Search Results (981)

In the last 32 years (1993–2024), the application of electric fields in soil management (soil electrokinetic, SEK) has undergone several stages of optimization and intensification. SEK has used both alternating current (AC) and direct current (DC). Numerous fields, including agriculture, sedimentation, phosphorus management in soil and sludge, fertilizer production, consolidation, reclaiming salt-affected soils, metal extraction, dewatering, remediation of contaminated soil (both organic, such as PFAS, and inorganic, such as heavy metals), and soil nutrient availability, have utilized the SEK concept. Numerous innovations were included in the SEK equipment’s design or combined with other biological, chemical, and physical processes. While we recently published a review article on soil electrokinetic/electroosmosis–vacuum systems for sustainable soil improvement and contaminant separation, the current study illustrates the role of applying the pressure-assisted soil electrokinetics technique and shows the effect of the opposite technique. Four points were used to show the function of pressure-assisted soil electrokinetics based on our analysis of six search engines from 1993 to 2024 (the previous 32 years), including (1) polluted soil remediation, (2) dewatering, (3) soil improvement, and (4) making soil ready for electrokinetic action by applying pressure. In contrast to other intensification methods (such as reverse polarity, pulsed electric field, and design change), we found very few publications addressing pressure-assisted soil electrokinetics throughout the literature search. Most investigations focused on the dewatering mechanism, despite the paucity of relevant papers. In contrast to conventional electrokinetic remediation, pump-assisted electrokinetic-flushing remediation increased the removal efficiencies of Cs⁺ and Co²⁺ from contaminated soil by 2% and 6%, respectively. Additionally, the results demonstrated that the pressured electro-osmotic dewatering approach outperformed the conventional electrokinetic techniques. At 40 kPa, hydraulic conductivity was reduced four-fold by electro-rehabilitation for alternative fuels, while at 100 kPa, it was reduced three-fold. It was also observed that pressure may be used to achieve the soil ready for electrokinetic action in order to guarantee proper operation. Since there are not many articles on the subject, future research may examine how pressure-assisted soil electrokinetics can be integrated with vacuum systems, reverse polarity mode, pulsed electric field mode, modifying the SEK design, overcoming the formation of cracks, etc. Full article

An imbalance between the supply and demand of nutrients within the crop–soil system has resulted from the prevalent practice of excessive fertilization in agricultural agriculture. In order to increase crop growth, improve resource usage efficiency, and reduce agricultural nonpoint source pollution, appropriate cropping management techniques are essential. This study examined the effects of four nitrogen application rates (0 kg·ha⁻¹ (C0), 80 kg·ha⁻¹ (C1), 160 kg·ha⁻¹ (C2), and 240 kg·ha⁻¹ (C3)) and three alfalfa cropping systems (traditional flat planting, FP; ridge-covered biodegradable mulch, JM; and ridge-covered conventional mulch, PM) on soil inorganic nitrogen transport, nitrogen allocation within alfalfa plants, and soil N₂O emissions. Throughout the alfalfa growth phase, the dynamics of nitrogen balance within the soil–plant–atmosphere system were quantitatively examined. The findings showed: (1) The concentrations of soil NO₃⁻–N and NH₄⁺–N rose with the rate of nitrogen application but decreased with soil depth. The PMC3 treatment had the largest inorganic nitrogen reserves at the end of the alfalfa growth period. (2) The pattern of PM > JM > FP for nitrogen uptake and nitrogen accumulation in biomass in alfalfa leaves and stems peaked at the C2 nitrogen treatment rate. (3) As nitrogen application rates increased, grass-land N₂O emission flow and total emissions also followed PM > JM > FP. (4) The PMC2 treatment showed apparent nitrogen balances of 9.73 kg·ha⁻¹ and 1.84 kg·ha⁻¹ during the two-year growing season, with apparent nitrogen loss rates of 6.08% and 1.15%, respectively, both significantly lower than other treatments, according to nitrogen balance analysis. In summary, the nitrogen application pattern combining ridge-covering conventional plastic mulch with moderate nitrogen application levels can achieve nitrogen balance in alfalfa grassland systems within the Yellow River irrigation district of Gansu Province, China, and similar ecological zones. Full article

Biochar produced from phosphorus (P)-rich feedstocks has often been promoted as an alternative P fertilizer. However, existing evidence has mainly been obtained from incubation experiments and field trials with a rather short duration, leaving uncertainty about whether repeated low-rate applications of biochar can meaningfully supply P and increase soil P pools over time. This study evaluates the agronomic effects of 10 years of application of biochar derived from plant biowaste (BIO) and bones (BC) at an application rate of 4 t ha⁻¹ yr⁻¹, compared with a mineral P fertilizer (MIN), compost application (COM), and a zero-P control. The application of P through BC and COM led to higher total soil P concentrations than the control. Changes in labile P pools (H₂O–P, NaHCO₃–P, Bray-P) were generally modest, but BC again tended to yield higher values relative to the other treatments. The ratio of organic to inorganic P was not influenced by fertilizer type. A clear effect of the amendments on maize yield was observed, with BC producing the highest yields among all amendments (6.4 t ha⁻¹; average 2020–2023), and yields were occasionally further increased when BC was combined with COM. The BIO treatments also achieved yields that were at least comparable to those of the MIN treatment (4.7 t ha⁻¹). Despite the limited effects on labile soil P pools, the amendments increased yields and can be considered effective substitutes for mineral P fertilizers at this application rate. Full article

Excessive fertilizer use poses environmental risks in the long term. Thus, plant growth-promoting rhizobacteria (PGPR) have been proposed as a complementary approach to reduce fertilizer use and prevent nutrient stress. Moreover, PGPR’s efficacy in sandy soil for sweet potato production in Northeast Thailand has not yet been reported. This study tested the hypothesis that PGPR inoculation could reduce fertilizer dependency while maintaining yield in nutrient-poor sandy soils. In this research, a field study was conducted from 2023 to 2024 in Chonnabot District, Khon Kaen, Thailand, to evaluate the effects of Azospirillum brasilense, Azotobacter vinelandii, Beijerinckia mobilis, and inorganic fertilizer on the Okinawan Orange and Carrot native sweet potato varieties. Treatments followed a factorial randomized complete block design with two factors, PGPR inoculation and fertilizer level (0%, 25%, 50%, 75%, and 100%), and were replicated three times. The results showed that PGPR dipping had no statistically detectable effect on sweet potato growth and yield (p > 0.05). However, a notable finding was that PGPR significantly increased the protein and fiber content of tubers (p < 0.01) while reducing carbohydrate content, which may have implications for the taste and the nutritional quality of sweet potatoes. In addition, the application of inorganic fertilizer had a significant effect on yield. The Carrot native variety achieved the highest yield (13,481.00 kg ha⁻¹) with 75% fertilizer, while the Okinawan Orange variety attained the highest yield (8866.00 kg ha⁻¹) with 100% fertilizer. These data could be used to assist farmers in determining their fertilizer usage. Full article

Long-term fertilization profoundly influences soil biochemical processes and microbial functionality, yet the coupling mechanisms between soil enzyme activities and functional genes in nutrient cycling remain unclear. This study investigated the effects of different fertilization regimes—nitrogen alone (N), nitrogen–phosphorus–potassium fertilizer (NPK), organic fertilizer (M), and combined organic–inorganic fertilizer (MNPK)—on soil properties, enzyme activities, N- and P-cycling-related functional gene abundances, and faba bean (Vicia faba L.) yield in a 45-year ongoing field experiment in subtropical eastern China. Results showed that long-term fertilization significantly affected soil pH, electrical conductivity, nutrient contents, and crop yield. Organic fertilizer addition (M and MNPK) markedly improved soil organic matter, total and available nutrients, and enhanced faba bean grain yield by 75.07–92.79% compared with NPK, whereas NPK had limited benefits on total and available soil nutrients compared with N-only application. Soil enzyme activity analysis revealed that the MNPK treatment achieved the highest urease and neutral protease activities, while acid and alkaline protease activities responded inconsistently. Phosphorus-related enzymes (acid, neutral, and alkaline phosphatases) were strongly stimulated by organic inputs, reflecting enhanced P mineralization potential. Functional gene analysis showed that N-fixation and assimilatory nitrate reduction genes increased under M and MNPK, while N assimilation, N mineralization, anammox, nitrification, denitrification, and dissimilatory nitrate reduction genes were enriched under N treatment. Phosphate uptake and transport genes were upregulated under NPK, M, and MNPK, whereas inorganic P solubilization genes were highest under N. Significant positive correlations were observed among soil enzyme activities, nutrient contents, and faba bean yield, whereas acid and alkaline protease activities showed opposite trends. The relative abundances of N- and P-cycling functional genes exhibited distinct yet coordinated relationships with soil fertility indicators and enzyme activities. These findings provide mechanistic insights into the long-term regulation of soil–microbe interactions and nutrient cycling, offering a scientific basis for sustainable fertilization strategies in agroecosystems. Full article

Flax (Linum usitatissimum L.) is a multipurpose crop known for its highly nutritious seeds. This study aimed to determine how plant density and fertilizer type influence the nutritional composition of flaxseed, addressing a gap in the literature where combined effects on seed quality have not been thoroughly evaluated. Two plant densities (D1, 500 plants m⁻²; D2, 300 plants m⁻²) and four fertilizers (control, C; inhibited urea, I; organic, O; and urea, U), were compared. According to the results, the interactions of these factors influenced most of the traits. The highest yields were reported at D1I. Organic fertilization improved protein (7%) and fat (28%) content and reduced fiber (46%) and carbohydrates. In contrast, inorganic fertilization increased fiber, NDF (10%) and ADF (8%) content. Mineral composition was also affected, with O and I increasing K, Mg, Fe and Cu by 31%, 6%, 14% and 24% for O and 48%, 1%, 17% and 18%, respectively, for I. The correlation matrix analysis revealed a positive relationship between protein and fat content, whereas both traits were negatively correlated with fiber and carbohydrates. Overall, optimized density and fertilizer can improve the quality of flaxseed, supporting its use as functional food and feed ingredient. Full article

Europe ranks second in global broccoli production and first in exports, with Spain leading the sector. In Spain, cultivation is concentrated in the southeast, especially the Region of Murcia, one of the main producing areas. The study has three objectives: (1) to establish the characteristic cultivation model of the region, (2) to perform an analysis of the cost structure, and (3) to carry out a sensitivity analysis considering variability in irrigation water prices and the use of organic fertilizers to assess their cost impact. The base information was obtained from surveys conducted with representative farmers of the production sector during the year 2025. The cost structure analysis highlights the dominance of labor-related tasks. Preparation and planting, along with harvesting, are especially significant, accounting for over 34% and 18% of total costs, respectively. Despite this, broccoli generates only 0.22 AWU·ha⁻¹, lower than other horticultural crops. Irrigation is another key cost factor, due to the high price of water. Sensitivity analysis shows that sharp increases in water costs significantly raise overall expenses. Likewise, the high cost of liquid organic fertilizers results in the crop being unfeasible, in contrast to the results obtained with solid organic and synthetic inorganic fertilizers, or the combination of solid and liquid organic fertilizers. Full article

To address soil degradation from long-term monoculture, rotary tillage, and excessive chemical fertilization in semi-arid regions of China, we conducted a three-year field experiment. We assessed the synergy of integrated management practices combined with both continuous and rotational tillage methods (including ploughing, rotary, moldboard ploughing) at varying tillage depths (10–15, 15–25, 25–35 cm) with different fertilization regimes (chemical vs. organic–inorganic). Among all treatments, the rotational tillage practice that integrates moldboard ploughing at 25–35 cm depth with organic–inorganic fertilization [1200 kg ha⁻¹ mature compost + 375 kg ha⁻¹ compound fertilizer (N:P₂O₅:K₂O = 15:15:15)] significantly reduces bulk density by 11.8% and increases total porosity by 17.9% in the 15–25 cm soil layer. This practice optimizes nutrient stratification, elevating available nitrogen and potassium in the shallow layer (10–15 cm) to 126.13 and 372.45 mg kg⁻¹, respectively, while boosting available phosphorus in the subsoil (25–35 cm) by 247.8%. Furthermore, it significantly enhances soil microbial activity, increasing populations of bacteria, actinomycetes, and fungi by 3.42 × 10⁵, 0.65 × 10⁵, and 2.40 × 10³ CFU g⁻¹, respectively, alongside a 49.4% rise in soil respiration. These synergistic improvements collectively promote stable maize yields (increasing by 1731.4 kg ha⁻¹) and high economic returns (net income increasing by 3301.6 CNY ha⁻¹). These findings support the promotion of integrated tillage–fertilization strategies to enhance maize productivity and soil ecological function in semi-arid regions. Full article

The excessive use of synthetic fertilizers in agriculture has raised environmental concerns, prompting the search for sustainable alternatives, such as organic amendments. This study evaluated the agronomic performance, nutrient use efficiency and metabolomic profiles of lettuce (Lactuca sativa L. var. baby leaf) cultivated using synthetic and organic (olive mill waste-based compost pellets and sewage sludge) in a controlled pot experiment. The treatments included three doses of inorganic fertilizer and two organic fertilizers applied at equivalent nitrogen (N) rates, alongside an unfertilized control. Soil physicochemical properties, plant biomass, nutrient uptake and metabolite profiles, including amino acids, sugars and organic acids, were analyzed. Inorganic fertilization rapidly increased soil mineral N and phosphorus (P), enhancing leaf chlorophyll, canopy development and fresh biomass, and promoting the accumulation of reducing sugars (p < 0.05). However, it reduced amino acid and phenolic levels, indicating a metabolic shift towards growth at the expense of stress and antioxidant compounds. Sewage sludge increased soil organic matter and amino acid and sucrose accumulation, but also induced stress-related metabolites. Pelletized compost maintained an intermediate level of nutrient availability, preserved phenolic compounds and improved phosphorus use efficiency. This surpassed the results achieved with sewage sludge in terms of dry matter yield, despite limited short-term growth stimulation. These findings highlight the potential of integrating moderate mineral fertilization with pelletized compost to balance immediate productivity, nutrient efficiency and long-term soil and metabolic quality in lettuce cultivation. Full article

The effects of selenium on poultry health and reproduction have been extensively studied using inorganic sodium selenite (SS). However, limited research has been done on organic selenium nanoparticles (Se-NPs). This study aimed to compare Se-NPs and SS on productivity, egg quality, reproductive performance, and male sexual behavior in Japanese quails. A total of 480 quails (8 weeks old) were assigned to 5 different experimental groups (96 birds in each group) with six replicates (pens) sex ratio 1 male: 3 females. One group was designated as control (fed by basal diet), whereas two groups were fed with different levels of Se-NPs (0.2 mg/kg and 0.4 mg/kg), and two groups with SS (0.2 mg/kg and 0.4 mg/kg). The trial lasted for 9 weeks. The highest productive performance was observed in quails supplemented with 0.4 mg/kg Se-NPs (p < 0.05). Quails supplemented with 0.2 mg/kg Se-NPs had the highest egg weight (p < 0.05). The highest shape and albumen index were identified in the group supplemented with 0.2 mg/kg Se-NPs (p < 0.05). However, the highest shell ratio, yolk ratio, yolk index, and Haugh unit were determined in the group supplemented with 0.4 mg/kg Se-NPs (p < 0.05). The group supplemented with 0.4 mg Se-NPs/kg had the highest fertility and hatchability, with the lowest embryo mortality. The group with 0.4 mg Se-NPs/kg exhibited the highest level of sexual behavior (wing flapping, waltzing, mounting, tidbitting, rear approach, treading). It was concluded that the supplementation of Se-NPs enhanced productive and reproductive performance, egg quality, and male sexual behavior compared to the supplementation of SS. Full article

Nutrient cycling has barely been studied in acidic environments and may have an important influence on the evolution of the microbial communities. In this research, we studied nutrient sources and fluxes in acidic metal-mine pit lakes to evaluate their relationship with the lakes’ microbial ecology. Nutrient concentrations (including phosphorus, nitrogen, and dissolved inorganic carbon) increase with depth in all the studied pit lakes. Phosphorus comes mainly from the leaching of the host rock and is rapidly scavenged from the aqueous phase in the oxygenic and Fe(III)-rich mixolimnion due to adsorption on ferric precipitates (schwertmannite, jarosite), which leads to an important P-limitation in the photic zone. Below the chemocline, however, the sum of phosphorus inputs (e.g., settling of algal biomass, desorption from the ferric compounds, microbial reduction of Fe(III)-sediments) sharply increases the concentration of this element in the anoxic monimolimnion. Nitrogen is very scarce in the host rocks, and only a limited input occurs via atmospheric deposition followed by N-uptake by algae, N-fixation by acidophilic microorganisms, sedimentation, and organic matter degradation in the sediments. The latter process releases ammonium to the anoxic monimolimnion and allows some nitrogen cycling in the chemocline. Soluble SiO₂ in the mixolimnion is abundant and does not represent a limiting nutrient for diatom growth. Differences in phytoplankton biomass and extent of bacterial sulfate reduction between relatively unproductive lakes (San Telmo) and the more fertile lakes (Cueva de la Mora) are likely caused by a P-limitation in the former due to the abundance of ferric iron colloids in the water column. Our results suggest that phosphorus amendment in the photic zone could be an efficient method to indirectly increase acidity-consuming and metal-sequestering bacterial metabolisms in these lakes. Full article

The scarcity and uneven distribution of precipitation present significant challenges for agriculture in arid regions. Fertilization can improve crop yields and water productivity (WP) under these conditions. However, the effects of different long-term fertilization practices on maize yield and WP under varying precipitation patterns require further research. A 30-year fertilization experiment was conducted to investigate the effects of different fertilization treatments on maize yield, WP, soil organic carbon (SOC), and the correlations among these factors. The treatments included no fertilization, application of chemical fertilizers alone, combined application of chemical fertilizers and cattle manure, and application of a high amount of cattle manure alone. Chemical fertilizers, cattle manure, and the combined application of chemical fertilizers and cattle manure significantly increased maize yield by 61.81–86.14%, 121.0%, and 114.5–125.5%, and increased WP by 59.4–84.9%, 119.4%, and 111.9–126.5%, respectively, compared to the unfertilized control. The combined application of chemical fertilizers and cattle manure resulted in optimal maize yield and WP, while also substantially reducing the coefficient of variation in maize yield (by 19.9–25.9% compared to the control) under interannual precipitation fluctuations. Compared with the no fertilization treatment, the average increase in maize yield peaks in very wet years, while WP reaches its highest level in relatively dry years. Maize yield was significantly positively related to SOC, WP, and water consumption during growth (p < 0.01). SOC was also significantly positively correlated with WP (p < 0.01). For every unit increase in SOC, the WP increased by 0.3955 kg ha⁻¹ mm⁻¹. In summary, the integrated application of organic and inorganic fertilizers is a proven strategy to enhance crop productivity and resilience, while concurrently improving WP and SOC. This synergistic approach represents a cornerstone for climate-resilient and sustainable dryland agriculture. Full article

The inconsistent efficacy of biochar in mitigating agricultural greenhouse gas emissions remains a major barrier to its widespread adoption and the realization of its environmental benefits. This study aimed to develop a stable and efficient mitigation strategy by optimizing biochar physicochemical properties through urea-N activation (corn stover: urea mass ratios of 5:1 and 15:1). Five treatments were established: CK (control), GC (fertilization), GB (fertilization + raw biochar), GAB5 (fertilization + low-N activated biochar), and GAB15 (fertilization + high-N activated biochar). Mechanisms were elucidated by monitoring soil profile (0–20 cm) gas concentrations and surface fluxes, combined with a comprehensive analysis of soil physicochemical properties, enzyme activities, and microbial biomass. Results demonstrated that activated biochar, particularly GAB15, significantly reduced cumulative CO₂ (9.4%, p < 0.05) and N₂O (45.2%, p < 0.05) emissions and their concentrations in the 0–10 cm layer. This superior efficacy was linked to profound improvements in key soil properties: GAB15 significantly enhanced soil cation exchange capacity (CEC, increased by 17.3%, p < 0.05), NH₄⁺-N content (increased by 88.2%, p < 0.05), Mean Weight Diameter (MWD, increased by 13.0%), the content of water-stable aggregates > 0.25 mm (R_>0.25mm, increased by 57.3%) (p < 0.05), dissolved organic carbon (DOC), and the MBC (microbial biomass carbon)/MBN (soil microbial biomass nitrogen) ratio. Redundancy analysis (RDA) and structural equation modeling (SEM) revealed core mechanisms: CO₂ mitigation primarily stemmed from the physical protection of organic carbon within macroaggregates and a negative priming effect induced by an elevated MBC/MBN ratio; N₂O mitigation was attributed to weakened nitrogen mineralization due to enhanced aggregate stability and reduced substrate (inorganic N) availability for nitrification/denitrification via strong adsorption at the biochar–soil interface. This study confirms that urea-activated biochar produced at a 15:1 corn stover-to-urea mass ratio (GAB15) effectively overcomes the inconsistent efficacy of conventional biochar by targeted physicochemical optimization, offering a promising and technically feasible approach for mitigating agricultural greenhouse gas emissions. Full article

Hygienization by hydrothermal carbonization (HTC) of chicken manure (CM) at 250 °C allows its valorization as soil amendment or even organic fertilizer. To test if this hypothesis is also valid for feedstocks from free-range breeding, respective material of a small farm in southern Spain was comprehensively chemically characterized. The hydrochar of the manure collected from the ground of the farm was rich in mineral matter. After HTC, 68% of the organic carbon (C) was recovered, whereas 82% of the nitrogen (N) was lost most likely by volatilization and with the discarded process water. Despite this, 2.8% of the total N in the hydrochar was identified as inorganic N (N_i). Solid-state ¹³C and ¹⁵N NMR spectroscopy revealed aromatization of organic C and N, although alkyl C and amide N still contributed with 23% and 35% to the total organic C and N, respectively. The obtained distribution of N-forms indicated that enough N_i is plant-available for early plant growth, while the remaining N occurs in structures that can be slowly mobilized during advanced plant development. Low heavy metal concentrations suggest low phytotoxicity. Pot experiments with lettuce, sunflower, and tomato plants confirmed species- and dosage-dependent effects. A dosage of 3.25 t ha⁻¹ improved lettuce and sunflower yields, whereas a dosage of 6.5 t ha⁻¹ provided no additional growth benefits but caused phytotoxic reactions of the tomato plants. Our results support HTC as a strategy to valorize CM from free-range farms, although, due to the high variability of such materials, we recommend a thorough chemical characterization and phytotoxic tests before its application. Full article

The mechanism of microbial-mediated mineralization of organic phosphorus (P) under nitrogen (N) addition in farmland soil is still unclear. To determine the effects of N addition on the composition, structure, and P transformation function of microbial community and soil P fractions in croplands, we conducted a field experiment on the Central Gansu Loess Plateau in 2017. The current study analyzed a subset of 12 plots from the 48-plot factorial experiment, comprising four levels of N addition in the absence of P fertilization. The treatment included control (0 kg N ha⁻¹ year⁻¹, N0), low N (75 kg N ha⁻¹ year⁻¹, N75), medium N (115 kg N ha⁻¹ year⁻¹, N115), and high N (190 kg N ha⁻¹ year⁻¹, N190). We determined soil P fractions and microbial properties in the 0–20 cm depth from 2019 to 2023. We found that N fertilization significantly enhanced the mineralization of soil organic P, primarily by altering microbial community structure and increasing the abundance of key taxa (e.g., RB41 and Filobasidium), which in turn boosted the activities of alkaline phosphatase (ALP) and phytase (PHY). The most pronounced stimulations in microbial biomass carbon (MBC) and ALP activity were observed under the N115 treatment. Concurrently, N addition led to substantial reductions in labile inorganic and organic P pools; for instance, the content of Ca₂-P decreased most markedly under N190, by 42.82% in 2023, while labile organic P forms (LOP, MLOP, MROP) also declined significantly. Structural Equation Modeling (SEM) confirmed that N addition influenced P availability through direct pathways and indirect pathways mediated by shifts in microbial community structure, ALP, and PHY. In conclusion, our study has identified the N115 treatment (115 kg N ha⁻¹ year⁻¹) as the optimal level for promoting microbial-mediated organic P mineralization. To maintain soil productivity in the rain-fed agricultural systems of the Loess Plateau, we recommend applying a moderate amount of N fertilizer at this optimal rate, along with strategic P supplementation. This approach can effectively mitigate soil P deficiency and enhance the availability of P. Full article