Nitrogen Uptake Efficiency Research Articles

DETERMINATION OF NITROGEN UTILISATION AND NITROGEN UPTAKE EFFICIENCY OF SOME WHEAT GENOTYPES UNDER LIMITED NITROGEN CONDITIONS

Wheat is one of the most important human foods in Turkey and the most important nutrient of wheat plant is nitrogen. Since the green revolution in wheat variety breeding, high nitrogen high yielding varieties have been bred. Nitrogen resources of our world are limited, the use of excess nitrogen fertilisers for years has caused environmental pollution. It is also one of the important costs in wheat farming. There is a need to breed new wheat varieties that will reduce the use of nitrogen fertiliser. In order to reduce the damage to the environment and economic damage to the producer, it is important to breed high yielding varieties that require less nitrogen fertiliser. Otherwise, the cost of nitrogen fertiliser and the depletion of its reserve will negatively affect wheat production. A total of 7 genotypes including 4 local bread wheat genotypes, 2 durum wheat varieties (svevo, fırat93), 1 local siyez wheat collected from the villages of the Southeastern Anatolia region which is the homeland of wheat plant were used. The experiment was established according to split-plot design with 4 nitrogen doses and four replications. Nitrogen uptake efficiency and nitrogen utilisation efficiency were inversely proportional to nitrogen dose and nitrogen uptake efficiency increased as nitrogen dose decreased. Increasing nitrogen doses had an inverse effect on nitrogen uptake efficiency and the nitrogen dose with the highest nitrogen uptake efficiency was in the lowest nitrogen dose application. The genotype with the highest value among the local genotypes was GYE4.

Estimating Nitrogen Uptake Efficiency of Mango Varieties from Foliar KNO3 Application Using a 15N Tracer Technique

Commercial mango growers commonly spray potassium nitrate (KNO3) solution to enhance flowering and fruit quality, yet there is limited information on the uptake efficiency of nitrogen (N) by mango cultivars through leaf cuticles. The study aimed to assess N uptake efficiency (NUpE) from foliar application of KNO3 solution and compare NUpE among mango varieties. Mango cultivars were ‘Kensington Pride’ (‘KP’), ‘B74’ (‘Calypso®’), and ‘NMBP 1201’ (‘AhHa!®’), ‘NMBP 1243’ (‘Yess!®’), and ‘NMBP 4069’ (‘Now®’) grafted onto ‘KP’ seedlings. Leaves of six-month-old seedlings were dipped in 15N-enriched KNO3 solution and analyzed for total N and 15N contents. A significant correlation was observed between the leaf area and the amount of solution retained after dipping the leaves in the KNO3 solution. Moreover, leaves treated with the KNO3 solution had higher 15N levels than the natural 15N abundance, indicating successful N uptake from the KNO3 solution. The NUpE ranged from 27% to 44% and varied with variety. Cultivar ‘NMBP 4069’ had the highest NUE (44%) which was comparable with that of ‘B74’ (40%). ‘NMBP 1201’ showed the lowest (27%) NUpE which was comparable with that of ‘NMBP 1243’ (30%) and ‘KP’ (33%). These data on 15N uptake through the mango leaf cuticle demonstrates the effectiveness of foliar application as a method of supplying N to mango trees, highlighting important varietal differences in foliar 15N uptake efficiency. Considering these differences in NUpE among mango varieties will help in making informed decisions about cultivar selection and N management strategies for sustainable mango production.

Corn nitrogen uptake and use efficiency under varying irrigation regimes

Corn currently ranks first in global cereal production with an estimated total production of 1.22 billion metric tons in 2023. However, corn is the principal consumer of nitrogen (N) fertilizer globally, accounting for 20% of world fertilizer N consumption. Nitrogen uptake and utilization by crops essentially constitute nitrogen use efficiency (NUE) and any constraint such as water-deficit stress in corn can reduce yield and NUE. Thus, a study was conducted to assess the two most limiting factors for corn productivity: water and N. Field studies were conducted in 2020 and 2021 using a randomized complete block design with four irrigation treatments. There were significant (p < 0.05) regression relationships between grain yield and chlorophyll index, N concentration, and normalized difference vegetation index (NDVI). The ability of corn plants to take up N from the soil (total N uptake and N uptake efficiency), to translocate N into grains (N harvest Index and N partitioning to grain), to produce grain dry matter per N unit accumulated in grains (Grain metabolic N use efficiency) and to utilize the absorbed N efficiently in grain mass formation (N utilization efficiency and N grain production efficiency) were significantly (p < 0.05) affected mostly by the yearly variation. There was no significant (p > 0.05) effect of the irrigation regimes on all the NUE indices except partial factor productivity which decreased significantly in the non-irrigated treatment compared to the irrigated. This indicated how supplemental irrigation supports increase in yield per unit of fertilizer N applied.

Scoping Opportunities for Nitrogen Use Efficiency Among Productive Agricultural Forage Grasses With Diverse Rooting Systems

ABSTRACTFor forage production to be efficient and environmentally sustainable, the extent and timing of nitrogen fertiliser applications should match the uptake and growth capabilities of a grass crop. A two‐year field experiment, comprising four diverse grass cultivars, was conducted to assess the impact of two contrasting N‐application rates on forage and root biomass (RB) production and nitrogen‐use‐efficiencies (NUEs). Replicated field plots of perennial ryegrass, tall fescue and two Festulolium (ryegrass × fescue hybrid) cultivars were compared at Low N (LN) 178 and High N (HN) 356 kg ha−1 over 2 years. HN applications increased dry matter yield (DMY) in Year 1 (p &lt; 0.05) but not in Year 2. Ryegrass outyielded all in Year 1 but in Year 2, fescue had the highest DMY at HN (p &lt; 0.05), but cultivars did not differ in yield at LN. Festulolium yields were consistently intermediate. Root biomass at LN in Yr1 was highest in the Festulolium (Lolium perenne × Festuca arundinacea var glaucescens) (p &lt; 0.05). For all grasses, and in both years, mean RB and nitrogen use efficiency (NUE) and nitrogen utilisation efficiency (NutE) were higher under LN, than HN. Nitrogen uptake efficiency (NupE) was similar in all grasses in Year 1, irrespective of N treatment, but in Year 2, excepting tall fescue, was greater in grasses grown under LN. Increasing RB correlated (p &lt; 0.05) with improved NUE and NutE, but no association was evident for NupE. Grass cultivars differed in their response to nitrogen applications. Whilst relative forage production of ryegrass and fescue contrasted over the 2 years, forage yields of Festulolium cultivars were more consistent. In conclusion, HN application depressed NUE by productive grass cultivars and correlations between RB and NUEs may indicate opportunities to help tailor grass cultivar/fertiliser combinations and achieve sustainable forage and root production.

Nitrogen use efficiency for seed and oil yield in some Moroccan rapeseed (Brassica napus L.) varieties under contrasting nitrogen supply

In the actual context of climate change and increasing oil and nitrogen prices, oil crops varieties with high nitrogen use efficiency (NUE) will be highly appreciated. As no studies on NUE in spring rapeseed have been carried out in Mediterranean area, including Morocco, this work aimed to assess responses of six rapeseed varieties to six nitrogen levels (0, 30, 60, 90, 120, and 150 Kg N/ha) and their NUE for grain and oil yields. The experiment was conducted according to a split-plot design with three replications, during two cropping seasons. Results showed that increasing nitrogen rate from 0 to 120 kg N/ha led to a significant increase in seed, oil and dry matter yields up to 85.3, 72.35 and 97.9%, respectively. NUE, NUpE (nitrogen uptake efficiency) and NUtE (nitrogen utilization efficiency) decreased by increasing nitrogen application. Regarding oil content, it was negatively affected by nitrogen fertilization, declining from 40.78% for control to 37.77% for 150 kg N/ha. Likewise, nitrogen use and nitrogen utilization efficiency for oil production (ONUE & ONUtE) were negatively affected by nitrogen application. The genotypic variation was statistically significant for all investigated traits. The variety hybrid ‘Trapper’ was the most interesting for ONUE, NUE, seed yield and dry matter. However, for oil yield it was comparable to ‘Moufida’ and ‘Alia’ which showed the highest values for harvest index, branching, pods number per plant, oil content and ONUE. These varieties grown under 120 kg N/ha treatment can be recommended for Morocco.

Co-application effects of rice husk biochar and different types of nitrogen fertilizers on rice yield, yield components, and nitrogen use efficiency

The Nitrogen (N) recovery index in rice paddy soils has never been exceeded by more than 30%, regardless of using proven fertilizer management strategies and amounting to significant N being out of rice plant use. Biochar application and the newly released N biofertilizers (singly or in combination) increase the N use efficiency by increasing the soil nutrient retention capacity. Therefore, a two-year pot experiment was conducted to explore the effects of the co-application of rice husk biochar and nitrogen fertilizers on rice yield, yield components, and nitrogen use efficiency indexes. The applied treatments were rice husk biochar at three levels (0, 20, and 40 tha−1) and N fertilizers at three levels (0, chemical (Urea), and N-biofertilizer). The most effective combination treatments (200 kg N ha−1 in source of urea plus 40 tha−1 rice husk biochar) significantly (p ≤ 0.01) increased the grain yield (2.38 times), straw and biological yield (2.83 and 2.62 times, respectively), N content of soil N (59%), nitrogen uptake efficiency (2.92 times), and nitrogen internal efficiency (59%), whereas, nitrogen recovery efficiency decreased by about 52%. Moreover, the maximum increase in N content of grain and harvest index was recorded at combination application of 20 tha−1 biochar plus urea by about 48 and 15%, respectively. It can be concluded that the co-application of rice husk biochar and N fertilizers has substantial advantages over their single applications in terms of N fertilizer recovery, N uptake. Thus, it might be an effective way to enhance rice yield.

Integrative physiological and transcriptome analysis unravels the mechanism of low nitrogen use efficiency in burley tobacco.

Burley tobacco, a chlorophyll-deficient mutant with impaired nitrogen use efficiency (NUE), generally requires three to five times more nitrogen fertilization than flue-cured tobacco to achieve a comparable yield, which generates serious environmental pollution and negatively affects human health. Therefore, exploring the mechanisms underlying NUE is an effective measure to reduce environmental pollution and an essential direction for burley tobacco plant improvement. Physiological and genetic factors affecting tobacco NUE were identified using two tobacco genotypes with contrasting NUE in hydroponic experiments. Nitrogen use inefficient genotype (TN90) had lower nitrogen uptake and transport efficiencies, reduced leaf and root biomass, lower nitrogen assimilation and photosynthesis capacity, and lower nitrogen remobilization ability than the nitrogen use efficient genotype (K326). Transcriptomic analysis revealed that genes associated with photosynthesis, carbon fixation, and nitrogen metabolism are implicated in NUE. Three nitrate transporter genes in the leaves (NPF2.11, NPF2.13, and NPF3.1) and three nitrate transporter genes (NPF6.3, NRT2.1, and NRT2.4) in roots were down-regulated by nitrogen starvation, all of which showed lower expression in TN90 than in K326. In addition, the protein-protein interaction (PPI) network diagram identified eight key genes (TPIP1, GAPB, HEMB, PGK3, PSBO, PSBP2, PSAG, and GLN2) that may affect NUE. Less advantageous changes in nitrogen uptake, nitrogen assimilation in combination with nitrogen remobilization, and maintenance of photosynthesis in response to nitrogen deficiency led to a lower NUE in TN90. The key genes (TPIP1, GAPB, PGK3, PSBO, PSBP2, PSAG, and GLN2) were associated with improving photosynthesis and nitrogen metabolism in tobacco plants grown under N-deficient conditions.

Enhancing Wheat Productivity in Pakistan through Nitrogen Management and NDVI Monitoring with Green Seeker

Enhancing sustainability in modern farming systems, it is crucial to minimize environmental pollution from nitrogenous fertilizers by optimizing their application rates. The cost of production for wheat is increasing in Pakistan due to irrational use of nitrogen fertilizers by farming community which are costly and sometimes lead to high vegetative growth causing severe lodging thereby reducing yield. Optimum use of nitrogen (N) fertilizer is therefore empirical to improve the productivity of wheat at a reasonable cost. A field study for two-year was conducted at Ayub Agricultural Research Institute, Faisalabad to manage N fertilizers to enhance nitrogen use efficiency and improve financial return. A sensor-based nitrogen application using Normalized Difference Vegetation Index (NDVI) was compared with farmer practice by using T-test. Results revealed that there was 29% reduction in the use of N and an increase of 12 % in wheat grain yield. Increase in yield with sensor base fertilization improved nitrogen uptake efficiency (39%) and nitrogen fertilizer productivity (59 %) compared to farmer-based N application. The sensor-based management system and the farmer's practices had nitrogen-use efficiencies of 49% and 44%, respectively. The highest net benefits (US$789), benefit cost ratio (1.92) and resource use efficiency (0.864) in sensor-based application of N revealed that the nitrogen management with the help of Green Seeker could be a viable option for enhancing NUE, financial returns and reduction of environmental contamination.

Short‐statured maize achieved similar growth and nitrogen uptake but greater nitrogen efficiencies than conventional tall maize

AbstractDespite a historical favoring of robust tall plants in maize (Zea mays L.) production systems as a potential indicator of increased total and/or grain biomass yields, short‐statured maize is receiving renewed commercial attention in North America. Little is known of the relative N efficiencies resulting from potential inter‐stature differences in dry matter formation and N processes during pre‐ and post‐silking stages. To investigate this, two field rainfed experiments were conducted in West Lafayette, IN. The experiments included factorial combinations of two tall‐ and two short‐statured maize hybrids subjected to three N rates: 0 (unfertilized), 168 (moderate), and 224 kg N ha−1 (elevated) applied at planting. Short hybrids with a 25% reduced stature showed no statistically significant differences in seasonal biomass accumulation and N uptake, or in biomass partitioning to grain (harvest index) versus stover at maturity relative to conventional tall hybrids. Increased leaf biomass and ear growth at silking, plus comparable quantities of N remobilization from stems during grain filling, with short‐stature maize contributed to its grain yield parity with tall‐stature maize. Additionally, our research revealed other noteworthy findings: short‐statured maize had higher N harvest index and N recovery efficiency than the tall maize, implying more N status resiliency at moderate N rates. The lack of interactions between N × stature in most studied traits suggests that short hybrids can perform at least as well as conventional tall hybrids across a range of N rates. Our findings provide insights for fine‐tuning of breeding and management programs.

Substituting partial chemical nitrogen fertilizers with organic fertilizers maintains grain yield and increases nitrogen use efficiency in maize

IntroductionLong-term application of excessive nitrogen (N) not only leads to low N use efficiency (NUE) but also exacerbates the risk of environmental pollution due to N losses. Substituting partial chemical N with organic fertilizer (SP) is an environmentally friendly and sustainable fertilization practice. However, the appropriate rate of SP in rainfed maize cropping systems in semi-arid regions of China is unknown.MethodsTherefore, we conducted a field experiment between 2021 and 2022 in a semi-arid region of Northern China to investigate the effects of SP on maize growth, carbon and N metabolism (C/NM), and NUE. The following treatments were used in the experiment: no N application (CK), 100% chemical N (SP0, 210 kg N ha–1), and SP substituting 15% (SP1), 30% (SP2), 45% (SP3), and 60% (SP4) of the chemical N. The relationship between these indicators and grain yield (GY) was explored using the Mantel test and structural equation modeling (SEM).Results and discussionThe results found that the SP1 and SP2 treatments improved the assimilates production capacity of the canopy by increasing the leaf area index, total chlorophyll content, and net photosynthetic rate, improving dry matter accumulation (DMA) by 6.2%–10.6%, compared to the SP0 treatment. SP1 and SP2 treatments increased total soluble sugars, starch, free amino acids, and soluble protein contents in ear leaves via increasing the enzymatic reactions related to C/NM in ear leaves during the reproductive growth stage compared with SP0 treatment. The highest plant nitrogen uptake (PNU) and nitrogen recovery efficiency were obtained under the SP2 treatment, and the GY and nitrogen agronomic efficiency were higher than the SP0 treatment by 9.2% and 27.8%. However, SP3 and SP4 treatments reduced DMA and GY by inhibiting C/NM in ear leaves compared to SP0 treatment. Mantel test and SEM results revealed that SP treatments indirectly increased GY and PNU by directly positively regulating C/NM in maize ear leaves. Therefore, in the semi-arid regions, substituting 30% of the chemical N with SP could be considered. This fertilizer regime may avoid GY reduction and improve NUE. This study provides new insights into sustainable cultivation pathways for maize in semi-arid regions.

Higher Seed Rates Enlarge the Effects of Wide-Belt Sowing on Root Length Density, Thereby Improving Nitrogen Uptake and Use Efficiencies in Winter Wheat.

The optimized sowing method and appropriate seed rate can improve wheat N use efficiency. However, the interactive effect of the sowing method and seed rate on N use efficiency, particularly N uptake and root length density, are unclear. A field experiment was conducted for two growing seasons in southern Shanxi province, China, using a split-plot design with the sowing method as the main plot (wide-belt sowing, WBS, and conventional narrow-drill sowing, NDS) and seed rate as the sub-plot (100-700 m-2). Our results showed that WBS had a significant and positive effect on N use efficiency (yield per unit of available N from the fertilizer and soil, by 4.7-15.4%), and the relatively higher seed rates (>300 or 400 m-2) enlarged the effects. The N use efficiency increases under WBS were mainly attributed to the increases in N uptake before anthesis, resulting from the promoted nodal roots per plant and per unit area, and root length density in the top layer(s). WBS promoted N translocation and the N harvest index, resulting in equivalent grain protein concentration and processing quality compared to NDS. Thus, adopting higher seed rates (>300 m-2) combined with WBS is recommended for achieving greater N efficiencies while maintaining the grain protein concentration and processing quality of winter wheat.

Drought Priming Promotes Nitrogen Use Efficiency in Wheat (Triticum aestivum L.) Under Drought Stress During Grain Filling

ABSTRACTDrought stress significantly challenges wheat production globally, and drought priming has emerged as an effective strategy to mitigate yield loss under drought stress events. However, the effect of drought priming on plant nitrogen use efficiency (NUE) remains insufficiently understood. This study investigates the effects of drought priming at the six‐leaf stage on NUE under drought stress during grain filling in four wheat varieties with distinct responses to drought priming. Our results indicate that there is no correlation between inherent drought tolerance and the effects of drought priming among the wheat varieties studied. In priming‐sensitive varieties, drought‐primed plants exhibited significant improvements in grain yield and NUE under drought stress compared to non‐primed plants. Conversely, priming‐insensitive varieties showed no significant differences in yield or NUE between primed and non‐primed plants under similar conditions. Notably, under drought stress, primed plants exhibited higher yield and NUE than non‐primed plants in drought priming positive variety, while the opposite trend was observed in drought priming negative response variety. The enhancement of NUE through drought priming was associated with improved nitrogen uptake efficiency and its allocation to spikes, with abscisic acid accumulation playing a pivotal role. These findings provide valuable insights into the mechanisms by which drought priming enhances NUE under drought stress, contributing to the development of sustainable agricultural practices amid climate change.

Root physiological and soil microbial mechanisms underlying responses to nitrogen deficiency and compensation in Indica and Japonica rice.

Compensatory effects are common biological phenomena in nature. In this study, we investigated the changes in root nitrogen uptake, root morphological and physiological responses, and changes in the rhizosphere soil microbial communities of indica and japonica rice during a nitrogen deficiency-sensitive period and an effective compensation period with double the nitrogen supply. We conducted a bucket experiment using Suxiu 867 (a japonica rice variety) and Yangxian You 918 (an indica rice variety). Treatments included CK (constant distribution of nitrogen fertilizer at each growth stage, represented by CK867 and CK918) and NDC (nitrogen deficiency in the tillering stage, double nitrogen application in the ear differentiation stage to compensate, represented by NDC867 and NDC918) variations. Both varieties presented the highest δ15N and 15N abundances and Ndff (refers to the proportion of nitrogen in a plant's body that comes directly from the fertilizer applied.) in rice under the NDC treatment. Metagenomic sequencing of rhizospheric soil showed that the dominant bacterial groups at the phylum level among each treatment were Actinobacteria, Proteobacteria, Chloroflexi, Acidobacteria, Gemmatimonadetes, and Nitrospirae. The rhizosphere of indica rice was more enriched with the microbial communities involved in nitrogen metabolism, which contributed to higher nitrogen utilization efficiency. A correlation-based network was constructed and provides insights into the formation of nitrogen deficiency compensation effects and contributes to the enhancement of nitrogen uptake and utilization efficiency in rice production.

Macrogenome-based study on the mechanism of Bacillus velezensis SX13 in regulating rhizophere environment and cucumber growth under different cultivation environments

Microbial activities are the dynamic core of nutrient cycling in organic substrates, and the exploitation of plant growth-promoting rhizobacteria strains contributes to sustainable agricultural development. This study aimed to investigate the effect and mechanism of Bacillus velezensis SX13 in nutrient cycling and plant promotion under different substrate supply conditions. The effects of reduced substrate amount (sCK) and inoculation of SX13 strain under both substrate supply conditions (Bv and sBv) on rhizosphere microenvironment and plant growth were investigated using conventional substrate amount (CK) as a control. Results showed no significant difference in the α-diversity indexes (Chao1 and Shannon) of the rhizospheric microbial community among the four treatments. However, nonmetric multidimensional scaling analysis and principal coordinate analysis revealed that compared with CK treatment, the inoculation of SX13 strain and reduced substrate supply reshaped the β-diversity structure of microbial communities. Furthermore, inoculation with B. velezensis SX13 under both substrate supply conditions increased the abundance of Proteobacteria (1.64%–2.46 %), Acidobacteria (14.09%–43.07 %), and Firmicutes (179.29%–861.29 %). The results of the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis showed that the metabolic pathway with the highest abundance of enriched genes was also the pathway with the most enriched differential genes caused by reducing substrate supply or inoculation of B. velezensis SX13. The rhizosphere inoculation of B. velezensis SX13 significantly up-regulated the top genes related to carbohydrate esterases, carbohydrate binding modules, glycoside hydrolases, glycoside transferases, and polysaccharide lyases. As a result, the activities of carbon and nitrogen cycle-related enzymes such as cellobiohydrolase, β-glucosidase, urease, l-leucine amino peptidase, and β-1 4-N-acetylglucosaminidase were increased, which in turn accelerated nutrient cycling. B. velezensis SX13 and its mediated improvement of the rhizospheric microenvironment resulted in the up-regulation of root CsNRT family genes (such as CsNRT1.1, CsNRT1.4a, CsNRT1.4b, CsNRT1.5a, CsNRT1.5b, CsNRT1.5c, and CsNRT1.8), which accelerated nitrogen uptake, accumulation, and utilization efficiency and ultimately improved the yield and quality of cucumber. The effect of SX13 strain was more stable and efficient under conventional substrate supply conditions than under reduced substrate supply conditions.

Nitrogen Uptake and Use Efficiency of Aerobic Rice as Affected by Different Nitrogen Management: A Review

Nitrogen Uptake and Use Efficiency of Aerobic Rice as Affected by Different Nitrogen Management: A Review

Deficit Irrigation and High Planting Density Improve Nitrogen Uptake and Use Efficiency of Cotton in Drip Irrigation

Deficit Irrigation and High Planting Density Improve Nitrogen Uptake and Use Efficiency of Cotton in Drip Irrigation

Impact of fertilization depth on sunflower yield and nitrogen utilization: a perspective on soil nutrient and root system compatibility.

The depth of fertilizer application significantly influences soil nitrate concentration (SNC), sunflower root length density (RLD), sunflower nitrogen uptake (SNU), and yield. However, current studies cannot precisely capture subtle nutrient variations between soil layers and their complex relationships with root growth. They also struggle to assess the impact of different fertilizer application depths on sunflower root development and distribution as well as their response to the spatial and temporal distribution of nutrients. The Agricultural Production Systems sIMulator (APSIM) model was employed to explore the spatial and temporal patterns of nitrogen distribution in the soil at three controlled-release fertilizer (CRF) placement depths: 5, 15, and 25 cm. This study investigated the characteristics of the root system regarding nitrogen absorption and utilization and analyzed their correlation with sunflower yield formation. Furthermore, this study introduced the modified Jaccard index (considering the compatibility between soil nitrate and root length density) to analyze soil-root interactions, providing a deeper insight into how changes in CRF placement depth affect crop growth and nitrogen uptake efficiency. The results indicated that a fertilization depth of 15 cm improved the modified Jaccard index by 6.60% and 7.34% compared to 5 cm and 25 cm depths, respectively, maximizing sunflower yield (an increase of 9.44%) and nitrogen absorption rate (an increase of 5.40%). This depth promoted a greater Root Length Density (RLD), with an increases of 11.95% and 16.42% compared those at 5 cm and 25 cm, respectively, enhancing deeper root growth and improving nitrogen uptake. In contrast, shallow fertilization led to higher nitrate concentrations in the topsoil, whereas deeper fertilization increased the nitrate concentrations in the deeper soil layers. These results provide valuable insights for precision agriculture and sustainable soil management, highlighting the importance of optimizing root nitrogen absorption through tailored fertilization strategies to enhance crop production efficiency and minimize environmental impact.

Comparison of Organic and Inorganic Fertilization in Fenugreek Cultivation Using Nitrogen Indicators

Nitrogen indices could be used to evaluate organic and inorganic fertilization because they provide quantitative measures of nitrogen availability in the soil, allowing for a more accurate assessment of nutrient-management practices and optimization of crop yields. This study investigates the impact of different fertilization types and salinity on various soil parameters in fenugreek (Trigonella foenum-graecum L.) cultivation and nitrogen indices. A field experiment was established at the Agricultural University of Athens during the cropping period of 2018–2019 (CP I), 2019–2020 (CP II), and 2020–2021 (CP III) in a split-plot design with two main salinity treatments (high salinity, HS, and conventional salinity, CS) and five fertilization treatments (biocyclic–vegan humus soil (BHS), manure (FYM), compost (COMP), inorganic fertilization (11–15–15), and the control (C). The Nitrogen Balance Intensity (NBI) was statistically significantly affected by the factors of fertilization (p ≤ 0.01) and salinity (p ≤ 0.001) for CP I. The maximum NUEcrop value was recorded in the FYM treatment (0.83 ± 0.04) and the minimum in the COMP treatment (0.64 ± 0.04). Physiological efficiency (PE) was not significantly affected by any treatment for CP III. The fertilization factor significantly affected the NUEsoil index (p ≤ 0.001) for all three CPs. For CP I, the highest Nitrogen Uptake Efficiency (NUpE) value was recorded in the BHS treatment (27.08 ± 7.31) and the lowest in the C treatment (13.22 ± 7.31). There were no significant differences in CP I and CP II NUEbalance values among the NPK, BHS, and FYM treatments. These findings underscore the potential of organic fertilizers in addressing the global nitrogen challenge and promoting environmentally sustainable farming practices.

Vertical non-uniform distribution of soil salinity enhances nitrogen utilization efficiency and influences δ15N distribution in tomato plants

Soil salinity typically exhibits non-uniform distribution in the natural environment. However, how vertically non-uniform distribution of soil salinity in the root zone (VNDSR) regulated plant nitrogen metabolism is still largely elusive. This study aimed to investigate the impact of VNDSR on leaf Malondialdehyde (MDA) content, upper and lower root activity, leaf Na+/Ca2+ and Na+/K+, various tomato organs’ nitrogen concentration (%) and natural abundance of nitrogen isotopes (δ15N,‰), and nitrogen utilization efficiency of tomato plants. Four treatments were established, including the upper layer of the root zone having soil salinity levels of 1 ‰, 1 ‰, 2 ‰, and 3 ‰, while the corresponding lower layer of the root zone had soil salinity levels of 1 ‰, 5 ‰, 4 ‰, and 3 ‰, respectively, denoted as T1:1, T1:5, T2:4, and T3:3. The results showed that under the same average soil salinity conditions and compared to the treatment with uniform soil salinity distribution in the root zone (T3:3), the VNDSR treatment (T1:5) significantly reduced leaf MDA content (p < 0.01), Na+/Ca2+ (p < 0.01) and Na+/K+ (p < 0.01), and stem δ15N values (p < 0.05). Moreover, the VNDSR treatment (T1:5) significantly increased the ratio of upper and lower root biomass-weighted root activity (p < 0.01), tomato fruit yield (p < 0.01), and nitrogen partial factor productivity (PFP, gg−1, p < 0.01) compared to uniform salt distribution treatment (T3:3). There were significant positive correlations (p < 0.05) between leaf δ15N values and Nitrogen Absorption Ratio (NAR, %, p < 0.05) and PFP (p < 0.05), indicating that under VNDSR, δ15N values can serve as an indicator that comprehensively reflects the information of plant nitrogen utilization efficiency. In conclusion, the VNDSR could mitigate the damage of salt stress to tomatoes, enhance plant nitrogen uptake and utilization efficiency, and promote the growth and development of tomatoes. Data AvailabilityThe datasets generated or analyzed during the current study are available from the corresponding author on reasonable request.

Straw returning and nitrogen reduction: Strategies for sustainable maize production in the dryland

Implementing continue straw returning practices and optimizing nitrogen application can mitigate nitrogen losses and enhance nitrogen use efficiency (NUE) in dryland. 15N-labeled technique offers a robust approach for tracking fertilizer nitrogen fate and assessing nitrogen use efficiency. Based on the continue (>6 yr) experiment, we conducted a two-year experiment (2020 and 2021) to evaluate the effects of straw returning and nitrogen management under plastic film mulching on 15N recovery rates, N2O emissions and maize yield with three treatments: no straw returning with 225 kg N·ha−1 under plastic film mulching (RP-N225), straw returning with 225 kg N·ha−1 under plastic film mulching (RPS-N225), and straw returning with 20% nitrogen reduction (180 kg N·ha−1) under plastic film mulching (RPS-N180). After six years, both continue straw returning with plastic film mulching increased uptake of fertilizer nitrogen, had higher 15N recovery rates than RP-N225, leading to increased 15N accumulation in grain and aboveground biomass, ultimately enhancing yield. The RPS-N225 treatment exhibited the highest spring maize yield and nitrogen harvest index. The RPS-N180 treatment significantly increased maize yield more than RP-N225 and had the highest NUE, partial factor productivity of nitrogen fertilizer, and nitrogen uptake efficiency, with improvements ranging from 1.7 to 2.4%, 19.3–29.6%, and 17.3–27.5%, respectively, compared to the other treatments. Moreover, RPS-N225 resulted in significantly higher cumulative N2O emissions and yield-scaled N2O emissions than the other treatments, whereas the RPS-N180 treatment significantly decreased yield-scaled N2O emissions compared to RP-N225. Hence, combining continue straw returning with appropriate nitrogen reduction can effectively increase maize yield and yield-scaled N2O emissions. By offering insights into optimizing nitrogen fertilizer management after continue maize straw return, this study is contributed to widespread adoption of straw return practices and sustainable agricultural development in semi-arid areas.