Search Results (348)

Saline irrigation is increasingly practiced in semi-arid regions to cope with freshwater scarcity; however, it strongly affects crop growth, water use, and soil salinity. This study aims to calibrate and validate the AquaCrop model to simulate key growth parameters of winter wheat (cv. Achtar) under saline irrigation conditions in the Tadla Plain, Morocco, focusing on canopy cover (CC), actual evapotranspiration (ETa), soil water content (SWC), biomass (B), and grain yield (GY). The model was first calibrated using observed data from the 2023 growing season and subsequently validated using data from the 2022 growing season. Overall, AquaCrop effectively reproduced crop growth during both calibration and validation phases. During calibration, canopy cover was accurately simulated, with average RMSE values below 1%, while biomass and grain yield were also well reproduced, with low RMSE values (0.25 t ha⁻¹ for B and 0.10 t ha⁻¹ for GY), confirming the robustness of the calibrated parameters. The model also performed well in simulating ETa and SWC, capturing the seasonal dynamics of crop water use and soil moisture. During validation, ETa was satisfactorily reproduced, with an RMSE of approximately 0.80 mm day⁻¹, while SWC showed good agreement with observations, with NRMSE values ranging from 7.9 to 10.5%. Grain yield and biomass were reliably predicted, with NRMSE values below 4%. These results demonstrate that AquaCrop is a reliable tool for simulating winter wheat under saline irrigation and for assessing crop response under salt-affected conditions, providing an integrated evaluation of crop performance, water use, and soil salinity dynamics to support improved irrigation management and water-use efficiency under semi-arid conditions. Full article

Based on eddy covariance data collected during March to June 2021 in the Gurbantunggut Desert, this study analyzed desert methane (CH₄) flux dynamics. Results show the following: (1) The desert functions as a weak methane sink from March to June in the growing season, with its CH₄ flux showing a U-shaped diurnal variation pattern. The absorption peak occurred in June, reaching −79.1 mg·m⁻²·month⁻¹. (2) Diurnally, CH₄ flux correlated negatively with soil temperature (Tsoil), vapor pressure deficit, and photosynthetically active radiation (r_Tsoil = −0.58, r_VPD = −0.49, r_PAR = −0.49), positively with soil water content (SWC) and relative humidity (RH) (r_RH = 0.53, r_SWC = 0.28). (3) Fixed-effects regression isolated individual and interactive effects of SWC and Tsoil, yielding the model: CH₄ = −0.002 − 0.017SWC − 0.00004Tsoil − 0.002(SWC × Tsoil). The model highlights CH₄ flux sensitivity to hydrothermal factors and underscores the importance of their interaction for accurate flux estimation and understanding arid zone carbon cycle-climate feedbacks. Full article

Mediterranean agricultural systems are highly vulnerable to increased climatic variability, which threatens soil water availability and the functionality of the soil carbon (C) cycle. Soil management practices strongly influence water dynamics and C-substrate quality, thus potentially affecting the temperature sensitivity of soil respiration. We evaluated the combined effects of tillage (traditional tillage, TT; reduced tillage, RT), fertilization (mineral, MF; addition of biosolid compost, BC), and rainfall inputs (ambient conditions, C; reduction of 30% rainfall inputs, EX) on soil water content (SWC) and storage (SWS), and in situ soil respiration (Resp) dynamics over three agricultural seasons in a Mediterranean legume–wheat rotation, using a factorial field experiment. We also evaluated how the sensitivity of soil respiration to temperature could be affected by tillage and fertilization types in a complementary laboratory experiment under controlled moisture and temperature conditions. RT was effective in improving SWS and mitigating surface desiccation, although this advantage was attenuated in wet years due to homogenization of moisture along the soil profile. Soil Resp was primarily controlled by SWC. BC stimulated soil respiration mainly during the first crop season, with a residual non-significant trend in the third season. This effect appeared constrained under dry periods, although no significant fertilization × rainfall exclusion interaction was detected. The diurnal cycle of Resp showed a clear decoupling from diurnal soil temperature. Crucially, the intrinsic thermal sensitivity of respiration (Q₁₀) remained stable across all tillage and fertilization treatments, suggesting that field variability is driven by water dynamics and crop phenology and not by microbial responses to changes in substrate availability. Our results confirmed the hierarchical role of climate on C-cycling processes. Full article

Sweet basil (Ocimum basilicum L.) is a member of the Lamiaceae family, which includes a wide variety of medicinal and aromatic herbs cultivated for their essential oils and bioactive compounds. However, prolonged drought stress can significantly impair growth and essential oil content. In this study, a two-season pot experiment was conducted under open-field conditions. The study was carried out at the Floricultural Nursery, Faculty of Agriculture and Natural Resources, Aswan University, Egypt, during 2024 and 2025, with the aim of assessing how foliar applications of silicon (Si) and zinc (Zn) impact the morphological, physiological, and biochemical responses of sweet basil under different soil water capacity (SWC) levels (80%, 60%, and 40% SWC). Drought stress markedly reduced plant height, branch number, leaf area, biomass, photosynthetic pigments, macronutrient content, and essential oil content, while increasing levels of proline and secondary metabolites such as phenolics, flavonoids, and ascorbic acid. Growth and productivity were highest under 80% SWC, followed by 60%, and lowest under 40%. Under drought stress (40% SWC), Si₂₀₀ increased plant dry biomass by approximately 12%, chlorophyll content by 53%, and essential oil content by 46% compared with untreated plants. Silicon application proved more effective at ameliorating the negative consequences of drought than Zn, with Si₂₀₀ combined with 80% SWC yielding the best results in terms of plant performance and essential oil percentage and content. Meanwhile, Si₂₀₀ under 40% SWC induced the highest accumulation of secondary metabolites. These results highlight the potential of silicon foliar application as a practical strategy to reduce drought stress in sweet basil, enhancing both yield and phytochemical quality, and offering valuable guidance for sustainable cultivation under water-limited conditions. Full article

Biological soil crusts (BSCs) play key roles in arid, semi-arid regions and ecological marginal habitats. This study focused on four types of sand-fixing plantations established in 1990 in alpine sandy land (Salix psammophila, SL; Caragana korshinskii, NT; Salix cheilophila, WL; Populus simonii, XYY). Soil samples were collected from bare sand, algae crusts, and moss crusts. Soil particle size distribution, physicochemical properties, and enzyme activity were determined. Then bacterial communities were analyzed using high-throughput (Illumina) sequencing and the correlations among these three factors were examined. The results showed that: (1) From bare sand to algae and moss crusts, the content of fine particles (clay + silt) gradually increased. (2) Soil water content (SWC), nutrients and enzyme activities increased progressively. (3) In the study area, the dominant bacterial phyla of BSCs included Pseudomonadota, Cyanobacteria, Actinobacteriota and Vibrionota. Principal Coordinates Analysis (PCoA) and Analysis of Similarities (ANOSIM) results showed that BSCs drive the differentiation of bacterial communities during succession, while forest stands influence their spatial distribution. (4) Spearman’s correlation and redundancy analysis (RDA) showed that available phosphorus (AP), alkaline hydrolyzable nitrogen (AN), soil organic matter (SOM), catalase (CAT), pH, soil water content (SWC), and alkaline phosphatase (ALP) are key physicochemical factors shaping the bacterial community structure of BSCs. Mantel’s test confirmed that these variables mediated BSCs’ bacterial community structure. This study elucidates the mechanisms underlying ecological restoration via BSCs and provides a theoretical basis for future restoration efforts in alpine sandy land. Full article

The utilization of saline–alkali lands and the competition between medicinal plants and grain crops are urgent issues. This study aimed to evaluate the effects of combined biochar and phosphogypsum application on soil physicochemical properties, microbial communities, and safflower growth, yield, and bioactive component accumulation in moderately saline–alkali soil of western Jilin, and to identify key soil factors driving these responses. To achieve this, outdoor pot experiments were conducted using safflower (Carthamus tinctorius L.), with the application of 1% biochar + 1% phosphogypsum to moderately saline–alkali soil. The results showed that the amendment significantly reduced bulk density (BD), pH, sodium adsorption ratio (SAR), total alkalinity (TA), and exchangeable sodium percentage (ESP), while increasing soil water content (SWC), soil organic matter (SOM), nitrogen, phosphorus, potassium, and beneficial ions. Soil sucrase, urease, alkaline phosphatase, and catalase activities were enhanced. Copiotrophic taxa (Pseudomonadota, Sphingomonas, Vicinamibacter) increased, whereas oligotrophic taxa (Gemmatimonadetes, Longimicrobium, Luteitalea) decreased, with stronger effects on bacteria than fungi. Safflower growth indices improved; leaf Na⁺/K⁺ ratio, superoxide radicals, and malondialdehyde decreased; and soluble protein, proline, and antioxidant enzyme activities increased. Bioactive components (hydroxysafflor yellow A, kaempferol) and yield reached 1.41%, 0.056%, and 343.23 mg/plant, representing 1.74–27.68-fold increases over moderate and mild saline–alkali soils. Correlation analysis identified SOM, total nitrogen (TN), available phosphorus (AP), BD, SWC, pH, SAR, TA, and ESP as key factors. In conclusion, co-application of 1% biochar and 1% phosphogypsum improves soil physicochemical and microbial properties, alleviates saline–alkali stress, and enhances safflower quality and yield. Full article

Structural and functional soil degradation under conventional tillage has reached a critical point, requiring a shift towards conservation practices to mitigate the negative effects of climate change. This study evaluated the multi-year effects (2021–2024) of conventional tillage (CT), conservation deep tillage (CD), and conservation shallow tillage (CS) on soil physical properties (density, air capacity, and water content), water distribution, infiltration rate, and maize yield in a silty Gleysol. Soil water content (SWC), i.e., distribution, was monitored using PR2 profile probes at depths of 10, 20, 30, and 40 cm. CT treatment resulted in impaired soil physical properties, characterized by a significant increase in air capacity (+233.9%) and with a significant decrease in volumetric water content (qw, ≈40%). In contrast to CT (47.91 cm h⁻¹), the CS treatment resulted in more favorable hydraulic properties, i.e., and infiltration rate of 102.29 cm h⁻¹, by 2024. Statistical analysis (R², RMSE) confirmed that CS provides the most reliable and consistent environment for monitoring SWC. While maize yields were significantly higher in CT during the initial year (2021; 9.5 t ha⁻¹ vs. 8.4 t ha⁻¹ in CS), no significant differences were observed by 2024, and all tillage systems reached yields of ≈13.0 t ha⁻¹. The results suggest that after the four-year study period, CS tillage stabilized soil hydraulic properties and pore continuity, thereby resulting in maize yields equivalent to those of CT. Therefore, CS has proven to be a more resilient and effective strategy for sustainable water management in silty Gleysols. Full article

Soil organic carbon (SOC) responds rapidly to vegetation changes, and exploring SOC sequestration mechanisms under different vegetation types is critical for optimizing wetland carbon sink functions. This study investigated the abiotic and biotic mechanisms driving SOC stability across four typical vegetation types (reed marsh, woodland, farmland, and wasteland) in the 0–10 cm and 10–20 cm soil layers of Hengshui Lake wetland. Results showed that reed marshes exhibited the highest total organic carbon (TOC) and particulate organic carbon (POC), owing to anaerobic soil conditions and stable macroaggregate physical protection. Woodlands accumulated higher dissolved organic carbon (DOC) and microbial biomass carbon (MBC) via an efficient microbial carbon pump, despite weaker aggregate stability. In contrast, farmlands and wastelands presented intense labile organic carbon (LOC) turnover and enzymatic decomposition, accelerating SOC mineralization and carbon dissipation with poor carbon sequestration capacity. Proteobacteria and Acidobacteriota dominated bacterial communities, while Ascomycota prevailed in fungi. Soil water content (SWC) and bulk density (BD) were the core drivers of microbial community succession, and fungi were more sensitive to vegetation changes. Conclusively, distinct vegetation types shape divergent SOC sequestration pathways. This work provides a theoretical basis for wetland restoration and regional carbon sink enhancement. Full article

Particulate organic carbon (POC) and mineral-associated organic carbon (MAOC) are two operationally defined fractions frequently used in studies related to soil organic carbon (SOC) dynamics. However, the changes and governing mechanisms of these fractions, particularly along a restoration chronosequence, remain poorly understood. Here, we investigated changes in SOC fractions, soil properties, and microbial communities across a restoration chronosequence (1, 5, 7, 13, and 20 years) of alpine meadows using a space-for-time substitution approach on the Qinghai–Tibet Plateau. We quantified the contributions of biotic and abiotic drivers using Spearman correlation analysis, linear regression and random forest analysis. The results revealed a unimodal pattern in SOC, POC, and MAOC contents, peaking at 7, 5, and 7 years, respectively, with no further increase thereafter. Restoration duration strongly shaped microbial community structure and observed species richness, but had no significant effect on Shannon index and Pielou index. Random forest analysis identified soil water content (SWC) and total nitrogen (TN) as the primary predictors of SOC. The microbial community composition dominated the variation in POC while enzyme activity was the key driver of MAOC. Our findings highlight that soil carbon accumulation during alpine meadow restoration is a nonlinear process with a temporal threshold, and POC and MAOC are regulated by distinct biotic and abiotic mechanisms. This study provides a theoretical basis for understanding carbon sequestration mechanisms during alpine meadow restoration and developing sustainable grassland management strategies. Full article

The distinct co-occurrence of soil water content (SWC) and vapor pressure deficit (VPD) influences ecosystem water use efficiency (WUE) by modifying the synergistic relationship between gross primary productivity (GPP) and evapotranspiration (ET), yet how they impact each other remains unclear in agricultural ecosystems. Based on long-term eddy covariance flux data (2005–2014) observed at a rainfed maize site in Northeast China, we examined how SWC and VPD affect WUE by decomposing it into gross primary productivity to transpiration ratio (GPP/T) and transpiration to evapotranspiration ratio (T/ET). Results showed that WUE was more sensitive to VPD than SWC. Increasing VPD directly suppressed WUE under all soil moisture conditions, whereas SWC had a context-dependent effect: higher SWC reduced WUE under low VPD but enhanced WUE under high VPD. The underlying mechanism was that changes in GPP/T (plant physiological regulation) dominated the WUE responses to both SWC and VPD (contributing 70.25–83.30% and 67.89–87.96%, respectively), while T/ET (evapotranspiration partitioning) played a minor role (<18%). Therefore, to improve WUE under future drier climates, agronomic practices should focus on enhancing photosynthetic capacity and stomatal regulation (e.g., selecting drought-tolerant varieties, optimizing nitrogen supply) rather than solely reducing soil evaporation. Furthermore, supplemental irrigation applied specifically during periods of high VPD (when atmospheric demand is strong) can effectively enhance WUE, as soil moisture becomes critically beneficial under such conditions. These findings provide a mechanistic basis for improving water use efficiency in rainfed maize systems under climate change. Full article

In arid and semi-arid regions, improving water use irrigation efficiency under limited seasonal water supply is critical for sustainable cotton production. While the effects of seasonal irrigation amount have been widely studied, the independent and interactive roles of irrigation interval under a fixed seasonal irrigation constraint remain insufficiently quantified. This study aimed to evaluate how irrigation amount and interval jointly regulate soil water dynamics, evapotranspiration partitioning, yield formation, and water use efficiency (WUE) in cotton. A two-year, controlled soil-column experiment was conducted using a full-factorial design with two seasonal irrigation amounts (350 and 200 mm) and four irrigation intervals (every 3, 6, 9, or 12 days). The AquaCrop model was locally calibrated with 2024 data and validated with independent 2025 observations. The validated model was then used to conduct scenario simulations across 16 irrigation combinations to analyze process-level responses. The model reproduced canopy cover and soil water storage (SWS) dynamics with good accuracy (R² > 0.89; NRMSE < 16%). The results showed that irrigation amount primarily controlled overall water availability, whereas irrigation interval reshaped the temporal fluctuation pattern of soil water content (SWC) in the shallow root zone. Under moderate irrigation levels, an intermediate interval (every 6 days) improved WUE by stabilizing SWC and maintaining high transpiration proportions. Under severe deficit conditions, prolonged intervals intensified periodic water stress and reduced yield. Simulated transpiration accounted for 95–97% of seasonal evapotranspiration in the controlled system, reflecting limited soil evaporation under column conditions. These findings highlight that irrigation interval, beyond total irrigation amount, is an important management variable for optimizing cotton irrigation scheduling under water-limited conditions. The combined experimental and modeling framework provides practical guidance for irrigation design in arid regions. Full article

Land-use change contributes significantly to climate change mitigation through biophysical changes (albedo, α) and biogeochemical (greenhouse gases, GHG) emissions (here refers to methane, CH₄, and nitrous oxide, N₂O). While the impact of grassland–cropland conversion on global warming potential (GWP) is well-documented globally, research remains scarce in the saline-alkaline agropastoral transition zone (APTZ) of the western Songnen Plain, Northeast China, an ecotone uniquely characterized by soil-crusting and seasonal inundation. We conducted in situ bi-weekly measurements of N₂O and CH₄ fluxes (June–September) to acquire growing season ${\mathrm{GWP}}_{{\mathrm{N}}_2\mathrm{O}}$ and ${\mathrm{GWP}}_{{\mathrm{C}\mathrm{H}}_4}$, alongside α. The study compared an undisturbed fenced meadow (FMD) with three adjacent land-use types, clipped meadow (CMD), saline-alkaline meadow (SAL), and paddy rice field (PDY), converted from FMD from 2018 to 2022. Annual α-induced GWP (GWPΔα) was positive across all converted sites (CMD, SAL, and PDY), indicating a warming effect due to lower α compared to FMD. The PDY exhibited the highest CH₄ emission (5.04 kg CO₂ m⁻² yr⁻¹), exceeding other land uses by three orders of magnitude (p < 0.05). Conversely, N₂O emissions remained consistently minimal and stable across all sites. When integrating the net ecosystem exchange of CO₂ (NEE), the PDY functioned as a net warming source. In contrast, the warming effects of α and non-CO₂ GHGs were effectively offset by the NEE in other land uses. Machine learning identified soil water content (SWC) as the dominant predictor of α across all land uses in growing season. However, a mechanistic divergence was observed, i.e., α in low saline-alkali ecosystems (FMD, CMD and PDY) was shaped by coupled biotic and soil moisture controls, whereas in the degraded SAL ecosystem, α is almost exclusively abiotic-driven. These findings demonstrate that land-use conversion in the Songnen Plain governs complex land-surface feedbacks through distinct pathways. This study provides a quantitative framework for integrating biophysical and biogeochemical impacts to optimize land management for climate resilience in saline-alkaline agropastoral ecotones. Full article

Assessing crop water status during the reproductive development of winter wheat is challenging because soil–plant–atmosphere interactions are strongly influenced by soil physical conditions, and measured soil water content (SWC) does not necessarily reflect plant-accessible water. This study applied an integrated, process-based multisensor approach to evaluate functional crop water status and its relationship to grain yield, combining hyperspectral canopy reflectance, atmospheric observations, in situ SWC, and pedological characterization. Five winter wheat cultivars were monitored at two contrasting pedoclimatic sites in continental Croatia during the 2022/2023 growing season. Hyperspectral canopy reflectance (350–2500 nm) was measured at reproductive stages (BBCH 61–83), and seventeen vegetation indices describing canopy water status, structure, pigments, and senescence were derived. Principal component analysis (PCA) identified location as the dominant source of spectral variability, while cultivar effects were secondary. Although atmospheric conditions were broadly comparable, the sites differed markedly in soil physical properties, resulting in contrasting soil water–air regimes. Despite consistently higher volumetric SWC at one site, hyperspectral indicators revealed lower canopy water status, reduced canopy structure, earlier senescence, and lower grain yield across all cultivars. Water-sensitive indices exploiting near-infrared (700–1300 nm) and shortwave infrared (1300–2400 nm) bands (NDWI, NDMI, NMDI, MSI) consistently indicated greater physiological stress. Conversely, the site with lower SWC but more favorable soil physical conditions exhibited higher values of water- and structure-related indices and achieved higher grain yield, with a mean increase of 669 kg ha⁻¹. The results demonstrate that hyperspectral canopy reflectance captures yield-relevant water stress that cannot be inferred from soil moisture alone, highlighting the importance of multisensor integration for interpreting soil–plant–atmosphere interactions under heterogeneous soil conditions. Full article

Soil organic carbon (SOC) and total nitrogen (TN) are key indicators of soil fertility; however, the dynamics of carbon (C) and nitrogen (N) fractions during winter wheat growth under different tillage systems remain poorly understood. This study examined the effects of three tillage practices: no tillage (NT), subsoiling tillage (SS), and deep tillage (DT) on four soil organic carbon fractions (SOC, soil organic carbon; EOC, easily oxidized organic carbon; DOC, dissolved organic carbon; POC, particulate organic carbon) and four nitrogen fractions (TN, total nitrogen; NO₃⁻-N, nitrate nitrogen; NH₄⁺-N, ammonium nitrogen; DON, dissolved organic nitrogen) across five winter wheat growth stages (sowing, overwintering, jointing, filling and harvest) in the 0–50 cm soil profile. The results showed that SOC, its labile fractions, and TN all decreased with increasing soil depth, with tillage effects mainly confined to the 0–20 cm layer. SS achieved the highest SOC and TN contents in the topsoil, while NT and SS significantly enhanced the surface enrichment of C and N. In contrast, DT promoted more uniform nutrient distribution into the 30–50 cm subsoil. DON continuously accumulated throughout the growing season with faster accumulation rates under SS and NT; DOC peaked at the jointing stage, while EOC and NH₄⁺-N followed a consistent “decline–recovery–decline” seasonal pattern. SS yielded the highest total SOC stock (166.20 t ha⁻¹) in the 0–50 cm profile, particularly in the 0–30 cm layer. Correlation analysis showed that the coupling relationships among C and N indicators varied with soil depth, with the strongest positive correlation between SOC and EOC in the topsoil. Both SS and DT maintained higher soil water content (SWC) than NT in the 20–50 cm layers throughout the experimental period. In conclusion, SS emerges as the optimal balanced tillage strategy for dryland wheat fields on the Loess Plateau, simultaneously improving topsoil fertility, water retention, and C sequestration; meanwhile, DT is more effective for enhancing subsoil water and nutrient conditions. These findings provide a scientific basis for targeted tillage management to sustain soil fertility and productivity in rainfed dryland farming systems. Full article

Background: The adaptability of leguminous plant–rhizobia symbionts enables enhanced plant stress tolerance in environmentally stressed areas. However, how rock desertification (RD) severity affects the endophytic and nitrogen-fixing bacterial communities in Pisum sativum root nodules remains unclear. Methods: We systematically surveyed the microbial communities of P. sativum nodules across a gradient of four RD areas. We sequenced 16S rRNA and nifH amplicons, determined soil physicochemical properties, and performed bioinformatic analyses to relate nodule microbiome diversity to soil variables. Results: The dominant endophytic genera across all sites were Allorhizobium–Neorhizobium–Pararhizobium–Rhizobium and Pseudomonas, with Rhizobium identified as the primary nitrogen-fixing taxon. Soil pH and total phosphorus (TP) showed significant correlations with the overall endophytic bacterial community, whereas total nitrogen (TN), TP, and soil water content (SWC) were associated with nitrogen-fixing taxa. Notably, P. sativum nodules from areas of slight rocky desertification (SRD) harbored higher endophytic bacterial diversity and enhanced carbohydrate metabolism compared to those from moderately rocky desertified (MRD) sites. Conclusions: This study sheds light on how bacterial communities within legume root nodules respond to RD stress, deepening our understanding of plant–microbe co-adaptation and informing microbial-assisted restoration strategies in karst desertification areas. Full article