N Harvest Index 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.

Spring wheat nitrogen-use indicators responses to cropping sequence and nitrogen fertilization

ABSTRACT Spring wheat (Triticum aestivum L.) nitrogen-use efficiency (NUE) and recovery with nitrogen (N) fertilization rates in crop rotations need further exploration. The effect of cropping sequence and N fertilization rate were evaluated on spring wheat N concentration and uptake, N harvest index (NHI), N-use efficiency (NUE), and N recovery index (NRI) from 2012 to 2019 in the northern Great Plains, USA. Cropping sequences were conventional till spring wheat-fallow (CTWF), no-till spring wheat-fallow (NTWF), no-till spring wheat-pea (Pisum sativum L.) (NTWP), and no-till continuous spring wheat (NTCW), and N fertilization rates to spring wheat were 0, 50, 100, and 150 kg N ha−1. Straw N concentration and N uptake were greater for CTWF than NTWP and NTCW in 4 out of 8 years and increased with increased N fertilization rate. Grain N concentration and NHI varied with treatments and years. Grain N uptake was greater for CTWF and NTWF than NTWP and NTCW at most N fertilization rates and years. In contrast, NUE was greater for NTCW than CTWF and NTWF at all N fertilization rates in most years. The NRI was greater for NTWP or NTCW than CTWF or NTWF in most years. Increasing N fertilization rate increased grain N uptake for most cropping sequences in all years but had a variable effect on NUE and NRI. Although spring wheat N concentration and N uptake were superior for CTWF and NTWF, and NUE for NTCW, NTWP with 50 to 100 kg N ha−1 can be used to sustain grain yield, N uptake, NUE, and NRI.

Optimization of carbon and nitrogen partitioning in DP202216 maize hybrids

ContextThe photoassimilates and nitrogen (N) allocation in grain crops can be studied via the harvest index (HI) and the N harvest index (NHI). These two variables should be considered in breeding programs seeking more effective use of resources in maize (Zea mays L.) and other grain crops. Molecular biotechnology has emerged as a complement to improve not only maize grain yield but also resource utilization efficiency. A recent study reported a beneficial impact of increasing and extending the expression of a maize MADS-box transcription factor (zmm28) on the NHI. ObjectiveThis research aimed to further identify enhancements of C-N partitioning (HI, NHI) in DP202216 maize hybrids recognizing the main physiological and morphological traits associated to the C-N dynamics via in-season intra-canopy measurements. MethodsTwo DP202216 elite hybrids were evaluated with their respective wild-type (WT) controls during two field growing seasons under two N regimes. The N nutrition index (NNI), as crop N status, was quantified to avoid misinterpretations of the results. ResultsThe DP202216 trait showed, on average, a ∼6% increase in the HI with a concomitant positive impact of ∼9% in the NHI across hybrids, N regimes, and seasons. Those increases were consistent at different crop NNI. After accounting for the NNI, it was shown that the increases in both HI and NHI were supported by the accumulation of more N in leaves (mainly in both lower and middle sections of the canopy vertical profile) and more water-soluble carbohydrates (WSC) in stems before flowering, combined with more aggressive post-anthesis remobilization. ConclusionIn this study, it was shown an increase in the efficient use of crop resources in DP202216 hybrids with respect to their isogenic WT controls at similar NNI via increments in C and N partitioning (HI and NHI). ImplicationsThis physiological and morphological understanding of C- and N-related traits addressed the challenge of optimizing the effective use of resources in maize breeding programs. To better understand traits by management interactions with yield and yield stability, DP202216 hybrid evaluations across a broad range of commercially relevant N scenarios would be valuable.

Optimizing rice yield, quality and nutrient use efficiency through combined application of nitrogen and potassium.

Reasonable nitrogen (N) and potassium (K) application rates can effectively improve fertilizer use efficiency, rice yield and quality. A two-year field experiment was conducted with combined application of three N rates (135, 180, and 225 kg ha-1, denoted as N1-N3) and four K rates (0, 90, 135, and 180 kg ha-1, denoted as K0-K3) using super indica hybrid rice cultivar Yixiangyou (YXY) 2115 to explore the effects of co-application of N and K on rice growth and development. The results indicated that the combined application of N and K had significantly interactive effects on dry matter (DM) accumulation, nutrients absorption, N harvest index (NHI), K harvest index (KHI), spikelets per panicle and most rice quality indexes. The highest total DM accumulation (17998.17-19432.47 kg ha-1) at maturity stage was obtained under N3K2. The effect of co-application of N and K on nutrients absorption and utilization varied between the two years and within each year. The highest total N and K accumulations at maturity stage were observed under N3K1 and N3K2, respectively, while the highest N recovery efficiency (NRE) and K recovery efficiency (KRE) were observed under N1K3. High expression levels of N and K metabolism-related genes in rice grains were observed under N3K2 or N3K3, consistent with N and K uptake. Co-application of N and K increased rice yield significantly and the highest yield (6745.02-7010.27 kg ha-1) was obtained under N2K2. As more N was gradually applied, rice appearance quality improved but milling, cooking and eating quality decreased. Although appropriate application of K could improve rice milling, cooking and eating quality, it reduced appearance quality. The optimal milling, cooking and eating quality were obtained under N1K2, while the best appearance quality was obtained under N3K0. Overall, a combination of 135-210 kg ha-1 N and 115-137 kg ha-1 K application rates was recommended for achieving relatively higher yield and better quality in rice production.

Eco-friendly cellulose hydrogels as controlled release fertilizer for enhanced growth and yield of upland rice

The effect of urea-loaded cellulose hydrogel, a controlled-release fertilizer (CRF) on growth and yield of upland rice were investigated in upland rice. As with the initial research, nitrogen (N) treatments were applied as CRF treatments; T2H (30 kg N ha−1), T3H (60 kg N ha−1), T4H (90 kg N ha−1), T5H (120 kg N ha−1) and recommended dose of fertilizer (RDF) at 120 kg N ha−1 RDF (T6U) in split application and T1 (0 N) as control. Results from this study indicated that applying CRF at the optimum N rate, T4H resulted in maximum grain yield, increasing by 71%. The analysis of yield components revealed that higher grain yield in T4H CRF was associated with an increase in panicle number and number of grains per panicle. Maximum grain N uptake of 0.25 g kg−1 was also observed in T4H CRF. In addition, T4H CRF recorded the highest harvest index (HI) and N harvest index (NHI) of 45.5% and 67.9%, respectively. Application of T4H CRF also recorded the highest N use efficiency (NUE) and N agronomic efficiency (NAE), 52.6% and 12.8 kg kg−1, respectively. Observations show that CRF with only 75% N applied (T4H) in soil improved grain yield when compared to CRF with 100% N and 100% RDF in farmers’ conventional split application. This suggested that CRF with a moderate N application might produce the highest potential yield and improved N efficiencies while enhancing crop production and further increase in N supply did not increase yield and N efficiencies. The results suggest that the application of T4H CRF for upland rice would enhance HI, N efficiencies and improve the yield of upland rice. Also, all growth parameters and yield were positively influenced by the application of CRF as a basal dose compared to split application of conventional urea fertilizers.

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

Nitrogen balance and gap of a high yield tropical soybean crop under irrigation.

Nitrogen (N) is the most extracted and exported element by the soybean crop. In high yield tropical environments with irrigation, little is known about N accumulation in different soybean plant organs as well as the N balance. The objective of this study was to characterize soybean growth, N accumulation in plant organs, N balance, and N gap in a high yield tropical environment. This study was performed in a homogeneous field, in a soil with low organic matter, with 20kg ha-1 of N, under furrow fertilization. Evaluations were performed ten times, temporally distributed from emergence to senescence. The soybean cultivar used was 'RK7518 IPRO' and was sown with row spacing of 0.45m and a seeding rate of 300,000 plants ha-1. Plant N partition, N from the biological N fixation (BNF), grain yield, crop harvest index (HI), N harvest index (NHI) with and without root contribution were evaluated. Also, at the grain filling stage the N gap was evaluated from the soil by difference between whole plant accumulated N and the amount of N from BNF. The average grain yield was 6,470 kg ha-1 and leads to a negative partial balance of N of -33.4 and -42.8 kg[N] ha-1 with and without roots, respectively. The N gap from the soil was 231.7 kg[N] ha-1. It is recommended to adopt techniques that increase the efficiency of BNF and the soil N accumulation to balance these production systems in the medium to long term.

Improving Wheat Grain Yield and Nitrogen Use Efficiency by Optimizing the Fertigation Frequency Using Center Pivot Irrigation System

High efficient nitrogen (N) application method and proper N management strategies can further reduce the losses and enhance N use efficiency. Field experiments were conducted in the 2015–2016 and 2016–2017 growing seasons to evaluate the effects of four fertigation frequencies treatments (FT-1: all the topdressing N was applied at the jointing stage; FT-2: 67% and 33% of the topdressing N was applied at the jointing and filling stages; FT-3: 33%, 50% and 17% of the topdressing N was applied at the regreening, jointing and filling stages; FT-4: 33%, 33%, 17% and 17% of the topdressing N were applied at the regreening, jointing, anthesis and filling stages) on wheat yield, water use efficiency (WUE), partial productivity of N fertilizer (PFPN) and N harvest index (NHI). In addition, one-time topdressing by surface broadcasting at the jointing stage was set up as a control (BC-1). The results showed that FT-3 and FT-4 supplied sufficient NO3−-N in the 0–40 cm soil layer, which reduced the risk of soil NO3−-N leaching to the deeper layers. FT-4 had the highest grain yield, WUE, PFPN and NHI, with average values of 9153.4 kg ha−1, 2.1 kg m−3, 0.74 kg kg−1 and 31.3 kg kg−1, respectively, followed by these values corresponding to the FT-3 in two years. These findings suggest that topdressing N split with 3–4 times, that is to say applying approximately 16.7% of topdressing N in anthesis and filling stages, respectively by the center pivot fertigation method can significantly improve yield, WUE, PFPN and NHI.

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.

Grain yield, yield components and nitrogen economy of irrigated second-crop common Buckwheat (Fagopyrum esculentum Moench) in a cold-temperate region

Common buckwheat (Fagopyrum esculentum Moench) is a species with great nutritional value and promising to be cultivated as a second crop in irrigated fields of cold-temperate regions with short growing seasons. However, little information exists regarding the nitrogen (N) economy of common buckwheat as a second crop following a high-yielding winter cereal. This study aimed to quantify grain yield, its components, and the grain protein content, and to evaluate N economy processes such as the initial N use efficiency (INUE), the N uptake efficiency (NUptE), the N internal efficiency (NIE) for biomass and grain yield and the N harvest index (NHI) among different treatments of N availability at sowing in four site-year experiments of common buckwheat as a second crop in irrigated fields of the southwestern Pampas of Argentina. The variety Mancan, used in this study, lasted between 73 and 92 days (888–1073 °C days) from sowing to harvest. Grain yield was highly correlated with achene number but not with achene weight. Grain yield ranged from 405 to 2725 kg ha-1, with an interaction between treatments and experiments, with major differences among experiments and minor differences among N availability treatments. Relative N uptake was maximized at a higher value of N availability (160 kg N ha-1) than grain yield (50 kg N ha-1), associated with higher responses of N uptake, vegetative N uptake and grain protein content than grain yield to N availability. However, NUptE featured a negative response to N availability in all experiments. NHI was highly variable among experiments, ranged between 0.51 and 0.83 and was affected by N availability in only two experiments. NIE for biomass and grain yield were 80 kg kg-1 and 36 kg kg-1, respectively, which were lower than those of most cereals but higher than those of other non-cereal grain crops. A short crop cycle of the variety Mancan, an average grain yield of 1594 kg ha-1 among experiments in this study, a low N availability requirement to maximize grain yield and high values of NIE for biomass and for grain yield suggest that buckwheat is a promising species for second crop sowing in cold-temperate regions.

Improved Nitrogen Utilization of Faba Bean (Vicia faba L.) Roots and Plant Physiological Characteristics under the Combined Application of Organic and Inorganic Fertilizers

As one of the most important edible legumes worldwide, faba bean can be grown for grain, feed, vegetable, fertilizer, medicine and deep processing. In this study, experiments were designed to determine the combined effect of organic and inorganic fertilizers on the growth and development of faba bean. Dabaipi (a cultivar of Vicia faba L.) was used for the experiments. Five treatments with different ratios of organic nitrogen (N) to total N were applied, including 0% organic fertilizer (0% OF), 25% OF, 50% OF, 75% OF, 100% OF and 0% OF. Chemical urea was used as an inorganic fertilizer. The experimental results showed that 50% OF resulted in the highest faba bean yield, up to 10,337.39 and 13,595.7 kg ha−1 in 2018 and 2019, respectively. Compared with 0% OF, 50% OF increased the yield by 84.47% and 183.17%, respectively. The regression analysis showed that the yield could be maximized when ROT accounted for 51.1%. The 50% OF treatment significantly increased N accumulation in seeds, resulting in higher N partial factor productivity and N harvest index (NHI). N accumulation in green seeds and aboveground plant parts had a significantly positive linear correlation with the yield and NHI, respectively. The 50% OF treatment maintained appropriate N accumulation in vegetative organs and higher N accumulation in reproductive organs and whole plants. Compared to 0% OF, the 50% OF treatment increased the total nodule number per plant (52.5%), fresh nodule weight (55.8%), nitrate reductase activity (70.7%), glutamine synthetase (18.2%) and glutamate synthase activity (42.4%). Therefore, the combined application of 50% OF and 50% inorganic fertilizer can be recommended for faba bean cultivation. This study will provide a theoretical basis for high-yield cultivation of faba bean.

Retrospective study in U.S. commercial sorghum breeding: III. Nitrogen internal efficiency

AbstractRetrospective studies are critical to investigate changes in physiological traits related to nitrogen (N) uptake and yield formation. N is a key yield‐limiting nutrient in sorghum (Sorghum bicolor L. Moench), as in most crops, so improving its N internal efficiency (NIE, yield to N uptake ratio) could increase productivity and sustainability. Understanding changes in N efficiency across time linked to carbon (C) economy can provide insights for future breeding targets. This study aims to characterize N and C dynamics (via studying changes in water‐soluble carbohydrates, WSC) of 20 commercial U.S. sorghum hybrids released from 1963 to 2017. Field trials were conducted during the 2018 and 2019 growing seasons in Riley County, KS. Seasonal changes in biomass accumulation, N uptake, and WSC were characterized during both vegetative and reproductive periods. Modern hybrids had greater NIE compared with those from the 1960s. Overall, beyond the yield gain documented for modern sorghum hybrids, the NIE increased at the expense of a reduction in grain N and, in minor proportion, due to increase in the N harvest index (NHI) at maturity for newer relative to older hybrids. Newer hybrids evidenced greater N remobilization from the stover to the grains during the reproductive period. This study demonstrates the physiological mechanisms for an increase in N and C utilization behind yield genetic gain for sorghum hybrids. Future yield gain in sorghum could be pursued by enhancing N uptake to sustain further genetic progress.

Different organic material amendments effects soil nitrogen utilization and crop yield in the North China Plain

AbstractOrganic materials incorporation and nitrogen utilization are both important measures to enhance soil fertility and crop productivity. To evaluate the effect of different organic materials on soil N utilization and crop yield, three kinds of organic materials, including straw (ST), pig manure (PM), and biogas residue (BR), were incorporated into the soil with equal N in the wheat (Triticum aestivum L.)–maize (Zea mays L.) cropping system with chemical fertilizers (CFs) as a control in Wuqiao County in the North China Plain. The contents of soil N, nitrate N, ammonium N, N use efficiency, N partial productivity (NPFP), N uptake efficiency (NUPE), and N harvest index (NHI) were measured and calculated. The results of 2‐yr field trials suggested that, compared with CF, soil total N (TN) content of ST, PM, and BR treatment increased by 3.04, 8.99, and 9.10%, respectively. An even larger increase was found in nitrate N, which was 25.87, 44.67, and 44.93% in ST, PM, and BR, respectively. For N utilization, PM significantly increased NPFP, NUPE, and NHI by 4.01, 5.86, and 3.04%, respectively, meanwhile decreasing soil N dependency rate by 4.64%; BR improved NUPE by 5.15%, while ST showed little improvement in the utilization of soil N. Overall, organic materials promoted soil N maintenance and increased N utilization. Among the kinds of organic material amendment in the study, PM had a better performance in improving soil N utilization and crop yield than BR and crop ST return in field experiments.

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.

Allometric Characteristics of Rice Seedlings under Different Transplanted Hills and Row Spacing: Impacts on Nitrogen Use Efficiency and Yield.

The number of seedlings per hill and the configuration of plant row spacing are important management measures to improve rice yield. In the present study, we evaluated the impact of various seedlings per hill (1, 3, 6, and 9 seedlings hill−1) under four different rice verities (two conventional rice, two hybrid rice) on allometric characteristics, nitrogen use efficiency (NUE) and yield in 2020 at early and late season. Results showed that compared with nine seedlings per hill (wide row spacing), the number of effective panicles, yield, grain biomass allocation, grain-to-leaf ratio, grain nitrogen accumulation, nitrogen dry matter production efficiency (NDMPE), N harvest index (NHI) of 1 seedling per hill increased by 21.8%, 10.91%, 10.5%, 32.25%, 17.03%, 9.67%, 6.5%, respectively. With the increase of seedlings per hill and the expansion of row spacing, stem biomass (SB) and reproductive biomass (RB) increased with the increase of above-ground biomass, mainly showing the relationship of isometric growth. Leaf biomass (LB) increased with above-ground biomass, mainly showing the relationship of allometric growth. The results suggested that under the same basic seedlings, transplanting 1 seedling per hill and dense planting was the most beneficial to improve rice yield.

Interaction of Biochar with Chemical, Green and Biological Nitrogen Fertilizers on Nitrogen Use Efficiency Indices

Chemical nitrogen (N) fertilizers are regarded as one of the environmental contaminants in addition to the necessity for fossil sources for their production. Conversely, it is impossible to neglect the supply of nitrogen needed as one of the essential ingredients for plant function. For organic agriculture, it is crucial to use alternative fertilizer management to reduce the harmful impacts and production costs of chemical fertilizers. In a one-year pot experiment, nitrate (NO−3) leaching and nitrogen efficiency of wheat were examined in relation to biochar (B) mixed with urea (U), legume residues (L), and azocompost (A), which represent chemical, green, and biological sources of N-fertilizers, respectively. Control (no biochar, no fertilizer), U (46 kg ha−1), A (5 t ha−1), L (5 t ha−1), B (10 t ha−1), UB, AB, and LB were the experimental treatments. Grain yield of wheat was enhanced by 337% and 312% with UB and UL, respectively. The LB produced the highest grain N yield, with a rise of 8.8 times over the control. L had the highest N-use efficiency, with an increase of 149% over the control. The highest N-harvest index and N-recovery efficiency were obtained by using LB, with values of 91 and 70 %, respectively. Nitrate leaching occurred in the following order: U > Control ≥ A ≥ L > UB > AB ≥ LB > B. Nitrogen is retained for the plant in the extensive specific surface of biochar when N-fertilizers are used in conjunction with them. This not only improves N-efficiency but also minimizes nitrogen loss through leaching. Additionally, the soil can benefit from the addition of leguminous organic fertilizer in a similar way as to urea fertilizer in terms of increasing wheat grain yield, particularly when combined with biochar.

Natural 15N abundance as an indicator of nitrogen utilization efficiency in rice under alternate wetting and drying irrigation in soils with high clay contents

The 15N natural abundance is an effective indicator of nitrogen dynamics in plants. The impact of different irrigation regimes as a function of varied soil clay contents on stable nitrogen isotope abundance (δ15N) in rice remains unknown. Therefore, the response of δ15N and nitrogen utilization efficiency (NUE) of rice to different combinations of alternate wetting and drying irrigation (AWD) and clay contents were investigated. The study included three AWD regimes, viz. I100, (100 % saturation, 30 mm flooded), I90 (90 % saturation, 30 mm flooded) and I70 (70 % saturation, 30 mm flooded), and three soil clay content treatments, viz. 40 % (S40), 50 % (S50), and 60 % (S60) clay content. Compared with I100, I90 and I70 with high clay content (S60) significantly increased the crack volumes and N leaching losses and reduced the total N accumulation and different forms of NUE of rice plants. The values of δ15N in above-ground organs and soil were greatly increased by I90 and I70 irrigation regimes compared to I100. An increasing trend of organs δ15N from root to shoot was found for all three irrigation regimes. Significant negative relationships were found between (i) N partial factor productivity (PFP) and grain 15N, (ii) PFP and leaf 15N, and (iii) N harvest index (NHI) and leaf 15N. These significant negative relationships might contribute to the increased N losses and changed N allocation under AWD with high clay contents. Hence, it is suggested that cracks should be taken into consideration in rice cultivation. Moreover, δ15N may serve as an effective indicator of NUE in rice grown under AWD irrigation with high clay contents as well as an indirect indicator for assessing the N loss in agro-ecosystems.

Aeroponic evaluation identifies variation in Indian potato varieties for root morphology, nitrogen use efficiency parameters and yield traits

Nitrogen (N) is an essential nutrient for plant growth and tuber yield in potato. Its excess application is harmful for environment, and therefore dissecting traits involved in improving nitrogen use efficiency (NUE) and yield is essential to address them. This study was conducted to analyze variation in 56 Indian potato varieties at optimal N concentration (2 milli molar) under aeroponics for two years based on 17 different traits for root system architecture (length, surface area, diameter and volume), plant height, leaf area, root and shoot dry weight, tuber traits (number, yield and dry matter), and NUE parameters viz., NUE, agronomic NUE (AgNUE), nitrogen uptake efficiency (NUpE), nitrogen utilization efficiency (NUtE), harvest index (HI) and N harvest index (NHI). Significant differences (p < 0.05) were observed in the varieties for most traits under the investigation. The Agglomerative hierarchical clustering (AHC) analysis clearly distinguished the varieties into two main groups, and principal component analysis (PCA) analysis showed total 64.78% variability in the first two components. Significant and positive correlations were found for tuber yield with AgNUE, NUE and NUpE. On the other hand, top 10 promising varieties under aeroponics for above traits were Kufri Badshah, Kufri Frysona, Kufri Chipsona-3, Kufri Pushkar, Kufri Lalit, Kufri Ashoka, Kufri Sutlej, Kufri Jyoti, Kufri Mohan and Kufri Khyati. This study implies that a great variation exists in the Indian potato varieties including old and new categories and they can be exploited in breeding for increasing resource capture to improve NUE in potato.

TaNRT2.1-6B is a dual-affinity nitrate transporter contributing to nitrogen uptake in bread wheat under both nitrogen deficiency and sufficiency

Multiple nitrate transporter (NRT) genes exist in the genome of bread wheat, and it is of great importance to identify the elite NRT genes for N-efficient wheat cultivar breeding. A candidate gene association study (CGAS) of six N use efficiency (NUE) related traits (grain N concentration (GNC), straw N concentration (SNC), grain yield (GY), grain N accumulation (GNA), shoot total N accumulation (STN) and N harvest index (NHI)) was performed based on SNPs in 46 NRT2 genes using a panel composed of 286 wheat cultivars. CGAS identified TaNRT2.1-6B as an elite NRT gene that is significantly associated with four (NHI, SNC, GNA and GY) of the six NUE-related traits simultaneously. TaNRT2.1-6B is located on the plasma membrane and acts as a dual-affinity NRT. The overexpression of TaNRT2.1-6B increased the N influx and root growth of wheat, whereas gene silence lines resulted in the opposite effects. The overexpression of TaNRT2.1-6B also improved GY and N accumulation of wheat under either limited or sufficient N conditions. The data provide the TaNRT2.1-6B gene and the two associated SNP markers as promising powerful tools for breeding wheat cultivars with high N uptake ability and NUE.