N Utilization Efficiency Research Articles

Does Nitrogen Fertilization Improve Nitrogen-Use Efficiency in Spring Wheat?

To investigate the effects and mechanism of prolonged inorganic nitrogen (N) fertilization on the N-use efficiency of spring wheat (Triticum aestivum L.), a long-term study initiated in 2003 was conducted. The study analyzed how N fertilization affects dry matter translocation, N translocation, soil NO3-N, and N-use efficiency. Five different N-fertilizer rate treatments were tested: N0, N52.5, N105, N157.5, and N210, corresponding to annual N fertilizer doses of 0, 52.5, 105.0, 157.5, and 210.0 kg N ha−1, respectively. Results showed that increasing N-fertilizer rates significantly enhanced the two-year average dry matter accumulation amount (DMA) at maturity by 22.97–56.25% and pre-flowering crop growth rate (CGR) by 17.11–92.85%, with no significant increase beyond 105 kg N ha−1. However, no significant correlation was observed between the dry matter translocation efficiency (DTE) and wheat grain yield. Both insufficient and excessive N applications resulted in an imbalanced N distribution favoring vegetative growth over reproductive growth, thus negatively impacting N-use efficiency. At maturity, the N-fertilized treatments significantly increased the two-year average N accumulation amount (NAA) by 52.04–129.98%, with no further increase beyond 105 kg N ha−1. N fertilization also improved the two-year average N translocation efficiency (NTE) by 56.89–63.80% and the N contribution proportion (NCP) of wheat vegetative organs by 27.79–57.83%, peaking in the lower-N treatment (N52.5). However, high-N treatment (N210) led to an increase in NO3-N accumulation in the 0–100 cm soil layer, with an increase of 26.27% in 2018 and 122.44% in 2019. This higher soil NO3-N accumulation in the 0–100 cm layer decreased NHI, NUE, NAE, NPFP, and NMB. Additionally, N fertilization significantly reduced the two-year average N harvest index (NHI) by 9.89–12.85% and N utilization efficiency (NUE) by 11.14–20.79%, both decreasing with higher N application rates. The NAA followed the trend of anthesis > maturity > jointing. At the 105 kg N ha−1 rate, the highest N agronomic efficiency (NAE) (9.31 kg kg−1), N recovery efficiency (NRE) (38.32%), and N marginal benefit (NMB) (10.67 kg kg−1) were observed. Higher dry matter translocation amount (DTA) and N translocation amount (NTA) reduced NHI and NUE, whereas higher NTE improved NHI, NUE, and N partial factor productivity (NPFP). Overall, N fertilization enhanced N-use efficiency in spring wheat by improving N translocation rather than dry matter translocation.

Comparative phenotypic and transcriptomic analysis reveals genotypic differences in nitrogen use efficiency in sorghum

Sorghum (Sorghumbicolor L.), a model for C4 grass and an emerging biofuel crop, is known for its robust tolerance to low input field. However, the focus on enhancing nitrogen use efficiency (NUE) in sorghum under low nitrogen (N) conditions has been limited. This study conducted hydroponic experiments and field trials with two sorghum inbred lines, contrasting in their N efficiency: the N-efficient (398B) and the N-inefficient (CS3541) inbred lines. The aim was to analyze the key factors influencing NUE by integrating phenotypic, physiological, and multi-omics approaches under N deficiency conditions. The field experiments revealed that 398B displayed superior NUE and yield performance compared to CS3541. In hydroponic experiments, the growth of 398B outperformed CS3541 following N deficiency, attributing to its higher photosynthetic and sustaining activity of N metabolism-related enzymes. Genomic and transcriptomic integration highlighted fewer genomic diversities and alterations in global gene expression in 398B, which were likely contributor to its high NUE. Additionally, co-expression network analysis suggested the involvement of key genes which impact N uptake efficiency (NUpE) and N utilization efficiency (NUtE) in both lines, such as an N transporter, Sobic.003G371000.v3.2leaf(NPF5.10) and a transcription factor, Sobic.002G202800.v3.2leaf(WRKY) in bolstering NUE under low-N stress. The findings collectively suggested that 398B achieved higher NUpE and NUtE, effectively coordinating photosynthesis and N metabolism to enhance NUE. The candidate genes regulating N uptake and utilization efficiencies could provide valuable insights for developing sorghum breeds with improved NUE, contributing to sustainable agricultural practices and bioenergy crop development.

Screening Cover Crops for Utilization in Irrigated Vineyards: A Greenhouse Study on Species' Nitrogen Uptake and Carbon Sequestration Potential.

This study examines the potential of 23 plant species, comprising 10 legumes, 9 grasses, and 4 forbs, as cover crops to enhance carbon (C) sequestration and soil nitrogen (N) in vineyards. After a 120-day evaluation period, cover crop biomass was incorporated into the soil, and grapevine seedlings were planted in its place. Among the established cover crops, the C input potential ranged from 0.267 to 1.69 Mg ha-1, and the N input potential ranged from 12.3 to 114 kg ha-1. Legume species exhibited up to threefold greater shoot dry weight (SDW) compared to grass species. Ladino white clover, Dutch white clover, and Clover blend were superior in SDW, total dry weight (TDW), total C content, and total N content. Legumes exhibited slightly higher root dry weight (RDW) than grasses, with the exception of Fall rye leading at 15 g pot-1, followed by Ladino white clover and Dutch white clover at an average of 12 g pot-1. Legumes, particularly clover blend and Alsike clover, displayed high shoot N concentration at an average of 2.95%. Root N concentration in Legumes (Fabaceae) were significantly higher at 1.82% compared to other plant families at 0.89%, while their root C/N ratio was lower at 18.3, contrasting with others at 27.7, resulting in a faster turnover. Biomass production exhibited a negative relationship (R2 = 0.51) with soil residual NO3-. Fall rye, Winfred brassica, and buckwheat had the highest N utilization efficiency (NUtE) values (ava. 121 g g-1). Alsike clover, Ladino white clover, and clover blend showed the highest N uptake efficiency (NUpE) values (ava. 75%). The Readily Available N (RAN) Reliance Index (RANRI) is introduced as a novel indicator for quantifying the extent to which a plant relies on RAN for its total N requirement. The RANRI value represents the percentage of the plant's total N sourced from RAN, ranging from 11% for legumes to 86% for grasses. This implies a substantial influx of nitrogen through a pathway independent of RAN in legumes. Grape shoot N concentration positively correlated with soil NO3- (R2 = 0.31) and cover crop C/N ratio (R2 = 0.17) but negatively correlated with cover crop TDW (R2 = 0.31). This study highlights legume plants as more effective in C and N assimilation during establishment but cautions about potential soil mineral N depletion before reaching their full biological N fixation capacity.

Experimental Warming Reduces the Grain Yield and Nitrogen Utilization Efficiency of Double-Cropping indica Rice in South China

The effect of climate warming on rice production in China is profound, yet there has been limited research on how it affects the grain yield, nitrogen (N) uptake, and N utilization efficiency (NUtE) of the double-cropping indica rice in South China. To address this gap, we conducted a free air temperature increase (FATI) experiment in Guangdong province during 2020 and 2021. Our findings revealed that warming led to a significant reduction in grain yield, with early rice (ER) and late rice (LR) experiencing average decreases of 5.2% and 6.3%, respectively, compared to control treatments. This decline was primarily attributed to the reduced grain weight of ER and the fewer spikelet numbers per panicle of LR under warming conditions. Although the dry matter translocation, harvest index, and N translocation efficiency of ER remained unchanged under warming conditions, these of LR decreased by an average of 58.1%, 8.8%, and 22.3%, respectively. Additionally, while warming did not affect the N uptake in ER at maturity, it significantly increased the N uptake in LR by an average of 11.0%. Therefore, under warming conditions, the NUtE of both ER and LR was markedly decreased by 6.9% and 15.5% over the two years. These results indicate that climate warming may have significant negative impacts on the grain yield and the NUtE of indica rice within double-rice cropping systems in South China. Understanding these dynamics is vital for maintaining the stability of rice yields in anticipation of future climate warming.

No-tillage with straw mulching restrained the vertical transportation of chemical fertilizer N and reduced its leaching loss in Northeast China

Intensified by the pursuit of food security, nitrogen (N) source pollution caused by excessive chemical N fertilizer application has emerged as a major environmental threat, especially through nitrate N (NO3--N) leaching. While no-tillage with straw mulching is recognized for mitigating NO3--N leaching from chemical fertilizer N, its efficacy in deep soil layers remains unclear. Thus, employing the 15N isotope labeling technique in Northeast China's black soil, we investigated the impact of no-tillage and/or straw mulching on the transformation, vertical transport, and leaching loss of fertilizer N under five treatments: conventional ridge tillage (RT), and no-tillage with varying straw coverages (NT-0, NT-33, NT-67, and NT-100). Our results revealed that over 98.3% of fertilizer-derived mineral N in the soil was NO3--N, with substantial downward movement beyond 120 cm, posing a leaching risk. Three years after N fertilizer application, no-tillage and/or straw mulching with varying coverages significantly reduced fertilizer-derived NO3--N by averaging 36.3% in 0–300 cm soil profile, compared to RT with 18.36 kg ha−1 fertilizer-derived NO3--N in soil. Notably, no-tillage and/or straw mulching of 33%, 67%, and 100% coverages effectively decelerated the vertical transport of fertilizer-derived NO3--N to 140–220 cm soil deeper layers by averaging 48.4%, where NO3--N accumulates in large quantities. The percentages of fertilizer-derived NO3--N leached to applied fertilizer N varied from 3.7% to 7.2% after three years of vertical migration. No-tillage with different straw coverages remarkably decreased this leaching percentage by 42.7% and 21.9% compared with RT and NT-0, respectively. Furthermore, we found that no-tillage with straw mulching enhanced fertilizer N utilization efficiency (NUE) and crop yields with NT-33, NT-67, and NT-100 demonstrating higher accumulative NUE of 58.4%, 56.2%, and 58.8% and average yields of 13.90, 13.48, and 13.21 Mg ha−1, respectively. Therefore, we preliminarily suggest that implementing no-tillage and straw mulching with 33% and 100% coverages in Northeast China holds promise for simultaneously enhancing crop yields and NUE, and mitigating N fertilizer leaching in the form of NO3--N. These findings offer valuable insights for optimizing field management and mitigating N pollution in agriculture, contributing to the achievement of sustainable agricultural development.

Effects of arbuscular mycorrhizal fungi on uptake, partitioning and use efficiency of nitrogen in wheat

Arbuscular mycorrhizal fungi (AMF) can promote the growth and yield of crops by increasing the use of nutrients. However, the influence of AMF on the uptake, utilization and partitioning of nitrogen (N) from different sources remain uncertain. Therefore, we investigated AMF inoculation on plant biomass, N-uptake (from fertilizers and soil), -partitioning and N use-efficiency (NUE) in two wheat cultivars using 15N isotope labeling in a field and pot experiment. Results showed that AMF inoculation increased both plant biomass and N accumulation, and altered N partitioning in wheat. AMF inoculation significantly increased root N concentration and decreased grain N concentration (GNC) and leaf N concentration. The decrease in GNC by the AMF was mainly attributed to the variations in pre-anthesis accumulated N in vegetative organs and a reduction in the amount of N translocation. AMF significantly increased root dry weight by 13.5–18.2%, N uptake of the root by 25.4–37.2%. The N partitioning ratio in roots increased, but decreased in grains. Further, AMF significantly increased plant uptake of top-dressed 15N-labeled fertilizer by 15.0–17.8%. AMF promoted grain N absorbed from fertilizer (basal and topdressing fertilizer) but reduced its uptake from soil. Importantly, fertilizer N recovery efficiency (FNRE), N utilization efficiency (NUtE) and NUE were higher in AMF than in the control (CK), demonstrating the benefits of AMF inoculation on growth in wheat. Therefore, using AMF as biofertilizers in field conditions may be an effective agronomic practice in order to ensure sustainable production.

Alteration of carbon and nitrogen allocation in winter wheat under elevated ozone

Tropospheric ozone accelerates senescence and shortens grain filling, consequently affecting the remobilization and allocation efficiency of aboveground biomass and nutrients into grains in cereal crops. This study investigated carbon (C) and nitrogen (N) concentrations repeatedly in shoot biomass during the growth period and in grain after the harvest in eighteen wheat genotypes under control and ozone treatments in open-top chambers. Season-long ozone fumigation was conducted at an average ozone concentration of 70 ppb with three additional acute ozone episodes of around 150 ppb. Although there were no significant differences in straw C and N concentrations between the two treatments, the straw C:N ratio was significantly increased after long-term ozone fumigation, and the grain C:N ratio decreased under elevated ozone without significance. Grain N concentrations increased significantly under ozone stress, whereas N yield declined significantly due to grain yield losses induced by ozone. Moreover, different indicators of N use efficiency were significantly reduced with the exception of N utilization efficiency (NUtE), indicating that elevated ozone exposure reduced the N absorption from soil and allocation from vegetative to reproductive organs. The linear regression between straw C:N ratio and productivity indicated that straw C:N was not a suitable trait for predicting wheat productivity due to the low coefficient of determination (R2). Nitrogen harvest index (NHI) was not significantly affected by ozone stress among all genotypes. However, elevated ozone concentration changed the relationship between harvest index (HI) and NHI, and the reduced regression slope between them indicated that ozone exposure significantly affected the relationship of N and biomass allocation into wheat grains. The cultivar “Jenga” showed optimal ozone tolerance due to less yield reduction and higher NUE after ozone exposure. The genotypes with higher nutrient use efficiencies are promising to cope with ozone-induced changes in nitrogen partitioning.

The responses of genotypes with contrasting NUtE to exogenous ABA during the flowering stage in Brassica napus

A large amount of nitrogen (N) fertilizer is applied to maintain a stable yield because of the low N utilization efficiency (NUtE) in rapeseed (Brassica napus L.), which increases production costs and has a negative impact on the environment. Abscisic acid (ABA) has been reported to have crosstalk with nitrate. In this study, exogenous ABA treatment and RNA-seq were used to explore the response patterns of rapeseed with contrasting NUtE to ABA signals. Our results showed that ABA application on leaf promoted the N allocation from vegetative organs to grain and increased the number of seeds per silique, grain yield, N harvest index (NHI), and the NUtE in N-efficient rapeseed. Transcriptome analysis showed the DEGs were mainly enriched in N metabolism, ABC transporters, and MAPK signaling pathways. Among them, the Glutamate dehydrogenase (GS) genes and the Glutamine synthetase gene were more highly expressed in the N-efficient genotype leaf than the N-inefficient genotype after ABA treatment. In contrast, the opposite expression level was observed in seven genes, including nitrate transporter 2.1, Nitrate Reductase genes, and GS genes in the root. In conclusion, the shoot and root of rapeseed may have different response mechanisms to ABA stimulation, and N-efficient rapeseed is more sensitive to ABA treatment, which may be one of the reasons for the difference in NUtE

Selection of the best nitrogen fertilizer management scenario in wheat based on Palmer drought severity index with an environmental perspective

In arid and semi-arid regions, where winter wheat relies partially on precipitation for its water requirements, the timing and amount of precipitation play a pivotal role in nitrogen (N) losses. Given the extensive cultivation of wheat in these areas, farmers' oversight of N rates, N splitting, and the impact of precipitation patterns on N losses have led to water resources contamination. Therefore, tailoring N management to drought condition fluctuations can reduce N losses. The goal was to boost wheat yield while minimizing N losses. The CERES-Wheat model was meticulously calibrated and evaluated over three years, involving an experimental field and five farmer fields. The calibrated model simulated twenty-five N fertilizer scenarios, spanning various N levels (50–250 kg ha−1) and split patterns. This conesidered soil textures and meteorological data from 1992 to 2020. The model's outcomes, encompassing various yield indices and performance metrics such as water productivity (WP), irrigation water productivity (IWP), N residual in soil (NR), N leaching (NL), available N use efficiency (ANUE), N absorption efficiency (NAE), and N utilization efficiency (NUE), were categorized into four distinct groups based on the Palmer's Drought Severity Index (PDSI): Group A: Positive PDSI all season, Group B: Negative PDSI all season, Group C: Positive early, negative later, and Group D: Negative early, positive later. Indices underwent thorough Principal Component Analysis (PCA) to identify the optimal scenario. Model evaluation represented key parameters comprehensively. Simulated total biomass matched real-world conditions (NRMSE 12.44–26.08%, d-index 0.86–0.97). Soil moisture and N fell within specific ranges (NRMSE 18.79–25.60%, RMSE 1.98–4.95 mg kg−1). Comparing different drought and soil conditions, significant performance metric differences emerged. Specifically, in Groups A and D, WP, IWP, ANUE, and NAE increased by 3.38%, 11.53%, 5.86%, and 5.76% compared to C and B. Group B had an 8.55-fold NL increase over A, while Group A saw a substantial 50.64% NR surge compared to B. In overall assessment, the study has identified that the optimal N application rate for the study area is 150 kg ha−1. However, determining the most appropriate N split pattern hinges on the dynamic interplay between PDSI and soil available water content (AWC).

Toward potential applications of the nitrogen nutrition index in Sweet basil (Ocimum basilicum L.) production under greenhouse conditions

The nitrogen nutrition index (NNI) as an effective indicator for monitoring crop nitrogen (N) status has multiple applications in agriculture, such as estimating in-season crop N requirement (NR), predicting crop biomass/yield, and improving N use efficiency. The present study was aimed to develop basil (Ocimum basilicum L.) NR and relative biomass (RB) prediction models based on the concept of critical N concentration. Two experiments were carried out with different N application rates in the research greenhouse of University of Tehran, Iran. Basil NNI values were calculated using the previously developed critical N dilution curve. Subsequently, the in-season basil NR estimation model was developed as a function of NNI, N recovery efficiency (NRE) and plant age. Additionally, basil RB was simulated as a function of the averaged and integrated NNI based on a linear-plateau model. Moreover, a theoretical relationship between N utilization efficiency (NUtE) and the NNI was established. The validation results of the developed NR-NNI model demonstrated a good performance with a root mean square error (RMSE) and a normalized root mean square error (NRMSE) less than 5.28 kg ha−1 and 4.72%, respectively. The results showed that crop biomass and NNI were the most significant explanatory factors for the variations in basil NUtE. Therefore, the crop NNI can serve as a practical in-season diagnostic tool for basil NR and RB prediction, while also contributing to the design of decision support systems and sustainable agro-ecosystems.

Maize nitrogen uptake and use efficiency, partial factor productivity of nitrogen, and yield response to different nitrogen and water applications under three irrigation methods

AbstractThe effects of irrigation and nitrogen (N) on grain yield, actual crop evapotranspiration (ETa), N uptake efficiency (NUE), partial factor productivity of N (PFPN), and N utilization efficiency (NUtE) of maize (Zea mays L.) under centre pivot (CP), subsurface drip (SDI) and gravity (furrow) irrigation (FI) were quantified. Field experiments were conducted in two growing seasons under the full irrigation treatment (FIT), limited irrigation treatments of 80% FIT and 60% FIT and rainfed treatment (RFT). The highest NUE was observed under limited irrigation in the order of 80% FIT > FIT ≥ 60% FIT in non‐traditional treatment‐1 (NT‐1) in both the CP and SDI methods. NUtE increased with irrigation amount. There were strong correlations between NUtE and grain yield regardless of irrigation method. ETa increased with N amount, and the slopes of these relationships varied substantially between irrigation and N levels and irrigation methods. PFPN increased with irrigation amount across the irrigation methods and N treatments. A higher PFPN was observed in the lowest total applied N plots and in‐season split N application treatments. The pooled data for the CP and SDI methods showed significantly higher PFPN (20.3%) than the FI method, whereas the PFPN values in the CP and SDI methods were equal.

Adaptability of agricultural soil microbial nutrient utilization regulates community assembly under mulching measures on the Loess Plateau

Soil microbial nutrients and resource availability improve with mulching in agroecosystems, resulting in changes of soil microbial nutrient utilization strategies. However, the responses of soil microorganisms to nutrient utilization processes to regulate community assembly and thus maintain resource availability have not been clarified. Here, we performed a long-term field experiment with mulching measures, including no-mulching (NM), straw mulching (SM), plastic mulching (PM), and ridge mulching (RM), conducted on the Loess Plateau of China, to explore the community assembly process in response to microbial nutrient utilization. Microbial nutrient utilization strategies were analysed by measuring soil nutrients, microbial biomass, and extracellular enzyme activities. The results showed that PM and RM acquired C and N nutrients by secreting C- and N-extracellular enzymes in response to C:N- and C:P imbalances in soil chemistry, thereby reducing the nutrient limitation on microbial metabolism and improving microbial C utilization efficiency (CUE). Soil extracellular enzymatic stoichiometry increased and N utilization efficiency (NUE) decreased under mulching and drove an increase in beta-diversity and dominant species abundance in fungal communities. Mulching measures promoted the modular distribution of sensitive microorganisms and aggregation of fungal networks under PM and RM by reducing the stoichiometric imbalance and extracellular enzymatic N:P. At the same time, the microbial community assembly gradually changed from a stochastic to a deterministic process in response to the alleviation of soil C:P imbalance and changes in microbial nutrient utilization, in which the fungal community was dominant. In conclusion, soil microorganisms adaptively responded to changes in soil microbial nutrient utilization through the enhancement of aggregation of fungal co-occurrence networks and deterministic assembly processes. This study provides a better understanding of the impact of mulching on microbial nutrient utilization strategies from a community assembly perspective.

Exploring the Potential of Heterosis to Improve Nitrogen Use Efficiency in Popcorn Plants.

Nitrogen is crucial for plant growth and development, and improving nitrogen use efficiency (NUE) is a viable strategy for reducing dependence on nitrogen inputs and promoting sustainability. While the benefits of heterosis in corn are well known, the physiological mechanisms underlying this phenomenon in popcorn are less understood. We aimed to investigate the effects of heterosis on growth and physiological traits in four popcorn lines and their hybrids under two contrasting nitrogen conditions. We evaluated morpho-agronomic and physiological traits such as leaf pigments, the maximum photochemical efficiency of PSII, and leaf gas exchange. Components associated with NUE were also evaluated. N deprivation caused reductions of up to 65% in terms of plant architecture, 37% in terms of leaf pigments, and 42% in terms of photosynthesis-related traits. Heterosis had significant effects on growth traits, NUE, and foliar pigments, particularly under low soil nitrogen conditions. N-utilization efficiency was found to be the mechanism favoring superior hybrid performance for NUE. Non-additive genetic effects were predominant in controlling the studied traits, indicating that exploring heterosis is the most effective strategy for obtaining superior hybrids to promote NUE. The findings are relevant and beneficial for agro farmers seeking sustainable agricultural practices and improved crop productivity through the optimization of nitrogen utilization.

Agronomic approach to evaluate the nitrogen use efficiency of liquid, solid, and composted swine manures in corn–soybean rotation

Evaluating the nitrogen (N) use efficiency of animal manure is essential to optimize its application for profitable crop production without impairing the environment. A four-year field study was conducted under corn (Zea mays L.)–soybean (Glycine max L.) rotation in a Brookston clay loam soil using the yield control approach. Treatments included inorganic fertilizer (IN), and liquid (LM), solid (SM), and composted (CM) swine manure applied at the rate equivalent to an available N of 200 kg ha−1 and a non-fertilization control (CT). Seven N use indices were employed to evaluate N use efficiency. LM obtained comparable corn yields relative to IN. Corn yield in SM was inconsistent from one year to another, and CM had minimal agronomical value in our study. Soybeans with IN posed the highest grain yields of 3,468 and 3,761 kg ha−1 in 2005 and 2007, respectively. In contrast to grain yield and total N uptake, the gain N removal of either corn or soybeans was comparable between the two alternative years. The distinctions between N supply dynamics of manures and their influences on yield, grain N removal, and total above-ground plant N uptake of corn were well discriminated by N use efficiency (NUE), N uptake efficiency (NUpE), N utilization efficiency (NUtE), N agronomic efficiency (NAE), and N recovery efficiency (NRE), but not by N physiological efficiency (NPE) and N harvest index (NHI). Legacy effects on soybean yield from the preceding corn were detected by NAE and NRE. Based on grain yield in conjunction with N use efficiency parameters, the IN performed the best, followed by LM. The NUE, NUpE, NUtE, NAE, and NRE parameters used to evaluate chemical fertilizer N were also applicable to evaluate manure N efficiency.

Overexpression of CsATG3a improves tolerance to nitrogen deficiency and increases nitrogen use efficiency in arabidopsis

Nitrogen (N) is a major nutrition element for tea plant. However, application of high levels of N negatively causes environmental problems. Therefore, improved N use efficiency (NUE) of tea plant will be highly desirable and crucial for sustainable tea cultivation. Autophagy plays a central role in N recycling and holds potential to improve N utilization, and many AuTophaGy-related genes (ATGs) are involved in the autophagy process. Here, CsATG3a was identified from Camellia sinensis, and the functions involved in N utilization was characterized in arabidopsis (Arabidopsis thaliana). The transcript level of CsATG3a in tea leaves increases with their maturity. Relative to the wild type (WT) arabidopsis, two CsATG3a-overexpressing (CsATG3a-OE) lines exhibited improved vegetative growth, delayed reproductive stage, and upregulated expression of AtATGs (AtATG3, AtATG5 and AtATG8b) in a low N (LN) hydroponic condition. The expression levels of AtNRT1.1, AtNRT2.1, AtNRT2.2, AtAMT1.1 and AtAMT1.3 for N uptake and transport in roots were all significantly higher in CsATG3a-OE lines compared with those in the WT under LN. Meanwhile, the overexpression of CsATG3a in arabidopsis also increased N and dry matter allocation into both rosette leaves and roots under LN. Additionally, compared with WT, improved HI (harvest index), NHI (N harvest index), NUtE (N utilization efficiency) and NUE (N use efficiency) of CsATG3a-OE lines were further confirmed in a low-N soil cultured experiment. Together, these results concluded that CsATG3a is involved in N recycling and enhances tolerance to LN, indicating that CsATG3a holds potential promise to improve NUE in tea plant.

Beneficial Effects of Biochar Application with Nitrogen Fertilizer on Soil Nitrogen Retention, Absorption and Utilization in Maize Production

The irrational use of nitrogen (N) fertilizer has become a major threat to soil quality and food security, resulting in serious ecological and environmental problems. Holistic approaches to N fertilizer application are required to maintain a high N utilization efficiency (NUE) and sustainable agriculture development. Biochar is an efficient carbon-rich material for amending soil quality and promoting crop N uptake, but knowledge pertaining to the promoting effects of biochar application on N fertilizers is still limited. In this study, a field plot experiment was designed to detect the combined effects of biochar (0, 15 and 30 t ha−1) and N fertilizer (204, 240 and 276 kg N ha−1) on the soil nutrient levels, NUE, plant growth performance and crop production of maize. The results demonstrated that the combined application of N fertilizer and biochar can significantly decrease the soil pH and increase the contents of soil organic carbon, mineral N, available phosphorus and potassium. The crop N uptake and N content were largely promoted by the addition of N fertilizer and biochar, resulting in higher leaf photosynthetic efficiency, dry matter accumulation and grain yields. The highest yields (14,928 kg ha−1) were achieved using 276 kg N ha−1 N fertilizer in combination with 15 t ha−1 biochar, and the highest NUE value (46.3%) was reached with 204 kg N ha−1 N of fertilizer blended with 30 t ha−1 of biochar. According to structural equation modeling, the beneficial effects of N fertilizer and biochar on the plant biomass of maize were attributed to the direct effects related to soil chemical properties and plant growth parameters. In conclusion, N fertilizer combined with biochar application is an effective strategy to enhance the utilization of N fertilizer and crop production for maize by increasing soil fertility, improving plant crop uptake and promoting plant growth.

QTL analysis for nitrogen use efficiency in wheat (Triticum aestivum L.)

The genetic architecture of nitrogen use efficiency (NUE) and its two component traits i.e. NUpE (N uptake efficiency) and NUtE (N utilization efficiency) was studied using a bi-parental RIL mapping population derived from a cross HUW468 (high NUE)/C306 (low NUE). The mapping population, two parental genotypes and three check genotypes were evaluated under four different N levels (0, 60, 120, and 180 kg/ha) over three years. A genetic map containing 456 SNP markers (2571.38 cM length) was used for QTL analysis. Thirty six main effect QTLs (17 QTLs for NUE, 13 NUpE and 6 QTLs for NUtE) distributed on 12 chromosomes (1B, 1D, 2A, 2B, 3A, 4B, 5A, 5B, 5D, 6A, 6D, and 7A) were identified at 2.52–9.27 LOD scores. Individual QTLs explained 6.65–22.89% phenotypic variation. Multi-traits QTLs (Mt-QTLs) and epistatic QTLs involving first-order epistatic (QTL × QTL) interactions were also discovered. Candidate genes (CGs, as many as 737) were mined from QTL regions which were mainly involved in metabolic process, cellular process and catalytic activity, etc.; differential expression was observed for 49 CGs in roots and 34 in shoots. The CGs encoded important transcription factors, transporters, etc. having a role in NUE. QTLs and CGs reported in this study enriched the available knowledge. Seven QTLs (including three Mt-QTLs) and QTLs involved in six epistatic interactions are recommended for MAS for improvement of NUE in wheat.

Maize yield as affected by the interaction of fertilizer nitrogen and phosphorus in the Guinea savanna of Nigeria

The soils of the Nigeria savannas are particularly low in nitrogen (N) and phosphorus (P) and negatively affects maize productivity. The main objective of the study was to evaluate the interactive effect of N and P fertilizers on maize growth, grain yield, nitrogen uptake and N use efficiency. Field experiments were conducted during the 2015 and 2016 cropping seasons at Iburu in southern Guinea and Zaria in northern Guinea savanna zones of Nigeria. The treatments consisted of three levels of nitrogen (0, 60, and 120 kg N ha−1) and three levels of phosphorus (0, 13, and 26 kg P ha−1). The experimental design consisted of three replications in a split-plot design, with N as the main plot and P as the subplot. Our results show that the response of maize to N depends on the application of P. Higher yields were obtained with the combined application of 120 kg N ha−1 and 26 kg P ha−1 in both locations. With no P applied, plant N uptake (PNU) was greater at N rate of 120 kg ha−1 at Iburu while in Zaria, it increases with increase in N from 0 to 60 kg ha−1. When P was applied at 13 kg ha−1, the PNU increased by 52 and 66% at Iburu while in Zaria the increases were 51 and 57% each with N application of 60 and 120 kg ha−1, respectively, compared with zero N rate. The values for N recovery efficiency (NRE) and agronomic efficiency (AE) were lower for N rate of 120 than for 60 kg ha−1 irrespective of P application rate at both locations. The N utilization efficiency (NUTE) however was higher at 120 N kg ha−1 under 26 kg P ha−1across locations. It can be concluded from these results that in low fertile soils environments such as the Nigeria savannas, N fertilizer should be applied along with P fertilizer for optimum growth, grain yield and nitrogen use efficiency of maize.

Simultaneously genetic selection of wheat yield and grain protein quality in rice-wheat and soybean-wheat cropping systems through critical nitrogen efficiency-related traits.

Analyzing the contribution of nitrogen (N) uptake and its utilization in grain yield and protein quality-related traits in rice-wheat (RW) and soybean-wheat (SW) cropping systems is essential for simultaneous improvements in the two target traits. A field experiment with nine wheat genotypes was conducted in 2018–19 and 2019–20 cropping years to investigate N uptake and utilization-related traits associated with high wheat yield and good protein quality. Results showed that N uptake efficiency (NUpE) in the RW cropping system and N utilization efficiency (NUtE) in the SW cropping system explained 77.6 and 65.2% of yield variation, respectively, due to the contribution of fertile spikes and grain number per spike to grain yield varied depending on soil water and N availability in the two rotation systems. Lower grain protein content in the RW cropping system in comparison to the SW cropping system was mainly related to lower individual N accumulation at maturity, resulting from higher fertile spikes, rather than N harvest index (NHI). However, NHI in the SW cropping system accounted for greater variation in grain protein content. Both gluten index and post-anthesis N uptake were mainly affected by genotype, and low gluten index caused by high post-anthesis N uptake may be related to the simultaneous increase in kernel weight. N remobilization process associated with gluten quality was driven by increased sink N demand resulting from high grain number per unit area in the RW cropping system; confinement of low sink N demand and source capability resulted in low grain number per spike and water deficit limiting photosynthesis of flag leaf in the SW cropping system. CY-25 obtained high yield and wet gluten content at the expense of gluten index in the two wheat cropping systems, due to low plant height and high post-anthesis N uptake and kernel weight. From these results, we concluded that plant height, kernel weight, and post-anthesis N uptake were the critically agronomic and NUE-related traits for simultaneous selection of grain yield and protein quality. Our research results provided useful guidelines for improving both grain yield and protein quality by identifying desirable N-efficient genotypes in the two rotation systems.

A Decreased Nitrogen Rate with Increased Planting Density Facilitated Better Palatability of Conventional japonica Rice at High Yield Levels

A decreased nitrogen (N) rate with increased planting density (DNID) is recommended as a feasible method to maintain rice grain yield and N-utilization efficiency. However, it is still unclear whether DNID could improve grain quality, particularly the edible quality of rice. Three high-yield rice with superior palatability (HYSP) and three high-yield rice with inferior palatability (HYIP) were grown under DNID and local cultivation practices (LCP) in the same paddy fields during the 2018 and 2019 rice planting seasons. HYSP exhibited similar grain yields to HYIP under both cultivation treatments. HYSP had more spikelets per m2 through panicles per m2, while having lower spikelets per panicle and 1000-kernel weight than HYIP. DNID increased panicles per m2 and 1000-kernel weight and decreased spikelets per panicle of HYSP and HYIP compared with LCP. HYSP exhibited more biomass accumulation during heading to maturity under NDID and LCP (p < 0.05), which is supported by a higher leaf area index (LAI) and SPAD values after heading. DNID reduced shoot biomass weight and non-structural carbohydrate, while increasing harvest index and NSC remobilization reserve, especially for HYSP (p < 0.05). HYSP had a higher amylopectin content, total starch content, gel consistency, stickiness, and overall palatability (p < 0.05), while it had a lower hardness (p < 0.05) than HYIP. Compared with LCP, DNID increased the amylose content, amylopectin content, total starch content, gel consistency, stickiness, and overall palatability, while it decreased grain protein content and hardness of HYSP and HYIP. HYSP showed consistently higher peak viscosity, breakdown, and gelatinization temperatures (p < 0.05), while it showed lower setback (p < 0.05) than HYIP. For HYSP and HYIP, DNID increased the peak viscosity, breakdown, and gelatinization temperatures (p < 0.05), while it decreased the setback compared with LCP. Generally, the results indicated that coordinated yield components, more post-heading biomass accumulation, lower amylose content, higher peak viscosity and breakdown with lower setback, and higher gelatinization temperatures facilitated high-level grain yield and excellent cooked rice palatability of HYSP. DNID is a feasible method to maintain rice grain yield and enhance the quality of cooked rice for edible properties.