Nitrogen

Nitrogen fertilization plays a critical role in promoting plant growth, improving physiological and biochemical traits, and enhancing wheat productivity. This study aimed to evaluate the effects of seven nitrogen (N) doses—0, 45, 90, 135, 180, 225, and 270 kg N ha⁻¹—on wheat performance under semi-arid subtropical conditions over three consecutive growing seasons (2015–2018). A randomized complete block design (RCBD) was used to assess a comprehensive set of agronomic, physiological, biochemical, and nutritional parameters. Key factors examined included grain yield, above-ground biomass, nitrogen harvest index, total nitrogen content in grains and straw, and physiological traits such as photosynthetic rate, stomatal conductance, transpiration rate, and the accumulation of soluble proteins, sugars, and amino acids. The study also incorporated multivariate statistical techniques, such as multi-trait genotype–ideotype distance index (MGIDI), principal component analysis (PCA), and descriptive statistics to identify the most effective nitrogen dose. Results indicated that 180 kg N ha⁻¹ (T₄) was the most effective treatment for improving wheat growth, physiological efficiency, and grain yield, with 135 kg N ha⁻¹ (T₃) also showing favorable outcomes. In contrast, higher doses (225 and 270 kg N ha⁻¹) led to diminished performance, suggesting a threshold beyond which nitrogen becomes counterproductive. These findings support 180 kg N ha⁻¹ as the optimal dose for maximizing yield and biochemical quality while contributing to more sustainable and profitable wheat production. Full article

Despite extensive research on how climate and environmental factors influence leaf stoichiometry at national and global scales, experimental evidence on their effects at the community level remains limited, particularly in extremely arid regions. Herein, we investigated the leaf stoichiometry including carbon (C), nitrogen (N), and phosphorus (P) along a fine-scale riparian gradient (50–1250 m from the riverbank) in an extremely arid Populus euphratica forest in northwest China. Our results show that the community-averaged leaf total carbon (TC), total nitrogen (TN), and total phosphorus (TP) contents were 442.58 mg/g, 21.69 mg/g, and 1.18 mg/g, respectively. The community-averaged C:N, C:P, and N:P ratios were 20.74, 379.97, and 18.43, respectively. Compared to findings from other studies, the P. euphratica community exhibited lower leaf TC and TP contents but higher TN content and N:P ratios. A high N:P ratio (mean = 18.43, N:P > 16) suggests that the P. euphratica community is more susceptible to phosphorus limitation. Along the riparian gradient, community-averaged leaf TC, C:N, and C:P increased significantly, reaching their maximum (479.49 mg/g, 27.12, and 478.06, respectively) at 1250 m from the riverbank. Conversely, leaf TN and TP contents, as well as N:P, decreased significantly with increasing distance from the river, reaching their minimum values (17.49 mg/g, 0.99 mg/g, and 17.17, respectively) at 1100–1250 m. Soil available phosphorus, soil water content, soil bulk density, and soil electrical conductivity significantly influenced the leaf stoichiometry of the P. euphratica community, collectively explaining 61.78% of the total variation. Among these factors, soil water content had the most pronounced effect, surpassing soil available phosphorus, bulk density, and electrical conductivity in shaping leaf stoichiometric characteristics. Our findings indicate that at fine spatial scales, the distribution of leaf nutrients and stoichiometry seem to be predominantly influenced by local-scale factors such as soil water content, soil nutrient levels, and salt stress; P. euphratica forests would be experiencing more negative impacts in leaf nutrients and stoichiometry due to increased droughts or salt stress. Full article

Rice is a major crop for half of the world’s population, and nitrogen (N) fertilizers play a crucial role in its production. However, imbalanced N fertilizer uses and traditional fertilization practices have led to low nitrogen use efficiency (NUE), increased N footprints, and reduced rice yields and farmers’ income. There are limited studies where the integration of both agronomic and molecular advancements to enhance NUE is discussed, particularly in developing countries. This review highlights novel agronomic and molecular strategies to enhance NUE, rice yields, and profitability, while minimizing environmental impact. The agronomic strategies include the 4R Nutrient Stewardship framework, enhanced efficiency nitrogen fertilizers (EENFs), nano-fertilizers, biochar-based fertilizers, biological N fixation, and sensor-based fertilizer management in major rice-growing countries. The molecular mechanisms focus on N uptake, assimilation, and utilization, highlighting the role of hormones, key genes, transcription factors (TFs), and regulatory pathways. Moreover, we examine promising rice genotypes and cultivars with improved NUE and grain yield. Additionally, this paper offers deep insights into recent advancements in molecular genetics, such as multi-omics approaches (transcriptomics, metabolomics, and metagenomics), the Genome-Wide Association Study (GWAS), Quantitative Traits Loci mapping (QTLs), Single Nucleotide Polymorphisms (SNPs) analysis, and Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR-Cas9)-mediated genome editing, which serve as valuable tools for developing rice cultivars with enhanced NUE and grain yield. Full article

Rosemary (Salvia rosmarinus L.) is a versatile and resilient plant with significant culinary, medicinal, and ecological value. This study evaluates the impact of four nitrogen (N) fertilization levels (0, 50, 100, and 150 kg N ha⁻¹) on the morphological, physiological, and agronomic traits, as well as vegetative indices, of rosemary over two growing seasons (2022 and 2023). The results indicate that plant height and leaf area index (LAI) increased with N application. Additionally, physiological characteristics such as chlorophyll content, photosynthetic efficiency, and assimilation rates (A) increased by an average of 32%, 17%, and 55%, respectively, compared to the control. Biomass production also improved with N fertilization, with yields rising by 32% in 2022 and 58% in 2023. Furthermore, both essential oil concentration and essential oil yield were enhanced by N application. Radiation use efficiency (RUE), water use efficiency (WUE), agronomic efficiency (AE), and partial factor productivity (PFP) also increased, indicating more efficient utilization of environmental resources. Moreover, higher N rates consistently enhanced vegetation indices, reflecting improved plant health, greenness, biomass, photosynthetic activity, and energy utilization. Therefore, this study highlights that the optimal N range appears to balance biomass yield and essential oil yield while maximizing the efficiency of environmental resource use. Full article

In Spain, several major cities face high rates of avoidable deaths due to NO₂ exposure. Understanding NO₂ atmospheric dynamics is essential to support public health efforts and policymaking. Recent satellite products have proven useful in characterizing urban atmospheric composition in various regions. This study compares NO₂ concentration data from in situ air quality monitoring networks and the Sentinel-5P TROPOMI satellite in Spain’s three largest cities (Madrid, Barcelona, and Valencia), alongside O₃ levels —due to its close photochemical relationship with NO_x—wind speed and direction, temperature, relative humidity, and solar radiation. Data from 2022 were analyzed using Pearson correlation coefficients and Principal Component Analysis (PCA) to identify key relationships and patterns. Results showed a consistent negative correlation between NO₂ and O₃, wind speed, temperature, and solar radiation. Differences between in situ and satellite data were more pronounced in coastal cities, influenced by wind patterns and urban morphology (Madrid: r = 0.86, v = 1.34 m/s; Valencia: r = 0.68, v = 2.97 m/s; Barcelona: r = 0.65, v = 8.04 m/s). These insights enhance the understanding of NO₂ behavior in urban environments and support the use of remote sensing to estimate surface-level pollution in areas lacking ground-based monitoring infrastructure. This is the first study in Spain to jointly evaluate NO₂ from satellite and in situ data across multiple cities, linking pollutant concentrations with meteorological and chemical drivers to improve surface-level estimation strategies and support air quality assessment in under-monitored areas. Full article

Although intensive farming practices have greatly increased food production, they have undermined the soil ecosystem services on which agriculture depends. Biochar application in soils is increasingly gaining worldwide acceptance as a means of addressing these environmental challenges while enhancing agricultural productivity. Biochar offers dual benefits that support food security and ecological well-being through enhanced soil fertility and plant nutrition. These benefits include water retention, promotion of soil microbial functioning, carbon sequestration, and nutrient absorption, among others. In spite of these known benefits, many studies continue to emphasize the roles biochar plays in enhancing soil health and crop yields but often neglect the influence of biochar characteristics, which are key in optimizing these soil ecosystem services. Thus, it is important to understand how biochar characteristics influence soil in supporting, regulating, and provisioning ecosystem services. This review offers a comprehensive and integrative assessment on how biochar’s characteristics influence key soil ecosystem services rather than examining each service individually. The focus is on how biochar feedstock material and pyrolysis temperature determine the characteristics of generated biochar and how these characteristics influence biochar’s efficacy in supplying soil ecosystem services and nutrient dynamics for enhanced crop yields. Full article

Wheat requires a high quantity of nitrogen to grow efficiently and produce a high number of nutritious grains (=high yield). The consequences of fertilizer use in uncontrolled conditions are well known, e.g., nitrogen leakage leading to impacts on ecosystems. One solution to reduce these impacts could be activated carbon, which is already used to treat wastewater. In this study, we assessed the efficiency of four activated carbon formulations applied to two agricultural soils in a column leaching test, a greenhouse pot experiment, and a field experiment. In the latter two experiments, wheat was grown with one dose of one selected activated carbon and several nitrogen fertilization conditions. The goal was to find an activated carbon that could stabilize nitrate while improving soil health and thus increase wheat yields. We showed that nitrogen leaching reduction (between 59% and 79% when significant in the column test) was dependent on the raw material used and the activation process. The controlled pot experiment demonstrated that wheat growth was dependent on nitrogen application (60 to 80% increase) and that the activated carbon addition did not enhance yields. Finally, field trials showed that the addition of 1% activated carbon did not result in higher wheat yields compared to those in the non-amended plots in both the absence and presence of nitrogen. In conclusion, although the activated carbon chosen is a strong nitrate-retaining agent, it does not deliver the expected yield gains, probably due to excessive retention, which prevents increased plant growth. More research is needed to improve activated carbon as a fertilizer. Full article

This study introduces a novel methodology for predicting cotton yield by integrating machine learning (ML) with mechanistic soil modeling. This hybrid approach enhances yield prediction by combining data-driven ML techniques with soil process modeling. Using the developed yield model, yield curves for various nitrogen (N) levels can be constructed to identify the optimal N dose that maximizes yield. Estimating cotton N requirements is crucial, as growers often apply excessive N, exceeding the amount needed for maximum yield. By comparing the Mean Absolute Error (MAE) between predicted and observed cotton yield values across three ML algorithms, i.e., Random Forest (RF), XGBoost, and LightGBM, the RF model achieved the lowest error (422.6 kg/ha), outperforming XGBoost (446 kg/ha) and LightGBM (449 kg/ha). Additionally, the RF model exhibited high sensitivity to N fertilization, ranking N as the most influential variable in feature importance analysis. Furthermore, phosphorus (P) availability in the soil model was found to be a significant factor influencing the RF yield model, highlighting P’s crucial role in cotton growth and productivity. Full article

Beef-cattle manure (BCM) can be an effective source of nitrogen (N) for crop production. However, N availability from manure can be difficult to quantify across varying environments. The Magruder Plots are a continuous winter wheat (Triticum aestivum L.) fertility study established in 1892 in Stillwater, OK, USA. In the study, wheat grain yield responses to BCM that is applied every four years are compared to those following annual applications of inorganic nitrogen (N), phosphorus (P), and potassium (K) fertilizers. This long-term, comprehensive dataset facilitates the evaluation of manure N availability and uptake across a wide range of growing environments; thus, the objective of this paper was to use 56 years of data from the Magruder Plots to benchmark current N-based manure application guidelines for Oklahoma. The results from this analysis revealed some discrepancies compared to regionally accepted guidelines for manure N availability. Existing guidelines for Oklahoma suggest that 50 to 70% of total N in BCM will become plant-available in the first year after application; however, the Magruder Plots have only averaged 23% total N availability in year one. The three seasons after manure application averaged total N availability of 20, 16, and 14%, respectively, which much more closely align with the existing estimates for Oklahoma of 10 to 20% N availability after year one. This study suggests that N availability of BCM in the first year after application in Oklahoma has a more accurate estimate of 10 to 30% of total N. Full article

Increasing soil salinity is threatening agricultural productivity which implies the development of new sustainable strategies to deal with this challenge. The main objective here is to assess the potential for improving the tolerance of alfalfa to salinity by combining inoculations with rhizobia and AMF. However, the distinguishing feature of this study is the comparison of two alfalfa varieties’ microbial response to salinity. The greenhouse trial was conducted on an Australian variety Siriver and an indigenous Demnate population, which were inoculated with Rhizoglomus irregulare and/or native AMF, and/or a RhOL1 rhizobial strain. The RhOL1 strain was selected from nine rhizobia tested for their plant growth promoting rhizobacteria (PGPR) activities. In addition to its ability to tolerate high salinity levels (769 mM) and solubilize insoluble phosphate as well as potassium, it can also synthesize auxins such as IAA. The application of these biofertilizers was carried out in the absence and the presence of the saline stress (0 and 120 mM NaCl). The double inoculations of native AMF and RhOL1 significantly improve the shoot and root dry biomass, plant elongation, number of formed leaves, and mineral nutrition, as well as the number of nodules and the rate of mycorrhizal root colonization. The synergistic effects between the native AMF and RhOL1 strain have been demonstrated in this study. However, the behavior of alfalfa genotypes towards microbial inoculation was significantly different. The ability to react to the double indigenous RhOL1 + AMF inoculation is more important in the Siriver than in the Demnate population. Thus, the possibility of formulating biofertilizers is based on the AMF–rhizobia–hote tripartite combination for alfalfa production in saline areas. Full article

This study investigated the effects of Bradyrhizobium elkanii inoculation and nitrogen (N) fertilization on the growth of Pseudalbizzia niopoides seedlings in a nursery and their subsequent performance in soil. P. niopoides is a legume tree native to Latin American tropical forests, known to nodulate but with no previously identified rhizobial partner. Seedlings were grown in a nursery under varying N fertilization rates (0, 250, 500, 1000, and 2000 mg L⁻¹) with and without B. elkanii inoculation. Morphological traits, nodulation, and post-planting growth were assessed. Both inoculation and N fertilization significantly enhanced seedling growth in the nursery. However, high N rates suppressed nodulation and caused root toxicity. Inoculated seedlings exhibited improved growth after planting, particularly at lower N rates. Notably, inoculated seedlings without added N demonstrated vigorous new root proliferation after three months, highlighting the beneficial effects of the symbiosis. In terms of nitrogen fertilization in nurseries, a N rate up to 500 mg L⁻¹ produced satisfactory plant growth and no prejudicial effects on the symbiosis establishment. However, it is possible to raise seedlings even in the 0 mg L⁻¹ N rate, with a vigorous root emission during the post-planting growth. This study provides valuable insights into the interaction between a specific rhizobia strain and P. niopoides, with implications for nursery practices and sustainable agroforestry systems. Full article

Alley cropping, an agroforestry system that integrates trees and arable crops, holds the potential to improve both crop yields and soil health. It has been found to be effective for upland crops in many countries of the world. However, the utilization of alley cropping to improve soil health in the terrace ecosystem of Bangladesh is poorly understood. Therefore, this study was undertaken to assess the changes in soil biochemical properties and quantify the cabbage yield under three alley widths of Leucaena leucocephala (3.0, 4.5, and 6.0 m size) and five nitrogen (N) levels [0, 40, 80, 120, and 160 kg N ha⁻¹ (0, 25, 50, 75, and 100% of recommended N rates, respectively) with the addition of pruned materials of L. leucocephala (Ipil-ipil)]. The field experiment was conducted following a split-plot design, where alley width was considered as the main-plot factor and N rate as the sub-plot factor. Within each main plot, the five N rates were replicated thrice. Control plots with similar N doses were applied accordingly without addition of pruned materials to compare the results with alley cropping. Data were collected on the biochemical properties of the soil [soil pH, organic carbon (C), total N, available phosphorus (P), exchangeable potassium (K), microbial biomass C, and biomass N] and the yield of cabbage quantified [edible head weight (kg plant⁻¹) and head yield (t ha⁻¹)] under different alley widths and control. Findings revealed that organic C, total N, available P, exchangeable K, microbial biomass C, and biomass N in the topsoil exhibited maximum values in the L. leucocephala-based alley plot, which is proved to be a possible solution of restoration of degradable land. Additionally, L. leucocephala-based alley cropping improved the soil pH, indicating a potential avenue for more-sustainable land management practices. Results also showed that alley widths and N rates have significant effects on cabbage (Brassica oleracea L. var. capitata) yield. Alley width of 6.0 m along with 100% N provided the highest cabbage yield followed by 75% N in 6.0 m alley, and the control with 100%. The wider alley minimizes tree–crop competition, allowing for optimal cabbage production. These aforementioned results suggest that alley cropping with L. leucocephala is a promising approach to enhance soil fertility and crop productivity in the terrace ecosystem of Bangladesh. Full article

This study explores the economic benefits and challenges associated with biodegradable waste composting, highlighting its role in promoting sustainability through a circular economy framework. We reviewed the relevant literature and found 160 articles for this study, including the keywords “Biodegradable waste”, “Compost production”, and “Economic Potential”. Considering quality studies, we employed the PRISMA technique to conduct a comprehensive data synthesis and evaluate 89 articles for the final review. Our findings highlight that composting offers significant advantages, including waste reduction, cost savings in waste management, carbon credit, a source of nitrogen, job creation, and reduced reliance on synthetic fertilizers. Further, it supports environmental sustainability by improving soil health, mitigating greenhouse gas emissions, and reducing landfill use. However, challenges such as high upfront costs, quality control, and market competition with chemical fertilizers remain barriers to widespread adoption. The study extends the literature by emphasizing that the integration of composting into a circular economy can foster innovation, enhance local economies, and contribute to climate change mitigation. Furthermore, it offers a promising pathway for advancing sustainability. Future research should focus on improving composting technologies, optimizing their applications, and developing stronger policy frameworks to ensure the successful implementation of biodegradable waste composting practices. Full article

Soil nitrogen (N) is a crucial nutrient for agricultural productivity and ecosystem health. The accurate and timely assessment of total soil N is essential for evaluating soil health. This study aimed to determine the impact of bootstrapping techniques on improving the predictive accuracy of indirect total soil N in conventional wheat fields in Al-Muthanna, Iraq. We integrated a novel methodological framework that integrated bootstrapped and non-bootstrapped total soil N data from 110 soil samples along with Landsat 9 imagery on the Google Earth Engine (GEE) platform. The performance of the proposed bootstrapping-enhanced random forest (RF) model was compared to standard RF models for soil N prediction, and outlier samples were analyzed to assess the impact of soil conditions on model performance. Principal components analysis (PCA) identified the key spectral reflectance properties that contribute to the variation in soil N. The PCA results highlighted NIR (band 5) and SWIR2 (band 7) as the primary contributors, explaining over 91.3% of the variation in soil N within the study area. Among the developed models, the log (B5/B7) model performed best in capturing soil N (R² = 0.773), followed by the ratio (B5/B7) model (R² = 0.489), while the inverse log transformation (1/log (B5/B7), R² = 0.191) exhibited the lowest performance. Bootstrapped RF models surpassed non-bootstrapped random forest models, demonstrating enhanced predictive capability for soil N. This study established an efficient framework for improving predictive capacity in areas characterized by limited, low-quality, and incomplete spatial data, offering valuable insights for sustainable nitrogen management in arid regions dominated by monoculture systems. Full article

Nitrate pollution in aquatic environments poses significant environmental and public health issues, mostly due to industrial activities and agricultural runoff. Biological denitrification, the favored method for removing nitrates, typically needs an external carbon source to support microbial processes. Traditional electron donors like methanol, ethanol, and acetate are effective but introduce economic, environmental, and operational challenges such as cost variability, flammability hazards, and excessive residual organic material. Recently, solid-phase carbon sources—like biodegradable polymers and organic agricultural waste—have shown promise as alternatives because they allow for controlled carbon release, improved safety, and enhanced long-term sustainability. This review systematically examines the performance of solid-phase carbon in wastewater denitrification by analyzing peer-reviewed studies and experimental data. The findings suggest that solid-phase carbon sources, including polycaprolactone (PCL) and polyhydroxyalkanoates (PHA), offer stable and extended carbon release, ensuring consistent denitrification effectiveness. Nonetheless, challenges remain, including optimizing biofilm development, balancing carbon availability, and reducing operational costs. Furthermore, the review emphasizes the potential for integrating machine learning in process optimization and highlights the need for more research to enhance the economic viability of these materials. The findings confirm the practicality of solid-phase carbon sources for extensive wastewater treatment and their capability to sustainably address nitrate contamination. Full article

Addressing the challenge of reducing environmental pollution from agricultural practices by improving nitrogen use efficiency (NUE) and water use efficiency (WUE) while ensuring high crop yields is essential for sustainable agriculture. Using a controlled glasshouse experiment, we evaluated the combined effects of biochar and bokashi under different irrigation regimes on NUE, WUE, and yield-related parameters in a wheat cropping system. The experiment followed a completely randomized design with three replications with four treatments: (1) control (C), (2) bokashi only (B₀), (3) bokashi +1% biochar (B₁), and (4) bokashi +2% biochar (B₂). These treatments were evaluated at three irrigation levels—30% (IR₃₀), 50% (IR₅₀), and 60% (IR₆₀) of field capacity (FC), resulting in a total of twelve treatments. Co-application of bokashi–biochar significantly (p < 0.050) improved grain yield (GY), straw yield (SY), total biomass (TB), total nitrogen uptake (TNU), grain protein content (GPC), NUE, and WUE, with the most notable benefits observed at 1% biochar application compared to C and B₀ treatments. In addition, both types of treatment (bokashi and bokashi with biochar) and the level of irrigation had a significant impact on GY, SY, TB, TNU, GPC, NUE, and WUE. The B₁ and B₂ treatments further improved yield and efficiencies compared to bokashi alone. The positive correlation between grain yield and WUE underscores the importance of optimizing irrigation strategies alongside soil amendments for improved crop productivity. These enhancements in yield and efficiency are likely attributed to the increased soil fertility, nutrient availability, and water retention resulting from the combination of biochar and bokashi. Full article

Sweet corn (Zea mays convar. saccharata var. rugosa) is an important crop in the United States (US), particularly in the southeastern region. While effective nitrogen (N) management is essential for optimizing yields, the sandy soils and variable precipitation in this region impact N uptake. This study evaluates the effects of several N rates (ranging from 224 to 336 kg ha⁻¹) and N fertilizer application timing (N fertilizer applied at emergence and side-dress stages) on sweet corn growth and yield under the subtropical environmental conditions of the southeastern US. Field experiments were conducted over three years in the states of Georgia (2020) and Alabama (2021 and 2022). In general, the weather conditions of each season had a direct impact on sweet corn growth, development, and yield parameters. Among all locations, the season in Alabama (2022) allowed for the highest yields (17,380 kg ha⁻¹), which could be attributed to favorable weather conditions that required moderate nitrogen application rates (224–280 kg ha⁻¹). Contrarily, the weather conditions of Alabama in 2021 and Georgia in 2020 impacted soil N availability, consequently leading to negative effects on sweet corn growth. Overall, N fertilizer management strategies are indicated to be region- and season-specific in order to enhance sweet corn production while protecting the environment from excessive N losses. Further research is still required to refine these strategies and improve predictive models for diverse climatic conditions. Full article

The development of critical levels for sap nitrate and chlorophyll meter reading (SPAD test) in the case of various crops is of great importance for growers in characterizing a plant’s N status. A field experiment with spring oat (Avena sativa L.) was carried out on loamy soil in Debrecen, Hungary, using a small-plot design. Ammonium nitrate was broadcast at rates of 0, 30, 60, and 90 kg N/ha in three replicates. The total N content of the plant, sap nitrate content, and SPAD values were measured at jointing when the first node appeared above the soil surface (Feekes 6) and at boot stage (Feekes 10). Regression analysis between total N content and sap nitrate showed cubic and linear relationships with r² = 0.7982 (Feekes 6, whole plant) and 0.9625 (Feekes 10, upper developed leaves), respectively. Optimal grain yield was obtained when sap nitrate exceeded 650 mg/L and 540 mg/L at Feekes 6 and Feekes 10, respectively. There were linear and logarithmic relationships between total N content and SPAD values with r² = 0.8058 and 0.6258 at Feekes 6 and 10. Optimal grain yield occurred over SPAD values of 43 and 48 at Feekes 6 and 10, respectively. Optimal N rate was 60 kg N/ha on the experimental site. Full article

Excessive irrigation in protected vegetable production often results in soil nutrient loss and groundwater contamination. Cucumber (Cucumis sativus L.) is a widely cultivated and important vegetable in the world and a sensitive plant to irrigation water supply. In order to obtain higher water use efficiency (WUE) and to assess the leaching loss of mineral elements under the current strategies of irrigation and fertilization in the production of protected crops, we conducted experiments with three irrigation levels, namely, normal (NI), optimized (OI), and deficit irrigation (DI), on cucumber in a solar greenhouse. The results indicated that the contents of nitrate–nitrogen (NO₃⁻–N) in the top soil layer increased significantly under the reduced irrigation condition (OI and DI) after two cultivation seasons compared with normal irrigation (NI). However, there were no significant differences in the contents of available phosphorus (A–P) and available potassium (A–K) between the three treatments in each soil layer during a single irrigation cycle and for the whole growth cycle. In addition, compared to the NI condition, reducing the amount of irrigation (OI and DI) decreased the amount of leaching of the soil mineral elements by more than half without jeopardizing the fruit yield of cucumber, particularly for DI. Under the three irrigation treatments, the economic yield of cucumber varied from 64,513 to 72,604 kg·ha⁻¹ in the autumn–winter season and from 89,699 to 106,367 kg·ha⁻¹ in the winter–spring season, but the differences among the treatments were not significant. Moreover, the reduced irrigation treatments (OI and DI) substantially improved WUE by 43.9% and 135.3% in the autumn–winter season, and by 82.2% and 173.7%, respectively, in the winter–spring season, compared to the NI condition. Therefore, deficit or optimized irrigation was a potential and suitable irrigation strategy in the solar greenhouse for increasing the water use efficiency, reducing the amount of leached soil mineral elements, and maintaining the economic yield of cucumber crop. Overall, our results provided some insight into the future applications of water-saving irrigation techniques in sustainable greenhouse vegetable production. Full article