Search Results (355)

Hydrogels are widely known for their ability to increase soil water retention and for their potential slow nutrient release mechanism. They have been constantly improved to meet the growing demand for sustainability in agriculture. Research focused on the development of biodegradable hydrogels, produced from industrial cellulose waste, are an ecological and efficient alternative soil ameliorant for the improvement of agricultural land. The objective of this study was to evaluate the impacts of two types of hydrogel (processed in a glass reactor versus a twin-screw extruder) on soils with different textures (clay and sandy loam), testing their water retention capacity, nitrogen leaching, and effects on seed germination. The methodology included the evaluation of water retention capacity at different pressures with different hydrogel addition rates in the soil, leaching tests in columns filled with soil and hydrogel layers, and germination tests of sorghum and corn. The results indicated that the addition of hydrogel significantly improved water retention, especially in sandy loam soils. The hydrogels also reduced nitrogen leaching, acting as nitrification inhibitors and limiting the conversion of ammonium to nitrate, with greater effectiveness in clayey soils. In the tested formulations, it was observed that the hydrogel doses applied to the columns favored nitrogen retention in the region close to the roots, directly influencing the initial stages of germination. This behavior highlights the potential of hydrogels as tools for directing nutrients in the soil profile, indicating that adjustments to the C:N ratio, nutrient release rate, and applied doses can optimize their application for different crops. Full article

Pyrochar has been identified as a favorable soil conditioner that can effectively ameliorate soil acidification. Hydrochar is considered a more affordable carbon material than pyrochar, but its effect on the process of soil acidification has yet to be investigated. An indoor incubation and a soil column experiment were conducted to study the effect of rice straw hydrochar application on nitrification and NO₃⁻-N leaching in acidic red soil. Compared to the control and pyrochar treatments, respectively, hydrochar addition mitigated the net nitrification rate by 3.75–48.75% and 57.92–78.19%, in the early stage of urea fertilization. This occurred mainly because a greater amount of dissolved organic carbon (DOC) was released from hydrochar than the other treatments, which stimulated microbial nitrogen immobilization. The abundances of ammonia-oxidizing archaea and ammonia-oxidizing bacteria were dramatically elevated by 25.62–153.19% and 12.38–22.39%, respectively, in the hydrochar treatments because of DOC-driven stimulation. The cumulative leaching loss of NO₃⁻-N in soils amended with hydrochar was markedly reduced by 43.78–59.91% and 61.70–72.82% compared with that in the control and pyrochar treatments, respectively, because hydrochar promoted the soil water holding capacity by 2.70–9.04% and reduced the residual NO₃⁻-N content. Hydrochar application can dramatically diminish total H⁺ production from soil nitrification and NO₃⁻-N leaching. Thus, it could be considered an economical soil amendment for ameliorating soil acidification. Full article

Volcanic ash from explosive eruptions can significantly alter lake water chemistry through ash–water interactions, potentially influencing primary productivity. Alkaline (soda) lakes, mostly found in volcanic regions, are particularly sensitive due to their unique geochemical properties. However, the effects of volcanic ash on the biogeochemistry and phytoplankton dynamics of soda lakes remain poorly understood. This study presents the first nutrient release experiments using natural alkaline water from Lake Van (Türkiye) and volcanic ash from four volcanoes (Hekla, Arenal, Sakurajima, Rabaul-Tavurvur) with different compositions. Sixteen abiotic leaching experiments were conducted over contact durations ranging from 1 to 24 h. Results show rapid increases in pH (~0.4–0.5 units), enhanced silica and phosphate concentrations, and elevated levels of Na, K, Ca, Sr, and S. Nitrate and Mg were generally depleted. The low N:P ratio (~0.06) in Lake Van water indicated nitrogen limitation, partially mitigated by ash-derived inputs. Cyanobacteria dominated the phytoplankton community (95%), consistent with nitrogen fixation under low-nitrate conditions. Elevated silica may promote diatom growth, while changes in Mg/Ca ratios suggest possible impacts on carbonate precipitation and microbialite development. These findings highlight the biogeochemical and ecological relevance of volcanic ash inputs to soda lakes. Full article

Variable-rate nitrogen (VR-N) application allows farmers to optimize nitrogen (N) input site-specifically within field boundaries, enhancing both economic efficiency and environmental sustainability. In this study, VR-N technology was applied to durum wheat in two small-scale commercial fields (3–4 ha each) located in distinct agro-climatic zones of Thessaly, central Greece. A real-time VR-N application algorithm was used to calculate N rates based on easily obtainable near-real-time data from unmanned aerial vehicle (UAV) imagery, tailored to the crop’s actual needs. VR-N implementation was carried out using conventional fertilizer spreaders equipped to read prescription maps. Results showed that VR-N reduced N input by up to 49.6% compared to the conventional uniform-rate N (UR-N) application, with no significant impact on wheat yield or grain quality. In one of the fields, the improved gain of VR-N when compared to UR-N was 7.2%, corresponding to an economic gain of EUR 163.8 ha⁻¹, while in the second field—where growing conditions were less favorable—no considerable VR-N economic gain was observed. Environmental benefits were also notable. The carbon footprint (CF) of the wheat crop was reduced by 6.4% to 22.0%, and residual soil nitrate (NO₃⁻) levels at harvest were 13.6% to 36.1% lower in VR-N zones compared to UR-N zones. These findings suggest a decreased risk of NO₃⁻ leaching and ground water contamination. Overall, the study supports the viability of VR-N as a practical and scalable approach to improve N use efficiency (NUE) and reduce the environmental impact of wheat cultivation which could be readily adopted by farmers. Full article

Precision agriculture increasingly relies on real-time data from soil sensors to optimize irrigation and nutrient application. Soil moisture and electrical conductivity (EC) are key indicators in irrigation and fertigation systems, directly affecting water-use efficiency and nutrient delivery to crops. This study evaluates the performance of an IoT-based soil-monitoring system for real-time tracking of EC and soil moisture under varied fertigation conditions in both laboratory and field scenarios. The EC sensor showed strong agreement with laboratory YSI measurements (R² = 0.999), confirming its accuracy. Column experiments were conducted in three soil types (sand, sandy loam, and loamy sand) to assess the EC and soil moisture response to fertigation. Sand showed rapid infiltration and low retention, with EC peaking at 420 µS/cm and moisture 0.33 cm³/cm³, indicating high leaching risk. Sandy loam retained the most moisture (0.35 cm³/cm³) and showed the highest EC (550 µS/cm), while loamy sand exhibited intermediate behavior. Fertilizer-specific responses showed higher EC in Calcium Ammonium Nitrate (CAN)-treated soils, while Monoammonium Phosphate (MAP) showed lower, more stable EC due to limited phosphorus mobility. Field validation confirmed that the IoT system effectively captured irrigation and fertigation events through synchronized EC and moisture peaks. These findings highlight the efficacy of IoT-based sensor networks for continuous, high-resolution soil monitoring and their potential to support precision fertigation strategies, enhancing nutrient-use efficiency while minimizing environmental losses. Full article

Pollution of soil and groundwater by chemical fertilizers is an alarming environmental problem. Both bamboo powder and charcoal are known to adsorb nitrates. This study aimed to recommend an effective method by applying a mixture of chemical fertilizers and bamboo charcoal to soil to prevent NO₃ leaching through adsorption. Magnesium treatment and hydrogelation were investigated to increase the amount of NO₃ adsorption and improve handling properties, and subsequently, their behavior in soil was examined. The maximum adsorption of nitrate in bamboo charcoal powder (BC) with a particle size of 15 µm or less was 4.44 mg/g. When the BC was treated with magnesium chloride (Mg-BC), the maximum adsorption capacity was 99.09 mg/g. The Langmuir adsorption model fits well for both BC and Mg-BC. When Mg-BC was hydrogelized (Gel-Mg-BC), the Freundlich equation provided a better fit, with the maximum adsorption estimated at 25–30 mg/g. When the soil was mixed with Mg-BC hydrogel and treated with a nitric acid solution, the nitrate concentration in the leachate decreased by approximately 15–60% (depending on the feed concentration) compared to that in the leachate from the soil alone. Full article

This study aimed to evaluate the agronomic performance and environmental impact of controlled-release coated fertilizers (CRCFs) in upland maize systems. Specifically, we sought to determine the optimal nitrogen (N) application rate that maximizes nitrogen use efficiency (NUE) and minimizes nutrient runoff, while maintaining yield comparable to conventional fertilization practices. A two-year field experiment (2017–2018) was conducted to assess CRCF formulations composed of urea, MAP, and potassium sulfate encapsulated in LDPE/EVA coatings with talc, humic acid, and starch additives. Treatments included various nitrogen application rates (33–90 kg N ha⁻¹) using CRCF and a conventional NPK fertilizer (150 kg N ha⁻¹). Measurements included fresh ear yield, aboveground biomass, NUE, and concentrations of total N (TN), nitrate N (NO₃⁻–N), and total P (TP) in surface runoff. Statistical analyses were performed using linear and quadratic regression models to determine yield responses and agronomic optimal N rate. CRCF treatments produced yields comparable to or exceeding those of conventional fertilization while using less than half the recommended N input. The modeled agronomic optimum N rate was 88.4 kg N ha⁻¹, which closely matched the maximum observed yield. CRCF application significantly reduced TN, NO₃⁻–N, and TP runoff in 2017 and improved NUE up to 71.2%. Subsurface placement and sigmoidal nutrient release contributed to reduced nutrient losses. CRCFs can maintain maize yield while reducing N input by approximately 40%, aligning with climate-smart agriculture principles. This strategy enhances NUE, reduces environmental risks, and offers economic benefits by enabling single basal application. Further multi-site studies are recommended to validate these findings under diverse agroecological conditions. Full article

Sustainable agriculture and food security are challenged by the indiscriminate use of synthetic nitrogen (N₂) fertilizers, inefficient water management, and land degradation. Hydroponic cultivation uses nutrient-rich aqueous media and is a climate-resilient and resource-efficient alternative to traditional farming methods, whose dependence on synthetic N₂ fertilizers reduces their long-term sustainability. Biological nitrogen fixation (BNF), which is mediated by diazotrophs that reduce atmospheric N₂ to plant-available ammonium, has emerged as a sustainable alternative to synthetic N₂ input in hydroponic systems. This review discusses the integration of BNF into hydroponic systems by exploring the functional diversity of diazotrophs, root–microbe interactions, and environmental constraints. It further highlights recent advances in strain improvement, microbial consortia development, nitrogenase protection, and genome editing tools, novel bioformulation strategies to enhance microbial compatibility with hydroponic nutrient regimes, and omics-based tools for the real-time assessment of N₂ fixation and microbial functionality. Key challenges, such as microbial leaching, nitrate-induced inhibition of nitrogenase activity, and the absence of standardized biostimulant protocols, are discussed. Case studies on staple crops have demonstrated enhanced NUE and yield productivity following diazotroph applications. This review concludes with future perspectives on synthetic biology, regulatory policies, and omics-based tools for the real-time assessment of N₂ fixation and microbial functionality. Full article

Efficient nitrogen management is key to maximizing production and minimizing the environmental impact of horticultural crops. This study analyses the effect of different doses of nitrogen on the development of broccoli (Brassica oleracea var. italica) (cultivar Parthenon), processing tomato (Solanum lycopersicum) (cultivar H1015), and processing pepper (Capsicum annuum) (cultivar Ramonete Lamuyo) in open fields in Extremadura and evaluates rapid and efficient methods for diagnosing their nutritional status. Trials were carried out at the La Orden Experimental Farm (CICYTEX) with different nitrogen fertilization rates. The N doses were 0–60–120–180 kg N/ha for peppers in 2020 and 2021 and 0–200–300 kg N/ha for 2022. For broccoli, the N doses were 0–100–200–300 kg N/ha in 2020 and 0–200–300 kg N/ha for 2022. For tomatoes, the N doses were 0–100–200–300 kg N/ha in 2021 and 0–200–350 kg N/ha for 2022. The following three indicators were compared: chlorophyll content measured with optical sensors, petiole sap nitrate concentration, and the nitrogen nutrition index (NNI). The results indicate that chlorophyll measurement is not suitable for broccoli due to the characteristics of its leaves, but is useful for tomatoes and peppers, providing a quick and non-destructive diagnosis. Nitrate concentration in sap, although more laborious and destructive, was found to be effective in discriminating nutritional status in the three species. However, the NNI did not prove to be a good reference method in open field conditions. These results highlight the importance of adapting nutrient monitoring strategies to the crop and management conditions, contributing to a more efficient use of nitrogen and a reduction in the environmental impact of nitrate leaching. Full article

The synthesis of oxide nanopowders through ultrasonic spray pyrolysis (USP) represents a sustainable method for producing high-purity, spherical particles tailored for advanced material applications. Recent developments in USP synthesis leverage the continuous transport of aerosols from an ultrasonic generator to a high-temperature furnace, with nanopowders collected efficiently using an electrostatic precipitator. This study explored the use of USP for titanium oxysulfate and aluminum nitrate solutions derived from the aluminum industry, focusing on resource recovery and waste reduction. Titanium oxysulfate was synthesized by leaching slag, generated during the reduction of red mud, with sulfuric acid under oxidizing, high-pressure conditions. After purification, the titanium oxysulfate solution was processed using USP in a hydrogen reduction atmosphere to yield spherical titanium dioxide (TiO₂) nanopowders. The hydrogen atmosphere enabled precise control over the nanoparticles’ morphology and crystallinity, enhancing their suitability for use in applications such as photocatalysis, pigments, and advanced coatings. In parallel, both synthetic and laboratory solutions of aluminum nitrate [Al(NO₃)₃] were prepared. The laboratory solution was prepared by leaching aluminum hydroxide oxide (AlOOH) with hydrochloric acid to form aluminum chloride (AlCl₃), followed by a conversion to aluminum nitrate through the addition of nitric acid. The resulting aluminum nitrate solution was subjected to USP, producing highly uniform, spherical alumina (Al₂O₃) nanopowders with a narrow size distribution. The resulting nanopowders, characterized by their controlled properties and potential applicability, represent an advancement in oxide powder synthesis and resource-efficient manufacturing techniques. Full article

Nitrogen fertilization plays a crucial role in optimizing plant growth, but excessive application can lead to nutrient leaching, environmental pollution, and soil degradation. This study investigates the impact of nitrogen application rates (0–400 kg·ha⁻¹) on the growth, biomass allocation, and carbon sequestration capacity of Pennisetum hydridum (Imperial Bamboo, PHY), a fast-growing tropical grass increasingly used for forage and bioenergy production in subtropical regions. Despite its agronomic potential, nutrient management strategies for P. hydridum remain poorly understood. We hypothesized that moderate nitrogen application (100–200 kg·ha⁻¹) would enhance growth and nutrient use efficiency, while maintaining environmental sustainability. Results show that moderate nitrogen levels (100–200 kg·ha⁻¹) significantly enhanced biomass production, with the highest aboveground biomass observed at 180 days under T2 (100 kg·ha⁻¹) and T3 (200 kg·ha⁻¹), reaching 166.5 g/plant and 140.6 g/plant, respectively. In contrast, excessive nitrogen application (400 kg·ha⁻¹) led to a decline in biomass (T4, 76.8 g/plant) and impaired carbon sequestration efficiency. In addition, it was found that nitrogen uptake increased with moderate fertilization, with T2 and T3 showing optimal nitrogen use efficiency. Soil analysis revealed that soil organic matter and total nitrogen content were positively correlated with root biomass, with significant linear relationships between soil nitrogen, carbon/nitrogen ratios, and PHY biomass. Specifically, the total nitrogen content in rhizomes and fibrous roots showed coefficients of determination (R²) of 0.65 and 0.67, indicating a strong correlation with soil nitrogen levels. Furthermore, nitrogen application increased soil nitrate (NO₃⁻-N) and ammonium (NH₄⁺-N) concentrations, with T4 showing the highest levels at 90 days (41.35 mg/kg for NO₃⁻-N and 15.6 mg/kg for NH₄⁺-N), signaling potential nutrient loss to the environment. These findings underscore the importance of sustainable nitrogen management for maximizing the growth potential of P. hydridum, while minimizing environmental risks in subtropical agricultural systems. Full article

Fertilizer application is a critical component of turfgrass management as it influences growth, color, stress tolerance, and overall quality. However, limited information exists on how fertilizer application, particularly nitrogen (N), affects hybrid bermudagrass performance and actual plant evapotranspiration (ET_a) in both well-watered and deficit irrigation scenarios. A 7-week greenhouse experiment was conducted over two replicated runs to evaluate responses of ‘TifTuf’ hybrid bermudagrass (Cynodon dactylon × C. traansvalensis Burtt Davy) to three nitrogen rates (0, 2.4, and 4.8 g N m⁻² month⁻¹) and three irrigation levels (1.0, 0.65, and 0.30 × ET_a). Fertilized turfgrass exhibited 11–12% greater ET_a compared to unfertilized turfgrass, with no significant differences between the two fertilizer rates. Under well-watered conditions (1.0 × ET_a), the high nitrogen rate significantly improved visual quality (7.8) relative to the unfertilized control (7.1) and the low-rate treatment (7.4). High-rate fertilizer application significantly enhanced visual quality at both deficit levels (7.2 and 6.6, at 0.65 and 0.30 × ET_a, respectively) compared to the unfertilized control (6.2 and 5.9, at 0.65 and 0.30 × ET_a, respectively). At 0.30 × ET_a, low-rate fertilizer application also significantly improved visual quality (7.0) compared to the unfertilized control. Soil nitrate-N levels increased with higher nitrogen application (1.30 ppm, 0.48 ppm, and 0.37 ppm, respectively, for high-rate, low-rate, and unfertilized), and shoot tissue analysis revealed greater N concentration in fertilized turfgrass (1.51%, 1.24%, and 0.85%, respectively, for high-rate, low-rate, and unfertilized). Clipping production and water use efficiency (WUE) were also improved with fertilization, although root development was hindered at the 0.30 × ET_a irrigation level. These findings demonstrate that nitrogen fertilization improves visual quality, shoot growth, WUE, and drought response; however, tradeoffs such as elevated water use and nitrate-N leaching risk necessitate careful management to balance turfgrass performance with water conservation and ecosystem service preservation. Full article

Nutrient leaching from agricultural fields can degrade soil fertility and groundwater quality, especially in coarse-textured soils. Use of biochar, lime, and hydrogel in these soils can enhance nutrient and water use efficiencies, thus reducing water pollution, and aiding in sustainable agricultural production. Amending soils with biochar, lime, hydrogel, or their combinations may reduce leaching, but the effects of single versus combined amendments remain unclear. A three-year pot experiment under field conditions was conducted on a loamy sand soil to enhance water and nutrient retention capacity of this soil. Soil samples were mixed with all possible combinations of 1% biochar (B), l% lime (L), and 0.5% hydrogel (H), i.e., BL, BH, HL, and BHL. The amendments were arranged in a randomized complete block design with four blocks. The results showed that compared to control, amendments B, H, BH, HL, and BHL significantly decreased (p ≤ 0.05) nitrate-N leaching per unit biomass by 58–88%, and L, H, BH, BHL significantly reduced (p ≤ 0.05) orthophosphate-P leaching per unit biomass by 34–98%. Compared to the control, the marketable yield significantly increased (p ≤ 0.05) by 24–38% under BH, HL, and BHL in 2019, and by 17–52% under amendments B, L, H, BL, BH, HL, and BHL in 2020. These results were not seen in the first year due to soil conditioning for biochar and lime. Amendments H, BH, HL, and BHL show potential to improve water use efficiency, reduce nutrient leaching, and support sustainable crop production. Full article

Understanding nitrogen (N) retention mechanisms in pristine humid temperate rainforest soils is critical for effective ecosystem management and nutrient conservation. The potential abiotic transformation of nitrite (NO₂⁻) into organic N forms in the absence of microbial activity in these ecosystems remains largely unexplored, despite its role in mitigating N leaching. This study focuses on the abiotic incorporation of nitrite (NO₂⁻) into dissolved organic nitrogen (DON) under anoxic conditions, a mechanistic step not directly evaluated in previous research, which employed ¹⁵N-labelled nitrate (NO₃⁻). To address this gap, we used ¹⁵N-labelled NO₂⁻ at 5 and 15 mg L⁻¹ in a lab incubation study under anoxic conditions to trace the contribution of abiotic nitrite transformation to organic N formation in organic matter-rich soils from temperate rainforests developed on both volcanic and non-volcanic parent materials. The added ¹⁵N declined rapidly after 15 min by 52% and 60% in both soil solutions, while it started to form labelled DON, increasing by 11% and 34%, after five days of incubation, with the highest accumulation at 15 mg L⁻¹ of ¹⁵N-NO₂⁻. These results show that up to 77% of the added ¹⁵N-NO₂⁻ can be abiotically incorporated into the DON of unpolluted old-growth temperate rainforest, whether developed on volcanic or non-volcanic soils. Nitrogen input has a stronger effect than soil parent material from which the soils originate. This reveals the natural resilience of unpolluted temperate rainforests to N loss, with implications for long-term ecosystem stability and nutrient cycling. Full article

This review assesses biochar’s potential to mitigate nitrogen (N) losses when co-applied with N fertilizers, emphasizing mechanisms linked to its measurable physicochemical properties. The mitigation of ammonia (NH₃) volatilization shows variable effects from its cation exchange capacity (−21.7% to 20.4%) and specific surface area (SSA; −23.8% to 39.1%). However, the biochar pH (influencing mitigation from −45.0% to −9.0%) and application rate are key factors, with clayey soils exhibiting the greatest mitigation (−52.2%), potentially due to their high bulk density. High SSA biochar, often from high pyrolysis temperatures, reduces nitrate-N (NO₃⁻-N) leaching (up to −26.6%) by improving the soil’s water-holding capacity. A co-application with organic fertilizers shows a pronounced mitigation (up to −39.0%) due to a slower N release coupled with biochar adsorption. A high SSA also plays an important role in mitigating nitrous oxide (N₂O) emissions (up to −25.9%). A higher biochar C/N ratio promotes microbial N immobilization, contributing to N₂O reductions (+1.5% to −34.2%). Mitigation is greater in sandy/loamy soils (−18.7% to −7.9%) than in clayey soils, where emissions might increase (+18.0%). Overall, biochar applications demonstrate significant potential to mitigate N losses and improve N use efficiency, thereby supporting sustainable agriculture; however, its effectiveness is optimized when biochar properties (e.g., high SSA and appropriate C/N ratio) and application strategies are tailored to specific soil types and N sources. Full article