Difference of Nitrogen Uptake and Use Efficiency in Conventional Indica Rice Cultivars with Different Nitrogen Use Efficiency for Grain Output

[Objective] The study aimed to confirm difference of nitrogen uptake and used efficiency with different nitrogen use efficiency for grain output (NUEg) types of indica rice.[Method] 88 and 122 conventional indica rice cultivars were solution-cultured in 2001 and 2002, respectively. Dry matter weight (including root system, culm and sheath, leaves, panicle), nitrogen content of different organs, yield and its components were measured. The tested rice cultivars were classified into 6 types (i.e. A, B, C, D, E and F, A was the lowest, and F was the highest) based on their NUEg level by the MinSSw method.[Result](1)Difference of NUEg of the cultivars used in this study were very large; (2) No significant difference of N content at heading stage was observed among different NUEg types of indica rice. In the cultivars with higher NUEg, however, N content in leaf, stem-sheath and entire rice plant were lower at mature stage. (3)Cultivars with higher NUEg were characterized with lower N uptake before heading and at mature stage; (4) Cultivars with higher NUEg were characterized with higher N use efficiency in biomass production and harvest index. [Conclusion] The cultivars with higher NUEg showed lower N uptake and N content, while nitrogen use efficiency was higher.

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.

Straw return and appropriate tillage method improve grain yield and nitrogen efficiency of winter wheat

Straw return is an important management tool for tackling and promoting soil nutrient conservation and improving crop yield in Huang-Huai-Hai Plain, China. Although the incorporation of maize straw with deep plowing and rotary tillage practices are widespread in the region, only few studies have focused on rotation tillage. To determine the effects of maize straw return on the nitrogen （N） efficiency and grain yield of winter wheat （Triticum aestivum L.）, we conducted experiments in this region for 3 years. Five treatments were tested： （i） rotary tillage without straw return （RT）; （ii） deep plowing tillage without straw return （DT）; （iii） rotary tillage with total straw return （RS）; （iv） deep plowing tillage with total straw return （DS）; （v） rotary tillage of 2 years and deep plowing tillage in the 3rd year with total straw return （TS）. Treatments with straw return increased kernels no. ear-1, thousand-kernel weight （TKW）, grain yields, ratio of dry matter accumulation post-anthesis, and nitrogen （N） efficiency whereas reduced the ears no. ha-1 in the 2011-2012 and 2012-2013 growing seasons. Compared with the rotary tillage, deep plowing tillage significantly increased the grain yield, yield components, total dry matter accumulation, and N efficiency in 2013-2014. RS had significantly higher straw N distribution, soil inorganic nitrogen content, and soil enzymes activities in the 0-10 cm soil layer compared with the DS and TS. However, significantly lower values were ob- served in the 10-20 and 20-30 cm soil layers. TS obtained approximately equal grain yield as DS, and it also reduced the resource costs. Therefore, we conclude that TS is the most economical method for increasing grain yield and N efficiency of winter wheat in Huang-Huai-Hai Plain.

Optimizing integrative cultivation management improves grain quality while increasing yield and nitrogen use efficiency in rice

A major challenge in rice(Oryza sativa L.)production is to cope with increasing grain yield and fertilizer use efficiency without compromising grain quality.This study was designed to determine if optimizing integrative cultivation management in rice could improve grain quality while increase yield and nitrogen use efficiency(NUE).An indica-japonica hybrid rice cultivar and a japonica rice cultivar were grown in the field,with five cultivation managements including no N application(0 N),local farmer's practice(LFP),and three optimizi ng in teg rati ve cultivati on managements,reducing N rate and increasi ng plant density(ND),ND+alternate wetting and moderate soil drying irrigation(NDW),and NDW+applying rapeseed cake fertilizer(NDWR).The results showed that the optimizi ng integrative cultivati on man ageme nts could not only in crease grain yield,but also enhance NUE compared to LFP.Compared to LFP,NDWR sign ifica ntly in creased brow n,milled,head milled rice rate,ratio of the kern el le ngth to breadth and breakdown value of starch,whereas decreased amylose content,gel consiste ncy,prolamin con tent,setback value,perce ntage of chalky kern els,and chalki ness.The three optimizing in tegrative cultivation managements increased con tents of total protei ns,albumin and glutelin,activities of the key enzymes involved in the sucrose-starch con version in grains,root oxidati on activity,and malic and succinic acid concentrations in root exudates during the grain-filling period.The results suggested that optimizing integrative cultivation managements could improve grain quality meanwhile increase grain yield and NUE by enhancing physiological activities of rice plants.

Delayed sowing can increase lodging resistance while maintaining grain yield and nitrogen use efficiency in winter wheat

Lodging resistance of winter wheat(Trnticum aestivum L.) can be increased by late sowing.However, whether grain yield and nitrogen use efficiency(NUE) can be maintained with delayed sowing remains unknown. During the 2013-2014 and 2014-2015 growing seasons, two winter wheat cultivars were sown on three dates(early sowing on October 1, normal so,wing on October8, and late sowing on October 15) to investigate the responses of lodging resistance, grain yield,and NUE to sowing date. No significant differences in lodging resistance, grain yield, or NUE between early and normal sowing were observed. Averaging over the two cultivars and years,postponing the sowing date significantly increased lodging resistance by 53.6% and 49.6%compared with that following early and normal sowing, respectively. Lodging resistance was improved mainly through a reduction in the culm height at the center of gravity and an increase in the tensile strength of the base internode. Late sowing resulted in similar grain yield as well as kernel weight and number of kernels per square meter, compared to early and normal sowing.Averaging over the two cultivars and years, delayed sowing resulted in a reduction in nitrogen uptake efficiency(UPE) by 11.0% and 9.9% compared to early and normal sowing, respectively,owing to reduced root length density and dry matter accumulation before anthesis. An average increase in nitrogen utilization efficiency(UTE) of 12.9% and 11.2% compared to early and normal sowing, respectively, was observed with late sowing owing to a reduction in the grain nitrogen concentration. The increase in UTE offset the reduction in UPE, resulting in equal NUEs among all sowing dates. Thus, sowing later than normal could increase lodging resistance while maintaining grain yield and NUE.

Effects of Different Tillage Systems on Soil Properties,Root Growth,Grain Yield,and Water Use Efficiency of Winter Wheat (Triticum aestivum L.) in Arid Northwest China

Studies on root development, soil physical properties, grain yield, and water-use efficiency are important for identifying suitable soil management practices for sustainable crop production. A field experiment was conducted from 2006 through 2008 in arid northwestern China to determine the effects of four tillage systems on soil properties, root development, water-use efficiency, and grain yield of winter wheat （Triticum aestivum L.）. The cultivar Fan 13 was grown under four tillage systems：conventional tillage （CT） without wheat stubble, no-tillage without wheat stubble mulching （NT）, no-tillage with wheat stubble standing （NTSS）, and no-tillage with wheat stubble mulching （NTS）. The soil bulk density （BD） under CT system increased gradually from sowing to harvest, but that in NT, NTSS, and NTS systems had little change. Compared to the CT system, the NTSS and NTS systems improved total soil water storage （0-150 cm） by 6.1-9.6 and 10.5- 15.3% before sowing, and by 2.2-8.9 and 13.0-15.1% after harvest, respectively. The NTSS and NTS systems also increased mean dry root weight density （DRWD） as compared to CT system. The NTS system significantly improved water-use efficiency by 17.2-17.5% and crop yield by 15.6-16.8%, and the NTSS system improved that by 7.8-9.6 and 7.0-12.8%, respectively, compared with the CT system. Our results suggested that Chinese farmers should consider adopting conservation tillage practices in arid northwestern China because of benefits to soil bulk density, water storage, root system, and winter wheat yield.

Grain yield and water use efficiency of super rice under soil water deficit and alternate wetting and drying irrigation

This study investigated if super rice could better cope with soil water deficit and if it could have better yield performance and water use efficiency （WUE） under alternate wetting and drying （AWD） irrigation than check rice. Two super rice cultivars and two elite check rice cultivars were grown in pots with three soil moisture levels, well watered （WW）, moderate water deficit （MWD） and severe water deficit （SWD）. Two cultivars, each for super rice and check rice, were grown in field with three irrigation regimes, alternate wetting and moderate drying （AWMD）, alternate wetting and severe drying （AWSD） and conventional irrigation （CI）. Compared with that under WW, grain yield was significantly decreased under MWD and SWD treatments, with less reduction for super rice than for check rice. Super rice had higher percentage of productive tillers, deeper root distribution, higher root oxidation activity, and greater aboveground biomass production at mid and late growth stages than check rice, especially under WMD and WSD. Compared with CI,AWMD increased, whereasAWSD decreased grain yield, with more increase or less decrease for super rice than for check rice. Both MWD and SWD treatments and eitherAWMD orAWSD regime significantly increased WUE compared with WW treatment or CI regime, with more increase for super rice than for check rice. The results suggest that super rice has a stronger ability to cope with soil water deficit and holds greater promising to increase both grain yield and WUE by adoption of moderate AWD irrigation.

Responses of Phosphorus Use Efficiency, Grain Yield, and Quality to Phosphorus Application Amount of Weak-Gluten Wheat

Phosphorus （P） is one of the most widely occurring nutrients for development and growth of wheat. In this study, the effects of P application amount on grain yield, protein content, and phosphorus use efficiency （PUE） were studied by agronomic management of P fertilizer on spring weak-gluten wheat （Triticum aestivum L.） grown under field conditions for 2 yr. The experiments were performed at five levels of P205 application amount, including 0, 72, 108, 144, and 180 kg ha-1. As a result, with increase in P fertilizer, grain yield, and P agricultural efficiency （AEp） increased in a quadratic equitation, but partial factor productivity of P （PFPp） decreased in a logarithmic eq. When 108 kg ha-1 P2Os was applied, the grain yield reached the highest level, but the protein content in gain was lower than 11.5%, a threshold for the protein content to evaluate weak-gluten wheat suitable for production of cake and biscuit. Yangmai 13 and Ningmai 9 could tolerate to higher P level of soils than Yangmai 9 that had more loss in grain yield when P fertilizer was over-applied. AEp had a concomitant relationship with grain yield and was a better descriptor for P use efficiency in the wheat. A high P use efficiency resulted in leaf area index （LAI）, increased chlorophyll content and photosynthetic rate, and stable acid phophatase （APase） activity to accumulate more dry matter after anthesis, which explained that the optimum P fertilizer increased grain yield and improved grain quality of weak-gluten wheat.

Effect of Nitrogen Regimes on Grain Yield,Nitrogen Utilization,Radiation Use Efficiency,and Sheath Blight Disease Intensity in Super Hybrid Rice

Poor nitrogen use efficiency in rice production is a critical issue in China. Site-specific N managements （SSNM） such as real-time N management （RTNM） and fixed-time adjustable-dose N management （FTNM） improve fertilizer-N use efficiency of irrigated rice. This study was aimed to compare the different nitrogen （N） rates and application methods （FFP, SSNM, and RTNM methods） under with- and without-fungicide application conditions on grain yield, yield components, solar radiation use efficiency （RUE）, agronomic-nitrogen use efficiency （AEN）, and sheath blight disease intensity. Field experiments were carried out at Liuyang County, Hunan Province, China, during 2006 and 2007. A super hybrid rice Liangyou 293 （LY293） was used as experimental material. The results showed that RTNM and SSNM have great potential for improving agronomic-nitrogen use efficiency without sacrificing the grain yield. There were significant differences in light interception rate, sheath blight disease incidence （DI） and the disease index （ShBI）, and total dry matter among the different nitrogen management methods. The radiation use efficiency was increased in a certain level of applied N. But, the harvest index （HI） decreased with the increase in applied N. There is a quadratic curve relationship between grain yield and applied N rates. With the same N fertilizer rate, different fertilizer-N application methods affected the RUE and grain yield. The fungicide application not only improved the canopy light interception rate, RUE, grain filling, and harvest index, but also reduced the degree of sheath blight disease. The treatment of RTNM under the SPAD threshold value 40 obtained the highest yield. While the treatment of SSNM led to the highest nitrogen agronomic efficiency and higher rice yield, and decreased the infestation of sheath blight disease dramatically as well. Nitrogen application regimes and diseases control in rice caused obvious effects on light interception rate, RUE, and HI. Optimal N rate is helpful to get higher light interception rate, RUE, and HI. Disease control with fungicide application decreased and delayed the negative effects of the high N on rice yield formation. SSNM and RTNM under the proper SPAD threshold value obtained high-yield with high efficiency and could alleviate environmental pollution in rice production.

Integrated agronomic practice increases maize grain yield and nitrogen use efficiency under various soil fertility conditions

Crop yield potential can be increased through the use of appropriate agronomic practices. Integrated agronomic practice (IAP) is an effective way to increase maize (Zea mays L.) grain yield and nitrogen use efficiency (NUE);however, the physiological processes associated with gains in yield potential obtained from IAP, particularly the different under various soil fertility conditions, remain poorly understood. An IAP strategy including optimal planting density, split fertilizer application, and subsoiling tillage was evaluated over two growing seasons to determine whether the effects of IAP on maize yield and NUE differ under different levels of soil fertility. Compared to farmers' practices (FP), IAP increased maize grain yield in 2013 and 2014 by 25% and 28%, respectively, in low soil fertility (LSF) fields and by 36% and 37%, respectively, in high soil fertility (HSF) fields. The large yield gap was attributed mainly to greater dry matter (DM) and N accumulation with IAP than with FP owing to increased leaf area index (LAI) and DM accumulation rate, which were promoted by greater soil mineral N content (Nmin) and root length. Post-silking DM and N accumulation were also greater with IAP than with FP under HSF conditions, accounting for 60% and 43%, respectively, of total biomass and N accumulation;however, no significant differences were found for post-silking DM and N accumulation between IAP and FP under LSF conditions. Thus, the increase in grain yield with IAP was greater under HSF than under LSF. Because of greater grain yield and N uptake, IAP significantly increased N partial factor productivity, agronomic N efficiency, N recovery efficiency, and physiological efficiency of applied N compared to FP, particularly in the HSF fields. These results indicate that considerable further increases in yield and NUE can be obtained by increasing effective soil N content and maize root length to promote post-silking N and DM accumulation in maize planted at high plant density, especially in fields with low soil fertility.

Improving grain yield, nitrogen use efficiency and radiation use efficiency by dense planting, with delayed and reduced nitrogen application, in double cropping rice in South China

Improving both grain yield and resource use efficiencies simultaneously is a major challenge in rice production.However,few studies have focused on integrating dense planting with delayed and reduced nitrogen application to enhance grain yield,nitrogen use efficiency (NUE) and radiation use efficiency (RUE) in rice (Oryza sativa L.) in the double rice cropping system in South China.A high-yielding indica hybrid rice cultivar (Yliangyou 143) was grown in field experiments in Guangxi,South China,with three cultivation managements:farmers’practice (FP),dense planting with equal N input and delayed N application (DPEN) and dense planting with reduced N input and delayed N application (DPRN).The grain yields of DPRN reached 10.6 and 9.78 t ha^(–1) in the early and late cropping seasons,respectively,which were significantly higher than the corresponding yields of FP by 23.9–29.9%.The grain yields in DPEN and DPRN were comparable.NUE in DPRN reached 65.2–72.9 kg kg^(–1),which was 61.2–74.1% higher than that in FP and 24.6–30.2% higher than that in DPEN.RUE in DPRN achieved 1.60–1.80 g MJ^(–1),which was 28.6–37.9% higher than that in FP.The productive tiller percentage in DPRN was 7.9–36.2% higher than that in DPEN.Increases in crop growth rate,leaf area duration,N uptake from panicle initiation to heading and enhancement of the apparent transformation ratio of dry weight from stems and leaf sheaths to panicles all contributed to higher grain yield and higher resource use efficiencies in DPRN.Correlation analysis revealed that the agronomic and physiological traits mentioned above were significantly and positively correlated with grain yield.Comparison trials carried out in Guangdong in 2018 and 2019 also showed that DPRN performed better than DPEN.We conclude that DPRN is a feasible approach for simultaneously increasing grain yield,NUE and RUE in the double rice cropping system in South China.

Bed planting of wheat(Triticum aestivum L.)improves nitrogen use efficiency and grain yield compared to flat planting

Conventional flat planting is commonly used for growing wheat in Pakistan and the crop is irrigated by flood irrigation, but it leads to ineffective use of applied nitrogen owing to poor aeration and leaching and volatilization losses. The practice also results in greater crop lodging, lower water use efficiency, and crusting of the soil surface. In contrast, bed planting of wheat not only saves water but improves fertilizer use efficiency and grain yield. Three years of pooled data from the present study showed that wheat planting on beds and nitrogen application at 120 kg ha-1produced 15.06% higher grain yield than flat planting at the same nitrogen rate. Similarly, 25.04%, 15.02%, 14.59%, and 29.83% higher nitrogen uptake, nitrogen use, and agronomic and recovery efficiencies, respectively, were recorded for bed compared to flat planting. Wheat planting on beds with a nitrogen application of80 kg ha-1gave a yield similar to that of flat planting with 120 kg ha-1nitrogen. However,the economic return was 29% higher in bed planting as compared to flat planting, when nitrogen was applied at 120 kg ha-1.

Effect of Nitrogen Application on Grain Filling in Maize with Different Nitrogen Efficiency

There are significant differences in nitrogen absorption and utilization effi- ciency among different maize varieties. So it is very essential to determine nitrogen efficiencies of different maize varieties. The effect of nitrogen application on maize growth can be reflected at the grain filling stage. Many scholars have researched the differences in grain filling characteristics among different maize varieties under the same nitrogen application conditions, but there are reare reports on the differ- ences under different nitrogen application conditions. In this study, the grain filling dynamics of maize were observed so as to determine the differences in nitrogen efficiency and to further compare the differences in grain filling characteristics a- mong different maize varieties. The test was carried out with Tunyu 99, Luyu 19 and Xianyu 335 as the materials during May 1st to October 7th, 2013. Under the nitrogen application levels of NO （0 kg/hm2 of pure nitrogen）, N1 （140 kg/hm2 of pure nitrogen） and N2 （210 kg/hm2 of pure nitrogen）, the filling dynamics of upper- and middle- lower-part grains of spring maize were studied. The results showed that among the three nitrogen application level, the grain fresh weight and dry weight of Tunyu 99 ranked as N2〉NI〉N0; the grain fresh weight and dry weight of Luyu 19 ranked as N1〉N2〉N0; the grain fresh weight and dry weight of Xianyu 335 ranked as （N1, N2）〉N0, and there was no significant difference between N1 and N2. Un- der the nitrogen application level of N1, Luyu 19 showed the best growth; under the nitrogen application level of N2, Tunyu 99 showed the best growth, The growth ad- vantage of Xianyu 335 was unobvious under neither N1 nor N2 nitrogen application levels. The development-promoting effect of nitrogen application was more obvious in upper-part grains than that in middle-lower-part grains.

Evaluation for Use Efficiency of Agricultural Resources in Grain Production:A Case Study of Changshu,Taihe and Ansai in China

This paper aims to establish an index system for evaluation of agricultural resources use efficiency(ARUE) in grain production and discuss the causes of low efficiency and high consumption of agricultural resources in Changshu of Jiangsu Province,Taihe of Jiangxi Province and Ansai of Shaanxi Province in China by analyzing the data about meteorology,soil,water consumption and grain production. Agro-ecological Zone(AEZ) method was adopted to calculate the potential productivity,and synthetically multivariate equation was used to evaluate the ARUE of study areas. This paper can be concluded as:1) the agricultural resources in grain production can be classified into five categories,i.e.,climatic resources,water resources,land resources,biological resources and assistant resources,and 15 indexes were selected to evaluate their use efficiency in grain production;2) the values of ARUE in grain production are 0.5868,0.6368 and 0.5390 respectively in Changshu,Taihe and Ansai;and 3) Changshu ranks the highest among the three study areas in terms of the use efficiency of climatic resources and biological resources(evaluation values are 0.0277 and 0.1530) ,but Taihe tops the three in terms of the use efficiency of water resources,land resources and assistant resources(evaluation values are 0.0502,0.2945 and 0.1379 respectively) . However,the ARUE remains always low in Ansai for all the resources. The inefficiencies are caused by poor grain revenue in Changshu,deficient agriculture investments in Taihe and unfavorable natural conditions in Ansai.

Review grain yield and nitrogen use efficiency in rice production regions in China

As one of the staple food crops, rice（Oryza sativa L.） is widely cultivated across China, which plays a critical role in guaranteeing national food security. Most previous studies on grain yield or/and nitrogen use efficiency（NUE） of rice in China often involved site-specific field experiments, or small regions with insufficient data, which limited the representation for the current rice production regions. In this study, a database covering a wide range of climate conditions, soil types and field managements across China, was developed to estimate rice grain yield and NUE in various rice production regions in China and to evaluate the relationships between N rates and grain yield, NUE. According to the database for rice, the values of grain yield, plant N accumulation, N harvest index（HIN）, indigenous N supply（INS）, internal N efficiency（IE_N）, reciprocal internal N efficiency（RIE_N）, agronomic N use efficiency（AE_N）, partial N factor productivity（PEPN）, physiological N efficiency（PE_N）, and recover efficiency of applied N（RE_N） averaged 7.69 t ha^（–1）, 152 kg ha^（–1）, 0.64 kg kg^（–1）, 94.1 kg kg^（–1）, 53.9 kg kg^（–1）, 1.98 kg kg^（–1）, 12.6 kg kg^（–1）, 48.6 kg kg^（–1）, 33.8 kg kg^（–1）, and 39.3%, respectively. However, the corresponding values all varied tremendously with large variation. Rice planting regions and N rates had significant influence on grain yield, N uptake and NUE values. Considering all observations, N rates of 200 to 250 kg ha^（–1） commonly achieved higher rice grain yield compared to less than 200 kg N ha^（–1） and more than 250 kg N ha^（–1） at most rice planting regions. At N rates of 200 to 250 kg ha^（–1）, significant positive linear relationships were observed between rice grain yield and AE_N, PE_N, RE_N, IE_N, and PFPN, and 46.49, 24.64, 7.94, 17.84, and 88.24% of the variation in AE_N, PE_N, RE_N, IE_N, and PFPN could be explained by grain yield, respectively. In conclusion, in a reasonable range of N application, an increase in grain yield can be achieved accompanying by an acceptable NUE.

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.

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.

Optimize nitrogen fertilization location in root-growing zone to increase grain yield and nitrogen use efficiency of transplanted rice in subtropical China

The optimized nitrogen fertilization location differs in different rice-growing regions. We optimized nitrogen deep-point application in root-growing zone（NARZ） for transplanted rice in subtropical China. Field plot experiments were conducted over two years（2014–2015） in a double-rice cropping system to evaluate the effects of nitrogen（N） fertilizer location on grain yield and N use efficiency（NUE）. Four different nitrogen deep-point application methods（DN） were compared with traditional broadcast application（BN） using granular urea. The results showed that grain yield, recovery efficiency of N（REN）, agronomic efficiency of N（AEN）, and partial factor productivity of N（PFP_N） significantly increased 10.3–63.4, 13.7–56.7, 24.7–201.9 and 10.2–63.4%, respectively, in DN treatment compared to BN, respectively. We also find that DN treatments increased grain yield as well as grain N content, and thus grain quality, in comparison with conventional BN treatment. Correlation analysis indicated that significant improvement in grain yield and NUE mainly resulted from increases in productive panicle number and grain N content. In our proposed NARZ method, granular urea should be placed 0 to 5 cm around the rice seeding at a 12-cm depth druing rice transplanting. In NARZ, balanced application of N, P and K further improved grain yield and NUE over treatments with a single N deep-point application. High N uptake by the rice plant did not cause significant soil fertility depletion, demonstrating that this method could guarantee sustainable rice production.

Assessing the yield difference of double-cropping rice in South China driven by radiation use efficiency

Double-cropping rice in South China continues to break the total yield record,but the yield potential of singlecropping rice is not being realized.Radiation use efficiency(RUE)has been singled out as an important determinant of grain yield in many cereal species.However,there is no information on whether the yield gaps in doublecropping rice involve differences in RUE.Field experiments were performed over two years to evaluate the effects of intercepted radiation(IP)and RUE on the above-ground biomass production,crop growth rate(CGR),and harvest index(HI),in four representative rice varieties,i.e.,Xiangyaxiangzhan(XYXZ),Meixiangzhan 2(MXZ2),Nanjingxiangzhan(NJXZ),and Ruanhuayoujinsi(RHYJS),during the early and late seasons of rice cultivation in South China.The results revealed that grain yield in the early season was 8.2%higher than in the late season.The yield advantage in the early season was primarily due to higher spikelets per panicle and above-ground biomass resulting from a higher RUE.The spikelets per panicle in the early season were 6.5,8.3,6.9,and 8.5%higher in XYXZ,MXZ2,NJXZ,and RHYJS,respectively,than in the late season.The higher early season grain yield was more closely related to RUE in the middle tillering stage(R^(2)=0.34),panicle initiation(R^(2)=0.16),and maturation stage(R^(2)=0.28),and the intercepted photosynthetically active radiation(IPAR)in the maturation stage(R^(2)=0.28),while the late season grain yield was more dependent on IPAR in the middle tillering stage(R^(2)=0.31)and IPAR at panicle initiation(R^(2)=0.23).The results of this study conclusively show that higher RUE contributes to the yield progress of early season rice,while the yield improvement of late season rice is attributed to higher radiation during the early reproductive stage.Rationally allocating the RUE of double-cropping rice with high RUE varieties or adjustments of the sowing period merits further study.

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.