Quantifying major sources of uncertainty in projecting the impact of climate change on wheat grain yield in dryland environments

Modelling the impact of climate change on cropping systems is crucial to support policy-making for farmers and stakeholders.Nevertheless,there exists inherent uncertainty in such cases.General Circulation Models(GCMs)and future climate change scenarios(different Representative Concentration Pathways(RCPs)in different future time periods)are among the major sources of uncertainty in projecting the impact of climate change on crop grain yield.This study quantified the different sources of uncertainty associated with future climate change impact on wheat grain yield in dryland environments(Shiraz,Hamedan,Sanandaj,Kermanshah and Khorramabad)in eastern and southern Iran.These five representative locations can be categorized into three climate classes:arid cold(Shiraz),semi-arid cold(Hamedan and Sanandaj)and semi-arid cool(Kermanshah and Khorramabad).Accordingly,the downscaled daily outputs of 29 GCMs under two RCPs(RCP4.5 and RCP8.5)in the near future(2030s),middle future(2050s)and far future(2080s)were used as inputs for the Agricultural Production Systems sIMulator(APSIM)-wheat model.Analysis of variance(ANOVA)was employed to quantify the sources of uncertainty in projecting the impact of climate change on wheat grain yield.Years from 1980 to 2009 were regarded as the baseline period.The projection results indicated that wheat grain yield was expected to increase by 12.30%,17.10%,and 17.70%in the near future(2030s),middle future(2050s)and far future(2080s),respectively.The increases differed under different RCPs in different future time periods,ranging from 11.70%(under RCP4.5 in the 2030s)to 20.20%(under RCP8.5 in the 2080s)by averaging all GCMs and locations,implying that future wheat grain yield depended largely upon the rising CO2 concentrations.ANOVA results revealed that more than 97.22% of the variance in future wheat grain yield was explained by locations,followed by scenarios,GCMs,and their interactions.Specifically,at the semi-arid climate locations(Hamedan,Sanandaj,Kermanshah and Khorramabad),most of the variations arose from the scenarios(77.25%),while at the arid climate location(Shiraz),GCMs(54.00%)accounted for the greatest variation.Overall,the ensemble use of a wide range of GCMs should be given priority to narrow the uncertainty when projecting wheat grain yield under changing climate conditions,particularly in dryland environments characterized by large fluctuations in rainfall and temperature.Moreover,the current research suggested some GCMs(e.g.,the IPSL-CM5B-LR,CCSM4,and BNU-ESM)that made moderate effects in projecting the impact of climate change on wheat grain yield to be used to project future climate conditions in similar environments worldwide.

Global sensitivity analysis of wheat grain yield and quality and the related process variables from the DSSAT-CERES model based on the extended Fourier Amplitude Sensitivity Test method

A crop growth model,integrating genotype,environment,and management factor,was developed to serve as an analytical tool to study the influence of these factors on crop growth,production,and agricultural planning.A major challenge of model application is the optimization and calibration of a considerable number of parameters.Sensitivity analysis(SA) has become an effective method to identify the importance of various parameters.In this study,the extended Fourier Amplitude Sensitivity Test(EFAST) approach was used to evaluate the sensitivity of the DSSAT-CERES model output responses of interest to 39 crop genotype parameters and six soil parameters.The outputs for the SA included grain yield and quality(take grain protein content(GPC) as an indicator) at maturity stage,as well as leaf area index,aboveground biomass,and aboveground nitrogen accumulation at the critical process variables.The key results showed that:(1) the influence of parameter bounds on the sensitivity results was slight and less than the impacts from the significance of the parameters themselves;(2) the sensitivity parameters of grain yield and GPC were different,and the sensitivity of the interactions between parameters to GPC was greater than those between the parameters to grain yield;and(3) the sensitivity analyses of some process variables,including leaf area index,aboveground biomass,and aboveground nitrogen accumulation,should be performed differently.Finally,some parameters,which improve the model’s structure and the accuracy of the process simulation,should not be ignored when maturity output as an objective variable is studied.

Grain yield and water use of winter wheat as affected by water and sulfur supply in the North China Plain

Water shortage has threatened sustainable development of agriculture globally as well as in the North China Plain（NCP）.Irrigation,as the most effective way to increase food production in dry land,may not be readily available in the situation of drought.One of the alternatives is to supply plants with enough nutrients so that they can be more sustainable to the water stress.The objective of this study was to explore effects of irrigation and sulphur（S）application on water consumption,dry matter accumulation（DMA）,and grain yield of winter wheat in NCP.Three irrigation regimes including no irrigation（rainfed,I0）during the whole growth period,once irrigation only at jointing stage（90 mm,I1）,and twice respective irrigation at jointing and anthesis stages（90 mm plus 90 mm,I2）,and two levels of S application including 0S0and 60 kg ha^–1（S60）were designed in the field experiment in NCP.Results showed that increasing irrigation times significantly increased mean grain yield of wheat by 12.5–23.7%and nitrogen partial factor productivity（NPFP）by 21.2–45.0%in two wheat seasons,but markedly decreased crop water use efficiency（YWUE）.Furthermore,S supply 60 kg ha^–1 significantly increased mean grain yield,YWUE,IWUE and NPFP by 5.6,6.1,23.2,and 5.6%（across two wheat seasons）,respectively.However,we also found that role of soil moisture prior to S application was one of important greater factors on improving the absorption and utilization of storage water and nutrients of soil.Thus,water supply is still the most important factor to restrict the growth of wheat in the present case of NCP,supplying 60 kg ha^–1 S with once irrigation 90 mm at the jointing stage is a relatively appropriate recommended combination to improve grain yield and WUE of wheat when saving water resources is be considered in irrigated wheat farmlands of NCP.

Contribution of ear photosynthesis to grain yield under rainfed and irrigation conditions for winter wheat cultivars released in the past 30 years in North China Plain

To understand the contribution of ear photosynthesis to grain yield and its response to water supply in the improvement of winter wheat, 15 cultivars released from 1980 to 2012 in North China Plain（NCP） were planted under rainfed and irrigated conditions from 2011 to 2013, and the ear photosynthesis was tested by ear shading. During the past 30 years, grain yield significantly increased, the flag leaf area slightly increased under irrigated condition but decreased significantly under rainfed condition, the ratio of grain weight：leaf area significantly increased, and the contribution of ear photosynthesis to grain yield changed from 33.6 to 64.5% and from 32.2 to 57.2% under rainfed and irrigated conditions, respectively. Grain yield, yield components, and ratio of grain weight：leaf area were positively related with contribution of ear photosynthesis. The increase in grain yield in winter wheat was related with improvement in ear photosynthesis contribution in NCP, especially under rainfed condition.

Slight shading after anthesis increases photosynthetic productivity and grain yield of winter wheat (Triticum aestivum L.) due to the delaying of leaf senescence

The solar radiation intensity and duration are continuously decreasing in the major wheat planting area of China. As a con- sequence, leaf senescence, photosynthesis, grain filling and thus wheat yield shall be affected by light deficiency. Therefore, two winter wheat （Triticum aestivum L.） cultivars, Tainong 18 （a large-spike cultivar） and Ji＇nan 17 （a multiple-spike cultivar）, were subjected to shading during anthesis and maturity under field condition in 2010-2011 and 2011-2012. Under the slight shading treatment （$1,88% of full sunshine）, leaf senescence was delayed, net photosynthesis rate （Po） and canopy apparent photosynthesis rate （CAP） were improved, and thus thousand-kernel weight （TKW） and grain yield were higher as compared with the control. However, mid and severe shading （S2 andS3, 67 and 35% of full sunshine, respectively） led to negative effects on these traits substantially. Moreover, superoxide dismutase （SOD）, peroxidase （POD） and cat- alase （CAT） activities in flag leaf were significantly greater under slight shading than those in other treatments, while the malondialdehyde （MDA） content was less than that under other treatments. In addition, the multiple-spike cultivar is more tolerant to shading than large-spike cultivar. In conclusion, slight shading after anthesis delayed leaf senescence, enhanced photosynthesis and grain filling, and thus resulted in higher grain yield.

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.

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.

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.

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.

QTL for grain yield and yield parameters in winter wheat(Triticum aestivum L.)

Field trials with a set of 108 doubled haploid lines(DHs) derived from a cross between the Chinese winter wheat cvs.CA9613 and H1488 were run at Beijing(China).Phenotypic data were recorded for major agronomic yield traits,i.e.grain weight per ear,grain number per ear and thousand grain weight(Tgw) in two field trials at Beijing.Based on the phenotypic data and a genetic map comprising 168 SSR markers,an analysis of quantitative trait loci(QTL) was carried out for yield and yield parameters using the composite interval mapping(CIM) approach.A total of 14 QTL were detected for these traits across two environments.Four of these QTL located on chromosomes 1A and 2B,respectively,exhibited pleiotropic effects.Loci showing pleiotropic effects will be very useful for understanding the homeologous relationships of QTL and designing an appropriate marker-assisted selection programme by multi-trait selection in order to accumulate("pyramide") favorable alleles at different loci.

Effects of Nitrogen Application in Different Wheat Growth Stages on the Floret Development and GrainYield of Winter Wheat

The study was carried out on the effect of nitrogen application in different wheat growth stage on the floret development, the photosynthetic rate, the yield and its components of winter wheat. The result indicated that nitrogen application in the pistil-stamen primordium formation stage and the tetrad formation stage of wheat growth prolonged the duration of floret development, promoted the balance growth of floret and reduced the floret decadence number, thus increased the grain number per spike. Nitrogen application in the middle and in the late stages of wheat development increased the photosynthetic ability of the plant leaves in the later stage, and also lengthened the peak of grain filling stage, thus enhanced the grain weight and yield of wheat significantly.

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.

Root carbon consumption and grain yield of spring wheat in response to phosphorus supply under two water regimes

In semiarid areas, cereal crops often alocate more biomass to root at the expense of aboveground yield. A pot experiment was conducted to investigate carbon consumption of roots and its impact on grain yield of spring wheat （Triticum aestivum L.） as affected by water and phosphorus （P） supply. A factorial design was used with six treatments namely two water regimes （at 80–75% and 50–45% ifeld capacity （FC）） and three P supply rates （P1=0, P2=44 and P3=109 μg P g–1 soil）. At shooting and lfowering stages, root respiration and carbon consumption increased with the elevate of P supply rates, regardless of water conditions, which achieved the minimum and maximum at P1 under 50–45% FC and P3 under 80–75% FC, respectively. However, total aboveground biomass and grain yield were higher at P2 under 80–75% FC; and decreased with high P application （P3）. The results indicated that rational or low P supply （80–75% of ifeld water capacity and 44 mg P kg–1 soil） should be recommended to improve grain yield by decreasing root carbon consumption in semiarid areas.

Effects of Nitrogen on Grain Yield,Nutritional and Processing Quality of Wheat for Different End Uses

The effects of nitrogen on grain yield, nutritional quality and processing quality of wheat for different end uses were studied in Yangzhou from 2000 to 2002. Increasing N application amount and/or the ratio of topdressing N after elongation stage could raise grain yield, protein content, wet gluten content, sedimentation, falling number, development time and stability time. To produce strong-gluten and medium-gluten wheat, the suitable ratio of basis : tillering : elongation : booting N fertilizer was 3:1:3:3or5:1:2:2 with 180 - 240 kg N ha-1. To produce weak-gluten wheat, the ratio of basis : tillering : elongation N fertilizer should be 7 : 1 : 2 with 180 kg N ha-1 and 240×104 ha-1 seedlings.

Effects of Delayed Nitrogen Topdressing on Grain Yield and Photosynthetic Characteristics of Flag Leaves of Wheat

Four wheat cultivars were used to study the effects of delayed nitrogen topdressing on population structure, grain yield and photosynthetic characteristics of flag leaves under high-yielding conditions. The results showed that the nitrogen topdressing delayed from overwintering-turning green stage (N1) to turning green-jointing stage(N2) and jointing-booting stage(N3) decreased ineffective tiller in spring, retarded the decline of green leaf area and chlorophyll content in late life span, promoted photosynthetic ability of flag leaves and significantly increased the grain yield. N3 treatment was suitable for most wheat cultivars except the genotypes with higher single spike productivity and less ears in unit area.

Yield of Wheat (<i>Triticum aestivum</i>) and Nutrient Uptake in Grain and Straw as Influenced by Some Macro (S &Mg) and Micro (B &Zn) Nutrients

A wheat variety BARI Gom 26 was cultivated with an objective of evaluating the effects of macro/secondary nutrients as S and Mg, and micro nutrients as B and Zn on yield, yield contributing traits and nutrient uptake status by the crop. The field experiment was con-ducted in the “North Eastern Barind Tract Soils” at Kushadaha, Nawabganj, Dinajpur, Bangladesh from November, 2014 to March, 2015. The surface soil was clay in texture, having pH 5.61, organic matter 1.58%, total N 0.10%, available P 7.03 ppm, exchangeable K 0.11 meq/100g, available S 2.57 ppm, exchangeable Mg 0.55 meq/100g, available Zn 1.30 ppm, available B 0.08 ppm. The experiment was designed with five treatments laid out in a randomized complete block design (RCBD) with three replications. The treatments were T1: NPK (control), T2: NPK + S, T3: NPK + S + Mg, T4: NPK + S + Mg + Zn and T5: NPK + S + Mg + Zn + B. All plots of wheat received 100 kg N/ha, 30 kg P/ha and 70 kg K/ha as basal dose. The secondary and micro nutrients doses were 15 kg S/ha, 6 kg Mg/ha, 2.5 kg Zn/ha and 1.5 kg B/ha. Results revealed that the plant height, tillers/hill, 1000-grain weight, yield of grain and straw, uptake of some specific nutrients in grain and straw were signifi-cantly influenced by all the treatments, though these treatments did not show any identical effect on spike length, content of P and Mg in wheat. Significantly highest amount of 1000-grain weight, yield of grain and straw weight of wheat were obtained in applying T2 treatment that employed the addition of S with recommended dose of NPK. Significant positive effects were also observed for the rest parameters in receiving the treatments composed of secondary and micronutrients (T3, T4, and T5). The highest concentration of nutrient uptake N, P, K and S in grain and straw of wheat were also obtained due to the application of T2 treatment. In the case of Mg, the maximum uptake was recorded in T4 where Mg was added as a component of this treatment. In contrast, the highest content of Zn and B were extracted in receiving the treatment T5 both for grain and straw. However, results suggested that T2 treatment comprising recommended dose of NPK with S might be economic and suitable as for better production of 1000-grain weight, yield of grain and straw, uptake of N, P, K and S in grain and straw of wheat cultivated in the North Eastern Barind Tract Soils of Bangladesh under winter condition. The treatment T5 would also be recommended in the context of addition of micronutrients.

Genotype by Environment Interaction for Grain Yield and Association among Stability Parameters in Bread Wheat (<i>Triticum aestivum</i>L.)

Bread wheat (Triticum aestivum L.) is most important cereal crop in Ethiopia. Lack of genotypes with wide stability across environments has been one of the most important constraints of wheat production in the country. Field experiments were conducted in Halaba and Bule, South Ethiopia, in 2016 and 2017, in order to estimate grain yield stability and association among stability parameters. Fifteen improved bread wheat genotypes were grown under randomized complete block design with three replications. Mean yield for Halaba 2016, Halaba 2017, Bule 2016 and Bule 2017 was 3.83, 1.89, 2.90 and 3.59 tons/ha, respectively. Genotypes Lemu (3.25 tons/ha) and Mandoyu (3.18 tons/ha) had high mean yield, and low values of environmental variance (S2i), coefficient of variation (CVi), stability variance (δ2i), ecovalence (Wi) and deviation from regression (S2di). Genotypes Biqa (3.69 tons/ha) and Shorima (3.66 tons/ha) had high mean yield, coefficient of regression (bi) and coefficient of determination (R2i ≥ 0.94) as well as low values of δ2i, Wi and S2di. Grain yield had positive rank correlation with bi (r = 0.75, p 2i (r = 0.70, p δ2i, Wi and S2di was high (r ≥ 0.98, p , Mandoyu and Hidase, and Biqa and Shorima would be recommended for wide adaption, and for more favorable environments, respectively. It could also be suggested that one of Wi, δ2i, S2di and rank sum would be used for ranking of genotypes.

Effect of Irrigation System, Tillage System, and Seeding Rates on Wheat (<i>Triticum aestivum</i>L.) Growth, Grain Yield and Its Water Consumption and Efficiency

A field trial was conducted at a private farm in AL-Hashimiya district Babylon Governorate—the republic of Iraq during the 2016-2017 and 2017-2018 growing seasons. This study was conducted using two irrigation methods, sprinkler and surface irrigation, for each of them had three Tillage methods (zero-tillage, medium-tillage, deep-tillage) and each tillage system had four seeding rate of wheat yield (120, 180, 240, 300) kg∙ha-1. Results indicated that the consumptive water use was 557.5 and 535.9 mm for surface irrigation and 460.9 and 442.6 mm for sprinkler irrigation in the 2016-2017 and 2017-2018 growing seasons. Sprinkler irrigation significantly increased the flag leaf area with no significant effect on plant height. However, the minimum tillage and seeding rate (240 kg∙ha-1) significantly increased the plant height and flag leaf area in both growing seasons. For the grain yield, the sprinkler irrigation, minimum tillage, and seeding rate (240 kg∙ha-1) also increased the plant height and flag leaf area by 13%, 10, % 11%, 11%, 12%, and 14% in both growing seasons, respectively, through an increased number of spikes/m2, the number of grain spike-1, and 1000-grain weight in both growing seasons, respectively. Interestingly the grain yield was increased by 33% and 32% in both growing seasons under the effects of these three factors altogether, respectively. It can be concluded that these factors act synergistically, resulting in a significant improvement in the wheat grain-yield of, less consumptive water use, and high water use efficiency.

Long-term inorganic plus organic fertilization increases yield and yield stability of winter wheat

An understanding of wheat yield and yield stability response to fertilization is important for sustainable wheat production. A 36-year long-term fertilization experiment was employed to evaluate the yield and yield stability of winter wheat. Five fertilization regimes were compared,including(1) CK, no fertilizer;(2) NPK, inorganic fertilizer only;(3) O, organic fertilizer only;(4)NPKO, 50% of NPK plus 50% of O, and(5) HNPKO, 80% of NPK plus 80% of O. The greatest yield increase was recorded in HNPKO, followed by NPKO, with O producing the lowest mean yield increase. Over the 36 years, the rate of wheat yield increase in fertilized plots ranged from95.31 kg ha-1 year-1 in the HNPKO to 138.65 kg ha-1 year-1 in the O. Yield stability analysis using the additive main effects and multiplicative interactions(AMMI) method assigned 62.3%, 26.3%,and 11.4% of sums of squares to fertilization effect, environmental effect, and fertilization ×environment interaction effect, respectively. The combination of inorganic and organic fertilization(NPKO and HNPKO) appeared to produce more stable yields than O or NPK, with lower coefficients of variation and AMMI stability value. However, wheat grown with O seemed to be the most susceptible to climate change and the least productive among the fertilized plots.Significant correlations of grain yield with soil properties and with mean air temperature were observed. These findings suggest that inorganic + organic fertilizer can increase wheat yield and its stability by improvement in soil fertility and reduction in variability to climate change.

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.