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Efficient nutrient management remains a critical challenge in wheat production, particularly in optimizing productivity while maintaining soil fertility. Among essential nutrients, nitrogen (N) and boron (B) play vital roles in plant growth and grain development, yet their combined effects are not fully understood. To address this gap, a field experiment was conducted from November 2019 to April 2020 in Khairahani, Chitwan, Nepal, to evaluate the effects of different N and B application levels on wheat performance and nutrient retention. The experiment followed a split-plot design, with four N levels (0, 80, 100, and 120 kg ha ⁻ ¹) as main plots and three B levels (0, 1, and 2 kg ha ⁻ ¹) as subplots, replicated three times. Results showed that 120 kg ha ⁻ ¹ of N significantly increased effective tillers (401 m ⁻ ²), 1000-grain weight (52.7 g), spike length (10.05 cm), and spike weight (2.3 g). B applied at 2 kg ha ⁻ ¹ reduced spikelet sterility (34.7%) and increased kernels spike -1 (29.6). The combined application of N and B produced the highest grain yield (6.26 t ha ⁻ ¹) and benefit-cost ratio (2.34). Grain N content (14.48 g kg ⁻ ¹), N uptake (88.5 kg ha ⁻ ¹), and protein content (9.05%) were maximized with 120 kg N ha ⁻ ¹. Likewise, 2 kg B ha ⁻ ¹ significantly improved B content and uptake in both grain and straw. The nutrient treatments had no significant effect on most soil chemical properties, except for residual soil N and B content. These findings indicate that integrating B with N fertilization can substantially enhance wheat productivity and profitability. However, multi-year studies across diverse agro-climatic conditions are necessary to validate these results and develop robust, site-specific nutrient management recommendations.

Background Nitrogen application can effectively mitigate the damage to crop growth and yield caused by drought. However, the efficiency of heavy nitrogen application before drought (NBD) and heavy nitrogen application after drought (NAD) to regulate rice response to drought stress remains controversial. In this study, we profiled physiology, proteomics and metabolomics in rice variety Wufengyou 286 of two nitrogen management modes (NBD and NAD) to investigate their yield formation and the mechanism of nitrogen regulation for drought resistance. Results Results revealed that the yield of NBD and NAD decreased significantly when it was subjected to drought stress at the stage of young panicle differentiation, while the yield of NBD was 33.85 and 36.33% higher than that of NAD in 2017 and 2018, reaching significant levels. Under drought conditions, NBD increased chlorophyll content and net photosynthetic rate in leaves, significantly improved the activities of antioxidant enzymes such as superoxide dismutase (SOD), peroxidase and catalase, and decreased malondialdehyde (MDA) content compared with NAD. NBD promoted nitrogen assimilation in leaves, which was characterized by increased activities of nitrate reductase (NR) and glutamine synthetase (GS). In addition, NBD significantly increased the contents of osmotic regulatory substances such as soluble sugar, soluble protein and free proline. Gene ontology and KEGG enrichment analysis of 234 differentially expressed proteins and 518 differential metabolites showed that different nitrogen management induced strong changes in photosynthesis pathway, energy metabolism pathway, nitrogen metabolism and oxidation-reduction pathways. Conclusion Different nitrogen management methods have significant differences in drought resistance of rice. These results suggest that heavy nitrogen application before drought may be an important pathway to improve the yield and stress resistance of rice, and provide a new ecological perspective on nitrogen regulation in rice.

Intercropping green manure (GM) may be a good solution to the problems of acid soil in tropical plantations. Soil organic nitrogen (No) may change due to the application of GM. A three-year field experiment was conducted to determine the effect of different utilization patterns of Stylosanthes guianensis GM on soil No fractions in a coconut plantation. Three treatments were set: no GM intercropping (CK), intercropping and mulching utilization pattern (MUP), and intercropping and green manuring utilization pattern (GMUP). The content dynamics of soil total N (TN) and soil No fractions including of non-hydrolysable N (NHNo) and hydrolyzable N (HN) in the cultivated soil layer was examined. The results showed that after three years of intercropping, the TN content of the MUP and GMUP treatment was 29.4% and 58.1% respectively higher ( P < 0.05) than those of the initial soil, and the No fractions content of GMUP and MUP treatment was 15.1%-60.0% and 32.7%-111.0% higher ( P < 0.05) than those of the initial soil. The further results indicated that after three years of intercropping, compared with CK, GMUP and MUP could increase the content of TN by 32.6% and 61.7% respectively, and No fractions content was also increased by 15.2%-67.3% and 32.3%-120.3%% respectively ( P < 0.05). The No fractions content of GMUP treatment was 10.3%-36.0% higher than those of MUP treatment ( P < 0.05). These results indicated that intercropping Stylosanthes guianensis GM could significantly increase the soil N including of the TN an No fractions content, and the GMUP was more effective than MUP, therefore, GMUP is a better GM utilization pattern to improve the soil fertility and should be popularized in the tropical fruit plantation.

Background Raising nitrogen use efficiency of crops by improving root system architecture is highly essential not only to reduce costs of agricultural production but also to mitigate climate change. The physiological mechanisms of how biochar affects nitrogen assimilation by crop seedlings have not been well elucidated. Results Here, we report changes in root system architecture, activities of the key enzymes involved in nitrogen assimilation, and cytokinin (CTK) at the seedling stage of cotton with reduced urea usage and biochar application at different soil layers (0–10 cm and 10–20 cm). Active root absorption area, fresh weight, and nitrogen agronomic efficiency increased significantly when urea usage was reduced by 25% and biochar was applied in the surface soil layer. Glutamine oxoglutarate amino transferase (GOGAT) activity was closely related to the application depth of urea/biochar, and it increased when urea/biochar was applied in the 0–10 cm layer. Glutamic-pyruvic transaminase activity (GPT) increased significantly as well. Nitrate reductase (NR) activity was stimulated by CTK in the very fine roots but inhibited in the fine roots. In addition, AMT1;1, gdh3 , and gdh2 were significantly up-regulated in the very fine roots when urea usage was reduced by 25% and biochar was applied. Conclusion Nitrogen assimilation efficiency was significantly affected when urea usage was reduced by 25% and biochar was applied in the surface soil layer at the seedling stage of cotton. The co-expression of gdh3 and gdh2 in the fine roots increased nitrogen agronomic efficiency . The synergistic expression of the ammonium transporter gene and gdh3 suggests that biochar may be beneficial to amino acid metabolism.

Rates of atmospheric deposition of biologically active nitrogen (N) are two to seven times the pre-industrial rates in many developed nations because of combustion of fossil fuels and agricultural fertilization. They are expected to increase similarly over the next 50 years in industrializing nations of Asia and South America. Although the environmental impacts of high rates of nitrogen addition have been well studied, this is not so for the lower, chronic rates that characterize much of the globe. Here we present results of the first multi-decadal experiment to examine the impacts of chronic, experimental nitrogen addition as low as 10 kg N ha-1 yr-1 above ambient atmospheric nitrogen deposition (6 kg N ha-1 yr-1 at our site). This total input rate is comparable to terrestrial nitrogen deposition in many industrialized nations. We found that this chronic low-level nitrogen addition rate reduced plant species numbers by 17% relative to controls receiving ambient N deposition. Moreover, species numbers were reduced more per unit of added nitrogen at lower addition rates, suggesting that chronic but low-level nitrogen deposition may have a greater impact on diversity than previously thought. A second experiment showed that a decade after cessation of nitrogen addition, relative plant species number, although not species abundances, had recovered, demonstrating that some effects of nitrogen addition are reversible.

Key messageGWAS identified 347 QTLs associated with eight traits related to nitrogen use efficiency in a 389-count wheat panel. Four novel candidate transcription factor genes were verified using qRT-PCR.Nitrogen is an essential nutrient for plants that determines crop yield. Improving nitrogen use efficiency (NUE) should considerably increase wheat yield and reduce the use of nitrogen fertilisers. However, knowledge on the genetic basis of NUE during wheat maturity is limited. In this study, a diversity panel incorporating 389 wheat accessions was phenotyped for eight NUE-related agronomic traits across five different environments. A total of 347 quantitative trait loci (QTLs) for low nitrogen tolerance indices (ratio of agronomic characters under low and high nitrogen conditions) were identified through a genome-wide association study utilising 397,384 single nucleotide polymorphisms (SNPs) within the MLM (Q + K) model, including 11 stable QTLs. Furthermore, 69 candidate genes were predicted for low nitrogen tolerance indices of best linear unbiased predictions values of the eight studied agronomic traits, and four novel candidate transcription factors (TraesCS5A02G237500 for qFsnR5A.2, TraesCS5B02G384500 and TraesCS5B02G384600 for qSLR5B.1, and TraesCS3B02G068800 for qTKWR3B.1) showed differing expression patterns in contrasting low-nitrogen-tolerant wheat genotypes. Moreover, the number of favourable marker alleles calculated using NUE that were significantly related to SNP in accessions decreased over the decades, indicating a decline in the NUE of the 389 wheat varieties. These findings denote promising NUE markers that could be useful in breeding high-NUE wheat varieties, and the candidate genes could further detail the NUE-related regulation network in wheat.

Autophagy, a conserved cellular process in eukaryotes, has evolved to a sophisticated process to dispose of intracellular constituents and plays important roles in plant development, metabolism, and efficient nutrients remobilization under suboptimal nutrients conditions. Here, we show that OsATG8b , an AUTOPHAGY-RELATED8 ( ATG8 ) gene in rice, was highly induced by nitrogen (N) starvation. Elevated expression of OsATG8b significantly increased ATG8 lipidation, autophagic flux, and grain yield in rice under both sufficient and deficient N conditions. Overexpressing of OsATG8b could greatly increase the activities of enzymes related to N metabolism. Intriguingly, the 15 N-labeling assay further revealed that more N was remobilized to seeds in OsATG8b -overexpressing rice, which significantly increased the N remobilization efficiency (NRE), N harvest index, N utilization efficiency (NUE), and N uptake efficiency (NUpE). Conversely, the osatg8b knock-out mutants had the opposite results on these characters. The substantial transcriptional changes of the overexpressed transgenic lines indicated the presence of complex signaling to developmental, metabolic process, and hormone, etc. Excitingly, the transgenic rice under different backgrounds all similarly be boosted in yield and NUE with OsATG8b overexpression. This work provides an excellent candidate gene for improving N remobilization, utilization, and yield in crops simultaneously.

Aims Plant available soil nitrogen (N) may affect deep root growth and soil N depletion by catch crops. We investigated the influence of topsoil N availability on root growth and uptake by fodder radish. Methods We conducted field and greenhouse experiments of root growth and late autumn N uptake at medium and high soil N availabilities, and root N inflow at medium and deep soil depths ( 15 N injection) in sandy loam and loamy sand, using the minirhizotron method in the field and rhizotrons in the greenhouse. Results High soil N availability resulted in lower root intensity in the field, but higher root intensity in the greenhouse experiment under both soil types. Radish had deeper roots and higher root intensity in sandy loam than in loamy sand. High soil N availability caused lower 15 N uptake at both soil depths in the field and lower N inflow rates at both soil depths in field and greenhouse. At medium soil N availability in the field, N inflow was twice as high in the deep than in the medium depth. Conclusions Higher soil N availability affects root growth and decrease N inflow, thus lowering late autumn N uptake and hampering deep N exploitation by fodder radish. At medium soil N availability, the potential for N uptake in deep soil is higher probably due to younger roots than at a medium soil depth. The shallower and less dense root growth in loamy sand is probably due to its lower clay and higher P contents.

Background Nitrogen availability plays a pivotal role in shaping the composition of root-associated microbial consortia in plants. Nevertheless, elucidating the mechanisms by which nitrogen availability regulates microbial populations and their metabolic activities across different root-associated ecological niches requires further investigation. This research employed an integrative approach combining microbiological approaches with non-targeted metabolomic analyses to examine nitrogen-mediated variations in microbial communities and metabolic processes within ginseng root systems. High-throughput sequencing alongside UPLC-MS/MS analytical platforms was utilized to conduct this multidimensional investigation. Results Our findings reveal that ginseng treated with N1 exhibited significantly increased yield by 29.90% compared to N0 and by 38.05% compared to N2 ( p  < 0.05). Additionally, nitrogen application markedly reduced the diversity of microbial communities within various segments of the root system, including rhizosphere soil (RS), rhizoplane soil (TS), fibrous roots (F), and phloem (P). Concurrently, there was a shift in bacterial communities from oligotrophic to eutrophic groups, with specific enrichment of groups such as Rhodanobacter and Burkholderia - Caballeronia - Paraburkholderia , which play crucial roles in the nitrogen cycling process. Metabolomic profiling revealed substantial modifications in soil metabolite profiles under nitrogen treatment, with marked alterations detected across 11 critical biochemical pathways encompassing plant-derived secondary metabolite biosynthesis and environmental microbial metabolic processes. Correlation analysis further indicated that the yield of ginseng and total ginsenoside content in F consistently varied in conjunction with soil nitrate nitrogen (NO₃⁻-N) content in the RS. Additionally, m-cresol was found to play a pivotal role in inhibiting the pathogenic fungus Alternaria , actively responding to pH fluctuations and promoting the synthesis of total ginsenosides in ginseng. Conclusion These insights elucidate the complex interplay between nitrogen levels and both microbial and metabolomic dynamics, providing a foundational understanding for the strategic manipulation of microbial communities to enhance the sustainability of ginseng agriculture.

Background Eutrophication of aquatic environments is a major environmental problem in large parts of the world. In Europe, EU legislation (the Water Framework Directive and the Marine Strategy Framework Directive), international conventions (OSPAR, HELCOM) and national environmental objectives emphasize the need to reduce the input of nutrients to freshwater and marine environments. A widely used method to achieve this is to allow water to pass through a created or restored wetland. However, the large variation in measured nutrient removal rates in such wetlands calls for a systematic review. Methods Searches for primary studies were performed in electronic databases and on the internet. One author performed the screening of all retrieved articles at the title and abstract level. To check that the screening was consistent and complied with the agreed inclusion/exclusion criteria, subsets of 100 articles were screened by the other authors. When screening at full-text level the articles were evenly distributed among the authors. Kappa tests were used to evaluate screening consistency. Relevant articles remaining after screening were critically appraised and assigned to three quality categories, from two of which data were extracted. Quantitative synthesis consists of meta-analyses and response surface analyses. Regressions were performed using generalized additive models that can handle nonlinear relationships and interaction effects. Results Searches generated 5853 unique records. After screening on relevance and critical appraisal, 93 articles including 203 wetlands were used for data extraction. Most of the wetlands were situated in Europe and North America. The removal rate of both total nitrogen (TN) and total phosphorus (TP) is highly dependent on the loading rate. Significant relationships were also found for annual average air temperature (T) and wetland area (A). Median removal rates of TN and TP were 93 and 1.2 g m −2  year −1 , respectively. Removal efficiency for TN was significantly correlated with hydrologic loading rate (HLR) and T, and the median was 37 %, with a 95 % confidence interval of 29–44 %. Removal efficiency for TP was significantly correlated with inlet TP concentration, HLR, T, and A. Median TP removal efficiency was 46 % with a 95 % confidence interval of 37–55 %. Although there are small differences in average values between the two quality categories, the variation is considerably smaller among high quality studies compared to studies with lower quality. This suggests that part of the large variation between studies may be explained by less rigorous study designs. Conclusions On average, created and restored wetlands significantly reduce the transport of TN and TP in treated wastewater and urban and agricultural runoff, and may thus be effective in efforts to counteract eutrophication. However, restored wetlands on former farmland were significantly less efficient than other wetlands at TP removal. In addition, wetlands with precipitation-driven HLRs and/or hydrologic pulsing show significantly lower TP removal efficiencies compared to wetlands with controlled HLRs. Loading rate (inlet concentrations × hydraulic loading rates) needs to be carefully estimated as part of the wetland design. More research is needed on the effects of hydrologic pulsing on wetlands. There is also a lack of evidence for long-term (>20 years) performance of wetlands.