OsNPF3.1,a nitrate,abscisic acid and gibberellin transporter gene,is essential for rice tillering and nitrogen utilization efficiency

Low-affinity nitrate transporter genes have been identified in subfamilies 4-8 of the rice nitrate transporter 1(NRT1)/peptide transporter family(NPF),but the OsNPF3 subfamily responsible for nitrate and phytohormone transport and rice growth and development remains unknown.In this study,we described OsNPF3.1 as an essential nitrate and phytohormone transporter gene for rice tillering and nitrogen utilization efficiency(NUtE).OsNPF3.1 possesses four major haplotypes of its promoter sequence in 517 cultivars,and its expression is positively associated with tiller number.Its expression was higher in the basal part,culm,and leaf blade than in other parts of the plant,and was strongly induced by nitrate,abscisic acid(ABA)and gibberellin 3(GA_3)in the root and shoot of rice.Electrophysiological experiments demonstrated that OsNPF3.1 is a pH-dependent low-affinity nitrate transporter,with rice protoplast uptake assays showing it to be an ABA and GA_3 transporter.OsNPF3.1 overexpression significantly promoted ABA accumulation in the roots and GA accumulation in the basal part of the plant which inhibited axillary bud outgrowth and rice tillering,especially at high nitrate concentrations.The NUtE of OsNPF3.1-overexpressing plants was enhanced under low and medium nitrate concentrations,whereas the NUtE of OsNPF3.1 clustered regularly interspaced short palindromic repeats(CRISPR)plants was increased under high nitrate concentrations.The results indicate that OsNPF3.1 transports nitrate and phytohormones in different rice tissues under different nitrate concentrations.The altered OsNPF3.1 expression improves NUtE in the OsNPF3.1-overexpressing and CRISPR lines at low and high nitrate concentrations,respectively.

Effects of the kinetic pattern of dietary glucose release on nitrogen utilization, the portal amino acid profile, and nutrient transporter expression in intestinal enterocytes in piglets

Background Promoting the synchronization of glucose and amino acid release in the digestive tract of pigs could effectively improve dietary nitrogen utilization.The rational allocation of dietary starch sources and the exploration of appropriate dietary glucose release kinetics may promote the dynamic balance of dietary glucose and amino acid supplies.However,research on the effects of diets with different glucose release kinetic profiles on amino acid absorption and portal amino acid appearance in piglets is limited.This study aimed to investigate the effects of the kinetic pattern of dietary glucose release on nitrogen utilization,the portal amino acid profile,and nutrient transporter expression in intestinal enterocytes in piglets.Methods Sixty-four barrows(15.00±1.12 kg)were randomly allotted to 4 groups and fed diets formulated with starch from corn,corn/barley,corn/sorghum,or corn/cassava combinations(diets were coded A,B,C,or D respectively).Protein retention,the concentrations of portal amino acid and glucose,and the relative expression of amino acid and glucose transporter m RNAs were investigated.In vitro digestion was used to compare the dietary glucose release profiles.Results Four piglet diets with different glucose release kinetics were constructed by adjusting starch sources.The in vivo appearance dynamics of portal glucose were consistent with those of in vitro dietary glucose release kinetics.Total nitrogen excretion was reduced in the piglets in group B,while apparent nitrogen digestibility and nitrogen retention increased(P<0.05).Regardless of the time(2 h or 4 h after morning feeding),the portal total free amino acids content and contents of some individual amino acids(Thr,Glu,Gly,Ala,and Ile)of the piglets in group B were significantly higher than those in groups A,C,and D(P<0.05).Cluster analysis showed that different glucose release kinetic patterns resulted in different portal amino acid patterns in piglets,which decreased gradually with the extension of feeding time.The portal His/Phe,Pro/Glu,Leu/Val,Lys/Met,Tyr/Ile and Ala/Gly appeared higher similarity among the diet treatments.In the anterior jejunum,the glucose transporter SGLT1 was significantly positively correlated with the amino acid transporters B0AT1,EAAC1,and CAT1.Conclusions Rational allocation of starch resources could regulate dietary glucose release kinetics.In the present study,group B(corn/barley)diet exhibited a better glucose release kinetic pattern than the other groups,which could affect the portal amino acid contents and patterns by regulating the expression of amino acid transporters in the small intestine,thereby promoting nitrogen deposition in the body,and improving the utilization efficiency of dietary nitrogen.

Effects of Green Manure Rotation on Rice Growth Dynamics and Nitrogen Uptake and Utilization

This study aimed to comprehensive evaluation of different winter green manure on characterization of nitrogen uptake and utilization, to provide the basis for N fertilizer reasonable operation and characteristics improvement of nitrogen nutrition in rice high-yield cultivation. This experiment was set to compare milk vetch, rapeseed,ryegrass and mixed of green manure on rice yield, rice growth dynamics and nitrogen uptake and utilization in rice. The results showed that among 4 different winter green manure, the treatment of MV-R-R（milk vetch-rice-rice） for the early rice yield was the most than others treatments. Compared with RG-R-R（ryegrass-rice-rice）, RPR-R（rapeseed-rice-rice）, MS-R-R（mixed green manure-rice-rice）, the treatment of MVR-R inceased by 6.61%, 3.29%, 0.78%, respectively. The treatment of MV-R-R in N content in plant of rice was maximized in the tillering, booting, heading and maturity periods, respectively higher than the average of other treatments 9.68%, 19.72%,6.23% and 8.66%. At tillering, booting, heading and maturity, the treatment of MV-R-R were the highest in N uptake, RP-R-R minimum. The N periodic accumulation for MV-R-R were higher than other treatments in the tillering to booting, booting to heading and heading to maturity periods. The rates respectively were 21.81%, 68.73% and286.5%. In addition, N periodic accumulation and its ratio to total in the heading to maturity was minimum, maximum before tillering under green manure rotation system.So the cropping system of milk vetch-rice-rice could increase nitrogen use efficiency and improve N cycling.

Variation of Nitrogen Uptake and Utilization Efficiency of Mid-Season Hybrid Rice at Different Ecological Sites under Different Nitrogen Application Levels

[Objective] The study aimed at investigating the effects of different geographic sites,soil chemical characteristics and nitrogen application levels on nitrogen accumulation and distribution in different organs and utilization efficiency for mid-season hybrid rice.[Method] By using mid-season rice varieties II-you 7 and Yuxiangyou203 as the experimental materials,field experiment was conducted at seven ecological sites in four provinces or cities in Southwestern China in 2009.A total of four nitrogen application levels were set as follows：by using 75 kg/hm2 of P2O5 and 75 kg/hm2 of K2O as the base fertilizer,extra 0,90,150 and 210 kg/hm2 of nitrogen fertilizer（in which,base fertilizer,base-tillering fertilizer and base-earing fertilizer respectively accounted for 60%,20% and 20%.） was applied,respectively.In the split-plot design,fertilizer was considered as the main factor while rice variety was taken as the secondary factor.A total of eight treatments were set with three replications.[Result] Highly significant differences of grain yield were found among seven locations,two varieties,four nitrogen application levels,interactions of site × variety and site × nitrogen application level,but the interaction of variety ×nitrogen application level had no significant influence on rice yield.There were highly significant effects of site,varieties and nitrogen application level on dry matter production,nitrogen content,nitrogen utilization efficiency.Highly significant negative correlations between uptake efficiency and utilization efficiency for nitrogen were found;and multiple stepwise regression analysis showed that nitrogen uptake-utilization efficiency were significantly influenced by different ecological sites,chemical quality of soil and the levels of nitrogen application.[Conclusion] The research will provide theoretical and practical basis for the highly efficient application of nitrogen in mid-season hybrid rice cultivation.

Effects of Continuous Nitrogen Application on Grain Yield and Nitrogen Uptake and Utilization in Winter Wheat-Summer Maize Rotation System

[Objective] This study aimed to achieve high yield and stable yield of win- ter wheat-summer maize rotation system and provide basis for rational application of nitrogen fertilizer. [Method] Effects of continuous nitrogen application on grain yield, economic profit, nitrogen uptake and utilization efficiency, and soil inorganic nitrogen accumulation in winter wheat-summer maize rotation system were investigated. [Re- sult] Nitrogen application could significantly increase the y（eld of the winter wheat- summer maize rotation system, which increased by 17.76%-30.32% and 22.24%- 46.63% in two rotation cycles, respectively. The yield of the winter wheat-summer maize rotation system was the maximum in two rotation cycles with nitrogen appli- cation amount of 660.0 kg/hm2, which reached respectively 23 391.19 and 23 444.35 kg/hm2, the yield and economic benefit were the highest, the nitrogen fertilizer use efficiency was 22.2% and 30.7%, the agronomic efficiency was 8.3 and 11.3 kg/kg. However, the nitrogen fertilizer use efficiency and agronomic efficiency between ni- trogen application amount of 540.0 and 660.0 kg/hm2 showed no significant differ- ence. After two rotation cycles, inorganic nitrogen accumulation in 0-40 cm soil with nitrogen application amount of 540.0 kg/hm2 was almost equal to that before experi- ment. [Conclusion] Under the experimental conditions, comprehensively considering the grain yield, economic profit, nitrogen fertilizer efficiency and soil inorganic nitro- gen balance, the optimal nitrogen application amount was 625.3-660.0 kg/hm2 in high-yield winter wheat-summer maize rotation system.

Effects of Increased Planting Density with ReducedNitrogen Application on Yield Formation and NitrogenUtilization of Autumn Maize

With the change of cropping system in the middle reaches of the Yangtze River,the planting area of autumn maize is gradually increasing.However,the cultivation techniques are still under improvement for higher yield and nitrogen efficiency of autumn maize.Increase in planting density with reduced nitrogen fertilizer application is one of the important paths to achieve high yield and high nitrogen utilization efficiency.Meanwhile,the effect needs to be verified for autumn maize.The semi-compact autumn maize variety Qinyu 58 was planted under different planting densities and nitrogen fertilizer amounts with the split plot design.Different nitrogen application rates were arranged in the main plots,including the conventional nitrogen application(N300,300 kg/hm^2),30%reduction from the conventional treatment(N210,210 kg/hm^2)and no nitrogen application(N0).Different planting densities were arranged in the sub-split plots,including the conventional planting density(D60,60000 plants/hm2),medium density(D78,78000 plants/hm^2)and high density(D93,93000 plants/hm2).The effects of nitrogen fertilizer,planting density and their interaction effects on canopy structure,dry matter accumulation,yield and nitrogen use efficiency of autumn maize were studied.The nitrogen application rate and planting density had obvious interaction effects on the yield formation of autumn maize.Compared with the conventional cultivation(N300D60),increasing the planting density with 30%reduction in nitrogen application(N210)can obviously increase the canopy light interception rate,LAI,dry matter accumulation and yield.However,there was no significant change in canopy light interception rate,LAI,dry matter accumulation,grain weight and yield between D93 and D78.Compared with N300D60,nitrogen translocation efficiency and nitrogen contribution proportion to grain nitrogen did not change significantly in autumn maize grown under N210 and D78 treatments,whereas nitrogen partial productivity,nitrogen agronomic efficiency and recovery and utilization efficiency of nitrogen fertilizer increased significantly.Moreover,high density(D93)planting at N210 plots significantly improved nitrogen transport efficiency and utilization efficiency in autumn maize.Therefore,the suitable planting density of the autumn maize variety Qinyu 58 in Hubei Province is recommended a value of 78000 plants/hm^2,with the nitrogen application rate of 210 kg/hm2,which can achieve the target of higher yield by increasing density and reducing nitrogen.

Effects of supplementary urea-minerals lick block on the kinetics of fibre digestion, nutrient digestibility and nitrogen utilization of low quality roughages

Three yearling lambs with a rumen cannula were used to investigate the effects of supplementation with an urea-minerals lick block （ULB） on the kinetics of ruminal fibre digestion, nutrient digestibility and nitrogen （N） utilization office straw （RS）, ammonia bicarbonate （AB）-treated RS （ABRS） and hay prepared from natural pasture. The digestibility of dry matter and organic matter of RS increased by 13.1% and 12.7% （P〈0.05） when the diet was supplemented with ULB, and approached to that of ABRS, indicating that the effect of ULB on digestibility of RS is similar to that of AB treatment. The digestibility of ABRS was slightly improved by the ULB feeding. Nitrogen retention was highest in lambs fed on ABRS alone, followed by hay with ULB, and was lowest in animals fed on RS with ULB. However, both the amount and proportion of N retention to N intake were enhanced by ULB supplementation to lambs fed on hay. The proportion of N retained to N digested decreased due to ULB supplementation to lambs fed on RS or ABRS. Supplementing ULB did not greatly influence the rumen degradation of either dry matter or crude protein in each of the three diets. RS and hay had similar values in the potential extent of digestion （PED） and digestion rate of PED （kd） of fibrous materials, but the discrete lag time for RS was lower than that for hay. The AB treatment significantly increased the PED （P〈0.05） and kd （P〈0.05） of RS. Neither the PED nor kd for RS and ABRS was influenced by ULB supplementation, but the kd for hay significantly increased due to ULB. The lag time for hay was also shortened by the ULB feeding. The ULB improved the digestion of fibre in the rumen of lambs fed on low quality roughage. It is inferred that while ULB is effective in increasing nutrient digestibility of low quality roughages by improving ruminal fibre digestion. A synchronized supply of N and energy to rumen microbes should be considered to improve the efficiency of N utilization when the basal diet is ammoniated straw.

Effect of Rural Sewage Irrigation Regime on Water-Nitrogen Utilization and Crop Growth of Paddy Rice in Southern China

Reclaimed water irrigation has become an effective mean to alleviate the contradiction between water availability and its consumption worldwide.In this study,three types of irrigation water sources(rural sewage’s primary treated water R1 and secondary treated water R2,and river water R3)meeting the requirements of water quality for farmland irrigation were selected,and three types of irrigation water levels(low water levelW1 of 0–80 mm,medium water level W2 of 0–100 mm,and high water level W3 of 0–150 mm)were adopted to carry out research on the influence mechanismS of different irrigation water sources and water levels on water and nitrogen use and crop growth in paddy field.The water quantity indicators(irrigation times and irrigation volume),soil ammonium nitrogen(NH4+-N)and nitrate nitrogen(NO3−-N),rice yield indicators(thousand-grain weight,the number of grains per spike,and the number of effective spikes),and quality indicators(the amount of protein,amylose,vitamin C,nitrate and nitrite content)of rice were measured.The results showed that,the average irrigation volume under W3 was 2.4 and 1.9 times of that under W1 and W2,respectively.Compared with R3,the peak consumption of rice was lagged behind under R1 and R2,and the nitrogen form in 0–40 cm soil layers under rural sewage irrigation was mainly NH4+-N.The changes of NO3−-N and NH4+-N in the 0–40 cm soil layer showed the trend of declining and then increasing.The water level control only had a significant effect on the change of NO3−-N in the 60–80 cm soil layer.Both irrigation water use efficiency and crop water use efficiency were gradually reduced with the increase of field water level control.The nitrogen utilization efficiency under rural sewage irrigation was significantly higher than that under R3.Compared with the R3,rural sewage irrigation could significantly increase the yield of rice,and as the field water level rose,the effect of yield promotion was more obvious.It was noteworthy that the grain of rice under R1 monitored the low nitrate and nitrite content,but no nitrate and nitrite was discovered under R2 and R3.Therefore,reasonable rural sewage irrigation(R2)and medium water level(W2)were beneficial to improve nitrogen utilization efficiency,crop yield and crop quality promotion.

Effect of nitrogen fertilizer on the uptake and utilization of potassium by various rice varieties in purple soil

Nitrogen and potassium are important nutrientelements for rice.Besides supplied by the or- ganic manure,potassium nutrition of ricecomes dominantly from purple soils in Sichuanbasin.Potassium exists abundantly in mineralforms in the purple soils.Availability of soilpotassium for crop depends on the potassiumforms,the uptake ability of crops,and fertiliz-er practices.A pot culture experiment wasconducted to study the kinetics of potassiumuptake in the purple soil(total N 22.64g·kg,total K 24.36g·kg,available N 102.6mg·kg,available K 140.6mg·kg,acidsoluble K 936.0mg·kg,and pH 6.8).Ma-terials used were three Fhybrid rices,Eryou

Improving winter wheat grain yield and water-/nitrogen-use efficiency by optimizing the micro-sprinkling irrigation amount and nitrogen application rate

Available irrigation resources are becoming increasingly scarce in the North China Plain (NCP),and nitrogen-use efficiency of crop production is also relatively low.Thus,it is imperative to improve the water-use efficiency (WUE) and nitrogen fertilizer productivity on the NCP.Here,we conducted a two-year field experiment to explore the effects of different irrigation amounts (S60,60 mm;S90,90 mm;S120,120 mm;S150,150 mm) and nitrogen application rates (150,195 and 240 kg ha^(–1);denoted as N1,N2 and N3,respectively) under micro-sprinkling with water and nitrogen combined on the grain yield(GY),yield components,leaf area index (LAI),flag leaf chlorophyll content,dry matter accumulation (DM),WUE,and nitrogen partial factor productivity (NPFP).The results indicated that the GY and NPFP increased significantly with increasing irrigation amount,but there was no significant difference between S120 and S150;WUE significantly increased first but then decreased with increasing irrigation and S120 achieved the highest WUE.The increase in nitrogen was beneficial to improving the GY and WUE in S60 and S90,while the excessive nitrogen application (N3) significantly reduced the GY and WUE in S120 and S150 compared with those in the N2 treatment.The NPFP significantly decreased with increasing nitrogen rate under the same irrigation treatments.The synchronous increase in spike number (SN) and 1 000-grain weight (TWG)was the main reason for the large increase in GY by micro-sprinkling with increasing irrigation,and the differences in SN and TGW between S120 and S150 were small.Under S60 and S90,the TGW increased with increasing nitrogen application,which enhanced the GY,while N2 achieved the highest TWG in S120 and S150.At the filling stage,the LAI increased with increasing irrigation,and greater amounts of irrigation significantly increased the chlorophyll content in the flag leaf,which was instrumental in increasing DM after anthesis and increasing the TGW.Micro-sprinkling with increased amounts of irrigation or excessive nitrogen application decreased the WUE mainly due to the increase in total water consumption (ET)and the small increase or decrease in GY.Moreover,the increase in irrigation increased the total nitrogen accumulation or contents (TNC) of plants at maturity and reduced the residual nitrate-nitrogen in the soil (SNC),which was conducive to the increase in NPFP,but there was no significant difference in TNC between S120 and S150.Under the same irrigation treatments,an increase in nitrogen application significantly increased the residual SNC and decreased the NPFP.Overall,micro-sprinkling with 120 mm of irrigation and a total nitrogen application of 195 kg ha^(–1) can lead to increases in GY,WUE and NPFP on the NCP.

Nitrogen acquisition,fixation and transfer in maize/alfalfa intercrops are increased through root contact and morphological responses to interspecies competition

Nitrogen(N)fixation by legumes and nitrogen transfer to cereals have been considered as important pathways for overyielding and higher N use efficiency in cereal/legume intercropping systems.However,the extent to which root morphology contributes to N fixation and transfer is unclear.A two-factorial greenhouse experiment was conducted to quantify the N fixation,transfer and root morphology characteristics of the maize/alfalfa intercropping system in two consecutive years using the 15N-urea leaf labeling method,and combining two N levels with three root separation techniques.N application could inhibit N fixation and transfer in a maize/alfalfa intercropping system.Irrespective of the N application level,compared with plastic sheet separation(PSS),no separation(NS)and nylon mesh separation(NNS)significantly increased the total biomass(36%)and total N content(28%),while the N fixation rate also sharply increased by 75 to 134%,and the amount of N transferred with no root barrier was 1.24–1.42 times greater than that with a mesh barrier.Redundancy analysis(RDA)showed that the crown root dry weight(CRDW)of maize and lateral root number(LRN)of alfalfa showed the strongest associations with N fixation and transfer.Our results highlight the importance of root contact for the enhancement of N fixation and transfer via changes in root morphology in maize/alfalfa intercropping systems,and the overyielding system was achieved via increases in maize growth,at the cost of smaller decreases in alfalfa biomass production.

Methods on Identification and Screening of Rice Genotypes with High Nitrogen Efficiency

In order to establish methods for indentification and screening of rice genotypes with high nitrogen （N） efficiency, N absorption efficiency （NAE）, N utilization efficiency （NUE） and N harvest index （NHI） in ten rice genotypes were investgated at the elongation, booting, heading and maturity stages under six N levels in a pot experiment with soil-sand mixtures at various ratios. NAE in various rice genotypes firstly increased, peaked under a medium nitrogen rate of 0.177 g/kg and then decreased, but NUE and NHI always decreased with increasing nitrogen levels. NAE in various rice genotypes ever increased with growing process and NUE indicated a descending tendency of elongation stage〉heading stage〉maturity stage〉booting stage. N level influenced rice NAE, NUE and NHI most, followed by genotype, and the both effects were significant at 0.01 level. In addition, the interaction effects of genotype and nitrogen level on rice NAE and NUE were significant at 0.01 level, but not significant on rice NHI. Because the maximum differences of NAE and NUE were found at the elongation stage, it was thought to be the most suitable stage for identification and screening these two paremeters. Therefore, the optimum conditions for identification and screening of rice NAE, NUE and NHI in a pot experiment were the nitrogen rate of 0.157 g/kg at the elongation stage, low nitrogen at the elongation stage, and the nitrogen rate of 0.277 g/kg at the maturity stage, respectively.

Effects of Nitrogen on N Uptake,Grain Yield and Quality of Medium-Gluten Wheat Yangmai 10

The effects of the basal and top-dressing nitrogen (N) on N uptake and translocation, N utilization efficiency, grain yieldand quality of medium-gluten winter wheat Yangmai 10 were studied from 2000 to 2002. The main results were as follows.Nitrogen content and nitrogen accumulation in plant at maturity increased with the amount of N application. Grain proteincontent and wet gluten content were significantly correlated with applied N. There was a significantly positive correlationbetween nitrogen accumulation before anthesis (NBA) and basal N fertilizer, and between nitrogen accumulation afteranthesis (NAA) and top-dressing N. N accumulated in grains was significantly correlated to NBA, NAA and N translocationfrom vegetative organs after anthesis (NTVA). NBA was significantly correlated with N application, but NAA and NTVAhad a quadratic curve correlation with applied N. N fertilizer use efficiency (NUE) had a quadratic curve correlation withapplied N, and the NUE was high when basal and top-dressing N was equally applied. For the medium-gluten wheatYangmai 10 under the same N application ratio, there was a N-regulating effect when the N application was less than266.55 kg ha-1, a stagnation of yield and quality when N application ranged from 266.55 to 309.08 kg ha-1, and an excessiveN application when the N application rate was greater than 309.08 kg ha-1. Under the conditions of this experiment, theprecise N application is 220-270 kg ha-1 with basal and top-dressing N equally used when a grain yield of more than 6 750kg ha-1, protein content higher than 12%, wet gluten content more than 30% and NUE greater than 40% could be obtained.

Effect of Nitrogen Applied Before Transplanting on NUE in Rice

Nitrogen （N） application before transplanting, where N fertilizers are applied in seedling-bed and carried to the paddy field with seedlings, is a novel method proposed in this article aiming for improving nitrogen utilization efficiency （NUE） in rice. The effect of this method on mineral N distribution in the rhizosphere soil was investigated in a field experiment with a japonica variety, Ningjing 2, in seasons of 2004 and 2005. There were four levels of N applied 16 h before transplanting： zero N （NO）, 207 kg ha^-1 （NL）, 310.5 kg ha^-1 （NM）, and 414 kg ha^-1 （NH）. The result indicated that N fertilizer before transplantation had positive effect of increasing mineral N content in the rhizosphere soil of rice. Generally, N content in the rhizosphere soil of rice tended to increase with the amount of N fertilizer before transplanting, with the NH treatment having the largest effect. Additionally, N fertilizer before transplanting had significant influence on rice NUE and grain yield. Compared with other treatments, the NM treatment showed the largest influence, with basal-tillering NUE, total NUE, and grain yield being 15%, 12%, and 529.5 kg ha^-1 higher than those of NO treatment. This result indicated that N fertilizer before transplantation had positive effect on mineral N distribution in the rhizosphere soil of rice, thus improving NUE and grain yield.

Integrated management strategy for improving the grain yield and nitrogen-use efficiency of winter wheat

Understanding of how combinations of agronomic options can be used to improve the grain yield and nitrogen use efficiency（NUE） of winter wheat is limited. A three-year experiment involving four integrated management strategies was conducted from 2013 to 2015 in Tai＇an, Shandong Province, China, to evaluate changes in grain yield and NUE. The integrated management treatments were as follows： current practice（T1）; improvement of current practice（T2）; high-yield management（T3）, which aimed to maximize grain yield regardless of the cost of resource inputs; and integrated soil and crop system management（T4） with a higher seeding rate, delayed sowing date, and optimized nutrient management. Seeding rates increased by 75 seeds m^-2 with each treatment from T1（225 seeds m^-2） to T4（450 seeds m^-2）. The sowing dates were delayed from T1（5 th Oct.） to T2 and T3（8 th Oct.）, and to T4 treatment（12 th Oct.）. T1, T2, T3, and T4 received 315, 210, 315, and 240 kg N ha^-1, 120, 90, 210 and 120 kg P2O5 ha^-1, 30, 75, 90, and 45 kg K2O ha^-1, respectively. The ratio of basal application to topdressing for T1, T2, T3, and T4 was 6：4, 5：5, 4：6, and 4：6, respectively, with the N topdressing applied at regreening for T1 and at jointing stage for T2, T3, and T4. The P fertilizers in all treatments were applied as basal fertilizer. The K fertilizer for T1 and T2 was applied as basal fertilizer while the ratio of basal application to topdressing（at jointing stage） of K fertilizer for both T3 and T4 was 6：4. T1, T2, T3, and T4 were irrigated five, four, four and three times, respectively. Treatment T3 produced the highest grain yield among all treatments over three years and the average yield was 9 277.96 kg ha^-1. Grain yield averaged across three years with the T4 treatment（8 892.93 kg ha^-1） was 95.85% of that with T3 and was 21.72 and 6.10% higher than that with T1（7 305.95 kg ha^-1） and T2（8 381.41 kg ha^-1）, respectively. Treatment T2 produced the highest NUE of all the integrated treatments. The NUE with T4 was 95.36% of that with T2 and was 51.91 and 25.62% higher than that with T1 and T3, respectively. The N uptake efficiency（UPE） averaged across three years with T4 was 50.75 and 16.62% higher than that with T1and T3, respectively. The N utilization efficiency（UTE） averaged across three years with T4 was 7.74% higher than that with T3. The increased UPE with T4 compared with T3 could be attributed mostly to the lower available N in T4, while the increased UTE with T4 was mainly due to the highest N harvest index and low grain N concentration, which consequently led to improved NUE. The net profit for T4 was the highest among four treatments and was 174.94, 22.27, and 28.10% higher than that for T1, T2, and T3, respectively. Therefore, the T4 treatment should be a recommendable management strategy to obtain high grain yield, high NUE, and high economic benefits in the target region, although further improvements of NUE are required.

The removal of nitrate reductase phosphorylation enhances tolerance to ammonium nitrogen deficiency in rice

Nitrate reductase(NR) is a key enzyme for nitrogen assimilation in plants,and its activity is regulated by posttranslational phosphorylation.To investigate the effects of dephosphorylation of the NIA1 protein on the growth and the physiological and biochemical characteristics of rice under different forms of nitrogen supplies,the phenotypes,nitrogen metabolism and reactive oxygen metabolism were measured in NIA1 phosphorylation site-directed mutant lines(S532 D and S532 A),an Os Nia1 over-expression line(OE) and Kitaake(wild type,WT).Compared with WT and OE,S532 D and S532 A have stronger nitrogen assimilation capacities.When ammonium nitrate served as the nitrogen source,the plant heights,dry weights of shoots and chlorophyll(Chl) contents of S532 D and S532 A were lower than those of the WT and OE,whereas hydrogen peroxide(H_(2)O_(2)),malondialdehyde(MDA) and nitrite contents were higher.When potassium nitrate served as the nitrogen source,the plant heights,dry weights of shoots and Chl contents of S532 D and S532 A were higher than those of the WT and OE,there were no significant differences in the contents of H_(2)O_(2) and MDA in the leaves of the test materials,and the difference in nitrite contents among different lines decreased.When ammonium sulfate served as the nitrogen source,there were no significant differences in the physiological indexes of the test materials,except NR activity.Compared with ammonium nitrate and ammonium sulfate,the content of NH_(4)^(+)-N in the leaves of each plant was lower when potassium nitrate was used as the nitrogen source.The q PCR results showed that Os GS and Os NGS1 were negatively regulated by downstream metabolites,and Os Nrt2.2 was induced by nitrate.In summary,when ammonium nitrate served as the nitrogen source,the weak growth of NIA1 phosphorylation site-directed mutant lines was due to the toxicity caused by the excessive accumulation of nitrite.When potassium nitrate served as the nitrogen source,the assimilation rates of nitrate,nitrite and ammonium salt were accelerated in NIA1 phosphorylation site-directed mutant lines,which could provide more nitrogen nutrition and improve the tolerance of rice to ammonium nitrogen deficiency.These results could provide a possible method to improve the efficiency of nitrogen utilization in rice under low-nitrogen conditions.

The Effects of Water and Fertilizer Coupling on Plant and Soil Nitrogen Characteristics and Fruit Growth of Rabbiteye Blueberry Plants in a Semi-Arid Region in China

To evaluate the effects of nitrogen(N)and irrigation coupling on the soil N distribution,plant N utilization,and fruit yield of rabbiteye blueberries(Vaccinium virgatum),a field experiment was designed using two factors(water and fertilizer application)with four levels of irrigation and three levels of fertilization,and a control.Under the different water and fertilizer combinations,N primarily accumulated in the leaves.Irrigation and N application within appropriate ranges(pure N≤29 g/plant and irrigation volume≤2.5 L/plant)significantly improved the blueberry fruit yield.Increases in water and N within these ranges promoted the effective accumulation of N in various organs and the absorption and utilization of N in the plants,which ultimately promoted blueberry yield.With increased N application rate,the nitrate N content of the 0–20 cm and 20–50 cm soil layers increased.With increased irrigation volume,the nitrate N content of the 0–20 cm soil layer decreased,while the nitrate content in the 20–50 cm soil layer increased.Low N and moderate water treatments resulted in high fruit yields and reduced nitrate N retention in the soil.Under these conditions,the economic input-output ratio was high and the soil N accumulation was low,and thus the economic and ecological benefits were maximized.

Potential role of N-carbamoyl glutamate in biosynthesis of arginine and its significance in production of ruminant animals

Arginine （ARG） exerts many beneficial effects on animal body and enhanced angiogenesis, lactogenesis, which finally leads to the improvement in nitrogen （N） metabolism, reproduction, lactation, immunity and growth. Unfortunately, unprotected ARG will be degraded in the rumen and its price is high, thus feeding rumen-protected ARG seems to be uneconomical. Alternatively, N-carbamoyl glutamate （NCG） is structural analogue of N-acetyl glutamate, cofactor of cabamoyl phosphate synthetasel, is lower in rumen degradation compared to ARG. Additionally, rumen epithelial and duodenal cells have potentially utilized the NCG for ureagenesis. Supplementation of NCG to high yielding dairy cows increased plasma concentration of ARG and nitric oxide, decreased the plasma ammonia N and improved lactation performance and N utilization. Supplementation of NCG enhanced pregnancy rates in rats, improved litter size and fetal survival rate, thereby improved the reproductive performance of sows. Oral NCG supplementation increases plasma ARG and somatotropin levels, and increased growth rate and muscle protein synthesis in nursing piglets. The NCG is potential a relatively cheaper source of feed additive to offer vital compensation over oral administration of ARG, resulting in improved ruminant animal health and production. In this article, we reviewed the mechanism of AfiG biosynthesis by NCG and their significance in growth, reproduction, milk production and N utilization in ruminant animals.

Function, transport, and regulation of amino acids: What is missing in rice?

Amino acids are essential plant compounds serving as the building blocks of proteins,the predominant forms of nitrogen(N)distribution,and signaling molecules.Plant amino acids derive from root acquisition,nitrate reduction,and ammonium assimilation.Many amino acid transporters(AATs)mediating transfer processes of amino acids have been functionally characterized in Arabidopsis,whereas the function and regulation of the vast majority of AATs in rice(Oryza sativa L.)and other crops remain unknown.In this review,we summarize the current understanding of amino acids in the rhizosphere and in metabolism.We describe their function as signal molecules and in regulating plant architecture,flowering time,and defense against abiotic stress and pathogen attack.AATs not only function in root acquisition and translocation of amino acids from source to sink organs,regulating N uptake and use efficiency,but also as transporters of non-amino acid substrates or as amino acid sensors.Several AAT genes show natural variations in their promoter and coding regions that are associated with altered uptake rate of amino acids,grain N content,and tiller number.Development of an amino acid transfer model in plants will advance the manipulation of AATs for improving rice architecture,grain yield and quality,and N-use efficiency.

Experimental study on water-saving and emission-reduction effects of controlled drainage technology

Field experiments and laboratory analysis were carried out to determine the effects of controlled drainage（CTD） and conventional drainage（CVD） technologies on drainage volume, concentrations of NH4^＋ -N, NO3^-N, and total phosphorus（TP）, nitrogen and phosphorus losses, rice yield,and water utilization efficiency. Results show that CTD technology can effectively reduce drainage times and volume; NH4^＋ -N, NO3^-N, and TP concentrations, from the first to the fourth day after four rainstorms decreased by 28.7%e46.7%, 37.5%e47.5%, and 22.7e31.2%, respectively,with CTD. These are significantly higher rates of decrease than those observed with CVD. CTD can significantly reduce nitrogen and phosphorus losses in field drainage, compared with CVD; the reduction rates observed in this study were, respectively, 66.72%, 55.56%, and 42.81% for NH4^＋ -N, NO3^-N, and TP. Furthermore, in the CTD mode, the rice yield was cut slightly. In the CVD mode, the water production efficiencies in unit irrigation water quantity, unit field water consumption, and unit evapotranspiration were, respectively, 0.85, 0.48, and 1.22 kg/m^3, while in the CTD mode they were 2.91, 0.84, and 1.61 kg/m^3 din other words, 3.42, 1.75, and 1.32 times those of CVD. Furthermore, the results of analysis of variance（ANOVA） show that the indicators in both the CVD and CTD modes, including the concentrations of NH4^＋ -N, NO3^-N, and TP, the losses of NH4^＋ -N, NO3^-N, and TP, irrigation water quantity, and water consumption, showed extremely significant differences between the modes, but the rice yield showed no significant difference.