Effects of water tables and nitrogen application on soil bacterial community diversity, network structure, and function in an alpine wetland, China

Nitrogen deposition and water tables are important factors to control soil microbial community structure.However,the specific effects and mechanisms of nitrogen deposition and water tables coupling on bacterial diversity,abundance,and community structure in arid alpine wetlands remain unclear.The nitrogen deposition(0,10,and 20 kg N/(hm^(2)•a))experiments were conducted in the Bayinbulak alpine wetland with different water tables(perennial flooding,seasonal waterlogging,and perennial drying).The 16S rRNA(ribosomal ribonucleic acid)gene sequencing technology was employed to analyze the changes in bacterial community diversity,network structure,and function in the soil.Results indicated that bacterial diversity was the highest under seasonal waterlogging condition.However,nitrogen deposition only affected the bacterial Chao1 and beta diversity indices under seasonal waterlogging condition.The abundance of bacterial communities under different water tables showed significant differences at the phylum and genus levels.The dominant phylum,Proteobacteria,was sensitive to soil moisture and its abundance decreased with decreasing water tables.Although nitrogen deposition led to changes in bacterial abundance,such changes were small compared with the effects of water tables.Nitrogen deposition with 10 kg N/(hm^(2)•a)decreased bacterial edge number,average path length,and robustness.However,perennial flooding and drying conditions could simply resist environmental changes caused by 20 kg N/(hm^(2)•a)nitrogen deposition and their network structure remain unchanged.The sulfur cycle function was dominant under perennial flooding condition,and carbon and nitrogen cycle functions were dominant under seasonal waterlogging and perennial drying conditions.Nitrogen application increased the potential function of part of nitrogen cycle and decreased the potential function of sulfur cycle in bacterial community.In summary,composition of bacterial community in the arid alpine wetland was determined by water tables,and diversity of bacterial community was inhibited by a lower water table.Effect of nitrogen deposition on bacterial community structure and function depended on water tables.

Water and nitrogen footprint assessment of integrated agronomic practice management in a summer maize cropping system

The footprints of water and nitrogen(WF and NF)provide a comprehensive overview of the type and quantity of water consumption and reactive nitrogen(Nr)loss in crop production.In this study,a field experiment over two years(2019 and 2020)compared three integrated agronomic practice management(IAPM)systems:An improved management system(T2),a high-yield production system(T3),and an integrated soil-crop management system(ISCM)using a local smallholder farmer’s practice system(T1)as control,to investigate the responses of WF,Nr losses,water use efficiency(WUE),and nitrogen use efficiency(NUE)to IAPM.The results showed that IAPM optimized water distribution and promoted water use by summer maize.The evapotranspiration over the whole maize growth period of IAPM increased,but yield increased more,leading to a significant increase in WUE.The WUE of the T2,T3,and ISCM treatments was significantly greater than in the T1 treatment,in 2019 and 2020respectively,by 19.8-21.5,31.8-40.6,and 34.4-44.6%.The lowest WF was found in the ISCM treatment,which was 31.0%lower than that of the T1 treatment.In addition,the ISCM treatment optimized soil total nitrogen(TN)distribution and significantly increased TN in the cultivated layer.Excessive nitrogen fertilizer was applied in treatment T3,producing the highest maize yield,and resulting in the highest Nr losses.In contrast,the ISCM treatment used a reduced nitrogen fertilizer rate,sacrificing grain yield partly,which reduced Nr losses and eventually led to a significant increase in nitrogen use efficiency and nitrogen recovery.The Nr level in the ISCM treatment was34.8%lower than in the T1 treatment while NUE was significantly higher than in the T1 treatment by 56.8-63.1%in2019 and 2020,respectively.Considering yield,WUE,NUE,WF,and NF together,ISCM should be used as a more sustainable and clean system for sustainable production of summer maize.

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.

Effects of nitrogen deposition on the carbon budget and water stress in Central Asia under climate change

Atmospheric deposition of nitrogen(N)plays a significant role in shaping the structure and functioning of various terrestrial ecosystems worldwide.However,the magnitude of N deposition on grassland ecosystems in Central Asia still remains highly uncertain.In this study,a multi-data approach was adopted to analyze the distribution and amplitude of N deposition effects in Central Asia from 1979 to 2014 using a process-based denitrification decomposition(DNDC)model.Results showed that total vegetation carbon(C)in Central Asia was 0.35(±0.09)Pg C/a and the averaged water stress index(WSI)was 0.20(±0.02)for the whole area.Increasing N deposition led to an increase in the vegetation C of 65.56(±83.03)Tg C and slightly decreased water stress in Central Asia.Findings of this study will expand both our understanding and predictive capacity of C characteristics under future increases in N deposition,and also serve as a valuable reference for decision-making regarding water resources management and climate change mitigation in arid and semi-arid areas globally.

Effects of Nitrogen Application Rate on Yield and Quality of Different Genotypes of Foxtail Millet

In order to elucidate the response mechanism of yield and quality of different genotypes of foxtail millet to nitrogen application.In this study,plant physiology and metabolomics were used to study the effects of different amounts of nitrogen(0,75,150,225 and 300 kg hm^(-2))on agronomic characters,yield and quality of Jingu 21 and Zhangza 10.The results showed that with the increase of nitrogen application,the plant height of different genotypes of foxtail millet increased gradually,and the content of stem diameter,yield,protein,fat,lysine,phenylalanine,isoleucine,arginine,aspartic,glutamic,glycine,and proline content of different genotypes of foxtail millet showed an increasing and then decreasing trend.The highest yield was recorded in Jingu 21 at 150 kg hm^(-2),and the highest yield was recorded in Zhangza 10 at 225 kg hm^(-2) of nitrogen application.Yield of Jingu 21 was positively correlated with protein and tryptophan content(r=0.91).The yield of Zhangza 10 was positively correlated with fibre content(r=0.89).The protein content of different genotypes of foxtail millet were negatively correlated with the peak viscosity(PV),trough viscosity(TV)and breakdown value(BD).The results of this study clarify that the optimal nitrogen application of Jinguu 21 was 150 kg hm^(-2),and that of Zhangza 10 was 225 kg hm^(-2).The regulation effect of nitrogen on foxtail millet was clarified,which laid the theoretical and technical foundation for foxtail millet cultivation with high yield and high quality.

Effects of water and nitrogen rate on grain-filling characteristics under high-low seedbed cultivation in winter wheat

A high-efficiency mode of high-low seedbed cultivation(HLSC)has been listed as the main agricultural technology to increase land utilization ratio and grain yield in Shandong Province,China.However,limited information is available on the optimized water and nitrogen management for yield formation,especially the grain-filling process,under HLSC mode.A three-year field experiment with four nitrogen rates and three irrigation rates of HLSC was conducted to reveal the response of grain-filling parameters,grain weight percentage of spike weight(GPS),spike moisture content(SMC),and winter wheat yield to water and nitrogen rates.The four nitrogen rates were N1(360 kg ha^(-1) pure N),N2(300 kg ha^(-1) pure N),N3(240 kg ha^(-1) pure N),and N4(180 kg ha^(-1) pure N),respectively,and the three irrigation quotas were W1(120 mm),W2(90 mm),and W3(60 mm),respectively.Results showed that the determinate growth function generally performed well in simulating the temporal dynamics of grain weight(0.989<R^(2)<0.999,where R2 is the determination coefficient).The occurrence time of maximum filling rate(T_(max))and active grain-filling period(AGP)increased with the increase in the water or nitrogen rate,whereas the average grain-filling rate(G_(mean))had a decreasing trend.The final 1,000-grain weight(FTGW)increased and then decreased with the increase in the nitrogen rates and increased with the increase in the irrigation rates.The GPS and SMC had a highly significant quadratic polynomial relationship with grain weight and days after anthesis.Nitrogen,irrigation,and year significantly affected the T_(max),AGP,G_(mean),and FTGW.Particularly,the AGP and FTGW were insignificantly different between high seedbed(HLSC-H)and low seedbed(HLSC-L)across the water and nitrogen levels.Moreover,the moderate water and nitrogen supply was more beneficial for grain yield,as well as for spike number and grain number per hectare.The principal component analysis indicated that combining 240-300 kg N ha^(-1) and 90^(-1)20 mm irrigation quota could improve grain-filling efficiency and yield for the HLSC-cultivated winter wheat.

The Impact of Nitrogen-Fixing Bacteria, Iron, and Zinc Foliar Application on Dry Land Yellow Mustard (Brassica juncea) Grain and Oil Production

The study, conducted at the Research Farm of the College of Agriculture, University of Tabriz in 2021, focused on the effects of various nitrogen-fixing bacterial isolates, biofertilizers containing nitrogen and phosphorus, as well as iron and zinc foliar applications on mustard growth under rainfed conditions. The results indicated that biofertilizers, whether used alone or in combination with chemical fertilizers, produced comparable grain and oil outputs compared to chemical fertilizers alone. Additionally, the application of iron and zinc through foliar spraying significantly enhanced both grain and oil production. These findings suggest that integrating nitrogen-fixing bacteria and biofertilizers could reduce reliance on chemical nitrogenous fertilizers, leading to decreased production expenses, improved product quality, and minimized environmental impact. This study highlights the potential for sustainable agricultural practices in dry land farming as a viable alternative to traditional chemical-intensive methods. Substituting chemical nitrogenous fertilizers with nitrogen-fixing bacteria or biofertilizers could result in cost savings in mustard grain and oil production while promoting environmental sustainability.

Seasonal constraint of dynamic water temperature on riverine dissolved inorganic nitrogen transport in land surface modeling

水体温度变化对河流可溶性无机氮(DIN)输送有着强烈控制作用.然而,在全球尺度上河流DIN输送量对水温度变化的响应尚不清楚.因此,本文基于陆面过程模式,耦合河流水温估算和DIN传输方案,设定有,无动态水温情景,对比研究陆面模拟中水温变化对河流DIN通量变化的影响.结果表明:在考虑水温动态变化后,在30°N和30°S之间, DIN通量年振幅减小5%–25%.在中国东部地区,水温动态变化使河流DIN通量在夏季减少1%–3%,在冬季增加1%–5%,对DIN通量具有明显的季节性约束作用,表明动态水温的表达在河流DIN输送模拟中的重要性.

Effects of water application uniformity using a center pivot on winter wheat yield, water and nitrogen use efficiency in the North China Plain

In recent years, the use of fertigation technology with center pivot irrigation systems has increased rapidly in the North China Plain (NCP). The combined effects of water and nitrogen application uniformity on the grain yield, water use efficiency (WUE) and nitrogen use efficiency (NUE) have become a research hotspot. In this study, a two-year field experiment was conducted during the winter wheat growing season in 2016–2018 to evaluate the water application uniformity of a center pivot with two low pressure sprinklers (the R3000 sprinklers were installed in the first span, the corresponding treatment was RS;the D3000 sprinklers were installed in the second span, the corresponding treatment was DS) and a P85A impact sprinkler as the end gun (the corresponding treatment was EG), and to analyze its effects on grain yield, WUE and NUE. The results showed that the water application uniformity coefficients of R3000, D3000 and P85A along the radial direction of the pivot (CUH) were 87.5, 79.5 and 65%, respectively. While the uniformity coefficients along the traveling direction of the pivot (CUC) were all higher than 85%. The effects of water application uniformity of the R3000 and D3000 sprinklers on grain yield were not significant (P>0.05);however, the average grain yield of EG was significantly lower (P<0.05) than those of RS and DS, by 9.4 and 11.1% during two growing seasons, respectively. The coefficients of variation (CV) of the grain yield had a negative correlation with the uniformity coefficient. The CV of WUE was more strongly affected by the water application uniformity, compared with the WUE value, among the three treatments. The NUE of RS was higher than those of DS and EG by about 6.1 and 4.8%, respectively, but there were no significant differences in NUE among the three treatments during the two growing seasons. Although the CUH of the D3000 sprinklers was lower than that of the R3000, it had only limited effects on the grain yield, WUE and NUE. However, the cost of D3000 sprinklers is lower than that of R3000 sprinklers. Therefore, the D3000 sprinklers are recommended for winter wheat irrigation and fertigation in the NCP.

Yield and water use responses of winter wheat to irrigation and nitrogen application in the North China Plain

With increasing water shortage resources and extravagant nitrogen application, there is an urgent need to optimize irrigation regimes and nitrogen management for winter wheat（Triticum aestivum L.） in the North China Plain（NCP）. A 4-year field experiment was conducted to evaluate the effect of three irrigation levels（W1, irrigation once at jointing stage; W2, irrigation once at jointing and once at heading stage; W3, irrigation once at jointing, once at heading, and once at filling stage; 60 mm each irrigation） and four N fertilizer rates（N0, 0; N1, 100 kg N ha-（-1）; N2, 200 kg N ha-（-1）; N3, 300 kg N ha-（-1）） on wheat yield, water use efficiency, fertilizer agronomic efficiency, and economic benefits. The results showed that wheat yield under W2 condition was similar to that under W3, and greater than that under W1 at the same nitrogen level. Yield with the N1 treatment was higher than that with the N0 treatment, but not significantly different from that obtained with the N2 and N3 treatments. The W2 N1 treatment resulted in the highest water use and fertilizer agronomic efficiencies. Compared with local traditional practice（W3 N3）, the net income and output-input ratio of W2 N1 were greater by 12.3 and 19.5%, respectively. These findings suggest that two irrigation events of 60 mm each coupled with application of 100 kg N ha-（–1） is sufficient to provide a high wheat yield during drought growing seasons in the NCP.

Study on the Relationship between the Main Secondary Metabolites and Polysaccharide in Fruits of Lycium barbarum at Different Application Amounts of Nitrogen

[Objective] The aim of this study is to investigate the optimum application amount of nitrogen in Lycium barbarum based on considering the relationship between main secondary metabolites and polysaccharide.[Method]Under field conditions,the effects of different application amounts of nitrogen on main secondary metabolites of betaine,carotenoid and flavone of Lycium barbarum and the relationship between main secondary metabolites and polysaccharide.[Result] The main secondary metabolites of betaine,carotenoid and flavone of Lycium barbarum varied under different application amounts of nitrogen.The proper application amount of nitrogen(600-900 kg/hm2)was beneficial to the formation and accumulation of secondary metabolites such as carotenoids.Correlation analysis results showed that polysaccharide were negatively correlated with betaine,carotenoid and flavone at significant probability level.[Conclusion]Considering the relationship between the output and quality of the fruits of Lycium barbarum,the optimum nitrogen application amount should be 600-900 kg/hm2.

Effects of Nitrogen Application Rate, Density and Seedling Age on Dry Matter Accumulation of No-tillage Rape in Seedling Stage

[Objective] The aim of the research was to find the optimal nitrogen application rate, density and seedling age for no-tillage rape in seedling stage. [Method] With the D-optimal quadratic regression design for three factors, the 310 scheme was designed to study the effects of nitrogen application rate, density and seedling age on dry matter accumulation of no-tillage rape in seedling stage. [Result] With the increase of nitrogen application rate, density and seedling age, the dry matter content appeared like a parabola, increasing firstly and then declining. The change of nitrogen application rate caused greater influence than that of density and seedling age; the interaction effects between nitrogen application rate and density were greater than that between nitrogen application rate and seedling age as well as between density and seedling age. [Conclusion] Considered comprehensively, the dry matter content of no-tillage rape in seedling stage reached the highest level (4 768.2 kg/hm2) when the nitrogen application rate, the density and the seedling age were 195 kg/hm2, 93 000 plants/hm2 and 33 d, respectively.

Effects of Application of Nitrogen, Potassium and Glycinebetaine on Alleviation of Water Stress to Summer Maize

A pot experiment was conducted under water deficit and adequate water-supplied conditions with two maize genetypic varieties （Shaandan 9 and Shaandan 911） to study the effects of nitrogen, potassium and glycinebetaine （GlyBet） on the dry matter and grain yields as well as water use efficiency （WUE）. Determinations were made at different stages of the two varieties for revealing the function of these factors in increasing plant resistance to drought. Results showed that under a water-stressed condition, dry matter and grain yield were significantly reduced. However, the response of the two varieties to water stress was different： Shaandan 9 was significantly higher in dry matter and grain yields, and therefore could be regarded as a drought-resistant variety compared to Shaandan 911.Application of nitrogen, potassium and glycinebetaine raised dry matter and grain yield to different levels, and thereby alleviated the water stress and increased water use efficiency. These effects were higher for Shaandan 911 than for Shaandan 9. Under water-stressed conditions application of N fertilizer, either at low rate or at high rate, significantly increased dry matter, grain yield and water use efficiency. A significant different effect was found for Shaandan 911 between N rates, but not so for Shaandan 9. However, with supplemental water supply, effects of N fertilization were obviously decreased, showing that in addition to supplying nutrient, N fertilizer has a function in increasing drought-resistance of the crop. Potassium and glycinebetaine exhibited a remarkable function in increasing dry matter and grain yields as well as water use efficiency under water stress while such effects were obviously declined, even vanished, with supplemental water supply, indicating the important contribution of these factors in rise of drought-resistance ability of a crop.

Modeling the Effect of Planting Dates and Nitrogen Application Rates on Potatoes Water Productivity in Jordan Valley

Agricultural sector in Jordan is facing serious challenges in meeting the growing needs of food security because of its low water availability. Maintaining and enhancing agricultural water productivity under such prevailing environmental constraints are hard to achieve. Potatoes water productively in Jordan Valley was modeled using Decision Support System for Agrotechnology Transfer (DSSAT) under six nitrogen applications (0, 60, 80, 100, 120 and 140 kg/ha) and twelve planting dates every two weeks from October 1 to March 15 scenarios. The potatoes yield increased from 0% to 100% nitrogen treatment and then no considerable increase occurred. The potatoes’ crop yield increased from October 1st to January 15 and then decreased after which until the last day of planting date. The seasonal cumulative crop evapotranspiration for potatoes about doubled from 0% to 60% nitrogen treatment and then kept increasing gradually until the last treatment. The growing season cumulative crop evapotranspiration for potatoes increased gradually from October 1 to March 1. The water productivity increased from 0% nitrogen treatment to 100% and then decreased. The potatoes’ water productivity increased from October 1 until November 15 and then decreased to the end. From these results, we recommend that 100% of nitrogen requirements should be applied. The best window for potatoes’ planting date is the last two weeks in November.

Effect of Varied Irrigation Scheduling with Levels and Times of Nitrogen Application on Yield and Water Use Efficiency of Aerobic Rice

More rice needs to be produced with lesser water to feed the increasing human population. Judicious water management practices and appropriate water saving technologies in rice cultivation are in need in the coming decades. Aerobic rice is one of water saving method of rice cultivation. The field experiment was conducted during Summer season of February 2018 to May 2018 at Tamil Nadu Agricultural University, Agricultural College and Research Institute, Madurai, to find out the effect of irrigation schedules with varied doses and time of nitrogen application on yield of aerobic rice. Irrigation scheduling of IW/CPE (Irrigation Water/Cumulative Pan Evaporation) 1.0 up to panicle initiation stage and thereafter IW/CPE 1.2 up to dough stage recorded higher yield attributes viz., number of panicles hill-1 (9.1), number of filled grains panicle-1 (87.9), test weight (15.3 g), grain yield (4462 kg·ha-1), straw yield (5977 kg·ha-1). However, the highest water use efficiency (6.8 kg·ha-1·mm-1) was recorded in the treatment of IW/CPE 1.0 throughout the crop growth period. Lower yield attributes, yield and water use efficiency were recorded with irrigation scheduling of IW/CPE 0.8 throughout the growth stage. Application of nitrogen at 150 kg·ha-1 in 5 equal splits at 20, 35, 50, 65 and 80 DAS (Days after sowing) recorded higher yield attributes viz., number of panicles hill-1 (9.3), number of filled grains panicle-1 (90.5), test weight (15.4 g), grain yield (4746 kg·ha-1), straw yield (6258 kg·ha-1) and WUE (7.5 kg·ha-1·mm-1). Application of nitrogen 100 kg·ha-1 in 4 equal splits at 20, 40, 60 and 80 DAS recorded lower yield attributes, yield and water use efficiency. The interaction effect between irrigation scheduling and nitrogen management on yield was significant. The combination of IW/CPE 1.0 up to panicle initiation stage and thereafter IW/CPE 1.2 up to dough stage along with application of nitrogen at 150 kg·ha-1 in 5 equal splits at 20, 35, 50, 65 and 80 DAS significantly produced higher number of panicles hill-1 (10.7), grain yield of 5419 kg·ha-1 and straw yield of 6906 kg·ha-1. However, IW/CPE 1.0 throughout the growth period along with application of nitrogen at 150 kg·ha-1 in 5 equal splits at 20, 35, 50, 65 and 80 DAS registered the highest water use efficiency (8.4 kg·ha-1·mm-1) in aerobic rice.

Adjusting Nitrogen Application in Accordance with Soil Water Availability Enhances Yield and Water Use by Regulating Physiological Traits of Maize under Drip Fertigation

Knowledge of the interactive effects of water and nitrogen(N)on physio-chemical traits of maize(Zea mays L.)helps to optimize water and N management and improve productivity.A split-plot experiment was conducted with three soil water conditions(severe drought,moderate drought,and fully water supply referring to 45%-55%,65%-75%,and 85%-95%field capacity,respectively)and four N application rates(N0,N150,N240,and N330 referring to 0,150,240,330 kg N ha^(-1)respectively)under drip fertigation in 2014 and 2015 in the Huang-Huai-Hai Plain of China.The results indicated that drought stress inhibited physiological activity of plants(leaf relative water content,root bleeding sap,and net photosynthetic rate),resulting in low dry matter accumulation after silking,yield,and N uptake,whereas increased WUE and NUE.N application rates over than 150 kg ha^(-1)aggravated the inhibition of physiological activity under severe drought condition,while it was offset under moderate drought condition.High N application rates(N330)still revealed negative effects under moderate drought condition,as it did not consistently enhance plant physiological activity and significantly reduced N uptake as compared to the N240 treatment.With fully water supply,increasing N application rates synergistically enhanced physiological activity,promoted dry matter accumulation after silking,and increased yield,WUE,and N uptake.Although the N240 treatment reduced yield by 5.4%in average,it saved 27.3%N under full water supply condition as compared with N330 treatment.The results indicated that N regulated growth of maize in aspects of physiological traits,dry matter accumulation,and yield as well as water and N use was depended on soil water status.The appropriate N application rates for maize production was 150 kg ha^(-1)under moderate drought or 240 kg ha^(-1)under fully water supply under drip fertigation,and high N supply(>150 kg ha^(-1))should be avoided under severe drought condition.

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 Postponing N Application on Metabolism,Absorption and Utilization of Nitrogen of Summer Maize in SuperHigh Yield Region

[Objective] The aim was to explore effects of application postponing of N fertilizer and the mechanism of yield increase in order to provide references for N fertilizer application in a rational way. [Method] In a super-high yielded region of summer maize, field experiment was conducted to research effects of N fertilizer postponing on key enzymes of N metabolism, yield of maize and N fertilizer use. [Result] After application of N fertilizer was postponed, NR, SPS and GS activities of ear-leaf of summer maize increased by 11.99%-34.87%, 8.25%-10.64% and 10.00%- 16.81% on the 28^th d of silking; content of soluble sugar in leaves enhanced signifi- cantly and accumulated nitrogen increased by 5.00%-9.74% in mature stage. The postponing fertilization of ＂30% of fertilizer in seedling stage＋30% of fertilizer in flare- opening stage＋40% of fertilizer in silking stage meets N demands of summer maize in late growth period. Compared with conventional fertilization, the maize yield, agro- nomic efficiency and use of N fertilizer all improved by 5.05%, 1.75 kg/kg and 6.87%, respectively, after application postponed. [Conclusion] Application postponing of N fertilizer maintains activity of NR, GS and SPS higher and coordinates metabolism of C and N in late growth period, to further improve yield of maize.

Effects of Nitrogen Application Amount on Growth Characteristics,Boll Development and Lint Yield of High Quality Cotton

[Objective] This study aimed to explore an optimum application amount of nitrogen for cotton cultivation. [Method] In this study, a field experiment was conducted to investigate the effects of nitrogen application amount on the growth characteristics, boll development and lint yield of high quality cotton line FZ-1. [Result] Compared with the nitrogen level of 225 kg/hm2, the lint yield had increased by 28.46% and 18.73%, respectively, with the nitrogen application amount of 300 and 375 kg/hm2. When the nitrogen application amount had increased from 225 to 300 kg/hm2, boll number per plant, boll weight and lint yield had significantly increased. At the nitrogen level of 375 kg/hm2, however, the effects of increasing lint yield were significantly less than that at the nitrogen level of 300 kg/hm2. Compared with the nitrogen levels of 225 and 375, 300 kg/hm2 of nitrogen was the optimum application amount to improve the plant height, daily increment of plant height, number of fruit branches, number ratio of nodes to fruit branches, boll volume and seed cotton weight per boll. [Conclusion] The rational management of nitrogen is the most effective way to promote the growth and development of cotton plants, ensure high yielding ability and minimize the environmental pollution caused by the overuse of nitrogen. This study had provided a sound nitrogen application strategy for the cultivation of this high-quality cotton line in the field plantation.

Effects of Panicle Fertilizer Application on Source-Sink Characteristics and Nitrogen Fertilizer Use Efficacy of Ganxin688

[Objective]The paper was to explore the effect of postponing application of N fertilizer on source-sink characteristics of super hybrid rice Ganxin688.[Method] With super hybrid rice Ganxin688 as test material,the source organ traits（leaf area index,leaf weight,chlorophyll content,photosynthetic rate of flag leaf,stem and sheath dry matter accumulation and output） and yield were measured,the effects of nitrogen application on source-sink relationship,yield and N fertilizer use efficiency were also studied.[Result] Appropriate postponing of N fertilizer was benefit for optimizing population quality,harmonizing source-sink relation,enhancing leaf function,prolonging leaf function period and increasing N fertilizer use efficiency.After heading,the leaves area index（LAI） and chlorophyll content increased with the increasing application amount of panicle fertilizer,and their reduction rate slowed down with the increased application amount of panicle fertilizer.Appropriate increased application of panicle fertilizer could prolong the function period of leaves in lower position,increase storage amount of stem and sheath matter,total sink capacity and sink capacity per unit leaf area during heading stage,improve panicle rate and seed setting rate,reduce the demand of grain sink on stem and sheath matter,and increase lodging resistance of plant,which could also increase dry matter productivity and rice productivity of N fertilizer,and increase absorption and application ratio and total accumulation amount of N fertilizer.For Ganxin 688,when N application amount was 175-205 kg/hm2,the proportion of panicle fertilizer in total nitrogen application should be better as 40%-45%.[Conclusion] The study provided basis for making reasonable and efficient N application strategy to establish a coordinated huge sink and strong source relationship for super rice.