Search Results (541)

Soil microbial carbon use efficiency (CUE) and nitrogen use efficiency (NUE) are fundamental parameters governing organic matter turnover in terrestrial ecosystems, yet how forest type-driven variation in litter quality propagates through the litter–soil–microbe continuum to regulate these efficiencies remains poorly resolved. Across three forest types in the Funiu Mountains, central China—a Larix gmelinii (LG) plantation, a Quercus aliena var. acuteserrata (QA) secondary forest, and a mixed Quercus aliena var. acutiserrata and Pinus armandii (QP) forest—we quantified litter chemistry, soil physicochemical properties, microbial biomass, extracellular enzyme activities, and microbial nutrient use efficiencies (MUE: NUE, and phosphorus use efficiency, PUE) derived from a modified saturation kinetics model. Principal coordinate analysis revealed significant multivariate differentiation among forest types across litter, soil, microbial biomass, and enzyme modules (Adonis R² = 0.198–0.427; all p < 0.05). Compared with LG and QA, QP exhibited a pronounced stoichiometric imbalance: it supported the highest litter organic carbon and total nitrogen, the lowest lignin-to-cellulose ratio, the largest soil C and N pools (SOC and STN), and the greatest microbial biomass carbon (MBC). However, despite this resource-rich environment, microbial biomass C:N:P ratios exhibited constrained variation, while soil C:P (SCP) and N:P ratios (SNP) in QP reached extreme values (112.3 and 7.25, respectively), generating severe stoichiometric imbalance. Vector analysis indicated that all forests were under relative nitrogen limitation (vector angle < 45°), with QP showing the strongest limitation (41.6 ± 0.4°). Critically, QP exhibited the highest NUE (0.47 ± 0.03) but the lowest CUE (0.95 ± 0.01), and CUE and NUE were nearly perfectly negatively correlated across all sites (R = −0.98, p < 0.001). Random forest analysis identified extracellular enzyme stoichiometry as the dominant proximate predictor of MUE. Partial least squares structural equation modeling (GOF = 0.673–0.674; R² = 0.592–0.603) revealed that litter and soil properties had no significant direct effects on CUE or NUE; instead, soil nutrients exerted strong indirect association through a cascade—soil → microbial biomass → enzyme activity—with opposite total effects on CUE (−0.731, p < 0.001) versus NUE (+0.755, p < 0.001). These findings reveal that the same soil nutrient enrichment that accompanies mixed-species afforestation drives divergent microbial metabolic responses—suppressing CUE while promoting NUE—through a shared cascading structure, with implications for predicting soil carbon and nutrient retention under shifting forest compositions. Full article

Nitrogen use efficiency (NUE) is commonly calculated as the ratio of milk nitrogen output to nitrogen intake in dairy cows. However, because milk nitrogen output is intrinsically determined by milk production and nitrogen intake is largely driven by dry matter intake, conventional NUE is mathematically dependent on production level and feed intake. This dependency makes it difficult to distinguish apparent efficiency caused by higher milk yield from intrinsic biological efficiency in nitrogen utilization. Therefore, this study aimed to evaluate NUE in dairy cows using a combined mathematical and metabolic framework based on residual NUE (rNUE) analysis. A total of 126 early-lactation Chinese Holstein cows were screened, and 16 high-NUE and 16 low-NUE cows were selected after matching for parity, days in milk, and dry matter intake. High-NUE cows had greater milk yield, milk nitrogen output, and NUE than low-NUE cows, despite similar nitrogen intake. They also exhibited higher ruminal microbial crude protein and ammonia nitrogen concentrations, a lower acetate-to-propionate ratio, and reduced circulating essential and total amino acid concentrations. Multiple regression analysis showed that energy-corrected milk and dry matter intake explained 71.4% of the variation in NUE. The residuals from this model were defined as rNUE, which was independent of milk production. After removing production-related effects, rNUE remained positively associated with ruminal microbial crude protein and ammonia nitrogen concentrations, and negatively associated with the acetate-to-propionate ratio and circulating amino acid pools. These findings indicate that conventional NUE in dairy cows is largely driven by production level, whereas residual-based modeling can identify a production-independent component associated with rumen nitrogen metabolism and amino acid utilization. The residual NUE approach provides a useful mathematical and metabolic framework for evaluating intrinsic NUE in dairy cows beyond milk production level. Full article

Eutric Regosols are globally important but low-fertility soils with poor nutrient retention, limiting crop productivity and increasing environmental risks. This study evaluated whether combining a moderate reduction in synthetic nitrogen (N) fertilizer with organic manure application could rapidly improve soil fertility, sustain maize yield, enhance nitrogen use efficiency (NUE), and increase yield resilience in these soils. A four-year field experiment was conducted on a purple soil (Eutric Regosol) with five treatments: no N (CK), conventional synthetic N (CN), a 20% synthetic N reduction (OP), and the OP treatment combined with 3000 (OPM1) or 6000 (OPM2) kg ha⁻¹ of organic fertilizer. Maize yield, yield components, NUE indices, soil properties, and net economic benefits (NEB) were measured. OP alone reduced yield by 7.57% compared to CN. OPM2 progressively increased yield, surpassing CN by 12.36% after four years, and indicated greater yield resilience during a high-rainfall year. OPM2 also significantly improved topsoil organic matter (+12.9%), total N (+46.3%), and NUE indices over time. Although initial NEB was lower for organic-amended treatments, OPM2 achieved higher economic returns than CN in the latter two years. Integrating a 20% synthetic N reduction with 6000 kg ha⁻¹ of organic manure is an effective strategy for rapid fertility improvement in Eutric Regosols. This approach compensates for yield reductions from less synthetic N, progressively enhances yield and NUE, improves soil health, increases economic returns, and strengthens buffering capacity against high-rainfall events. Full article

Reducing nitrogen (N) fertilization is essential for sustainable agriculture, but it frequently suppresses photosynthetic capacity and diminishes grain yield in sorghum. To determine whether exogenous brassinolide (BL) can offset these negative effects, a two-year field experiment was conducted using foliar BL application (0.1 mg L⁻¹) under three N levels (0, 75, and 150 kg N ha⁻¹), with assessments of grain yield, photosynthetic parameters, dry matter accumulation, and nitrogen use efficiency (NUE). Results showed that BL significantly increased grain yield under zero N (by 15.47%) and moderately under 50% N reduction (by 4.32%), primarily by increasing grains per panicle. Under N-reduced conditions, BL enhanced net photosynthetic rate (Pn), chlorophyll content, Rubisco/PEPC activities, and dry matter partitioning to panicles, with these traits positively correlated with yield. Under 50% N reduction, BL improved N recovery efficiency (RE) and agronomic efficiency (AE) while leaf N content correlated positively with SPAD, Pn, and yield. No significant BL effects occurred under normal N. Thus, exogenous BL application partially compensates for N reduction-induced yield loss by enhancing photosynthesis, source–sink partitioning, and NUE, providing a promising, environmentally sustainable strategy for sorghum production under reduced N input. Full article

Enhancing nitrogen (N) use efficiency (NUE) is crucial for reconciling food security with fertilizer reduction and environmental protection in Sichuan province. This study used statistical data of rice, wheat, maize, and rapeseed in Sichuan Province from 2008 to 2022 to evaluate crop NUE within a regional N balance framework and compare spatiotemporal differences across the five major economic zones. Results showed that provincial NUE presented a distinct three-stage pattern: a gradual increase from 2008 to 2014, a significant surge in 2015, and a period of high-level but fluctuating NUE after 2016, the drivers of which require further investigation. By 2022, rice and rapeseed demonstrated the highest NUE values (42.89% and 42.90%, respectively), followed by maize (35.46%) and wheat (28.77%). Notable spatial heterogeneity was detected, with a general tendency of higher NUE in the southeastern and basin areas and lower NUE in the northwestern mountainous areas. Northeastern Sichuan, Southern Sichuan and the Chengdu Plain consistently exhibited better performance, while Northwest Sichuan remained the region with the weakest performance. These findings suggest that improving NUE in Sichuan province necessitates region- and crop-specific strategies, with priority being given to stabilizing the high NUE of rice and rapeseed, while targeting infrastructure improvement and precision fertilizer management in wheat-dominated and low-efficiency areas. Full article

Optimizing the interaction between planting density and nitrogen (N) application rate is critical for simultaneously improving grain yield and nitrogen use efficiency (NUE) in winter wheat (Triticum aestivum L.). However, the underlying regulatory mechanism remains poorly understood in the fluvo-aquic soil region of the southern Huang–Huai–Hai Plain. This study aimed to elucidate the physiological mechanism by which planting density and nitrogen application interactively regulate source–sink coordination to achieve synergistic high grain yield and high NUE, and to screen the optimal local cultivation combination for winter wheat in southeastern Henan. A two-year consecutive field experiment was conducted from 2018 to 2020 in Shangshui, Henan, using a split-plot design. Three planting densities (D1: 225 × 10⁴ plants ha⁻¹; D2: 375 × 10⁴ plants ha⁻¹; D3: 525 × 10⁴ plants ha⁻¹) and five N rates (N0: 0; N1: 180; N2: 240; N3: 300; N4: 360 kg N ha⁻¹) were established. Results demonstrated that planting density, N rate, and their interaction significantly regulated grain yield, NUE, and dry matter and N allocation, with consistent trends across both years. Increasing density enhanced total biomass and N accumulation, but dry matter and N partitioning to grains declined when density exceeded 375 × 10⁴ plants ha⁻¹. Grain yield exhibited a quadratic response to N rate; the optimal N rate for maximum yield decreased from 296.33 kg ha⁻¹ at low density (D1) to 237.50–245.38 kg ha⁻¹ at medium and high densities. The combination of 240 kg N ha⁻¹ and 375 × 10⁴ plants ha⁻¹ (D2N2) produced the highest average grain yield (8875.35 kg ha⁻¹), with simultaneous improvements in spike number and kernels per spike as well as superior dry matter and N partitioning to grains. This combination also maintained high nitrogen recovery efficiency (NRE) and nitrogen agronomic efficiency (NAE). Correlation analysis revealed that grain yield and NUE were significantly positively correlated with dry matter accumulation, N accumulation, and their partitioning proportions to grains. Overall, D2N2 achieved simultaneous high yield and high NUE by coordinately optimizing dry matter and N partitioning to grains. We therefore recommend reducing N fertilizer to approximately 240 kg ha⁻¹ combined with a moderate planting density of 375 × 10⁴ plants ha⁻¹ as the preferred strategy for sustainable and intensive winter wheat production in the fluvo-aquic soil region of southeastern Henan and adjacent areas. Full article

Rational regulation of nitrogen input represents a crucial approach for simultaneously boosting cereal productivity and enhancing the efficiency of agricultural input use. Nevertheless, the intrinsic mechanisms of how nitrogen application regimes in the North China Plain (NCP) regulate grain yield and nitrogen use efficiency (NUE) of winter wheat (Triticum aestivum L.) by modulating tiller physiological traits remain elusive. A two-year field experiment from 2023 to 2025 was carried out with four nitrogen application levels: conventional rate of 210 kg N ha⁻¹ (N2), 10% nitrogen increase (N1), 10% nitrogen reduction (N3), and 20% nitrogen reduction (N4). Physiological traits of the wheat population were systematically investigated, and the correlations among grain yield, NUE and physiological indices were analyzed. The results indicated that moderate nitrogen reduction (N3) effectively inhibited ineffective tillers and maintained sufficiently stable stems at maturity. Meanwhile, N3 enhanced flag leaf photosynthesis, sucrose synthase and sucrose phosphate synthase activities, delayed flag leaf senescence during mid-late grain filling, and facilitated grain photoassimilate accumulation. On average across two years, N3 increased yield by 6.53% and 9.49% compared with N1 and N4, showing no remarkable difference from N2, while achieving the highest NUE. Further analysis demonstrated that tiller establishment and photoassimilate accumulation dominate wheat yield formation. In conclusion, optimized nitrogen management of N3 realizes synergistic improvement of yield and NUE, reduces agricultural resource input, and promotes sustainable green development of winter wheat production in the NCP. Full article

The ecological restoration of degraded sandy land in the Yarlung Zangbo River Valley is constrained by the metabolic functions of soil microorganisms. This study investigates the dynamic mechanisms of microbial elemental use efficiency in walnut plantations, with a focus on seasonal variations in soil chemical stoichiometry, extracellular enzyme activity, and microbial nutrient efficiency in rhizosphere and bulk soils. This paper explores the effects of conventional organic fertilizer (CF) and organic–inorganic compound fertilizer (OIF) on microbial nutrient use strategies and their seasonal dynamics. The results showed significant seasonal fluctuations in soil active nutrients and microbial biomass, while the total nutrient content remained stable. OIF enhanced microbial chemical stoichiometric homeostasis but simultaneously triggered a “carbon–phosphorus metabolic trade-off”, leading to a restraint of microbial carbon use efficiency (CUE) during the growing season. Microbial elemental use efficiency (EUE) exhibited clear seasonal differentiation: CUE was higher in summer, promoting biomass accumulation, whereas NUE and PUE increased in winter and spring, reflecting a nutrient conservation strategy. The EUE pathways were decoupled between rhizosphere and non-rhizosphere microenvironments. The rhizosphere was more directly driven by soil chemical stoichiometry and microbial biomass, while the non-rhizosphere was influenced by nutrient limitation states, represented by vector characteristics. This study provides insights into the seasonal adaptability and microenvironmental heterogeneity of microbial metabolism during the restoration of cold sandy land. It is suggested that future ecological management should focus on N-P balanced fertilization and consider the differential responses between rhizosphere and non-rhizosphere zones to enhance ecosystem productivity and soil carbon, nitrogen, and phosphorus sequestration potential. Full article

The increasing demand for resilient and multifunctional crops in the Mediterranean region has renewed interest in Urtica dioica L. as a potential alternative crop. This study evaluated the combined effects of fertilization and row spacing on the growth, yield, and nitrogen use efficiency of nettle in Athens, Greece. A split-plot experimental design was employed in a three-year experiment, with three fertilization treatments (C = control, U = urea, and I = urea with urease inhibitor) and two different row spacings (D1 = 30 cm × 20 cm, and D2 = 50 cm × 20 cm). Agronomic traits, seed yield, nitrogen content, vegetation indices (NDVI), chlorophyll content (SPAD), and nitrogen efficiency indices were assessed. Fertilization significantly enhanced plant performance, with the application of I consistently producing the highest values for plant height (increased by 10–30%), biomass (increased by 10–20%), and seed yield (increased up to 30%) compared to C. Row spacing influenced crop performance, with D2 favoring plant height (up to 9% compared to D1), while D1 generally increased biomass production per unit area (up to 20% compared to D2). Nitrogen-related indices (NUE, NAE, and NUtE) were markedly improved under fertilized treatments, particularly when I was applied (up to 20%, 100%, and 19% compared to U). NDVI and SPAD values were also influenced by fertilization and row spacing at early growth stages. The findings demonstrate that both factors play critical roles in optimizing nettle cultivation under Mediterranean conditions, highlighting the importance of integrated agronomic management practices. Full article

Soil organic matter (SOM) is a recognized determinant of nitrogen-use efficiency (NUE), but its quantitative control over the fate of fertilizer N remains unclear. Using a ¹⁵N tracer study within a winter wheat–summer maize region, we quantified the recovery of initially applied N from wheat and subsequent crops in relation to SOM and N application rates. We found that while N fertilization boosted yields by 85–340% in low-fertility soil, its effectiveness exhibited diminishing returns in high-fertility soils. Crucially, the total recovery efficiency of fertilizer N (cumulative ¹⁵NUE) across three cropping seasons was fundamentally governed by SOM content, following a linear–plateau relationship. The model revealed that the maximum ¹⁵NUE (54.3%) at an optimal application rate (105 kg N ha⁻¹) was achieved when SOM exceeded a critical threshold of 21.3 g kg⁻¹ (equivalent to 57.51 t ha⁻¹ in the 0–20 cm soil layer). Below this threshold, ¹⁵NUE increased linearly with SOM (R² = 0.956). Furthermore, residual ¹⁵N in soil was primarily stabilized in organic forms (58–64%), while recovery by subsequent crops was minimal (≤4.3%). This confirms that high SOM content minimizes the amount of unaccounted ¹⁵N by enhancing N fixation within the soil organic pool. Our findings establish a quantifiable SOM threshold for maximizing NUE, thereby providing a scientific basis for reducing fertilizer waste and enhancing the sustainability of intensive agriculture in the region. Full article

Nitrogen (N) is an essential macronutrient for plant growth. NIN–like protein (NLP) transcription factors play important roles in nitrate signaling and response in plants. However, a comprehensive analysis of the NLP gene family in sorghum is still lacking. In this study, we identified five NLP genes in sorghum, and a high collinearity of NLP was detected in sorghum, rice and maize. N deficiency decreased SbNLP3 and SbNLP4 expression levels in roots, and the expression of SbNLP1 and SbNLP2 declined in roots during nitrate resupply. Subcellular localization analysis revealed that SbNLP1 was mostly detected in nuclei and cytoplasm. Compared with wild–type rice ZH11 plants, SbNLP1 overexpression plants showed improved low nitrogen (LN) tolerance, with longer roots and shoots under LN conditions. Transcriptome analysis between overexpression lines OE1–5 and ZH11 showed that 773 and 967 differentially expressed genes (DEGs) were identified in roots and shoots under LN conditions, respectively. In contrast, 674 and 1283 DEGs were identified in roots and shoots under normal nitrogen (NN) conditions, respectively. Thirty–seven N–related DEGs were identified in roots through GO enrichment under LN conditions, and terms of plant hormone signal transduction, biosynthesis of secondary metabolites and plant–pathogen interaction were identified through KEGG enrichment. WGCNA analysis also revealed plant hormone signal transduction pathways and plant pathogen interaction pathways in OE1–5 under LN conditions. These results provide a basis for N use efficiency (NUE) improvement in sorghum and functional analysis of SbNLPs. Full article

China produces 61.0% of the world’s watermelons, yet a life cycle assessment (LCA) of its production system is lacking. Here, we combined farmer surveys and field experiments to assess resource depletion and environmental impacts across North China (NC), Northwest China (NW), and Southwest China (SW), and to quantify the mitigation potential through optimized nitrogen (N) management. NC achieved the highest yield but also the highest resource use and emissions per hectare. In contrast, SW performed best per ton of fruit produced due to lower input intensity. Nitrogen fertilizer dominated greenhouse gas emissions and eutrophication potential, with over 85% of its impact arising during the field application stage. Grouping farms by yield and N partial factor productivity revealed a mitigation potential of 46.5–55.4%, enabling both high yield and high efficiency. Field experiments confirmed that reducing N input by 14.3–40.0%, as recommended regionally, stabilizes yield while significantly lowering environmental burdens. Our findings validate that region-specific N optimization is a key strategy for achieving sustainable watermelon production in China. Full article

This study investigated how different organic fertilization practices affect productivity, stability, and nitrogen use efficiency in the rotation systems of the Hetao Irrigation District. The research was based on a long-term field experiment (2015–2025), with a chemical fertilizer-only treatment as the control (CK). Four organic fertilization treatments were evaluated: farmyard manure application (CM), straw incorporation (CS), green manure cultivation and incorporation (CG), and a combined green manure plus straw treatment (CGS). Based on three consecutive years of observations (2023–2025), the impacts of these treatments on crop yield, yield composition and stability, plant nitrogen accumulation and allocation, and nitrogen use efficiency were systematically analyzed. Both CM and CS significantly increased maize equivalent yield (MEY) compared with the other treatments, by 33.68–66.04% and 16.05–24.21%, respectively. CM’s productivity advantage was primarily driven by higher biomass accumulation, whereas CS’s advantage was largely due to improvements in the harvest index. In terms of stability, CM exhibited the lowest coefficient of variation (CV), indicating the highest static stability, while CS showed a regression coefficient (b_i) close to 1, indicating stronger dynamic stability. CM also significantly enhanced total plant nitrogen accumulation, nitrogen recovery efficiency (NRE), and nitrogen use efficiency (NUE), while optimizing nitrogen allocation to grain. CS significantly improved nitrogen internal efficiency (NIE), promoting more efficient conversion of absorbed nitrogen into grain yield. CG and CGS did not show clear advantages across productivity, stability, or most nitrogen use efficiency-related indices. Overall, in the Hetao Irrigation District, farmyard manure application is an effective strategy for achieving both high and stable yields, whereas straw incorporation offers stronger environmental adaptability. Both practices represent practical and effective approaches for improving the sustainability of rotation systems. Full article

Nitrogen use efficiency (NUE) is a major determinant of maize (Zea mays L.) productivity and sustainability, yet the regulatory changes associated with modern breeding remain incompletely understood. Here, we used breeding-era transcriptomic data from 137 elite Chinese maize inbred lines to identify transcriptional regulators associated with maize NUE. Breeding-era expression shifts in NUE effector genes were modest but tissue-specific, pointing to pathway-level transcriptional rewiring during modern breeding. Focusing on the first leaf above the uppermost ear at silking, we identified 69 breeding-era-responsive genes, including 10 transcription factors, and prioritized ZmSPL19 through Pearson correlation analysis with curated NUE-related genes. ZmSPL19 expression declined during modern breeding and showed a nitrate-repressed expression, with lower transcript abundance under nitrogen-sufficient conditions and rapid downregulation upon nitrate resupply. Loss of ZmSPL19 function promoted primary root elongation, biomass accumulation, leaf nitrogen content, soil–plant analysis development (SPAD), photosynthetic rate, kernel number, and grain yield under nitrogen-sufficient conditions. These results identify ZmSPL19 as a breeding-associated negative regulator of growth and yield formation under nitrogen-sufficient conditions and support the value of a breeding-informed strategy for discovering regulators with potential relevance to maize NUE improvement. Full article

Nitrate (NO₃⁻) serves as a critical nitrogen source and signaling molecule essential for its growth and quality formation. Although substantial genetic variation in nitrogen use efficiency (NUE) has been documented among tea cultivars, a systematic characterization of nitrate (NO₃⁻) absorption kinetics and the associated genome-wide transcriptional regulatory networks across varying nitrate concentrations remains lacking. This study employed ¹⁵N isotope labeling and transcriptome sequencing to systematically analyze the absorption characteristics and molecular response mechanisms of the cultivars ‘Longjing 43’ and ‘Zhongming 6 hao’ under varying NO₃⁻ concentrations. Results revealed significant differentiation in absorption strategies: ‘Zhongming 6 hao’ exhibited a significantly higher absorption rate at low concentrations, whereas ‘Longjing 43’ demonstrated enhanced performance at high concentrations. Transcriptome analysis indicated that both cultivars shared coordinated regulation of ‘photosynthesis’ and ‘nitrogen metabolism’ pathways. Furthermore, 14 nitrogen metabolism genes and 64 differentially expressed transcription factors (including MYB, NAC, and LBD families) were identified. Specifically, the CsNiR gene (encoding nitrite reductase) was functionally validated; silencing of CsNiR significantly reduced nitrite reductase activity, confirming its positive regulatory role. This study provided a theoretical framework and key candidate genes for breeding nitrogen-use-efficient varieties, which is essential for sustainable tea production. Full article