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Maize (Zea mays L.), a multi-utility cereal crop, has a high requirement for nitrogen (N). However, conventional N application methods fail to achieve potential yield and contribute to environmental pollution. Thus, a 2-year (2022 and 2023) field investigation was conducted to understand the effect of sub-surface drip-fertigation (SSDF) and legume residue incorporation (3 t ha−1) on improving maize yield, uptake, remobilization, and use-efficiency of N. Four N levels, viz., 0, 50, 75, and 100% recommended dose of N (RDN) applied in 3-splits (3S) and 4-splits (4S), were compared with conventional maize cultivation, fertilized with 150 kg N ha−1 (CMC-N150). Variable N fertigation with SSDF significantly affected the dry matter (DM) and N remobilization from leaves towards kernel; at lower doses of N maize tended to mobilize higher DM and N towards kernel. Better growth, higher nutrient uptake, and better remobilization efficiency of DM/N led to higher grain yield under 75% RDN (19–23% increase) and 100% RDN (20–25% increase) sub-surface drip-fertigated, compared to CMC-N150. Using 50% RDN through SSDF yielded grain on par with CMC-N150, thus saving 50% N. Moreover, applying N in 4-splits (4S) gave 3–5% yield advantage over 3-splits. Partial factor productivity of N (PFPN) and agronomic N-use efficiency (AEN) of different SSDF treatments increased by 18–100% and 40–99%, respectively over CMC-N150. Greengram residue incorporation improved maize yield by 5–8%, PFPN by 4–5% over no-residue incorporation. Overall, there was a 25–50% N economy with concomitant yield improvement under SSDF over conventional N management. The SSDF coupled with legume residue incorporation could be a promising technology for enhancing N-use efficiency globally; however, it needs policy support for adoption in the producer's field. [ABSTRACT FROM AUTHOR]

The production of huge amounts of biogas slurry during livestock breeding has resulted in pressing environmental issues. Although paddy fields can be potential sinks for the disposal of biogas slurry, the impacts of biogas slurry on rice production, grain quality, and relevant environmental risks in the Yangtze Delta region remain unclear. Herein, we conducted a field trial from 2021 to 2023 which involved different gradients of biogas slurry utilization, including CK (no fertilizer), CN (100% chemical nitrogen (N) of 240 kg ha−1), NBS (biogas slurry replacing 50% chemical N), BS1 (replacing 100% chemical N), BS1.5 (replacing 150% chemical N), and BS2 (replacing 200% chemical N). The results showed that there were no significant differences in average rice yields between CN, NBS, BS1.5, and BS2 over the three-year study period, with an average yield of 8283 kg ha−1, and the average yields of BS1 and CK were 7815 kg ha−1 and 6236 kg ha−1, respectively. However, heavy utilization of biogas slurry (BS1.5 and BS2) not only significantly reduced the rice seed-setting rate, the 1000-grain weight, and the processing quality, but also significantly increased the protein, amylose, Cu, and Zn content in rice grains; additionally, higher N losses occurred via surface water and increased NH3 volatilization was observed, finally resulting in lower nitrogen-use efficiency. Meanwhile, moderate utilization of biogas slurry (NBS and BS1) led to better rice quality and nitrogen-use efficiency, lower potential food safety risk, and N loss. Further, compared to BS1, NBS showed higher yield, harvest index, processing quality, gel consistency, palatability scores, and nitrogen-use efficiency, but lower N losses were present. Overall, the NBS treatment balanced the agronomic benefits and environmental risks in the Yangtze River Delta region. In the future, more attention should be paid to food safety and environmental risks when using biogas slurry. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Pistachio hull (PH), a rich source of tannin, may interact with nitrogen (N) and affect N metabolism in dairy cows. This investigation aimed to assess the effects of feeding PH and two N sources (soybean meal: SBM or slow-release urea: SRU) on milk production, digestibility, and N metabolism in lactating dairy cows. The study utilized a 4 × 4 Latin square design with 12 Holstein dairy cows (body weight = 611 ± 39 kg; 84 ± 14 days in milk; 45.6 ± 5.3 kg/d milk), with treatments arranged in a 2 × 2 factorial configuration. The main factors were (1) the tannin source [without or with dried PH included at 76.5 g/kg of diet DM] and (2) two N sources [SBM vs. SRU]. Crude protein and total phenolic and tannin contents were greater, but NDF was lower in PH than in sugar beet pulp. Feeding diets containing 7.65% PH resulted in reductions in milk yield, milk urea N, and milk efficiency but milk fat and protein concentration increased. Milk yield was similar between SBM and SRU. Feeding PH in replacement to sugar beet pulp did not interact with N sources, except for feed intake, as the PH + SRU diet tended to decrease feed intake (P = 0.09). Feeding PH was also associated with decreased dry matter, crude protein, and NDF digestibility. Dry matter digestibility decreased when a portion of SBM was replaced by SRU. Feeding PH in replacement to sugar beet pulp lowered ruminal ammonia-N concentration and increased acetate-to-propionate proportion. Feeding PH vs. sugar beet pulp had no effect on N intake and N excretion in urine and milk, but it increased the amount of N excretion in feces and decreased apparent N efficiency (milk N/N intake). Alanine aminotransferase was lower in cows fed SRU only in PH- but not sugar beet pulp-containing diets. Blood creatinine was lower when SRU was included in the PH-containing diet, but the opposite was observed in diets containing sugar beet pulp. Feeding PH instead of sugar beet pulp did not affect blood urea-N but resulted in lower glucose and aspartate aminotransferase concentrations. Overall, cows fed PH in replacement to sugar beet pulp were less efficient in converting feed nutrients into milk production, likely because of its negative effect on nutrient digestion. Partial replacement of SBM with SRU had no influence on lactation productivity and urea-N concentration in milk and blood. This may imply the suitability of SRU in providing a sustained supply of N in the rumen, likely qualifying it as a viable source of N to replace a portion of SBM in dairy diets. [ABSTRACT FROM AUTHOR]

Perennial biomass cropping systems are generally considered to be more environmentally friendly and sustainable compared to annual cropping systems, largely due to reduced input requirements. Nitrogen fertilizer is, by far, the most expensive input into perennial grass-based bioenergy systems, demanding research efforts focused on increasing nitrogen-use efficiency of biomass crops. The purpose of this study was to identify genetic variability for nitrogen-use efficiency and to determine if it is possible to identify genotypes that can produce high biomass yields without nitrogen fertilizer applications. A total of 83 half-sib families were grown in replicated paired plots on two different marginal soils. Paired plots consisted of 0 or 100 kg N ha−1, allowing for a highly precise computation of the direct impact of nitrogen fertilizer. There were strong genotype x location interactions, as well as strong genotype x nitrogen rate interactions at one of the two locations. For both locations, the direct response to nitrogen fertilization on biomass yield was strongly and negatively related to biomass yield without nitrogen fertilizer. Many families had high yield without fertilizer application, but also had non-significant responses to the fertilizer application. However, the ranking of these families was highly inconsistent between the two locations and soil types. These results suggested that certain families were likely responding to favorable associations with nitrogen-fixing microbes and that those associations were inconsistent between the two soil types. Development of new switchgrass cultivars that can form associations with nitrogen-fixing microbes should be conducted under conditions that favor such associations, strictly avoiding application of nitrogen fertilizers. [ABSTRACT FROM AUTHOR]

Biological nitrification inhibitors (BNIs) are released from plant roots and inhibit the nitrification activity of microorganisms in soils, reducing NO3‒ leaching and N2O emissions, and increasing nitrogen- use efficiency (NUE). Several recent studies have focused on the identification of new BNIs, yet little is known about the genetic loci that govern their biosynthesis and secretion. We applied a combined transcriptomic and metabolomic analysis to investigate possible biosynthetic pathways and transporters involved in the biosynthesis and release of BNI 1,9-decanediol (1,9-D), which was previously identified in rice root exudates. Our results linked four fatty acids, icosapentaenoic acid, linoleate, norlinolenic acid, and polyhydroxy-α,ω-divarboxylic acid, with 1,9-D biosynthesis and three transporter families, namely the ATP-binding cassette protein family, the multidrug and toxic compound extrusion family, and the major facilitator superfamily, with 1,9-D release from roots into the soil medium. Our finding provided candidates for further work on the genes implicated in the biosynthesis and secretion of 1,9-D and pinpoint genetic loci for crop breeding to improve NUE by enhancing 1,9-D secretion, with the potential to reduce NO3‒ leaching and N2O emissions from agricultural soils.

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.

The production of huge amounts of biogas slurry during livestock breeding has resulted in pressing environmental issues. Although paddy fields can be potential sinks for the disposal of biogas slurry, the impacts of biogas slurry on rice production, grain quality, and relevant environmental risks in the Yangtze Delta region remain unclear. Herein, we conducted a field trial from 2021 to 2023 which involved different gradients of biogas slurry utilization, including CK (no fertilizer), CN (100% chemical nitrogen (N) of 240 kg ha−1), NBS (biogas slurry replacing 50% chemical N), BS1 (replacing 100% chemical N), BS1.5 (replacing 150% chemical N), and BS2 (replacing 200% chemical N). The results showed that there were no significant differences in average rice yields between CN, NBS, BS1.5, and BS2 over the three-year study period, with an average yield of 8283 kg ha−1, and the average yields of BS1 and CK were 7815 kg ha−1 and 6236 kg ha−1, respectively. However, heavy utilization of biogas slurry (BS1.5 and BS2) not only significantly reduced the rice seed-setting rate, the 1000-grain weight, and the processing quality, but also significantly increased the protein, amylose, Cu, and Zn content in rice grains; additionally, higher N losses occurred via surface water and increased NH3 volatilization was observed, finally resulting in lower nitrogen-use efficiency. Meanwhile, moderate utilization of biogas slurry (NBS and BS1) led to better rice quality and nitrogen-use efficiency, lower potential food safety risk, and N loss. Further, compared to BS1, NBS showed higher yield, harvest index, processing quality, gel consistency, palatability scores, and nitrogen-use efficiency, but lower N losses were present. Overall, the NBS treatment balanced the agronomic benefits and environmental risks in the Yangtze River Delta region. In the future, more attention should be paid to food safety and environmental risks when using biogas slurry.

Biological nitrification inhibitors (BNIs) are released from plant roots and inhibit the nitrification activity of microorganisms in soils, reducing NO 3 ‒ leaching and N 2 O emissions, and increasing nitrogen- use efficiency (NUE). Several recent studies have focused on the identification of new BNIs, yet little is known about the genetic loci that govern their biosynthesis and secretion. We applied a combined transcriptomic and metabolomic analysis to investigate possible biosynthetic pathways and transporters involved in the biosynthesis and release of BNI 1,9-decanediol (1,9-D), which was previously identified in rice root exudates. Our results linked four fatty acids, icosapentaenoic acid, linoleate, norlinolenic acid, and polyhydroxy-α,ω-divarboxylic acid, with 1,9-D biosynthesis and three transporter families, namely the ATP-binding cassette protein family, the multidrug and toxic compound extrusion family, and the major facilitator superfamily, with 1,9-D release from roots into the soil medium. Our finding provided candidates for further work on the genes implicated in the biosynthesis and secretion of 1,9-D and pinpoint genetic loci for crop breeding to improve NUE by enhancing 1,9-D secretion, with the potential to reduce NO 3 ‒ leaching and N 2 O emissions from agricultural soils. [ABSTRACT FROM AUTHOR]

Polyaspartic acid (PASP) is widely used in agriculture owing to its role in promoting crop growth and nutrient absorption, and its effects are correlated with its molecular weight. In this study, a field soil column experiment using a 15N tracer was conducted to compare the effects of urea enhanced by PASPs with different molecular weights on wheat yield, nitrogen uptake by wheat, and nitrogen residue in the soil. The results showed that urea enhanced with PASPs (PASPUs) increased the wheat yield by 2.02–9.77% than conventional urea (CU) through enhancing the wheat spike number. PASPUs promoted wheat nitrogen uptake, and urea enhanced with PASPs of high molecular weight (>10 kDa) significantly promoted total nitrogen uptake, fertilizer–N uptake, and soil–N uptake by 9.92%, 4.65%, and 19.62%, respectively, compared with CU. PASPUs reduced fertilizer–N leaching by increasing its residue in the 30–60 cm soil layer and decreasing its amount in the 60–90 cm soil layer. A comprehensive evaluation based on radar charts showed that PASPs of high molecular weight showed a significant improvement in wheat yield and nitrogen–use efficiency, compared with CU and urea enhanced with other molecular weights, and is the most recommended PASP fraction for enhancing nitrogen utilization. [ABSTRACT FROM AUTHOR]

In crop species, nutrient deficiency severely damages plant growth and developmental processes, leading to end-yield penalties. Root architecture remodelling is considered a key factor underpinning nutrient-poor soil environments. Adequate nitrogen (N) supply can play a significant role in sustaining crop productivity on nutrient-deficient soils. However, excessive application of nitrogenous fertilizer may pollute the soil and increase the production cost for the growers. To tackle this problem, crop breeders have made tremendous efforts to improve the N-use efficiency of agricultural crops. This article summarizes the recent progress in identifying QTLs/genes, regulatory pathways, and hormonal crosstalk involved in the growth and development of legumes roots system. Moreover, we have described the progress in microbe–root symbiosis via QTLs/genes regulations, which results in improved N acquisition. Understanding the molecular mechanisms that regulate the root architecture in response to N availability may help to strengthen the root system of legumes and promote environmental friendly and sustainable agriculture. [ABSTRACT FROM AUTHOR]

Rising demand for protein-rich foods can impact N 2 O emissions from croplands. Recent research has pointed to the role of modified plant vasculature in grain protein increase. Here we highlight how discovering the mechanistic role of plant vasculature in protein improvement and nitrogen-use efficiency could reduce global N 2 O emissions. [ABSTRACT FROM AUTHOR]

A modern green revolution is needed to ensure global food security. Recently, Song et al. reported a new strategy to create high-yielding, semi-dwarf wheat varieties with improved nitrogen-use efficiency by inhibiting brassinosteroid (BR) signaling through clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein9 (Cas9)-mediated knockout of the ZnF-B gene encoding a zinc-finger RING-type E3 ligase. [ABSTRACT FROM AUTHOR]

Imbalanced nutrient fertilization adversely affects root growth and alters the nutrient use efficiency of a crop. This study aimed to understand the influence of integrated nutrient management on root characteristics and nitrogen use efficiency in the vegetable-based agroecosystem. The field trial was conducted at the Department of Soil Science and Water Management of Dr. Y S Parmar University of Horticulture and Forestry Nauni, Solan (HP) India in 2019 and 2020. There were nine treatments viz. T1- control, T2-100% farmyard manure (FYM; N equivalent basis), T3-100% N, T4-100% NP, T5-100% NK, T6-100% PK, T7-100% NPK, T8-100% NPK + FYM (recommended practice), and T9-150% NPK + FYM on root densities (mass, volume, and length) and N use efficiency of cauliflower and capsicum. The results observed that different treatments exert significant effects on measured as well as derivative parameters. In detail, the application of 150% NPK + FYM recorded significantly higher root-mass density (0.72 and 1.71 g m−3 × 10−3), root-volume density (4.49 and 2.52 m3 m−3 × 10−3), and root-length density (1.21 and 0.81 cm m−3 × 10−4) in cauliflower and capsicum, respectively, which was statistically at par with treatment T9 (100% NPK + FYM). Similarly, this treatment (150% NPK + FYM) resulted in a maximum positive N (774.6 kg ha−1), P (650.4 kg ha−1), and K (334.9 kg ha−1) balance of soil after the complete harvest of two cropping-sequence cycles. However, maximum agronomic N use efficiency (59.9 and 67.9 kg kg−1) and apparent recovery of N (39.3 and 59.7%) were recorded under 100% FYM (N equivalence) in cauliflower and capsicum, respectively, but this treatment produced the negative N balance (−91.7 kg ha−1) and K (−340.3 kg ha−1) in soil, whereas significant improvement in agronomic use efficiency, apparent recovery of applied N, as well as in soil, and the NPK balance was recorded under 100% NPK + FYM over the other treatment. This study recommended an integrated nutrient module that is the application of 100% NPK + FYM to ensure better root growth and positive nutrient balance in the soil. [ABSTRACT FROM AUTHOR]

Improving plant nitrogen-use efficiency (NUE) has great significance for various crops, particularly in hybrid breeding. Reducing nitrogen inputs is key to achieving sustainable rice production and mitigating environmental problems. In this study, we analyzed the transcriptomic and physiological changes in two indica restorer lines (Nanhui511 [NH511] and Minghui23 [MH23]) under high nitrogen (HN) and low nitrogen (LN) conditions. Compared to MH23, NH511 was more sensitive to different nitrogen supplies and exhibited higher nitrogen uptake and NUE under HN conditions by increasing lateral root and tiller numbers in the seedling and maturation stages, respectively. NH511 also exhibited a lower survival rate than MH23 when planted in a chlorate-containing hydroponic solution, indicating its HN uptake ability under different nitrogen-supply conditions. Transcriptomic analysis showed that NH511 has 2456 differentially expressed genes, whereas MH23 had only 266. Furthermore, these genes related to nitrogen utilization showed differential expression in NH511 under HN conditions, while the opposite was observed in MH23. Our findings revealed that NH511 could be regarded as elite rice and used for breeding high-NUE restorer lines by regulating and integrating nitrogen-utilization genes, which provides novel insights for the cultivation of high-NUE hybrid rice. [ABSTRACT FROM AUTHOR]

Nitrogen (N) is essential for sustaining life on Earth and plays a vital role in plant growth and thus agricultural production. The excessive use of N fertilizers not only harms the economy, but also the environment. In the context of the environmental impacts caused by agriculture, global maize improvement programs aim to develop cultivars with high N-use efficiency (NUE) to reduce the use of N fertilizers. Since N is highly mobile in plants, NUE is related to numerous little-known morphophysiological and molecular mechanisms. In this review paper we present an overview of the morpho-physiological adaptations of shoot and root, molecular mechanisms involved in plant response to low nitrogen environment, and the genetic effects involved in the control of key traits for NUE. Some studies show that the efficiency of cultivars growing under low N is related to deep root architecture, more lateral roots (LR), and sparser branching of LR, resulting in lower metabolic costs. The NUE cultivars also exhibit more efficient photosynthesis, which affects plant growth under suboptimal nitrogen conditions. In this sense, obtaining superior genotypes for NUE can be achieved with the exploitation of heterosis, as non-additive effects are more important in the expression of traits associated with NUE.

Nitrogen (N) in different forms has been demonstrated to play significant roles in plants. However, little is known about molybdenum (Mo) effects on N absorption and utilization in grapevine seedlings grown under different N sources. The present study used a sand culture system to analyze the impact of Mo application (0 μM; 1 μM) on N absorption and utilization in grapevine (Vitislabrusca × V. vinifera ‘Shine Muscat’ (rootstock 3309 m)) young potted seedlings under different N sources (NO3−, NH4NO3 and NH4+). The different N forms and Mo application significantly influenced dry matter accumulation, and root architecture and activity. The effects of Mo on total N content followed the order of (NH4NO3 > NO3− > NH4+). Moreover, Mo and N induced VvMOT1 and VvNRT1.1 expression synergistically. Mo supply altered the utilization of NO3−, NO2−, and NH4+ in grapevines under different N sources. NH4NO3 showed the highest effect while NH4+ the least. Furthermore, the 15N-labeling experiment showed that the 15N content in shoot and root and the 15N-use efficiency were the highest after Mo application under NH4NO3 source, indicating the synergistic effects of Mo with the co-application of NO3− and NH4+ sources. The study’s findings provide insights on Mo and N fertilizer utilization for cultivation and production practices in fruits.

Sesame is mainly cultivated under traditional, low-input agro-systems. Recent breeding developments promoted the modernization and mechanization of sesame cultivation. However, only a few articles have been published concerning fertilization requirements for both modern and traditional agro-systems. In field trials at two locations, we determined the response of irrigated sesame to nitrogen (N). Three promising sesame lines were tested combining two irrigation levels with four N levels. At a high irrigation level, N had a significant effect on growth, branching, and consequently, seed yield exceeding two-ton ha−1. A high N doze was accompanied by a decrease in the photosynthetic rate and leaf water potential. The δ13C confirmed lower stomatal conductance under high N treatments. Under deficit irrigation, the N level had a minor effect on the monitored parameters, indicating N fertilization was not efficient. Seed oil content was negatively correlated with seed N concentration. Our results question the necessity of N application when water is limited, as N fertilization promotes vigorous development that rapidly depletes soil water. Thus, water availability should be considered when developing an N management strategy. For high-yielding agro-systems, roughly 80–120 ​kg ​ha−1 N is required for optimal yield, bearing in mind the negative association between seed-N and oil content.

● The Green Revolution broadened the trade-off between yield and nitrogen-use efficiency. ● Root developmental and metabolic adaptations to nitrogen availability. ● Mechanisms of nitrogen uptake and assimilation have been extensively studied. ● Modulating plant growth-metabolic coordination improves nitrogen-use efficiency in crops. The Green Revolution of the 1960s boosted crop yields in part through widespread production of semidwarf plant cultivars and extensive use of mineral fertilizers. The beneficial semidwarfism of cereal Green Revolution cultivars is due to the accumulation of plant growth-repressing DELLA proteins, which increases lodging resistance but requires a high-nitrogen fertilizer to obtain high yield. Given that environmentally degrading fertilizer use underpins current worldwide crop production, future agricultural sustainability needs a sustainable Green Revolution through reducing N fertilizer use while boosting grain yield above what is currently achievable. Despite a great deal of research efforts, only a few genes have been demonstrated to improve N-use efficiency in crops. The molecular mechanisms underlying the coordination between plant growth and N metabolism is still not fully understood, thus preventing significant improvement. Recent advances of how plants sense, capture and respond to varying N supply in model plants have shed light on how to improve sustainable productivity in agriculture. This review focuses on the current understanding of root developmental and metabolic adaptations to N availability, and discuss the potential approaches to improve N-use efficiency in high-yielding cereal crops.

Applications of plant growth regulators such as paclobutrazol (PAC) to grain maize frequently caused depressions in grain yield. This negative impact probably originated from treatments at an early growth stage during plant ontogenesis when the determination of potential kernel number coincided with time of regulator application. However, stability of grain yield itself is of high relevance, and it is also the key determinant for harvest index (HI) and the use efficiencies of water (WUE) and nutrients (NUE). Therefore, in a container experiment, the effect of delayed PAC application at growth stage V8 was tested with the maize (Zea mays L.) cultivars Galactus and Fabregas. Immediately after PAC treatment, differential N fertilization was introduced in order to meet the demand of the control plants (100% N), and with a supply of 75% N. With late PAC application (V8), grain yield depressions could not only successfully be avoided; moreover, in Galactus‐75%N, a significant increase in grain yield was achieved combined with an extended duration of pollen shed by 28%. Straw yield decreased less strongly after late compared with early PAC application, leading to small, but significant increases in HI for the maize plants with 75% N supply. An increase in PAC dosage combined with later application will certainly lead to stronger decreases in straw yield, but it will also enhance the risk for grain yield depressions, and thus, an overall stronger improvement of HI is uncertain. For the time around silking, remarkable improvements of WUEgrain by 18% were achieved after delayed PAC application to Galactus‐75%N. After PAC treatment, significant increases in nitrogen‐harvest index (NHI) and thus N partitioning to grain were achieved for Fabregas and for Galactus‐75%N. Although luxurious N consumption did not occur, late PAC application showed neither an effect on N‐utilization efficiency (NUtEgrain) nor on N‐uptake efficiency (NUpE). It can be concluded that it is a very complex task to achieve the right balance between PAC dosage, stability of grain yield and optimal N supply in order to avoid both, luxurious N consumption and N deficiency, and to achieve an improvement of NUtEgrain of maize plants. [ABSTRACT FROM AUTHOR]

Modern semi-dwarf rice varieties of the "Green Revolution" require a high supply of nitrogen (N) fertilizer to produce high yields. A better understanding of the interplay between N metabolism and plant developmental processes is required for improved N-use efficiency and agricultural sustainability. Here, we show that strigolactones (SLs) modulate root metabolic and developmental adaptations to low N availability for ensuring efficient uptake and translocation of available N. The key repressor DWARF 53 (D53) of the SL signaling pathway interacts with the transcription factor GROWTH-REGULATING FACTOR 4 (GRF4) and prevents GRF4 from binding to its target gene promoters. N limitation induces the accumulation of SLs, which in turn promotes SL-mediated degradation of D53, leading to the release of GRF4 and thus promoting the expression of genes associated with N metabolism. N limitation also induces degradation of the DELLA protein SLENDER RICE 1 (SLR1) in an D14- and D53-dependent manner, effectively releasing GRF4 from competitive inhibition caused by SLR1. Collectively, our findings reveal a previously unrecognized mechanism underlying SL and gibberellin crosstalk in response to N availability, advancing our understanding of plant growth–metabolic coordination and facilitating the design of the strategies for improving N-use efficiency in high-yield crops. Modern semi-dwarf rice varieties depend on a high nitrogen fertilizer supply to achieve high yields. A better understanding of nitrogen metabolic processes that respond to nitrogen supply is essential for improving nitrogen-use efficiency. This study reveals a novel mechanism underlying strigolactone and gibberellin crosstalk in metabolic adaptations to changes in nitrogen availability, which will facilitate the design of the strategies for improving nitrogen-use efficiency in rice. [ABSTRACT FROM AUTHOR]

Nitrogen (N) is essential for sustaining life on Earth and plays a vital role in plant growth and thus agricultural production. The excessive use of N fertilizers not only harms the economy, but also the environment. In the context of the environmental impacts caused by agriculture, global maize improvement programs aim to develop cultivars with high N-use efficiency (NUE) to reduce the use of N fertilizers. Since N is highly mobile in plants, NUE is related to numerous little-known morphophysiological and molecular mechanisms. In this review paper we present an overview of the morpho-physiological adaptations of shoot and root, molecular mechanisms involved in plant response to low nitrogen environment, and the genetic effects involved in the control of key traits for NUE. Some studies show that the efficiency of cultivars growing under low N is related to deep root architecture, more lateral roots (LR), and sparser branching of LR, resulting in lower metabolic costs. The NUE cultivars also exhibit more efficient photosynthesis, which affects plant growth under suboptimal nitrogen conditions. In this sense, obtaining superior genotypes for NUE can be achieved with the exploitation of heterosis, as non-additive effects are more important in the expression of traits associated with NUE. [ABSTRACT FROM AUTHOR]

BACKGROUND: Improving the nitrogen-use efficiency (NUE) of wheat can help mitigate the problems of poor soil fertility under dryland conditions. We conducted field experiments using three nitrogen (N) fertilization levels (0, 120, and 180 kg ha-1) applied to eight dryland wheat cultivars to assess NUE and its associated traits. RESULTS: The grain yield significantly increased with the improvement in variety, mainly as a result of a substantial increase in 1000-grain weight and harvest index. Modern wheat varieties have stabilized at an optimal plant height and exhibited improved performance in terms of NUE, partial N productivity, N harvest index, and grain protein content compared to older varieties. The NUE of wheat gradually increased with variety replacement. The net photosynthesis rate of the flag leaves in the filling stage improved with the year of cultivar release; Increasing soil-plant analysis development (SPAD) values of flag leaves in the flowering and filling stages were observed over time, with the flag leaves of modern varieties showing a high chlorophyll content in the filling stage. Additionally, the principal component analysis showed that the SPAD value, grain number per unit area, transpiration rate, leaf area, and grain protein content positively contributed to the clustering of the N180 and modern cultivars (from the 2000s to 2010s). CONCLUSION: Overall, high levels of N application did not significantly improve the NUE of wheat. However, modern wheat varieties can optimize N distribution, increase flag leaf photosynthetic capacity, and improve photosynthesis ability, thus enhancing NUE to achieve high yields under a suitable level of N supply. [ABSTRACT FROM AUTHOR]

It is critical for spring wheat (Triticum aestivum L.) production in the semi-arid Loess Plateau to understand the impact of nitrogen (N) fertilizer on changes in N metabolism, photosynthetic parameters, and their relationship with grain yield and quality. The photosynthetic capacity of flag leaves, dry matter accumulation, and N metabolite enzyme activities from anthesis to maturity were studied on a long-term fertilization trial under different N rates [0 kg ha−1(N1), 52.5 kg ha−1 (N2), 105 kg ha−1 (N3), 157.5 kg ha−1 (N4), and 210 kg ha−1 (N5)]. It was observed that N3 produced optimum total dry matter (5407 kg ha−1), 1000 grain weight (39.7 g), grain yield (2.64 t ha−1), and protein content (13.97%). Our results showed that N fertilization significantly increased photosynthetic parameters and N metabolite enzymes at all growth stages. Nitrogen harvest index, partial productivity factor, agronomic recovery efficiency, and nitrogen agronomic efficiency were decreased with increased N. Higher N rates (N3–N5) maintained higher photosynthetic capacity and dry matter accumulation and lower intercellular CO2 content. The N supply influenced NUE by improving photosynthetic properties. The N3 produced highest chlorophyll content, photosynthetic rate, stomatal conductance and transpiration rate, grain yield, grain protein, dry matter, grains weight, and N metabolite enzyme activities compared to the other rates (N1, N2, N4, and N5). Therefore, increasing N rates beyond the optimum quantity only promotes vegetative development and results in lower yields. [ABSTRACT FROM AUTHOR]

Polyaspartic acid (PASP) is widely used in agriculture owing to its role in promoting crop growth and nutrient absorption, and its effects are correlated with its molecular weight. In this study, a field soil column experiment using a 15N tracer was conducted to compare the effects of urea enhanced by PASPs with different molecular weights on wheat yield, nitrogen uptake by wheat, and nitrogen residue in the soil. The results showed that urea enhanced with PASPs (PASPUs) increased the wheat yield by 2.02–9.77% than conventional urea (CU) through enhancing the wheat spike number. PASPUs promoted wheat nitrogen uptake, and urea enhanced with PASPs of high molecular weight (>10 kDa) significantly promoted total nitrogen uptake, fertilizer–N uptake, and soil–N uptake by 9.92%, 4.65%, and 19.62%, respectively, compared with CU. PASPUs reduced fertilizer–N leaching by increasing its residue in the 30–60 cm soil layer and decreasing its amount in the 60–90 cm soil layer. A comprehensive evaluation based on radar charts showed that PASPs of high molecular weight showed a significant improvement in wheat yield and nitrogen–use efficiency, compared with CU and urea enhanced with other molecular weights, and is the most recommended PASP fraction for enhancing nitrogen utilization.

Agriculture is facing a massive increase in demand per hectare as a result of an ever-expanding population and environmental deterioration. While we have learned much about how environmental conditions and diseases impact crop yield, until recently considerably less was known concerning endogenous factors, including within-plant nutrient allocation. In this review, we discuss studies of source–sink interactions covering both fundamental research in model systems under controlled growth conditions and how the findings are being translated to crop plants in the field. In this respect we detail efforts aimed at improving and/or combining C 3 , C 4 , and CAM modes of photosynthesis, altering the chloroplastic electron transport chain, modulating photorespiration, adopting bacterial/algal carbon-concentrating mechanisms, and enhancing nitrogen- and water-use efficiencies. Moreover, we discuss how modulating TCA cycle activities and primary metabolism can result in increased rates of photosynthesis and outline the opportunities that evaluating natural variation in photosynthesis may afford. Although source, transport, and sink functions are all covered in this review, we focus on discussing source functions because the majority of research has been conducted in this field. Nevertheless, considerable recent evidence, alongside the evidence from classical studies, demonstrates that both transport and sink functions are also incredibly important determinants of yield. We thus describe recent evidence supporting this notion and suggest that future strategies for yield improvement should focus on combining improvements in each of these steps to approach yield optimization. In this review, we discuss studies of source–sink interactions in model systems under controlled growth conditions and how these findings are being translated to crop plants in the field. A significant number of recent studies show that source, transport and sink are all critical yield determinants. We categorise the various strategies used to optimise photosynthesis based on the main process in the plant, as well as the origin and outcome of the intervention and discuss the need to combine such strategies in order to achieve yield optimization. [ABSTRACT FROM AUTHOR]

The indispensable role of nitrogen fertilizer in ensuring world food security together with the severe threats it poses to the ecosystem makes the usage of nitrogen fertilizer a major challenge for sustainable agriculture. Genetic improvement of crops with high nitrogen-use efficiency (NUE) is one of the most feasible solutions for tackling this challenge. In the last two decades, extensive efforts toward dissecting the variation of NUE-related traits and the underlying genetic basis in different germplasms have been made, and a series of achievements have been obtained in crops, especially in rice. Here, we summarize the approaches used for genetic dissection of NUE and the functions of the causal genes in modulating NUE as well as their applications in NUE improvement in rice. Strategies for exploring the variants controlling NUE and breeding future crops with "less-input-more-output" for sustainable agriculture are also proposed. The Green Revolution not only boosted the world's crop production but also large-scale application of nitrogen fertilizers, which brought severe environmental problems. Improving nitrogen-use efficiency (NUE) is critical and urgent for sustainable agriculture. In this paper, the authors summarize the approaches for genetically dissecting NUE and modulating nitrogen utilization. They also provide prospects for comprehensive genomic dissection of NUE traits and strategies for high-NUE breeding. [ABSTRACT FROM AUTHOR]

Direct-seeded rice has the potential to address labor and water shortage problems, and avoid possible deleterious effects of puddling on sequence crops. However, the integrated effect of irrigation and nitrogen management on crop and water productivity is not well understood in alluvial soils of India. Therefore, a field study was conducted to evaluate different irrigation thresholds and N split applications on water use and productivity and N use efficiency in DSR. Treatments were established in a split-plot design with three replications. Main plots compared irrigation thresholds based on soil water tension: (i) 0 kPa; (ii) 10 kPa; (iii) 20 kPa; and (iv) 40/10 kPa). Sub plots evaluated N management practices: (i) no N application, (ii) 120 kg N ha−1 as three equal splits, and (iii) 120 kg N ha−1 as four equal splits. Irrigation at 0 and 10 kPa recorded the highest biomass accumulation which decreased by 10-16% with higher water stress. However, irrigation water productivity increased with an increase in water stress. Irrigation at 10 and 20 kPa combined with four N splits resulted in grain yield similar to when irrigation was applied at 0 kPa with three or four N splits. There was a saving of irrigation water up to 17 to 36%, 30 to 46% and 54- 61% with 10 kPa, 20 kPa, and 40/10 kPa, respectively. It was concluded that irrigation at 10 and 20 kPa, and four N splits were beneficial for increasing grain yield and water productivity of DSR. [ABSTRACT FROM AUTHOR]

Nitrogen (N) in different forms has been demonstrated to play significant roles in plants. However, little is known about molybdenum (Mo) effects on N absorption and utilization in grapevine seedlings grown under different N sources. The present study used a sand culture system to analyze the impact of Mo application (0 μM; 1 μM) on N absorption and utilization in grapevine (Vitislabrusca × V. vinifera 'Shine Muscat' (rootstock 3309 m)) young potted seedlings under different N sources (NO3−, NH4NO3 and NH4+). The different N forms and Mo application significantly influenced dry matter accumulation, and root architecture and activity. The effects of Mo on total N content followed the order of (NH4NO3 > NO3− > NH4+). Moreover, Mo and N induced VvMOT1 and VvNRT1.1 expression synergistically. Mo supply altered the utilization of NO3−, NO2−, and NH4+ in grapevines under different N sources. NH4NO3 showed the highest effect while NH4+ the least. Furthermore, the 15N-labeling experiment showed that the 15N content in shoot and root and the 15N-use efficiency were the highest after Mo application under NH4NO3 source, indicating the synergistic effects of Mo with the co-application of NO3− and NH4+ sources. The study's findings provide insights on Mo and N fertilizer utilization for cultivation and production practices in fruits. [ABSTRACT FROM AUTHOR]

Background: Excessive application of N fertilizer can inhibit plant growth, reduce N-use efficiency (NUE) and lead to production reduction. Watermelon is an important crop that often restricted by inappropriate N supply. The study aims to test whether grafting with bottle gourd rootstock can improve the NUE and growth performance of watermelon under reduced nitrate application and to clarify the underlying mechanism. Methods: Grafted (self-grafted and rootstock-grafted watermelon) and ungrafted (watermelon and bottle gourd) seedlings were treated separately with 9 mM (control) and 4 mM (reduced-nitrate) N concentrations for 18 days under hydroponic conditions. Results: The growth and NUE of bottle gourd rootstock-grafted watermelon seedlings increased under reduced-nitrate, while decreased slightly in self-grafted seedlings compared with the control. Rootstock-grafted plants had higher root morphological traits, NO3− accumulation, NR and GS activities, photosynthesis, and NUE traits than self-grafted plants under reduced-nitrate. Reduced-nitrate treatment significantly up-regulated the expression of nitrate transporter genes NRT1.5 and NRT2.1 and N metabolizing enzyme genes NR2, NR3, NiR, GS1 and GS2 in rootstock-grafted plants. Conclusion: Under reduced-nitrate treatment, grafted watermelon can make better use of the developed rootstock roots to increase the NO3− absorption and transportation to the shoot, so as to enhance the N metabolism potential and photosynthetic capacity of scions, and finally improve plant growth and NUE. The enhanced NO3− uptake and utilization of rootstock-grafted plants were regulated at the transcriptional level. Grafting with the bottle gourd rootstock may be beneficial to the efficient production of watermelon and economic application of N fertilizer. [ABSTRACT FROM AUTHOR]

It has been demonstrated that biochar has a great potential to reduce volatilisations of ammonia (NH3) from fertilised agricultural soils. While there have been several laboratory studies to demonstrate the effects of biochar on gaseous NH3 emissions, there is hardly any data on the influence of biochar amendments on NH3 volatilisations from the soils under a field environment. Modifying biochar or enriching it with nitrogen (N) may maximise its capacity to abate gaseous NH3 emissions from the soil. Three biochars, i.e. SAB, HPB, and KHB modified through post-pyrolysis treatment with sulphuric acid, hydrogen peroxide, and potassium hydroxide, respectively as well as two biochars enriched with either molten urea (URB) or ammonium nitrate (ANB), were used alongside the pristine biochar (PRB) for comparisons. The quantity of gaseous NH3 evolved from each the biochar amendments including their effects on the growth and yield of the Chinese cabbage plus selected soil chemical properties were evaluated through a field experiment. The control experiment consisted of urea applied alone. In comparison with the control, PRB, KHB, HPB, SAB, URB, and ANB amendments abated NH3 volatilisations from the soil by 44.18%, 45.91%, 63.23%, 65.62%, 72.66%, and 76.71%, respectively. Additionally, PRB, SAB, KHB, HPB, ANB, and URB amendments increased Chinese cabbage yields by 138.5%, 172.0%, 117.3%, 181.1%, 194.0%, and 181.1%, respectively in comparison with the control. The strong linear relationship (r2 = 0.97) between cumulative NH3 emissions and nitrogen use efficiencies indicates that biochar-induced reductions in emissions of gaseous NH3 concomitantly increased the use-efficiencies of the applied N. [ABSTRACT FROM AUTHOR]

Polymer-coated rock mineral fertiliser (RMF) has the potential to increase wheat growth and yield; however, its effect on grain protein concentration (GPC) and nitrogen-use efficiency (NUE) remains unclear. Therefore, we examined the efficacy of slow-release RMF combined with microbial consortium inoculant (MI) compared with inorganic fertiliser (IF) with or without the MI to explore their effects on wheat growth, NUE, GPC, grain protein yield and grain yield. The glasshouse experiment was conducted with three factors (fertiliser type (control, RMF and IF), fertiliser rate (0, 23 and 46 mg N kg−1 soil), and MI (with or without)) replicated four times and harvested twice (anthesis and maturity). The treatments were arranged in a randomised complete block design. NUE was higher in plants treated with RMF plus MI compared to IF (with or without MI), likely due to extensive root system, higher shoot N content (at anthesis and maturity) and grain N content in plants treated with RMF plus MI than IF. The application of RMF enhanced grain yield and GPC compared with IF. The grain yield increased due to more grains in RMF-treated than IF-treated plants. The RMF application increased N content in shoots at anthesis and maturity and grain N content, which increased GPC compared to IF-treated plants. RMF in combination with MI can be viewed as a practical approach to assist RMF in supplying nutrients to improve NUE, grain yield and GPC in wheat. [ABSTRACT FROM AUTHOR]

Studies of traits related to nitrogen (N)-use efficiency (NUE) in wheat cultivars are important for breeding N-efficient cultivars. Canopy structure has a major effect on NUE, as it determines the distribution of light and N. However, the mechanism by which canopy structure affects the distribution of light and N within the canopy remains unclear. The N-efficient winter wheat varieties YM49 and ZM27 and N-inefficient winter wheat varieties XN509 and AK58 were grown in the field under two N levels. Light transmittance was enhanced, and the leaf area index and photosynthetically active radiation were lower in the N-efficient cultivar population, which was characterized by moderately sized flag leaves, a low frequency of canopy leaf curling, a low light attenuation coefficient (KL), and high plant compactness. Reductions in the amount of shade increased the distribution of light and N resources to the middle and lower layers. The photosynthetic rate, transpiration rate, instant water-use efficiency, and canopy photosynthetic NUE were higher, N remobilization of the upper and middle canopy leaves was reduced, and the leaf N content was high in the N-efficient cultivars. A higher ratio of the N extinction coefficient (KN) to KL reflects the assimilation ability of the N-efficient winter wheat cultivars, resulting in improved canopy structure and distribution of light and N, higher 1000-grain weight and grain yield, and significantly increased light and NUE. An improved match between gradients of light and N in the leaf canopy promotes balanced C and N metabolism and reduces energy and nutrient losses. This should be a goal when breeding N-efficient wheat cultivars and implementing tillage regimes. [ABSTRACT FROM AUTHOR]

Sesame is mainly cultivated under traditional, low-input agro-systems. Recent breeding developments promoted the modernization and mechanization of sesame cultivation. However, only a few articles have been published concerning fertilization requirements for both modern and traditional agro-systems. In field trials at two locations, we determined the response of irrigated sesame to nitrogen (N). Three promising sesame lines were tested combining two irrigation levels with four N levels. At a high irrigation level, N had a significant effect on growth, branching, and consequently, seed yield exceeding two-ton ha-1. A high N doze was accompanied by a decrease in the photosynthetic rate and leaf water potential. The d13C confirmed lower stomatal conductance under high N treatments. Under deficit irrigation, the N level had a minor effect on the monitored parameters, indicating N fertilization was not efficient. Seed oil content was negatively correlated with seed N concentration. Our results question the necessity of N application when water is limited, as N fertilization promotes vigorous development that rapidly depletes soil water. Thus, water availability should be considered when developing an N management strategy. For high-yielding agro-systems, roughly 80-120 kg ha-1 N is required for optimal yield, bearing in mind the negative association between seed-N and oil content. [ABSTRACT FROM AUTHOR]

Nitrogen-use efficiency (NUE) in rice is a complex quantitative trait involved in multiple biological processes and agronomic traits; however, the genetic basis and regulatory network of NUE remain largely unknown. We constructed a high-resolution microarray-based genetic map for 261 recombinant inbred lines derived from two indica parents. Using 2,345 bin markers, comprehensive analyses of quantitative trait loci (QTLs) of seven key agronomic traits under two different N levels were performed. A total of 11 non-redundant QTLs for effective panicle number (EPN), 7 for grain number per panicle, 13 for thousand-grain weight, 2 for seed-setting percentage, 15 for plant height, 12 for panicle length, and 6 for grain yield per plant were identified. The QTL regions were as small as 512kb on average, and more than half spanned an interval smaller than 100kb. Using this advantage, we identified possible candidate genes of two major EPN-related QTLs. One QTL detected under both N levels possibly encodes a DELLA protein SLR1, which is known to regulate NUE, although the natural variations of this protein have not been reported. The other QTL detected only under a high N level could encode the transcription factor OsbZIP59. We also predicted the possible candidate genes for another three of the NUE-related QTLs. Our results provide a reference for improving NUE-related QTL cloning and promote our understanding of NUE regulation in indica rice. [ABSTRACT FROM AUTHOR]

Nitrogen fertiliser application can effectively increase the net primary productivity (NPP) of agriculture and grassland ecosystems. There is some long-term retention of nitrogen applied to soils, but much is lost to runoff, to in situ denitrification and to gaseous forms of nitrogen (such as NH3 and NOX). So it is particularly important to improve nitrogen-use efficiency through various ways. Therefore, the effects of the urea with urease inhibitor N-(n-butyl)thiophosphoric triamide (NBPT) or/and nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) on the NPP, NH3 and 15N recovery were researched on the alpine grassland ecosystem. The results showed that the addition NBPT to urea can significantly reduce the cumulative NH3 emission of urea-N compared with urea alone. The NBPT or DMPP addition to urea significantly increased the above-ground NPP and the economic efficiency. Urea added to NBPT or NBPT+DMPP could increase the 15N recovery rate of plant and soil (0-40 cm) by nearly 20%. The results indicated that urea combined with DMPP may be a good way to nitrogen fertiliser retention and reduction of NH3 emission for the alpine grassland of the northeast of the Qinghai-Tibet Plateau.

Due to the introduction of zero-till wheat in the Indo-Gangetic plains (IGP) in India, irrigation and fertilizer nitrogen (N) management needs to be modified from that followed under conventionally tilled fields. A field experiment was conducted to study the effect of irrigation and N levels on yield and N uptake by zero-till wheat, fertilizer N-use efficiency, and distribution of nitrate-N (NO3-N) in a soil profile under zero-till conditions in an acidic alluvial soil of the eastern IGP. The experiment was laid out in a split-plot design with four levels of irrigation as main plots (I0-no irrigation, rain-fed, I1-122 mm in one irrigation at 21 days after sowing (DAS), I2-263 mm in two irrigations at 21 and 42 DAS, and I3-386 mm in three irrigations at 21, 42, and 84 DAS) and 4 N levels [0 (N0), 60 (N1), 120 (N2), and 150 (N3) kg N ha−1] as subplots. Grain and straw yields were significantly higher at the irrigation level-I2 and 120 kg N ha−1-N2 over the control (I0 and N0) and were at par with the highest applied levels of irrigation and N (I3 and N3). The nitrogen uptake by wheat followed a trend similar to yield for irrigation levels; however, it increased significantly up to 150 kg N ha−1. After the harvest of wheat crop, more NO3-N was observed in the 60–90 cm subsurface soil layer than in the surface 0–15 cm and/or 15–30 cm and 30–60 cm subsurface soil layers. The highest NO3-N concentration was recorded in the treatment I2N2. Accumulation of NO3-N in the soil increased up to irrigation levels I2 and with increasing doses of fertilizer N application. Combined applications of irrigation and N had a positive and significant influence on agronomic efficiency (AE) and apparent N recovery (ANR) but had no significant effect on physiological efficiency (PE). This study suggests that an appropriate combination of irrigation and N levels in zero-till wheat can lead to not only high-yield levels and N-use efficiency but also adequately control NO3-N leaching under acidic alluvial soils in the eastern IGP.

Improving plant nitrogen-use efficiency (NUE) has great significance for various crops, particularly in hybrid breeding. Reducing nitrogen inputs is key to achieving sustainable rice production and mitigating environmental problems. In this study, we analyzed the transcriptomic and physiological changes in two indica restorer lines (Nanhui511 [NH511] and Minghui23 [MH23]) under high nitrogen (HN) and low nitrogen (LN) conditions. Compared to MH23, NH511 was more sensitive to different nitrogen supplies and exhibited higher nitrogen uptake and NUE under HN conditions by increasing lateral root and tiller numbers in the seedling and maturation stages, respectively. NH511 also exhibited a lower survival rate than MH23 when planted in a chlorate-containing hydroponic solution, indicating its HN uptake ability under different nitrogen-supply conditions. Transcriptomic analysis showed that NH511 has 2456 differentially expressed genes, whereas MH23 had only 266. Furthermore, these genes related to nitrogen utilization showed differential expression in NH511 under HN conditions, while the opposite was observed in MH23. Our findings revealed that NH511 could be regarded as elite rice and used for breeding high-NUE restorer lines by regulating and integrating nitrogen-utilization genes, which provides novel insights for the cultivation of high-NUE hybrid rice.

The Green Revolution allowed a large amount of nitrogen (N) fertilization to increase crop yield but has led to severe environmental pollution. Therefore, increasing the crop grain yield must be achieved without such considerable input of N fertilization. A large‐grain japonica rice cultivar, Akita 63, significantly increased grain yield and improved N‐use efficiency (NUE) for yield per amount of N absorbed by plants. This study found that the nonsense mutated GS3 gene, the gs3 allele of Akita 63, has a superior yield production with enlarged grain size. The gs3 allele increased the yield with improvements in harvest index and NUE for yields per plant N content by analyzing the near‐isogenic line of rice plants with a large grain (LG‐Notohikari), which was developed by introducing the gs3 allele of Akita 63 into normal‐grain japonica cultivar, Notohikari. Thus, the gs3 allele would be promising for further yield increase without additional large input of N fertilization in non‐gs3‐allele rice varieties. Highlight: The gs3 allele transfer from large‐grain japonica rice cultivar, Akita 63, into normal‐grain japonica rice cultivar, Notohikari, increases yield and improves nitrogen‐use efficiency. [ABSTRACT FROM AUTHOR]

Ratoon rice (RR) has been regarded as a labor-saving and beneficial production system. Nitrogen (N) surplus and reactive N losses (Nr losses) are effective environmental indicators used to evaluate the performance of N management. Few studies have assessed N surplus and Nr losses for Chinese RR. In this study, Chinese RR planting areas were divided into South China (SC), the southern part of East China (SEC), Central China (CC), the northern part of East China (NEC), and Southwest China (SW). N surplus and Nr losses were also calculated based on 782 studies using a quadratic model under optimized N management for the highest yield (OPT-yield), the highest N-use efficiency (NUE) (OPT-NUE), and the highest grain N uptake (OPT-N uptake). The RR yields in the five regions ranged from 9.98 to 13.59 t ha−1. The high-yield record was observed in SEC, while the low-yield record was observed in NEC. The highest and the lowest Nr losses were found in NEC and SC, respectively. N surplus was reduced, while the yield was maintained in SEC, CC, NEC, and SW under OPT-yield and OPT-N uptake, and N surplus and Nr losses were reduced in the five regions when targeting the highest NUE. Farmers should be encouraged to plant RR in SEC and CC. RR was also a good choice when N management measures were conducted in three other regions. To achieve a win–win situation for both yield and the environment, OPT-yield could serve to improve the N management of current conventional practices. [ABSTRACT FROM AUTHOR]

Simple Summary: We used light and confocal microscopy to visualize bacteria in leaf and bract cells of more than 30 species in 18 families of seed plants. We detected chemical exchanges between intracellular bacteria and plant cells. We found that endophytic bacteria that show evidence of the transfer of nitrogen to plants are present in non-photosynthetic cells of leaves and bracts of diverse plant species. Nitrogen transfer from bacteria was observed in epidermal cells, various filamentous and glandular trichomes, and other non-photosynthetic cells. The most efficient of the nitrogen-transfer endosymbioses were seen to involve glandular trichomes, as seen in hops (Humulus lupulus) and hemp (Cannabis sativa). Trichome chemistry is hypothesized to function to scavenge oxygen around bacteria to facilitate nitrogen fixation. We used light and confocal microscopy to visualize bacteria in leaf and bract cells of more than 30 species in 18 families of seed plants. Through histochemical analysis, we detected hormones (including ethylene and nitric oxide), superoxide, and nitrogenous chemicals (including nitric oxide and nitrate) around bacteria within plant cells. Bacteria were observed in epidermal cells, various filamentous and glandular trichomes, and other non-photosynthetic cells. Most notably, bacteria showing nitrate formation based on histochemical staining were present in glandular trichomes of some dicots (e.g., Humulus lupulus and Cannabis sativa). Glandular trichome chemistry is hypothesized to function to scavenge oxygen around bacteria and reduce oxidative damage to intracellular bacterial cells. Experiments to assess the differential absorption of isotopic nitrogen into plants suggest the assimilation of nitrogen into actively growing tissues of plants, where bacteria are most active and carbohydrates are more available. The leaf and bract cell endosymbiosis types outlined in this paper have not been previously reported and may be important in facilitating plant growth, development, oxidative stress resistance, and nutrient absorption into plants. It is unknown whether leaf and bract cell endosymbioses are significant in increasing the nitrogen content of plants. From the experiments that we conducted, it is impossible to know whether plant trichomes evolved specifically as organs for nitrogen fixation or if, instead, trichomes are structures in which bacteria easily colonize and where some casual nitrogen transfer may occur between bacteria and plant cells. It is likely that the endosymbioses seen in leaves and bracts are less efficient than those of root nodules of legumes in similar plants. However, the presence of endosymbioses that yield nitrate in plants could confer a reduced need for soil nitrogen and constitute increased nitrogen-use efficiency, even if the actual amount of nitrogen transferred to plant cells is small. More research is needed to evaluate the importance of nitrogen transfer within leaf and bract cells of plants. [ABSTRACT FROM AUTHOR]

Asian cultivated rice consists of two main subspecies, xian / indica (XI) and geng / japonica (GJ), and GJ accessions have significantly lower nitrogen-use efficiency (NUE) than XI accessions. In order to facilitate genetic improvement of NUE in GJ accessions, we conducted haplotype analysis of 14 cloned NUE genes using 36 rice germplasm accessions with high-quality reference genome and developed 18 intragenic markers for elite haplotypes, which were then used to evaluate NUE genes in another 41 genetically diverse germplasm accessions from 12 countries and 71 approved GJ cultivars from northern provinces of China. Our results show that elite haplotypes of 12 NUE genes are mainly existed in XI accessions, but few is distributed in GJ accessions. The number of elite haplotypes carried by an XI accession can reach 10, while that carried by a GJ accession is less than 3. Surprisingly, the elite haplotype of gene DEP1 is nearly fixed in approved GJ cultivars, and elite haplotypes of gene MYB61 and NGR5 have been introduced into some approved GJ cultivars. The developed intragenic markers for NUE genes and evaluated 77 genetically diverse rice accessions could be of great use in the improvement of NUE in GJ cultivars. [ABSTRACT FROM AUTHOR]

The yield and nitrogen use efficiency (NUE) of hybrid rice combinations are closely related to restorer line. Therefore, it is essential to evaluate the agronomic characteristics of restorer lines with high yield and high NUE (HYHN). However, it is unclear which restorer lines are HYHN, and neither have the common agronomic traits of the HYHN restorer lines been identified. Aiming to address this issue, we conducted two filed experiments using three nitrogen applications, which screened five HYHN restorer lines from 15 indica restorer lines. Yield, NUE and nutrient transportation of restorer lines with different yields and NUE types were examined. Yield and total nitrogen absorption in aboveground biomass (TNA) increased, whereas NUE for grain production decreased with increasing nitrogen application levels. The HYHN restorer lines had large spikelets and high weight per panicle that were significantly positively correlated with yield and NUE. Therefore, large sink potential may be beneficial for both yield and NUE. We further studied the differences in nutrient transportation to panicles between the HYHN and low yield and low NUE (LYLN) restorer lines and found that the former had a higher nitrogen absorption level and dry matter weight ratios of panicle in maturity. Moreover, the HYHN lines also had a higher root and neck-panicle node bleeding intensity per stem after heading and more developed vascular bundles of neck-panicle nodes and leaves than the LYLN lines, which could contribute to the transportation of nutrients from root to ground and from stem and leaf to spike. Therefore, the advantages of large sink potential of the HYHN restorer lines include large nutrient accumulation in and distribution to the panicles and smooth flow of nutrients along the transportation channels.

Abstract The Green Revolution allowed a large amount of nitrogen (N) fertilization to increase crop yield but has led to severe environmental pollution. Therefore, increasing the crop grain yield must be achieved without such considerable input of N fertilization. A large‐grain japonica rice cultivar, Akita 63, significantly increased grain yield and improved N‐use efficiency (NUE) for yield per amount of N absorbed by plants. This study found that the nonsense mutated GS3 gene, the gs3 allele of Akita 63, has a superior yield production with enlarged grain size. The gs3 allele increased the yield with improvements in harvest index and NUE for yields per plant N content by analyzing the near‐isogenic line of rice plants with a large grain (LG‐Notohikari), which was developed by introducing the gs3 allele of Akita 63 into normal‐grain japonica cultivar, Notohikari. Thus, the gs3 allele would be promising for further yield increase without additional large input of N fertilization in non‐gs3‐allele rice varieties.

Asian cultivated rice consists of two main subspecies, xian/indica (XI) and geng/japonica (GJ), and GJ accessions have significantly lower nitrogen-use efficiency (NUE) than XI accessions. In order to facilitate genetic improvement of NUE in GJ accessions, we conducted haplotype analysis of 14 cloned NUE genes using 36 rice germplasm accessions with high-quality reference genome and developed 18 intragenic markers for elite haplotypes, which were then used to evaluate NUE genes in another 41 genetically diverse germplasm accessions from 12 countries and 71 approved GJ cultivars from northern provinces of China. Our results show that elite haplotypes of 12 NUE genes are mainly existed in XI accessions, but few is distributed in GJ accessions. The number of elite haplotypes carried by an XI accession can reach 10, while that carried by a GJ accession is less than 3. Surprisingly, the elite haplotype of gene DEP1 is nearly fixed in approved GJ cultivars, and elite haplotypes of gene MYB61 and NGR5 have been introduced into some approved GJ cultivars. The developed intragenic markers for NUE genes and evaluated 77 genetically diverse rice accessions could be of great use in the improvement of NUE in GJ cultivars.