Integrated assessment of yield,nitrogen use efficiency and ecosystem economic benefits of use of controlled-release and common urea in ratoon rice production

Controlled-release urea(CRU)is commonly used to improve the crop yield and nitrogen use efficiency(NUE).However,few studies have investigated the effects of CRU in the ratoon rice system.Ratoon rice is the practice of obtaining a second harvest from tillers originating from the stubble of the previously harvested main crop.In this study,a 2-year field experiment using a randomized complete block design was conducted to determine the effects of CRU on the yield,NUE,and economic benefits of ratoon rice,including the main crop,to provide a theoretical basis for fertilization of ratoon rice.The experiment included four treatments:(i)no N fertilizer(CK);(ii)traditional practice with 5 applications of urea applied at different crop growth stages by surface broadcasting(FFP);(iii)one-time basal application of CRU(BF1);and(iv)one-time basal application of CRU combined with common urea(BF2).The BF1 and BF2 treatments significantly increased the main crop yield by 17.47 and 15.99%in 2019,and by 17.91 and 16.44%in 2020,respectively,compared with FFP treatment.The BF2 treatment achieved similar yield of the ratoon crop to the FFP treatment,whereas the BF1 treatment significantly increased the yield of the ratoon crop by 14.81%in 2019 and 12.21%in 2020 compared with the FFP treatment.The BF1 and BF2 treatments significantly improved the 2-year apparent N recovery efficiency,agronomic NUE,and partial factor productivity of applied N by 11.47-16.66,27.31-44.49,and 9.23-15.60%,respectively,compared with FFP treatment.The BF1 and BF2 treatments reduced the chalky rice rate and chalkiness of main and ratoon crops relative to the FFP treatment.Furthermore,emergy analysis showed that the production efficiency of the BF treatments was higher than that of the FFP treatment.The BF treatments reduced labor input due to reduced fertilization times and improved the economic benefits of ratoon rice.Compared with the FFP treatment,the BF1 and BF2 treatments increased the net income by 14.21-16.87 and 23.76-25.96%,respectively.Overall,the one-time blending use of CRU and common urea should be encouraged to achieve high yield,high nitrogen use efficiency,and good quality of ratoon rice,which has low labor input and low apparent N loss.

Regulation effects of water and nitrogen on yield,water,and nitrogen use efficiency of wolfberry

Wolfberry(Lycium barbarum L.)is important for health care and ecological protection.However,it faces problems of low productivity and resource utilization during planting.Exploring reasonable models for water and nitrogen management is important for solving these problems.Based on field trials in 2021 and 2022,this study analyzed the effects of controlling soil water and nitrogen application levels on wolfberry height,stem diameter,crown width,yield,and water(WUE)and nitrogen use efficiency(NUE).The upper and lower limits of soil water were controlled by the percentage of soil water content to field water capacity(θ_(f)),and four water levels,i.e.,adequate irrigation(W0,75%-85%θ_(f)),mild water deficit(W1,65%-75%θ_(f)),moderate water deficit(W2,55%-65%θ_(f)),and severe water deficit(W3,45%-55%θ_(f))were used,and three nitrogen application levels,i.e.,no nitrogen(N0,0 kg/hm^(2)),low nitrogen(N1,150 kg/hm^(2)),medium nitrogen(N2,300 kg/hm^(2)),and high nitrogen(N3,450 kg/hm^(2))were implied.The results showed that irrigation and nitrogen application significantly affected plant height,stem diameter,and crown width of wolfberry at different growth stages(P<0.01),and their maximum values were observed in W1N2,W0N2,and W1N3 treatments.Dry weight per plant and yield of wolfberry first increased and then decreased with increasing nitrogen application under the same water treatment.Dry weight per hundred grains and dry weight percentage increased with increasing nitrogen application under W0 treatment.However,under other water treatments,the values first increased and then decreased with increasing nitrogen application.Yield and its component of wolfberry first increased and then decreased as water deficit increased under the same nitrogen treatment.Irrigation water use efficiency(IWUE,8.46 kg/(hm^(2)·mm)),WUE(6.83 kg/(hm^(2)·mm)),partial factor productivity of nitrogen(PFPN,2.56 kg/kg),and NUE(14.29 kg/kg)reached their highest values in W2N2,W1N2,W1N2,and W1N1 treatments.Results of principal component analysis(PCA)showed that yield,WUE,and NUE were better in W1N2 treatment,making it a suitable water and nitrogen management mode for the irrigation area of the Yellow River in the Gansu Province,China and similar planting areas.

Grain yield and nitrogen use efficiency of an ultrashort-duration variety grown under different nitrogen and seeding rates in direct-seeded and double-season rice in Central China

Nitrogen(N) and seeding rates are important factors affecting grain yield and N use efficiency(NUE) in directseeded rice. However, these factors have not been adequately investigated on direct-seeded and double-season rice(DDR) in Central China. The objective of this study was to evaluate the effects of various N and seeding rates on the grain yield and NUE of an ultrashort-duration variety grown under DDR. Field experiments were conducted in 2018 in Wuxue County and 2019 in Qichun County, Hubei Province, China with four N rates and three seeding rates.The results showed that the grain yield of the ultrashort-duration variety ranged from 6.32 to 8.23 t ha–1with a total growth duration of 85 to 97 days across all treatments with N application. Grain yield was increased significantly by N application in most cases, but seeding rate had an inconsistent effect on grain yield. Furthermore, the response of grain yield to the N rates was much higher than the response to seeding rates. The moderate N rates of 100–150 and 70–120 kg N ha–1in the early and late seasons, respectively, could fully express the yield potential of the ultrashort-duration variety grown under DDR. Remarkably higher N responses and agronomic NUE levels were achieved in the early-season rice compared with the late-season rice due to the difference in indigenous soil N supply capacity(INS) between the two seasons. Seasonal differences in INS and N response should be considered when crop management practices are optimized for achieving high grain yield and NUE in ultrashort-duration variety grown under DDR.

Carbon sequestration rate,nitrogen use efficiency and rice yield responses to long-term substitution of chemical fertilizer by organic manure in a rice–rice cropping system

Combined application of chemical fertilizers with organic amendments was recommended as a strategy for improving yield,soil carbon storage,and nutrient use efficiency.However,how the long-term substitution of chemical fertilizer with organic manure affects rice yield,carbon sequestration rate(CSR),and nitrogen use efficiency(NUE)while ensuring environmental safety remains unclear.This study assessed the long-term effect of substituting chemical fertilizer with organic manure on rice yield,CSR,and NUE.It also determined the optimum substitution ratio in the acidic soil of southern China.The treatments were:(i)NPK0,unfertilized control;(ii)NPK1,100%chemical nitrogen,phosphorus,and potassium fertilizer;(iii)NPKM1,70%chemical NPK fertilizer and 30%organic manure;(iv)NPKM2,50%chemical NPK fertilizer and 50%organic manure;and(v)NPKM3,30%chemical NPK fertilizer and 70%organic manure.Milk vetch and pig manure were sources of manure for early and late rice seasons,respectively.The result showed that SOC content was higher in NPKM1,NPKM2,and NPKM3 treatments than in NPK0 and NPK1 treatments.The carbon sequestration rate increased by 140,160,and 280%under NPKM1,NPKM2,and NPKM3 treatments,respectively,compared to NPK1 treatment.Grain yield was 86.1,93.1,93.6,and 96.5%higher under NPK1,NPKM1,NPKM2,and NPKM3 treatments,respectively,compared to NPK0 treatment.The NUE in NPKM1,NPKM2,and NPKM3 treatments was higher as compared to NPK1 treatment for both rice seasons.Redundancy analysis revealed close positive relationships of CSR with C input,total N,soil C:N ratio,catalase,and humic acids,whereas NUE was closely related to grain yield,grain N content,and phenol oxidase.Furthermore,CSR and NUE negatively correlated with humin acid and soil C:P and N:P ratios.The technique for order of preference by similarity to ideal solution(TOPSIS)showed that NPKM3 treatment was the optimum strategy for improving CSR and NUE.Therefore,substituting 70%of chemical fertilizer with organic manure could be the best management option for increasing CSR and NUE in the paddy fields of southern China.

Co-overexpression of genes for nitrogen transport, assimilation, and utilization boosts rice grain yield and nitrogen use efficiency

Nitrogen(N)fertilization is necessary for obtaining high rice yield.But excessive N fertilizer reduces rice plant N efficiency and causes negative effects such as environmental pollution.In this study,we assembled key genes involved in different nodes of N pathways to boost nitrate and ammonium uptake and assimilation,and to strengthen amino acid utilization to increase grain yield and nitrogen use efficiency(NUE)in rice.The combinations OsNPF8.9a×OsNR2,OsAMT1;2×OsGS1;2×OsAS1,and OsGS2×OsAS2×OsANT3 optimized nitrate assimilation,ammonium conversion,and N reutilization,respectively.In co-overexpressing rice lines obtained by co-transformation,the tiller number,biomass,and grain yield per plant of the OsAMT1;2×OsGS1;2×OsAS1-overexpressing line exceeded those of wild-type ZH11,the OsNPF8.9a×OsNR2×OsGS1;2×OsAS1-overexpressing line,and the OsGS2×OsAS2×OsANT3-overexpressing line.The glutamine synthase activity,free amino acids,and nitrogen utilization efficiency(NUt E)of the OsAMT1;2×OsGS1;2×OsAS1-overexpressing line exceeded those of ZH11 and other lines that combined key genes.N influx efficiency was increased in the OsAMT1;2×OsGS1;2×OsAS1-overexpressing line and OsNPF8.9a×OsNR2×OsGS1;2×OsAS1-overexpressing line under a low ammonium and a low nitrate treatment,respectively.We propose that combining overexpression of OsAMT1;2,OsGS1;2,and OsAS1 is a promising breeding strategy for systematically increasing rice grain yield and NUE by focusing on key nodes in the N pathway.

Grain yield,nitrogen use efficiency and physiological performance of indica/japonica hybrid rice in response to various nitrogen rates

Utilizing the heterosis of indica/japonica hybrid rice(IJHR)is an effective way to further increase rice grain yield.Rational application of nitrogen(N)fertilizer plays a very important role in using the heterosis of IJHR to achieve its great yield potential.However,the responses of the grain yield and N utilization of IJHR to N application rates and the underlying physiological mechanism remain elusive.The purpose of this study was to clarify these issues.Three rice cultivars currently used in rice production,an IJHR cultivar Yongyou 2640(YY2640),a japonica cultivar Lianjing 7(LJ-7)and an indica cultivar Yangdao 6(YD-6),were grown in the field with six N rates(0,100,200,300,400,and 500 kg ha^(-1))in 2018 and 2019.The results showed that with the increase in N application rates,the grain yield of each test cultivar increased at first and then decreased,and the highest grain yield was at the N rate of 400 kg ha^(-1)for YY2640,with a grain yield of 13.4 t ha^(-1),and at 300 kg ha^(-1)for LJ-7 and YD-6,with grain yields of 9.4–10.6 t ha^(-1).The grain yield and N use efficiency(NUE)of YY2640 were higher than those of LJ-7 or YD-6 at the same N rate,especially at the higher N rates.When compared with LJ-7 or YD-6,YY2640 exhibited better physiological traits,including greater root oxidation activity and leaf photosynthetic rate,higher cytokinin content in the roots and leaves,and more remobilization of assimilates from the stem to the grain during grain filling.The results suggest that IJHR could attain both higher grain yield and higher NUE than inbred rice at either low or high N application rates.Improved shoot and root traits of the IJHR contribute to its higher grain yield and NUE,and a higher content of cytokinins in the IJHR plants plays a vital role in their responses to N application rates and also benefits other physiological processes.

Predicting nitrogen use efficiency,nitrogen loss and dry matter intake of individual dairy cows in late lactation by including mid‑infrared spectra of milk samples

Background Nitrate leaching to groundwater and surface water and ammonia volatilization from dairy farms have negative impacts on the environment.Meanwhile,the increasing demand for dairy products will result in more pollution if N losses are not controlled.Therefore,a more efficient,and environmentally friendly production system is needed,in which nitrogen use efficiency(NUE)of dairy cows plays a key role.To genetically improve NUE,extensively recorded and cost-effective proxies are essential,which can be obtained by including mid-infrared(MIR)spectra of milk in prediction models for NUE.This study aimed to develop and validate the best prediction model of NUE,nitrogen loss(NL)and dry matter intake(DMI)for individual dairy cows in China.Results A total of 86 lactating Chinese Holstein cows were used in this study.After data editing,704 records were obtained for calibration and validation.Six prediction models with three different machine learning algorithms and three kinds of pre-processed MIR spectra were developed for each trait.Results showed that the coefficient of determination(R2)of the best model in within-herd validation was 0.66 for NUE,0.58 for NL and 0.63 for DMI.For external validation,reasonable prediction results were only observed for NUE,with R2 ranging from 0.58 to 0.63,while the R2 of the other two traits was below 0.50.The infrared waves from 973.54 to 988.46 cm−1 and daily milk yield were the most important variables for prediction.Conclusion The results showed that individual NUE can be predicted with a moderate accuracy in both within-herd and external validations.The model of NUE could be used for the datasets that are similar to the calibration dataset.The prediction models for NL and 3-day moving average of DMI(DMI_a)generated lower accuracies in within-herd validation.Results also indicated that information of MIR spectra variables increased the predictive ability of models.Additionally,pre-processed MIR spectra do not result in higher accuracy than original MIR spectra in the external validation.These models will be applied to large-scale data to further investigate the genetic architecture of N efficiency and further reduce the adverse impacts on the environment after more data is collected.

OsAMT1.1 Expression by Nitrate-Inducible Promoter of OsNAR2.1 Increases Nitrogen Use Efficiency and Rice Yield

Nitrate(NO_(3)^(-))and ammonium(NH_(4)^(+))are two main inorganic nitrogen(N)sources during crop growth.Here,we enhanced the expression of OsAMT1.1,which encodes a NH_(4)^(+)transporter,using the NO_(3)^(-)-inducible promoter of OsNAR2.1 and an ubiquitin promoter in transgenic rice plants.Under field condition of 120 kg/hm2 N,agronomic N use efficiency,N recovery efficiency and N transport efficiency,and grain yield of the pOsNAR2.1:OsAMT1.1 transgenic lines were increased compared with those of the wild type(WT)and the pUbi:OsAMT1.1 transgenic plants.Under 2.0 mmol/L NO_(3)^(-)+0.5 mmol/L NH_(4)^(+)and 0.5 mmol/L NO_(3)^(-)+2.0 mmol/L NH_(4)^(+)conditions of hydroponic culture,compared with the WT,both biomass and total N content were increased in the pOsNAR2.1:OsAMT1.1 transgenic lines.However,biomass was significantly reduced in pUbi:OsAMT1.1 transgenic plants under 0.5 mmol/L NO_(3)^(-)+2.0 mmol/L NH_(4)^(+)condition.The lines expressing pOsNAR2.1:OsAMT1.1 exhibited increased OsAMT1.1 expression and 15NH_(4)^(+)influx in roots under both 2.0 mmol/L NO_(3)^(-)+0.5 mmol/L NH_(4)^(+)and 0.5 mmol/L NO_(3)^(-)+2.0 mmol/L NH_(4)^(+)conditions.Our study showed that expression of OsAMT1.1 can be promoted when driven by the OsNAR2.1 promoter,especially under high-level nitrate condition,leading to enhancement of NH_(4)^(+)uptake,N use efficiency and grain yield.

Heterosis Analysis of Nitrogen Use Efficiency for Grain Production of Brassica napus L.

[Objective]The aim was to study heterosis of N use efficiency for grain production （NUEg） of Brassica napus L. and provide theoretical basis for breeding N-efficient cultivars. [Method]Dry matter production and N content of six B.napus parents （Zheshuang 3,Yangyou 7,ZJ1,Shilijia,Ningyou 14 and Huyou 16） and their F1 combinations from 6 × 6 complete diallel cross in maturity stage under two N levels were measured; heterosis of NUEg,combining ability and heritability size were analyzed and calculated. [Result]The results showed that NUEg has obvious heterosis; combining ability variance analysis indicated that NUEg was mainly controlled by additive,dominant and cytoplasmic effects; genetic variance analysis showed that additive effects and dominance effects were all significant in low nitrogen fertilizer and dominance effects were significant in high nitrogen fertilizer. [Conclusion]NUEg of B.napus has obvious heterosis.

Effects of Controlled-Release Nitrogen on Yield and Nitrogen Use Efficiency of Summer Maize

The field experiments were conducted in Anhui during 2016 to investigate the effects of controlled-release nitrogen （CRN） rates and mixture of controlled-re- lease nitrogen and conventional nitrogen （CN） on the yield and nitrogen efficiency of summer maize. Six treatments included CK （with no application of N）, CNIO0% splits （CN）, CRFIO0% （CRN1）, CRN60%＋CN40% （CRN2）, CRN85% （CRN3） and CRN70% （CRN4）. The results showed proper CRN increased yields and output val- ue. Compared with CN, CRN2 significantly increased by 13.74%, CRN1 increased by 4.84%, and CRN3 was equal to CN. CRN increased yield by grain number per spike of yield components. CRN2 had the highest apparent nitrogen fertilizer recov- ery efficiency and CRN1 was the second, which were significantly higher than CN. Nitrogen agronomic efficiency of CRN2 was significantly higher than CN. Nitrogen physiological efficiency of CRN2 was higher than CN. The partial productivity of CRN1 was higher than that with CN. And the effect of nitrogen fertilizer of CRN2 was the highest, which was increased 758 yuan/hm2. Considering yield, nitrogen use efficiency and economic benefit, applying the mixture of CRN and CN was the most beneficial treatment. CRN1 was the second treatment, and CRN3 didn＇t reduce yield.

Effects of Nitrogen Application on Nitrogen Dynamic Changes and Nitrogen Use Efficiency in Maize

[Objective] This study and nitrogen use efficiency in aimed to investigate the nitrogen dynamic changes maize under different nitrogen application patterns. [Method] Maize cultivar Xianyu 335 was selected as the experimental material and was planted at two densities 85 000 and 95 000 plants/hm2. The total amount of fertilizers applied kept constant. The nitrogen content in leaves, stems, sheathes, husks, grains, cobs, tassels and filaments of maize plants in jointing stage, silking stage, 15, 30, 45 and 60 d after silking stage was measured. [Result] Total nitrogen content in maize plant reached the peak around 45 d after silking stage and a higher population was helpful to nitrogen accumulation. Total nitrogen content of maize plant was positively correlated with yield and it got closer in higher popula- tion. Grain nitrogen content and nitrogen harvest index were significantly positively correlated with yield in higher population. High ratio of nitrogen fertilizer in silking stage was beneficial to nitrogen accumulation in leaf and ear, as well as nitrogen translocation in stem and sheath, but high ratio of nitrogen fertilizer in earlier stage delayed nitrogen metabolism. Nitrogen uptake peak was from silking stage to 15 d after silking stage, and nitrogen uptake rate increased high ratio of nitrogen fertilizer was applied in later growth stages and moved forward in higher plant population. [Conclusion] It was advantaged for nitrogen fertilizer efficiency on condition that ni- trogen application was moved backward. Accumulating too much nitrogen in earlier stages inhibited nitrogen uptake in later periods

Yield potential and nitrogen use efficiency of China's super rice

In 1996, a mega project that aimed to develop rice varieties with super-high yield potential （super rice） was launched by the Ministry of Agriculture （MOA） in China using a combination of the ideotype approach and intersubspecific heterosis. Significant progress has been made in the last two decades, with a large number of super rice varieties being approved by the MOA and the national average grain yield being increased from 6.21 t ha^-1 in 1996 to 6.89 t ha^-1 in 2015. The increase in yield potential of super rice was mainly due to the larger sink size which resulted from larger panicles. Moreover, higher photosynthetic capacity and improved root physiological traits before heading contributed to the increase in sink size. However, the poor grain filling of the later-flowering inferior spikelets and the quickly decreased root activity of super rice during grain filling period restrict the achievement of high yield potential of super rice. Furthermore, it is widely accepted that the high yield potential of super rice requires a large amount of N fertilizer input, which has resulted in an increase in N consumption and a decrease in nitrogen use efficiency （NUE）, although it remains unclear whether super rice per se is responsible for the latter. In the present paper, we review the history and success of China＇s Super Rice Breeding Pro- gram, summarize the advances in agronomic and physiological mechanisms underlying the high yield potential of super rice, and examine NUE differences between super rice and ordinary rice varieties. We also provide a brief introduction to the Green Super Rice Project, which aims to diversify breeding targets beyond yield improvement alone to address global concerns around resource use and environmental change. It is hoped that this review will facilitate further improvement of rice production into the future.

Optimized nitrogen application methods to improve nitrogen use efficiency and nodule nitrogen fixation in a maize-soybean relay intercropping system

In China, the abuse of chemical nitrogen （N） fertilizer results in decreasing N use efficiency （NUE）, wasting resources and causing serious environmental problems. Cereal-legume intercropping is widely used to enhance crop yield and improve resource use efficiency, especially in Southwest China. To optimize N utilization and increase grain yield, we conducted a two-year field experiment with single-factor randomized block designs of a maize-soybean intercropping system （IMS）. Three N rates, NN （no nitrogen application）, LN （lower N application： 270 kg N ha-1）, and CN （conventional N application： 330 kg N ha-1）, and three topdressing distances of LN （LND）, e.g., 15 cm （LND1）, 30 cm （LND2） and 45 cm （LND3） from maize rows were evaluated. At the beginning seed stage （R5）, the leghemoglobin content and nitrogenase activity of LND3 were 1.86 mg plant-1 and 0.14 mL h-1 plant-1, and those of LND1 and LND2 were increased by 31.4 and 24.5%, 6.4 and 32.9% compared with LND3, respectively. The ureide content and N accumulation of soybean organs in LND1 and LND2 were higher than those of LND3. The N uptake, NUE and N agronomy efficiency （NAE） of IMS under CN were 308.3 kg ha-1, 28.5%, and 5.7 kg grain kg-1 N, respectively; however, those of LN were significantly increased by 12.4, 72.5, and 51.6% compared with CN, respectively. The total yield in LND1 and LND2 was increased by 12.3 and 8.3% compared with CN, respectively. Those results suggested that LN with distances of 15-30 cm from the topdressing strip to the maize row was optimal in maize-soybean intercropping. Lower N input with an optimized fertilization location for IMS increased N fixation and N use efficiency without decreasing grain yield.

Postponed and reduced basal nitrogen application improves nitrogen use efficiency and plant growth of winter wheat

Excessive nitrogen(N) fertilization with a high basal N ratio in wheat can result in lower N use efficiency(NUE) and has led to environmental problems in the Yangtze River Basin, China. However, wheat requires less N fertilizer at seedling growth stage, and its basal N fertilizer utilization efficiency is relatively low; therefore, reducing the N application rate at the seedling stage and postponing the N fertilization period may be effective for reducing N application and increasing wheat yield and NUE. A 4-year field experiment was conducted with two cultivars under four N rates(240 kg N ha–1(N240), 180 kg N ha–1(N180), 150 kg N ha–1(N150), and 0 kg N ha–1(N0)) and three basal N application stages(seeding(L0), fourleaf stage(L4), and six-leaf stage(L6)) to investigate the effects of reducing the basal N application rate and postponing the basal N fertilization period on grain yield, NUE, and N balance in a soil-wheat system. There was no significant difference in grain yield between the N180 L4 and N240 L0(control) treatments, and the maximum N recovery efficiency and N agronomy efficiency were observed in the N180 L4 treatment. Grain yield and NUE were the highest in the L4 treatment. The leaf area index, flag leaf photosynthesis rate, flag leaf nitrate reductase and glutamine synthase activities, dry matter accumulation, and N uptake post-jointing under N180 L4 did not differ significantly from those under N240 L0. Reduced N application decreased the inorganic N content in the 0–60-cm soil layer, and the inorganic N content of the L6 treatment was higher than those of the L0 and L4 treatments at the same N level. Surplus N was low under the reduced N rates and delayed basal N application treatments. Therefore, postponing and reducing basal N fertilization could maintain a high yield and improve NUE by improving the photosynthetic production capacity, promoting N uptake and assimilation, and reducing surplus N in soil-wheat systems.

Differences of yield and nitrogen use efficiency under different applications of slow release fertilizer in spring maize

Excessive or insufficient application of fertilizer has raised broader concerns regarding soil and environmental degradation.One-time application of slow release fertilizer (SF) has been widely used to reduce yield gap with potential maize yield and improve nitrogen use efficiency (NUE).A 2-year field experiment (2018–2019) was conducted to evaluate the effects of SF rates from 0 to 405 kg N ha^(–1) (named F0,SF225,SF270,SF315,SF360,and SF405) and 405 kg N ha^(–1) of common fertilizer(CF405) on the grain yield,biomass and N accumulation,enzymatic activities related with carbon–nitrogen metabolism,NUE and economic analysis.Results indicated that the highest grain yields,NUEs and economic returns were achieved at SF360in both varieties.The enzymatic activities related with carbon–nitrogen metabolism,pre-and post-silking accumulation of biomass and N increased with increasing SF rate,and they were the highest at SF360 and SF405.The grain yield at SF360had no significant difference with that at SF405.However,the N partial factor productivity,N agronomic efficiency and N recovery efficiency at SF360 were 9.8,6.6 and 8.9% higher than that at SF405.The results also indicated that the average grain yields,NUE and economic benefit at SF405 were 5.2,12.3 and 18.1% higher than that at CF405.In conclusion,decreasing N rate from 405 kg ha^(–1)(CF) to 360 kg ha^(–1)(SF) could effectively reduce the yield gap between realized and potential maize yields.The N decreased by 11.1%,but the yield,NUE and economic benefit increased by 3.2,22.2 and 17.5%,which created a simple,efficient and business-friendly system for spring maize production in Jiangsu Province,China.

Top-grain filling characteristics at an early stage of maize(Zea mays L.) with different nitrogen use efficiencies

Maize genotypes vary significantly in their nitrogen use efficiencies（NUEs）.Better understanding of early grain filling characteristics of maize is important,especially for maize with different NUEs.The objectives of this research were（i）to investigate the difference in apical kernel development of maize with different NUEs,（ii）to determine the reaction of apical kernel development to N application levels,and（iii）to evaluate the relationship between apical kernel development and grain yield（GY）for different genotypes of maize.Three maize hybrid varieties with different NUEs were cultivated in a field with different levels of N fertilizer arranged during two growing seasons.Kernel fresh weight（KFW）,volume（KV）and dry weight（KDW）of apical kernel were evaluated at an early grain filling stage.Ear characteristics,GY and its components were determined at maturity stage.Apical kernel of the high N and high efficiency（HN-HE）type（under low N,the yield is lower,and under higher N,the yield is higher）developed better under high N（N210 and N240,pure N of 210 and 240 kg ha^–1）than at low N（N120 and N140,pure N of 120 and 140 kg ha^–1）.The low N and high efficiency（LN-HE）type（under low N,the yield is higher,while under higher N,the yield is not significantly higher）developed better under low N than at high N.The double high efficiency（D-HE）type（for both low and high N,the yield is higher）performed well under both high and low N.Apical kernel reacted differently to the N supply.Apical kernel developed well at an early grain filling stage and resulted in a higher kernel number（KN）,kernel weight（KW）and GY with better ear characteristics at maturity.

Mapping of QTLs for Nitrogen Use Efficiency and Related Traits in Rice(Oryza sativa L.)

Current rice production is usually guaranteed by applying large amount of chemical nitrogen fertilizers to paddy soils. The improvement of nitrogen use efficiency is of great importance not only in rice production itself but in environmental protection as well. In this study we performed a molecular marker-based genetic analysis of nitrogen use efficiency for biomass production （NUEp） and several other related traits in a recombinant inbred line （RIL） population, derived from a cross of the parents of Shanyou 63, the most widely cultivated indica hybrid in China. A total of 12 QTLs were detected using interval mapping with a LOD threshold of 2.0, among which one QTL controlling NUEp was located at the marker interval of Waxy-C1496 on chromosome 6, and the rest 11 QTLs associated nitrogen concentration and accumulation in rice plant were positioned on chromosomes 1, 2, 4 and 6, respectively. Correlation between NUEp and other traits was analyzed and the implications of the results with respect to the improvement of the hybrid rice were discussed.

Modified fertilization management of summer maize(Zea mays L.) in northern China improves grain yield and efficiency of nitrogen use

Improving the yield of maize grain per unit area is needed to meet the growing demand for it in China, where the availability of fertile land is very limited.Modified fertilization management and planting density are efficient methods for increasing crop yield.Field experiments were designed to investigate the influence of modified fertilization management and planting density on grain yield and nitrogen use efficiency of the popular maize variety Zhengdan 958, in four treatments including local farmer＇s practice（FP）, high-yielding and high efficiency cultivation（HH）, super high-yielding cultivation（SH）, and the control（CK）.Trials were conducted in three locations of the Huang-Huai-Hai Plain in northern China.Compared with FP, SH was clearly able to promote N absorption and dry matter accumulation in post-anthesis, and achieve high yield and N use efficiency by increasing planting density and postponing the supplementary application of fertilizers.However, with an increase in planting density, the demand of N increased along with grain yield.Due to the input of too much N fertilizer, the efficiency of N use in SH was low.Applying less total N, ameliorating cultivation and cropping management practices should be considered as priority strategies to augment production potential and finally achieve synchronization between high yield and high N efficiency in fertile soils.However, in situations where soil fertility is low, achieving high yield and high N use efficiency in maize will likely depend on increased planting density and appropriate application of supplementary fertilizers postpone to the grain-filling stage.

Effect of side deep placement of nitrogen on yield and nitrogen use efficiency of single season late japonica rice

Side deep placement of nitrogen plays an important role in improving rice yield and nitrogen use efficiency.Few studies have examined the effects of reducing the times of nitrogen(RTN)application and reducing the nitrogen rate(RNR)of application on rice yield and nitrogen use efficiency under side deep placement of nitrogen in paddy fields.Therefore,a field experiment of RNT and RNR treatments was conducted with nine fertilization modes during the 2018–2019 rice growing seasons in a rice–wheat cropping system of the lower reaches of the Yangtze River,China.Rice yield and nitrogen use efficiency were investigated under side deep placement of nitrogen.We found that under the same nitrogen application rate,the yield of RTN3 increased by 9.64 and 10.18%in rice varieties NJ9108 and NJ5718,respectively,compared with the farmers’fertilizer practices(FFP).The nitrogen accumulation of RTN3 was the highest at heading stage,at 11.30 t ha^(–1)across 2018 and 2019.Under the same nitrogen application rate,the N agronomic use efficiency(NAE),N physiological efficiency(NPE)and N recovery efficiency(NRE)of RTN3 were 8.1–21.28%,8.51–41.76%and 0.28–14.52%higher than those of the other fertilization modes,respectively.RNR led to decreases in SPAD value,leaf area index(LAI),dry matter accumulation,nitrogen accumulation,and nitrogen use efficiency.These results suggest that RTN3 increased rice yield and nitrogen use efficiency under the side deep placement of nitrogen,and RNR1 could achieve the goals of saving cost and increasing resource use efficiency.Two fertilization modes RTN3 and RNR1 both could achieve the dual goals of increasing grain yield and resource use efficiency and thus are worth further application and investigation.

Nitrogen Deep Placement Combined with Straw Mulch Cultivation Enhances Physiological Traits,Grain Yield and Nitrogen Use Efficiency in Mechanical Pot-Seedling Transplanting Rice

To assess the effects of straw return coupled with deep nitrogen(N)fertilization on grain yield and N use efficiency(NUE)in mechanical pot-seedling transplanting(MPST)rice,the seedlings of two rice cultivars,i.e.,Yuxiangyouzhan and Wufengyou 615 transplanted by MPST were applied with N fertilizer at 150 kg/hm2 and straw return at 6 t/hm2 in early seasons of 2019 and 2020.The experiment comprised of following treatments:CK(no fertilizer and no straw return),MDS(deep N fertilization and straw return),MBS(broadcasting fertilizer and straw return),MD(deep N fertilization without straw return),MB(broadcasting fertilizer without straw return).Results depicted that the MDS treatment significantly increased the rice yield by 41.69%-72.22%due to total above-ground biomass,leaf area index and photosynthesis increased by 54.70%-55.80%,38.52%-52.17%and 17.89%-28.40%,respectively,compared to the MB treatment.In addition,the MDS treatment enhanced the total N accumulation by 37.74%-43.69%,N recovery efficiency by 141.45%-164.65%,N agronomic efficiency by 121.76%-134.19%,nitrate reductase by 46.46%-60.86%and glutamine synthetase by 23.56%-31.02%,compared to the MB treatment.The average grain yield and NUE in both years for Yuxiangyouzhan were higher in the MDS treatment than in the MD treatment.Hence,deep N fertilization combined with straw return can be an innovative technique with improved grain yield and NUE in MPST in South China.