conventional fertilization, all organic substitution treatments significantly reduced fertilizer nitrogen leaching loss, apparent loss, and increased nitrogen soil residue. Compared with the 20% reduction of nitrogen, organic nitrogen substituting 30% of the 20% reduction of nitrogen significantly increased nitrogen utilization by 16.34% and soil residue rate by 13.26%, and reduced nitrogen leaching loss by 35.46%. The results of the present study revealed that a 20% reduction of nitrogen fertilizer with a 30% organic substitution application promoted matter accumulation, enhanced the physiological resistance of banana seedlings, increased the utilization and residue of nitrogen fertilizer, and reduced nitrogen pollution.

Long term effects of crop rotation and fertilization on crop yield stability in southeast China

The objective of this study was to determine the effects of different fertilizer treatments and crop rotations on crop yield stability. A 9 years field experiment was conducted from 2013 to 2021 to evaluate the effects of combinations of two annual crop rotations and two methods of applying fertilizer on crop yield stability. Crop rotations were kidney bean–mustard–rice (P–B–O) and kidney bean–mustard–cowpea (P–B–V) each year. Fertilization methods were recommended fertilization (RF) and conventional fertilization (CF). The indexes Wi² (Wricke’s ecovalance), coefficient of variation (CV), and sustainable yield index (SYI) were used to quantify the long term effects of crop rotation and fertilization on crop yield stability, and a yield change trend model was used to predict future production. For fertilization program RF, average kidney bean and mustard yields in rotation P–B–O increased respectively by 7.47% and 19.37% over P–B–V in the 9 years of the project. For CF, average kidney bean and mustard yields for P–B–O increased respectively by 14.99% and 18.33% over P–B–V. Wi² indexes of kidney bean and mustard for P–B–O (respectively 116 and 956) were significantly less than for P–B–V (respectively 147.87 and 1259.67). SYI for kidney beans and mustard in P–B–O (respectively 0.63 and 0.57) were significantly greater than for P–B–V (respectively 0.50 and 0.42). The trends of crop average yields for RF and CF show that the average yield trends of kidney bean in P–B–O (respectively 32.41 and 32.34) were greater than in P–B–V (respectively 29.56 and 27.45). The trends of average yields of mustard for RF and CF in P–B–O (respectively 64.18 and 60.87) were greater than in P–B–V (respectively 51.74 and 51.87). The preceding results led to the conclusion that long term annual P–B–O rotation combined with RF considerably increased yield and maintained yield stability, thus establishing the sustainability of this cropping system.

Physicochemical and fertility characteristics of microalgal soil ameliorants using harvested cyanobacterial microalgal sludge from a freshwater ecosystem, Republic of Korea

The recovery and reuse strategy of cyanobacterial microalgal sludge (CyanoMS) is a novel sustainable platform that can mitigate cyanobacterial harmful algal blooms (CyanoHABs) in the freshwater system. This study aimed to assess the nutritional feasibility of harvested CyanoMS for microalgal soil ameliorants (MSAs) as efficient biofertilizers by the composting process. Most MSAs exhibited stable nutrient levels during the sequential metabolic phases for the entire period. The qualitative value of all MSAs using CyanoMS as a biofertilizer was verified by the excellent Fertility Index (FI), Clean Index (CI), and plant growth values. Also, successfully matured MSAs provided long-term support for retarded release of nutrients along the microbial transitional pathway. However, suitable CyanoMS contents of 11.7-37.6% (w/w) in MSAs were critical for efficient microbial activation and substrate inhibition. Since these results were fundamentally based on microbial transition on the CyanoMS content, optimum weight content and composting period were required. Nevertheless, MSAs were commercially applicable to high value-added crops due to their high fertilization potential and recyclable value.

Effects of nitrogen and phosphorus addition on growth and leaf nitrogen metabolism of alfalfa in alkaline soil in Yinchuan Plain of Hetao Basin

Alkaline soil is widely distributed in China. Its rational utilization is an effective measure to solve land shortage and improve the environment. Alfalfa is characterized by strong salt and alkali tolerance and high yield and protein content. Nitrogen (N) and phosphorus (P) are the main nutrients for plant growth, and N metabolism is one of the primary forms of plant metabolism, which plays a vital role in quality and yield formation. The exploration of the effect of N and P on N metabolism and alfalfa growth will provide a theoretical basis for scientific fertilization for alfalfa in the alkaline soil of the Yinchuan Plain of the Hetao Basin. Therefore, a 2-year experiment of N and P addition was conducted. Six treatments were set up with a randomized block design, including without N (WN), medium N (MN), high N (HN), without P (WP), medium P (MP), and high P (HP). It was found that the MN and MP treatments increased plant height, stem diameter, stem/leaf, dry/fresh, and dry matter of alfalfa. The HN and HP treatments inhibited alfalfa biomass formation. The MN and MP treatments increased key products and enzymes of leaf N metabolism of alfalfa and promoted activities of leaf nitrate reductase (NR), glutamine synthase (GS), glutamate synthase (GOGAT), glutamic-oxalacetic transaminase (GOT), and glutamic-pyruvate transaminase (GPT), and inhibited activities of leaf protease of alfalfa. The MN and MP treatments increased contents of leaf N, P, ammonium nitrogen (NH₄ ⁺-N), nitrate nitrogen (NO₃ ^--N), total chlorophyll, and protein and reduced leaf chlorophyll a/b and amino acid, results after HN and HP treatments were opposite. The correlation among leaf P, N, NO₃ ^--N, amino acid, and protein reached significant levels (P < 0.01). It is suggested that MN and MP treatments can improve the yield and quality of alfalfa by increasing key products and enzymes of N metabolism and can be adopted to promote alfalfa production in the alkaline soil of the Yinchuan Plain of the Hetao Basin.

Minimalizing Non-point Source Pollution Using a Cooperative Ion-Selective Electrode System for Estimating Nitrate Nitrogen in Soil

Nitrate nitrogen ( NO 3 - -N) in the soil is one of the important nutrients for growing crops. During the period of precipitation or irrigation, an excessive NO 3 - -N readily causes its leaching or runoff from the soil surface to rivers due to inaccurate fertilization and water management, leading to non-point source pollution. In general, the measurement of the NO 3 - -N relies upon the laboratory-based absorbance, which is often time-consuming, therefore not suitable for the rapid measurements in the field directly. Ion-selective electrodes (ISEs) support the possibility of NO 3 - -N measurement by measuring the nitrate ( NO 3 - ) ions in soil quickly and accurately due to the high water solubility and mobility of NO 3 - ions. However, such a method suffers from a complicated calibration to remove the influences caused by both temperature and other ions in the measured solution, thus limiting field use. In this study, a kind of all-solid ISE system combined with a temperature sensor and a pH electrode is proposed to automatically measure the concentrations of the NO 3 - -N. In this study, a soil water content calibration function was established, which significantly reduces a relative error (RE) by 13.09%. The experimental results showed that the stabilization time of this electrode system was less than 15 s with a slope of -51.63 mV/decade in the linear range of 10^-5-10^-2.2 mol/L. Both the limit of detection of 0.5 ppm of the NO 3 - -N and a relative SD of less than 3% were obtained together with the recovery rate of 90-110%. Compared with the UV-Vis spectroscopy method, a correlation coefficient (R ²) of 0.9952 was obtained. The performances of this all-solid ISE system are satisfied for measuring the NO 3 - -N in the field.

Melatonin Enhances Drought Tolerance by Regulating Leaf Stomatal Behavior, Carbon and Nitrogen Metabolism, and Related Gene Expression in Maize Plants

It is commonly known that exogenously applied melatonin can alleviate the impact of drought stress, but the mechanism used by melatonin to regulate stomatal behavior and carbon (C) and nitrogen (N) metabolism to increase drought resistance remains elusive. Herein, our aim was to investigate the influence of exogenous melatonin on the regulation of C and N metabolism in maize plants under water deficit. In this study, we analyzed stomatal behavior, the key components of C and N metabolism, and the gene expression and activity of enzymes involved in the C and N metabolism in maize plants. The results showed that the application of melatonin (100 μM) significantly increased maize growth and sustained the opening of stomata, and secondarily increased the photosynthetic capacity in maize. Under drought stress, foliar application of melatonin induced the gene transcription and activities of sucrose phosphate synthetase, ADP-glucose pyrophosphorylase, phosphoenolpyruvate carboxylase, and citrate synthase, resulting in the enhancement of sucrose and starch synthesis and the tricarboxylic acid (TCA) cycle. This enhancement in sugar biosynthesis and the TCA cycle might lead to stronger N assimilation. As anticipated, NO₃ ^- reduction and NH₄ ⁺ assimilation were also strengthened after melatonin treatment under drought stress. An increase was observed in some key enzymatic activities and transcription involved in nitrogen metabolism, such as that of nitrate reductase, nitrite reductase, glutamate synthase, and glutamine synthetase, in melatonin-treated, drought-stressed maize. Moreover, melatonin attenuated the drought-induced damage by reducing protein degradation and increasing the level of proline. Conclusively, our results indicate that exogenous melatonin enhances drought tolerance in maize via promoting stomatal opening and regulating C and N metabolism and related gene expression.