Search Results (575)

In response to increasing environmental protection requirements and the rapid advancement of analytical technologies, particular attention is being paid to the development of environmentally friendly, cost-effective, and sensitive measurement tools. One of the key challenges in modern analytics is the effective monitoring of inorganic nitrogen in the natural environment. In this review, we present a variety of ammonium and nitrate ion-selective electrodes. The review includes the years 2020–2026. It was divided into sections based on sensitivity to a given ion, as well as into subsections based on application: monitoring of soil and aquatic environments, the use of sensors for the determination of specific ions in a wide range of samples, and electrode designs that were used only in laboratory studies. A total of 64 nitrate electrodes and 22 ammonium electrodes were analyzed. Comparisons were made based on electrode type, type of internal contact, materials used to enhance ion-to-electron conductivity, and type of ionophore. Additionally, analytical parameters were compiled, including sensitivity, detection limit, linearity range, potential stability, operating pH range, and actual application scenarios. This review allows for an assessment of current trends and may serve as a basis for the design of new potentiometric sensors. Full article

In southern China, Chinese milk vetch is used as green manure to substitute for inorganic nitrogen (N) fertilizers and improve soil fertility, but how different incorporation methods affect its decomposition and underlying microbial mechanisms is unclear. This study used four fertilization regimes (CK: no N; CF: sole chemical N; CM: sole vetch; CMCF: vetch + 40% reduced N) to evaluate bacterial diversity, community composition and life history strategies during early vetch decomposition, and the nylon bag method to compare decomposition and C/N release dynamics. The results show that vetch dry matter decomposition reached 81.9–85.2% in 34 days, slowing to 11.8–14.4% after 192 days. CMCF significantly accelerated early decomposition and N release compared with CM. While CMCF reduced the bacterial Ace and Chao indices compared to CK with similar community structure, CF/CM exhibited distinct community structures. Compared to CM, CMCF increased r-strategy bacteria (e.g., Proteobacteria, Bacteroidota) and decreased K-strategy ones (e.g., Chloroflexi). Furthermore, decomposition rate positively correlated with r-strategy and negatively with K-strategy bacteria, with soil temperature as the primary driver. Compared to CMCF, CM reduced bacterial network complexity, decreasing nodes by 63.6% and average degree by 68.5%. In conclusion, combining vetch with chemical N enhances vetch residue decomposition while preserving microbial network structure and functional diversity. Full article

Reclaiming saline–alkaline soil is critical for food security and land expansion. While paddy rice is the key pioneer crop for remediation, the soil fertility–yield relationship remains poorly understood. To optimize remediation strategies, this study evaluated soil fertility under 16 agronomic treatments—integrating irrigation quality, fertilizer regimes, and soil amendments—across three rice growth stages (tillering, heading, and maturity) in the Yellow River Delta using the minimum data set (MDS), integrated soil fertility index (SFI), and random forest models. Saline water irrigation increased soil salinity by 24.6%, while straw returning and desulfurization gypsum reduced salinity by 18.3% and 22.7%, respectively. Straw, biochar, and desulfurization gypsum significantly influenced soil organic carbon (SOC), total nitrogen (TN), inorganic nitrogen (NH₄⁺-N, NO₃⁻-N), and available phosphorus (AP), with effects varying across growth stages. Growth-stage-specific MDS indicators were significantly correlated with SFI based on the total data set (R² = 0.70, 0.65, and 0.81, p < 0.01), and stage-specific SFI was significantly positively related to rice yield. Notably, heading-stage SFI, although relatively low, explained the highest yield variance (R² = 0.51, p < 0.01) and prediction accuracy (%IncMSE = 25.22), especially under conventional NPK combined with full straw incorporation and desulfurization gypsum. These findings highlight the critical role of heading-stage soil fertility in regulating rice production, providing a targeted nutrient management blueprint for saline–alkaline paddy fields in the Yellow River Delta. Overall, this study offers a reliable scientific template to enhance yield and promote sustainable agriculture in comparable saline–alkaline paddy fields globally. Full article

Soil salinization is a significant environmental factor limiting agricultural production. Developing salt–alkali-tolerant microbial resources is important for the improvement of saline–alkali land. Plant growth-promoting rhizobacteria stimulate crop growth by producing the plant growth hormone indole-3-acetic acid (IAA), but their fermentation process under salt stress still needs optimization. Single-factor experiments and response surface methodology (RSM) were used to systematically optimize the fermentation conditions of the salt–alkali-tolerant Vreelandella titanicae J113. Key influencing factors were screened using the single-factor experiment design, and optimal process parameters were determined using the Box–Behnken design. IAA production and cell biomass were used as evaluation indicators to study the interactions of carbon sources, nitrogen sources, inorganic salts, temperature, cultivation time, and inoculum size. The optimal fermentation process was obtained: starch concentration 17.5 g/L, NaCl concentration 32.5 g/L, yeast extract 5 g/L, cultivation temperature 30 °C, inoculum size 3%, and cultivation time 144 h. After optimization, IAA production reached 23.02 μg/mL, an increase of 115% compared with before optimization. Salt stress experiments showed that the strain could still maintain high IAA production under 3% NaCl, demonstrating good salt tolerance. Maize seed germination experiments demonstrated that the optimized fermentation broth significantly promoted seed germination and seedling growth under salt stress conditions, with root length, fibrous root number, and fresh weight increasing by 61–86%, 137–200%, and 25–57%, respectively, compared to the control group. This study established an efficient IAA fermentation process for the salt–alkali-tolerant Vreelandella titanicae J113, providing technical support for developing microbial plant growth regulators suitable for saline–alkali land. The optimized strain exhibits excellent growth-promoting potential under salt stress conditions, offering favorable application prospects. Full article

(1) Background: We investigated the effects of nutrient levels on rice yield and nitrogen uptake, with the aim of improving rice yield and nitrogen use efficiency. (2) Methods: A 3-year field experiment was conducted using the rice variety Changliangyou Fuxiangzhan, with six treatments: no nitrogen application (CK), conventional fertilization (FP), single basal application of 60-day slow-release urea (CRU1), single basal application of urea combined with 40-day and 90-day slow-release urea (CRU2), partial substitution of chemical fertilizer with bio-organic manure (FPM), and conventional fertilization combined with straw return (FPS). (3) Results: Different nutrient management regimes significantly affected rice yield and nitrogen uptake and use, as well as soil nitrogen content. CRU2 achieved the highest performance across most indicators, with grain yield averaging 9.6% higher than that of FP and 36.4% higher than that of CK, alongside consistently greater effective panicle numbers. It also significantly enhanced nitrogen uptake, with higher grain and straw N accumulation, and showed the best nitrogen use efficiencies. Soil responses varied by treatment: FPS and FPM increased total nitrogen, while CRU2 and CRU1 had the highest inorganic nitrogen, and microbial biomass nitrogen peaked under FPM, CRU2, and FPS. Despite these benefits, CRU2 showed the largest negative nitrogen balance, averaging −33.0 kg ha⁻¹ over 3 years. (4) Conclusions: The CRU2 treatment achieved efficient synchronization between nitrogen supply and demand, with the highest yield, nitrogen uptake, and soil nitrogen levels. Full article

The excessive use of inorganic nitrogen (N) fertilizers in rice production poses significant environmental and economic challenges, particularly in intensive farming systems such as those in the Mekong Delta, Vietnam. This study aimed to evaluate the potential of Herbaspirillum seropedicae (H. seropedicae), an endophytic N-fixing bacterium, to enhance soil fertility, improve rice growth, and maintain yield while reducing N fertilizer inputs in Dai Thom 8 rice under field conditions. A randomized complete block design with five treatments, including different nitrogen reduction levels combined with bacterial inoculation, was employed. The results showed that treatments integrating H. seropedicae significantly improved soil properties, including soil organic matter, total nitrogen, and available nutrients, compared to the control. Growth parameters such as plant height, tiller density, and chlorophyll content were also enhanced, particularly in treatments with bacterial inoculation. Yield components, including grain number and filled grains per panicle, were significantly increased, leading to higher grain yield. The highest yield was observed in T5 (5.72 t ha⁻¹), while T3 and T4 achieved comparable yields with reduced N inputs. Additionally, grain quality analysis revealed increased protein content without negatively affecting starch composition. These findings highlight the potential of H. seropedicae as a biofertilizer to improve N use efficiency and reduce dependency on chemical fertilizers. The study provides strong evidence for integrating microbial inoculants into sustainable rice production systems. Among the treatments, T3 (50% N reduction combined with bacterial inoculation) is recommended as the optimal strategy due to its balance between high yield and reduced input costs, contributing to environmentally friendly and economically viable agriculture. Full article

Optimizing nitrogen form under drip fertigation may improve wheat productivity by regulating the root-zone inorganic N environment during early vegetative growth. A two-year field experiment evaluated nitrate-dominant (N1), balanced ammonium–nitrate (N2), and ammonium-enriched nitrogen strategies (N3) during GS13–GS31, with conventional farmer practice (CK) and a zero-N control (N0) for comparison. Nitrogen-form regulation markedly altered the soil NH₄⁺-N ratios, especially in the 0–20 cm soil layer, with N3 highest, N1 lowest, and N2 intermediate. Compared with the nitrate- or ammonium-dominant strategy, the balanced treatment N2 improved spike formation rate and maintained relatively higher N accumulation at GS31 and GS65, and showed greater N translocation and contribution of translocated N to grain N than N1. Correlation analyses indicated that spike formation rate was closely related to spike number (R² = 0.764) and N accumulation at GS31 was positively related to Ntrans (R² = 0.588). N2 showed the most favorable overall performance, with the highest numerical values for grain yield, nitrogen recovery efficiency, irrigation water use efficiency, and net profit among the fertigation treatments. However, the advantages of N2 over N3 in grain yield and SPAD-AUC were modest and not consistently significant. These results indicate that balancing ammonium and nitrate supply during GS13–GS31 under drip fertigation can improve root-zone N conditions and support better overall agronomic performance in winter wheat under the alkaline soil conditions of the North China Plain. Full article

Decades of traditional fertilizer subsidies have yielded modest maize productivity gains for Malawian farmers, mainly due to the twin challenges of soil degradation and intermittent weather patterns. Increasing nitrogen intake through subsidies without addressing these structural constraints has failed to close the country’s yield gap. Although climate-smart agriculture (CSA) technologies offer options for sustainable productivity growth, low and inconsistent adoption among farmers has led to insufficient evidence. Most existing studies that have examined the complementarity between CSA and inorganic fertilizers rely on experimental plot data, with limited evidence from actual farmer-managed fields. We use farm-level data collected in 2022 from 307 smallholder farmers across central and southern Malawi to investigate whether integrating CSA technologies with subsidized inorganic fertilizers enhances maize productivity. We apply the Inverse Probability Weighted Regression Adjustment (IPWRA) model to estimate the effects of CSA adoption and its integration with subsidized fertilizer. Results indicate that CSA adoption increased maize yields by 30%, confirming significant productivity gains from technologies such as mulching, agroforestry, and organic manure. However, integrating these technologies with subsidized fertilizers produced no additional yield advantage, suggesting that farmers often substitute CSA with inorganic inputs rather than combining them effectively. These findings imply that the potential synergies between CSA and subsidy programs remain unrealized under current practices. Policy reforms under Malawi’s current farm input subsidy program (FISP) should therefore emphasize extension and incentive mechanisms that promote complementary—not substitutive—use of CSA technologies and fertilizers at recommended application rates. Full article

Coffee (Coffea arabica) is a very important world commodity because of the countries involved in its production, along with the total cultivated area, production volume, consumption and economic impact. In Mexico, the coffee producing areas are located mainly in the hilly terrain of southern Mexico under agroforestry systems predominantly owned by smallholders. Low productivity is faced especially in the state of Oaxaca as a result of inadequate management practices such as aged plantations and deficient practices of pruning and plant nutrition. In order to evaluate the effect of inorganic fertilization on coffee yield, an experiment was carried out at three plantations located in the coastal coffee producing region of the state of Oaxaca, Mexico. Six treatments considering varied amounts of inorganic nitrogen (N), phosphorus (P) and potassium (K) and lime application were applied in coffee plantations with the varieties Typica and Oro azteca. A randomized complete block design with four replications was used. The experiments were conducted in areas with three- or four-year-old plants, with the objective of having at least one harvest for yield evaluation. The variables’ plant height and coffee yield per plant were registered. The soil was classified based on soil profile description and lab analyses. The results showed that the soil in the study area is a Lithic Ustorthent with low pedogenic evolution and the application of inorganic nitrogen, phosphorus and potassium along with dolomitic lime, increased coffee yield on both varieties of arabica coffee: Typica and Oro azteca. Full article

Intensive nitrogen (N) fertilization in Phyllostachys edulis (Carrière) J.Houz. forests increases productivity but also accelerates nitrous oxide (N₂O) emissions, posing a challenge to balancing forest yield with environmental sustainability. Silicon (Si), a beneficial element for bamboo, has emerged as a potential regulator of soil nitrogen (N) cycling, but its role in controlling N₂O emissions in forest ecosystems is not fully understood. In this study, we conducted a factorial pot experiment using P. edulis forest soil, with data collected over two years, but only the second-year results were analyzed, with controlled N (0, 80, and 160 mg kg⁻¹) and Si (0, 25, and 50 mg kg⁻¹) additions. The experiment lasted two years, but only the second-year data were used for analysis. We investigated how Si affected soil inorganic N dynamics, enzyme activities, plant growth, and cumulative N₂O emissions. Si addition significantly reduced N-induced N₂O emissions by up to 53%, with the strongest mitigation observed under moderate N input (p < 0.05, two-way ANOVA). This effect was associated with lower activities of AMO, NaR, and NiR, together with reduced availability of oxidized N substrates, indicating that Si mitigated N₂O emissions mainly by constraining upstream N transformation processes rather than by directly suppressing N₂O fluxes. Si addition also tended to promote plant biomass accumulation. These findings suggest that integrating Si fertilization into bamboo forest management may help improve nutrient use efficiency while mitigating greenhouse gas emissions. Full article

This study focused on alfalfa (Medicago sativa cv. Xinmu No. 4) as the experimental material, and a two-year field plot controlled experiment was conducted to compare the effects of different co-application ratios of organic and chemical fertilizers on alfalfa yield, soil nutrient status, and soil biological characteristics. The six fertilization treatments were as follows: CM0 (100% cattle manure), CM1 (75% cattle manure + 25% chemical fertilizer), CM2 (50% cattle manure + 50% chemical fertilizer), CM3 (25% cattle manure + 75% chemical fertilizer), CM4 (100% chemical fertilizer), and CK (no fertilizer application). The results showed that alfalfa hay yield was highest under the CM3 treatment in both 2024 and 2025, representing increases of 38.03% and 40.85%, respectively, compared with the control (CK). Relative to the other treatments, CM3 significantly increased soil total nitrogen, alkali-hydrolyzable nitrogen, available phosphorus, readily available potassium, and organic matter contents. In addition, CM3 markedly enhanced the activities of soil nitrate reductase (NR), nitrite reductase (NiR), and the root enzymes glutamate synthase (GOGAT) and glutamine synthase (GS). The combined application of organic and chemical fertilizers significantly reshaped the soil bacterial community structure associated with alfalfa. Under the CM3 treatment, Chao1, Shannon, and ACE indices of soil bacterial diversity increased, whereas the Simpson index decreased. Moreover, the CM3 treatment was associated with higher relative abundances of several key bacterial phyla and genera. The 25% cattle manure plus 75% chemical fertilizer (CM3) treatment exhibited the strongest overall effects, significantly increasing total alfalfa hay yield, enhancing soil macronutrient availability and key enzyme activities, improving soil microbial α-diversity, and optimizing soil bacterial community structure. This treatment consistently outperformed the no-fertilizer control (CK) and all other organic–inorganic fertilizer combinations. Collectively, these findings provide robust scientific evidence supporting strategies to increase forage productivity, mitigate environmental impacts, and promote the sustainable development of the grassland industry. Full article

To further enhance nutrient use efficiency for maize cultivation in the Changbai Mountains—Liaodong Hilly Region and to safeguard both grain production and soil quality, 2441 pairs of data points extracted from 47 publicly published papers were selected for analysis to investigate the effects of different fertilizer types, their application rates, and field management practices on spring maize yield enhancement, crop growth, and soil physicochemical properties. According to the subgroup analysis of the above indicators, the results demonstrated that various fertilization management practices can effectively increase maize yield and soil nutrient content. Specifically, applications of nitrogen fertilizer (39.78%) and top-dressing (34.10%) had the best effect on increasing maize yield. The combination of organic–inorganic application (22.93%) and straw returning (20.46%) had the best effect on increasing soil organic matter. Based on grain yield and its components, crop physiology and soil physicochemical properties, we recommend an optimal nutrient management strategy for this region: an application rate of 180 kg/ha for nitrogen and 70–100 kg/ha for both phosphorus and potassium, and the field management practice of combined application of chemical fertilizers and manure based on full-amount straw returning in the field. This study provides a reference for nutrient management of maize fields in the Changbai Mountains—Liaodong Hilly Region. Full article

Baby maize (Zea mays L.) is widely cultivated across Asia due to its short growth cycle and adaptability to diverse agroecological conditions. However, its production is frequently constrained by low soil fertility, leading to the excessive use of chemical fertilizers, which in turn contributes to environmental degradation. Endophytic bacteria with the ability to fix atmospheric nitrogen and solubilize inorganic phosphate represent a sustainable alternative for improving nutrient availability. This study aimed to isolate and characterize endophytic bacteria exhibiting dual nitrogen-fixing and phosphate-solubilizing capabilities from baby maize roots. A total of ten bacterial isolates were obtained and screened using nitrogen-free Burk medium and NBRIP medium. Among these, strain CMB2 demonstrated superior functional traits. Molecular identification based on 16S rRNA gene sequencing confirmed that the isolate belongs to Bacillus stercoris. In vitro assays revealed that B. stercoris CMB2 exhibited significant nitrogenase activity, as determined by the acetylene reduction assay, and strong phosphate-solubilizing ability, indicated by a clear halo zone and a high solubilization index. These findings suggest that B. stercoris CMB2 is a promising multifunctional endophytic bacterium for enhancing nutrient availability under controlled conditions. Further validation under greenhouse and field conditions is required to assess its potential for improving plant growth and nutrient uptake in baby maize. Full article

To investigate the long-term effects of combined organic and inorganic fertilizer application on the structural stability and fertility of soil in paddy fields located in the cool northeastern region of China, a long-term fixed-site experiment was initiated in 2017. The experiments included the following five treatments: 100% conventional chemical fertilizer NPK (CK), conventional PK fertilizer without N fertilizer (T1), 30% organic N and 70% chemical N fertilizers with conventional PK fertilizer (T2), 50% organic N and 50% chemical N fertilizers with conventional PK fertilizer (T3), and 100% organic N fertilizer (T4). Notably, the total amount of fertilizer applied remained consistent across treatment groups. The results revealed that the combination of organic and inorganic fertilizers significantly increased rice yields and nitrogen use efficiency, with the T3 treatment performing the best. Compared with CK, T3 resulted in a 24.26% greater rice yield, and it increased the nitrogen agronomic efficiency by 71.05%. There were no significant differences among the treatment groups in terms of the proportions of soil aggregates larger than 2 mm or smaller than 0.053 mm. Nitrogen fertilizer application reduced the proportion of 0.053–0.25 mm aggregates and promoted the formation of predominantly 0.25–2 mm aggregates. However, the different organic–inorganic combinations did not cause significant differences in soil aggregate structure or stability. Compared with the CK treatment, the application of both organic and inorganic fertilizers increased soil organic matter content, decreased N₂O emissions, and increased soil catalase activity. In summary, the application of 50% organic N and 50% chemical N fertilizers with conventional PK fertilizer (T3) was determined to be the optimal combination for achieving high and stable rice yields in the cool northeastern region of China while increasing the structural stability and fertility of the soil. Full article

Mulberry (Morus alba L.) is a woody plant primarily cultivated for silkworm breeding, with significant economic and ecological functions. Its nitrogen use efficiency directly affects leaf yield, quality, and environmental adaptability. The main inorganic nitrogen forms available for plant uptake in soil are ammonium nitrogen and nitrate nitrogen, and plant uptake and assimilation of these two nitrogen sources often exhibit species-specific preferences. This review systematically summarizes the research progress on nitrogen uptake preferences in mulberry, confirming that this species generally shows a preferential uptake of nitrate. Specifically, when supplied with nitrate or a mixed nitrogen source dominated by nitrate, mulberry exhibits better performance in growth and development, photosynthetic efficiency, and accumulation of secondary metabolites. This review further discusses the physiological characteristics and underlying regulatory mechanisms responsible for this preference, and analyzes key factors affecting nitrogen uptake preferences, including soil properties, environmental stresses, and microbial interactions. It should be noted that while controlled experiments have yielded important insights, the applicability of these findings under complex field conditions still requires further validation through field trials. Finally, future research directions are prospected, including in-depth dissection of molecular mechanisms, field validation, plant-microbe interactions, and nutritional strategies for stress resistance, aiming to provide a theoretical basis for efficient cultivation and precise nitrogen management of mulberry. Full article