IMPACT OF CLIMATE ON GRAIN YIELD PER UNIT AREA IN CHINA DURING THE YEARS OF 1949～1992

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Grain yield and N uptake of maize in response to increased plant density under reduced water and nitrogen supply conditions

The development of modern agriculture requires the reduction of water and chemical N fertilizer inputs.Increasing the planting density can maintain higher yields,but also consumes more of these restrictive resources.However,whether an increased maize density can compensate for the negative effects of reduced water and N supply on grain yield and N uptake in the arid irrigated areas remains unknown.This study is part of a long-term positioning trial that started in 2016.A split-split plot field experiment of maize was implemented in the arid irrigated area of northwestern China in 2020 to 2021.The treatments included two irrigation levels:local conventional irrigation reduced by 20%(W1,3,240 m^(3)ha^(-1))and local conventional irrigation(W2,4,050 m^(3)ha^(-1));two N application rates:local conventional N reduced by 25%(N1,270 kg ha^(-1))and local conventional N(360 kg ha^(-1));and three planting densities:local conventional density(D1,75,000 plants ha^(-1)),density increased by 30%(D2,97,500 plants ha-1),and density increased by 60%(D3,120,000 plants ha^(-1)).Our results showed that the grain yield and aboveground N accumulation of maize were lower under the reduced water and N inputs,but increasing the maize density by 30% can compensate for the reductions of grain yield and aboveground N accumulation caused by the reduced water and N supply.When water was reduced while the N application rate remained unchanged,increasing the planting density by 30% enhanced grain yield by 13.9% and aboveground N accumulation by 15.3%.Under reduced water and N inputs,increasing the maize density by 30% enhanced N uptake efficiency and N partial factor productivity,and it also compensated for the N harvest index and N metabolic related enzyme activities.Compared with W2N2D1,the N uptake efficiency and N partial factor productivity increased by 28.6 and 17.6%under W1N1D2.W1N2D2 had 8.4% higher N uptake efficiency and 13.9% higher N partial factor productivity than W2N2D1.W1N2D2 improved urease activity and nitrate reductase activity by 5.4% at the R2(blister)stage and 19.6% at the V6(6th leaf)stage,and increased net income and the benefit:cost ratio by 22.1 and 16.7%,respectively.W1N1D2 and W1N2D2 reduced the nitrate nitrogen and ammoniacal nitrogen contents at the R6 stage in the 40-100 cm soil layer,compared with W2N2D1.In summary,increasing the planting density by 30% can compensate for the loss of grain yield and aboveground N accumulation under reduced water and N inputs.Meanwhile,increasing the maize density by 30% improved grain yield and aboveground N accumulation when water was reduced by 20% while the N application rate remained constant in arid irrigation areas.

Enriching Iodine and Regulating Grain Aroma,Appearance Quality,and Yield in Aromatic Rice by Foliar Application of Sodium Iodide

Applying iodine fertilizers to cultivate iodine-rich crops for daily intake is an effective approach for iodine supplementation,especially for aromatic rice.Field experiments were conducted during the early growing seasons of 2021 and 2022 to evaluate the impacts of foliar application of iodine fertilizer on aromatic rice and to explore the optimal iodine fertilizer concentration.At the full heading stage,six different concentrations of sodium iodide solutions of 0%(CK),0.010%(T1),0.025%(T2),0.050%(T3),0.075%(T4),and 0.100%(T5)were applied to indica aromatic rice cultivars Meixiangzhan 2 and Xiangyaxiangzhan.The results showed that sodium iodide treatments significantly increased the iodine and sodium contents in both leaves and grains.Compared with the CK,the T1 and T2 treatments increased the 2-acetyl-1-pyrroline(2-AP)content in mature grains by 8.41%-101.66%and 13.58%-74.60%,respectively.Improvements in the contents of 1-pyrroline-5-carboxylic acid,proline,1-pyrroline,and methylglyoxal,as well as the activity of proline dehydrogenase were also detected.Additionally,sodium iodide treatments remarkably decreased the chalky grain rate,chalkiness area,and chalkiness degree of aromatic rice,with the T2 treatment exhibiting a 17.79%-47.42%decrease in chalkiness degree compared with the CK.Meanwhile,T1 and T2 treatments showed beneficial impacts on chlorophyll content,photosynthetic characteristics,and yield components,while T3,T4,and T5 treatments exhibited adverse effects on leaf and grain yields.The linear discriminant analysis revealed significant differences between treatments.The correlation analysis and piecewise structural equation modeling showed that the iodine and sodium influenced the photosynthetic characteristics and chlorophyll content of the leaves,thereby regulating the 2-AP biosynthesis and yield components,ultimately affecting the 2-AP content and yield.Overall,this study suggests that foliar application of 0.025%sodium iodide is an effective method to enrich the iodine content in rice grains,improve the grain aroma and appearance quality of aromatic rice,without detrimental effects on grain yield.

A novel Effective Panicle Number per Plant 4 haplotype enhances grain yield by coordinating panicle number and grain number in rice

Increasing effective panicle number per plant(EPN)is one approach to increase yield potential in rice.However,molecular mechanisms underlying EPN remain unclear.In this study,we integrated mapbased cloning and genome-wide association analysis to identify the EPN4 gene,which is allelic to NARROW LEAF1(NAL1).Overexpression lines containing the Teqing allele(TQ)of EPN4 had significantly increased EPN.NIL-EPN4^(TQ) in japonica(geng)cultivar Lemont(LT)exhibited significantly improved EPN but decreased grain number and flag leaf size relative to LT.Haplotype analysis indicated that accessions with EPN4-1 had medium EPN,medium grain number,and medium grain weight,but had the highest grain yield among seven haplotypes,indicating that EPN4-1 is an elite haplotype of EPN4 for positive coordination of the three components of grain yield.Furthermore,accessions carrying the combination of EPN4-1 and haplotype GNP1-6 of GNP1 for grain number per panicle showed higher grain yield than those with other allele combinations.Therefore,pyramiding of EPN4-1 and GNP1-6 could be a preferred approach to obtain high yield potential in breeding.

Effect of Planting Date on Yield and Yield Components of Grain Sorghum Hybrids

In Kansas, productivity of grain sorghum [Sorghum bicolor (L.) Moench] is affected by weather conditions at planting and during pollination. Planting date management and selection of hybrid maturity group can help to avoid severe environmental stresses during these sensitive stages. The hypothesis of the study was that late May planting improves grain sorghum yield and yield components compared with late June planting. The objectives of this research were to investigate the influence of planting dates yield and yield components of different grain sorghum hybrids, and to determine the optimal planting date and hybrid combination for maximum biomass and grains production. Three sorghum hybrids (early, medium, and late maturing) were planted in late May and late June without irrigation in Kansas at Manhattan/Ashland Bottom Research Station, and Hutchinson in 2010;and at Manhattan/North Farm and Hutchinson in 2011. Data on dry matter production, yield and yield components were collected. Grain yield and yield components were influenced by planting date depending on environmental conditions. At Manhattan (2010), greater grain yield, number of heads per plant, were obtained with late-June planting compared with late May planting, while at Hutchinson (2010) greater yield was obtained with late May planting for all hybrids. The yield component most affected at Hutchinson was the number of kernels∙panicle−1 and plant density. Late-May planting was favorable for late maturing hybrid (P84G62) in all locations. However, the yield of early maturing hybrid (DKS 28-05) and medium maturing hybrid (DKS 37-07) was less affected by delayed planting. The effects of planting dates on yield and yield components of grain sorghum hybrids were found to be variable among hybrid maturity groups and locations.

Tiller fertility is critical for improving grain yield,photosynthesis,and nitrogen efficiency in wheat

Genetic improvement has promoted wheat’s grain yield and nitrogen use efficiency(NUE)during the past decades.Therefore,the current wheat cultivars exhibit higher grain yield and NUE than previous cultivars in the Yangtze River Basin,China since the 2000s.However,the critical traits and mechanisms of the increased grain yield and NUE remain unknown.This study explores the mechanisms underlying these new cultivars’increased grain yield and NUE by studying 21 local cultivars cultivated for three growing seasons from 2016 to 2019.Significantly positive correlations were observed between grain yield and NUE in the three years.The cultivars were grouped into high(HH),medium(MM),and low(LL)grain yield and NUE groups.The HH group exhibited significantly high grain yield and NUE.High grain yield was attributed to more effective ears by high tiller fertility and greater single-spike yield by increasing post-anthesis single-stem biomass.Compared to other groups,the HH group demonstrated a longer leaf stay-green ability and a greater flag leaf photosynthetic rate after anthesis.It also showed higher N accumulation at pre-anthesis,which contributed to increasing N accumulation per stem,including stem and leaf sheath,leaf blade,and unit leaf area at pre-anthesis,and promoting N uptake efficiency,the main contribution of high NUE.Moreover,tiller fertility was positively related to N accumulation per stem,N accumulation per unit leaf area,leaf stay-green ability,and flag leaf photosynthetic rate,which indicates that improving tiller fertility promoted N uptake,leaf N accumulation,and photosynthetic ability,thereby achieving synchronous improvements in grain yield and NUE.Therefore,tiller fertility is proposed as an important kernel indicator that can be used in the breeding and management of cultivars to improve agricultural efficiency and sustainability.

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

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

Grain yield 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.

Differing responses of root morphology and physiology to nitrogen application rates and their relationships with grain yield in rice

Root morphology and physiology influence aboveground growth and yield formation in rice.However,root morphological and physiological differences among rice varieties with differing nitrogen(N)sensitivities and their relationship with grain yield are still unclear.In this study,rice varieties differing in N sensitivity over many years of experiments were used.A field experiment with multiple N rates(0,90,180,270,and 360 kg ha^(-1))was conducted to elucidate the effects of N application on root morphology,root physiology,and grain yield.A pot experiment with root excision and exogenous application of 6-benzyladenine(6-BA)at heading stage was used to further verify the above effects.The findings revealed that(1)under the same N application rate,N-insensitive varieties(NIV)had relatively large root biomass(root dry weight,length,and number).Grain yield was associated with root biomass in NIV.The oxidation activity and zeatin(Z)+zeatin riboside(ZR)contents in roots obviously and positively correlated with grain yield in N-sensitive varieties(NSV),and accounted for its higher grain yield than that of NIV at lower N application rates(90 and 180 kg ha^(-1)).(2)The root dry weight required for equal grain yield of NIV was greater than that of NSV.Excision of 1/10 and 1/8 of roots at heading stage had no discernible effect on the yield of Liangyoupeijiu(NIV),and it significantly reduced yield by 11.5%and 21.3%in Tianyouhuazhan(NSV),respectively,compared to the treatment without root excision.The decrease of filled kernels and grain weight after root excision was the primary cause for the yield reduction.Root excision and exogenous 6-BA application after root excision had little influence on the root activity of NIV.The oxidation activity and Z+ZR contents in roots of NSV decreased under root excision,and the increase in the proportion of excised roots aggravated these effects.The application of exogenous 6-BA increased the root activity of NSV and increased filled kernels and grain weight,thereby reducing yield loss after root excision.Thus,the root biomass of NIV was large,and there may be a phenomenon of"root growth redundancy."Vigorous root activity was an essential feature of NSV.Selecting rice varieties with high root activity or increasing root activity by cultivation measures could lead to higher grain yield under lower N application rates.

Combining controlled-release urea and normal urea with appropriate nitrogen application rate to reduce wheat stem lodging risk and increase grain yield and yield stability

A mixture of controlled-release urea and normal urea(CRUNU)is an efficient nitrogen(N)fertilizer type,but little is known about its effects on stem lodging resistance,grain yield,and yield stability of wheat.In this study,a 4-year field experiment(from 2017 to 2021)was conducted to analyze the effects of N fertilizer types(CRUNU and normal urea(NU))and application rates(low level(L),135 kg ha^(–1);medium level(M),180 kg ha^(–1);high level(H),225 kg ha^(–1))on population lodging resistance,basal internode strength,lignin content and synthetase activity,stem lodging resistance,grain yield,and yield stability of wheat.Our results showed that the two N fertilizer types had the highest lodging rate under high N application rates,and the M-CRUNU treatment showed the lowest lodging rate.Compared with NU,CRUNU improved the wheat population lodging resistance under the three N application rates,mainly related to improving wheat population characteristics and breaking the strength of the second basal internode.Correlation analysis showed that the breaking strength of the second basal internode was related to the physical characteristics,chemical components,and micro-structure of the internode.Compared with NU,CRUNU significantly increased wheat grain yield by 4.47,14.62,and 3.12%under low,medium,and high N application rates,respectively.In addition,CRUNU showed no significant difference in grain yield under medium and high N application rates,but it presented the highest yield stability under the medium N application rate.In summary,CRUNU,combined with the medium N application rate,is an efficient agronomic management strategy for wheat production.

Decreased panicle N application alleviates the negative effects of shading on rice grain yield and grain quality

Light deficiency is a growing abiotic stress in rice production.However,few studies focus on shading effects on grain yield and quality of rice in East China.It is also essential to investigate proper nitrogen(N)application strategies that can effectively alleviate the negative impacts of light deficiency on grain yield and quality in rice.A two-year field experiment was conducted to explore the effects of shading(non-shading and shading from heading to maturity)and panicle N application(NDP,decreased panicle N rate;NMP,medium panicle N rate;NIP,increased panicle N rate)treatments on rice yield-and quality-related characteristics.Compared with non-shading,shading resulted in a 9.5-14.8%yield loss(P<0.05),mainly due to lower filled-grain percentage and grain weight.NMP and NIP had higher(P<0.05)grain yield than NDP under non-shading,and no significant difference was observed in rice grain yield among NDP,NMP,and NIP under shading.Compared with NMP and NIP,NDP achieved less yield loss under shading because of the increased filled-grain percentage and grain weight.Shading reduced leaf photosynthetic rate after heading,as well as shoot biomass weight at maturity,shoot biomass accumulation from heading to maturity,and nonstructural carbohydrate(NSC)content in the stem at maturity(P<0.05).The harvest index and NSC remobilization reserve of NDP were increased under shading.Shading decreased(P<0.05)percentages of brown rice,milled rice,head rice,and amylose content while increasing(P<0.05)chalky rice percentage,chalky area,chalky degree,and grain protein.NMP demonstrated a better milling quality under non-shading,while NDP demonstrated under shading.NDP exhibited both lower chalky rice percentage,chalky area,and chalky degree under non-shading and shading,compared with NMP and NIP.NDP under shading decreased amylose content and breakdown but increased grain protein content and setback,contributing to similar overall palatability to non-shading.Our results suggested severe grain yield and quality penalty of rice when subjected to shading after heading.NDP improved NSC remobilization,harvest index,and sink-filling efficiency and alleviated yield loss under shading.Besides,NDP would maintain rice’s milling,appearance,and cooking and eating qualities under shading.Proper N management with a decreased panicle N rate could be adopted to mitigate the negative effects of shading on rice grain yield and quality.

Irrigating with cooler water does not reverse high temperature impact on grain yield and quality in hybrid rice

Rice grain yield and quality are negatively impacted by high temperature stress.Irrigation water temperature significantly affects rice growth and development,thus influencing yield and quality.The role of cooler irrigation water in counteracting high temperature induced damages in rice grain yield and quality are not explored.Hence,in the present study two rice hybrids,Liangyoupeijiu(LYPJ)and IIyou 602(IIY602)were exposed to heat stress and irrigated with water having different temperatures in a splitsplit plot experimental design.The stress was imposed starting from heading until maturity under field-based heat tents,over two consecutive years.The maximum day temperature inside the heat tents was set at 38℃.For the irrigation treatments,two different water sources were used including belowground water with cooler water temperature and pond water with relatively higher water temperature.Daytime mean temperatures in the heat tents were increased by 1.2–2.0℃ across two years,while nighttime temperature remained similar at both within and outside the heat tents.Cooler belowground water irrigation did have little effect on air temperature at the canopy level but decreased soil temperature(0.2–1.4℃)especially under control.Heat stress significantly reduced grain yield(33%to 43%),panicles m^(-2)(9%to 10%),spikelets m^(-2)(15%to 22%),grain-filling percentage(13%to 26%)and 1000-grain weight(3%to 5%).Heat stress significantly increased chalkiness and protein content and decreased grain length and amylose content.Grain yield was negatively related to air temperature at the canopy level and soil temperature.Whereas grain quality parameters like chalkiness recorded a significantly positive association with both air and soil temperatures.Irrigating with cooler belowground water reduced the negative effect of heat stress on grain yield by 8.8%in LYPJ,while the same effect was not seen in IIY602,indicating cultivar differences in their response to irrigation water temperature.Our findings reveal that irrigating with cooler belowground water would not significantly mitigate yield loss or improve grain quality under realistic field condition.The outcome of this study adds to the scientific knowledge in understanding the interaction between heat stress and irrigation as a mitigation tool.Irrigation water temperature regulation at the rhizosphere was unable to counteract heat stress damages in rice and hence a more integrated management and genetic options at canopy levels should be explored in the future.

Translocation and Distribution of Carbon-Nitrogen in Relation to Rice Yield and Grain Quality as Affected by High Temperature at Early Panicle Initiation Stage

Due to climate change, extreme heat stress events have become more frequent, adversely affecting rice yield and grain quality. The accumulation and translocation of dry matter and nitrogen substances are essential for rice yield and grain quality. To assess the impact of high temperature stress(HTS) at the early panicle initiation(EPI) stage on the accumulation, transportation, and distribution of dry matter and nitrogen substances in various organs of rice, as well as the resulting effects on rice yield and grain quality, pot experiments were conducted using an indica rice cultivar Yangdao 6(YD6) and a japonica rice cultivar Jinxiangyu 1(JXY1) under both normal temperature(32 ℃/26 ℃) and high temperature(38 ℃/29 ℃) conditions. The results indicated that exposure to HTS at the EPI stage significantly decreased rice yield by reducing spikelet number per panicle, grain-filling rate, and grain weight. However, it improved the nutritional quality of rice grains by increasing protein and amylose contents. The reduction in nitrogen and dry matter accumulation accounted for the changes in spikelet number per panicle, grain-filling rate, and grain size. Under HTS, the decrease in nitrogen accumulation accompanied by the reduction in dry matter may be due to the down-regulation of leaf net photosynthesis and senescence, as evidenced by the decrease in nitrogen content. Furthermore, the decrease in sink size limited the translocation of dry matter and nitrogen substances to grains, which was closely related to the reduction in grain weight and the deterioration of grain quality. These findings significantly contribute to our understanding of the mechanisms of HTS on grain yield and quality formation from the perspective of dry matter and nitrogen accumulation and translocation. Further efforts are needed to improve the adaptability of rice varieties to climate change in the near future.

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

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

Identification of genetic loci for grain yield-related traits in the wheat population Zhongmai 578/Jimai 22

The identification of stable quantitative trait locus(QTL)for yield-related traits and tightly linked molecular markers is important for improving wheat grain yield.In the present study,six yield-related traits in a recombinant inbred line(RIL)population derived from the Zhongmai 578/Jimai 22 cross were phenotyped in five environments.The parents and 262 RILs were genotyped using the wheat 50K single nucleotide polymorphism(SNP)array.A high-density genetic map was constructed with 1501 non-redundant bin markers,spanning 2384.95 cM.Fifty-three QTLs for six yield-related traits were mapped on chromosomes 1D(2),2A(9),2B(6),2D,3A(2),3B(2),4A(5),4D,5B(8),5D(2),7A(7),7B(3)and 7D(5),which explained 2.7-25.5%of the phenotypic variances.Among the 53 QTLs,23 were detected in at least three environments,including seven for thousand-kernel weight(TKW),four for kernel length(KL),four for kernel width(KW),three for average grain filling rate(GFR),one for kernel number per spike(KNS)and four for plant height(PH).The stable QTLs QKl.caas-2A.1,QKl.caas-7D,QKw.caas-7D,QGfr.caas-2B.1,QGfr.caas-4A,QGfr.caas-7A and QPh.caas-2A.1 are likely to be new loci.Six QTL-rich regions on 2A,2B,4A,5B,7A and 7D,showed pleiotropic effects on various yield traits.TaSus2-2B and WAPO-A1 are potential candidate genes for the pleiotropic regions on 2B and 7A,respectively.The pleiotropic QTL on 7D for TKW,KL,KW and PH was verified in a natural population.The results of this study enrich our knowledge of the genetic basis underlying yield-related traits and provide molecular markers for high-yield wheat breeding.

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.

Optimized tillage methods increase mechanically transplanted rice yield and reduce the greenhouse gas emissions

Biaxia lrotary tillage in dryland(DBRT)can complete biaxial rotary tillage with straw incorporation,secondary suppression,and ditching,and it has been previously studied in direct-seeded rice and wheat.However,the effects of DBRT on the mechanically transplanted rice yield and greenhouse gas emissions remain unclear.To evaluate the effects of DBRT on improving the food security of mechanically transplanted rice and reducing the greenhouse gas emissions,we conducted an experiment for two years with wheat straw incorporation.Three tillage methods were set up:DBRT,uniaxial rotary tillage in dryland and paddy(DPURT),and uniaxial rotary tillage in paddy(PURT).The results showed that compared with DPURT and PURT,DBRT increased the yield of machine-transplanted rice by 7.5-11.0%and 13.3-26.7%,respectively,while the seasonal cumulative CH_(4) emissions were reduced by 13.9-21.2%and 30.2-37.0%,respectively,and the seasonal cumulative N_(2)O emissions were increased by 13.5-28.6%and 50.0-73.1%,respectively.Consequently,DBRT reduced the global warming potential by 10.7-15.5%and 23.7-28.6%,respectively,andtheyield-scaledglobalwarmingpotentialby18.2-21.8%and36.4-39.3%,respectively,compared to DPURT and PURT.These results were mainly related to the fact that DBRT significantly reduced soil bulk density and increased soil redox potential(Eh).Therefore,implementing DBRT in machine-transplanted rice fields is feasible,which cannot only increase the rice yield,but also reduce the greenhouse gas emissions.

Genetic and Agronomic Parameter Estimates of Growth, Yield and Related Traits of Maize (Zea mays L.) under Different Rates of Nitrogen Fertilization

This study evaluated the genetic and agronomic parameter estimates of maize under different nitrogen rates. The trial was established at the Njala Agricultural Research Centre experimental site during 2021 and 2022 in a split block design with three maize varieties (IWCD2, 2009EVDT, and DMR-ESR-Yellow) and seven nitrogen (0, 30, 60, 90, 120, 150 and 180 kg∙N∙ha−1) rates. Findings showed that cob diameter and anthesis silking time (ASI) had intermediate heritability, ASI had high genetic advance, ASI and grain yield had high genotypic coefficient of variation (GCV), while traits with high phenotypic coefficient of variation (PCV) were plant height, ASI, grain yield, number of kernel per cob, number of kernel rows, ear length, and ear height. The PCV values were higher than GCV, indicating the influence of the environment in the studied traits. Nitrogen rates and variety significantly (p < 0.05) influenced grain yield production. Mean grain yields and economic parameter estimates increased with increasing nitrogen rates, with the 30 and 180 kg∙N∙ha−1 plots exhibiting the lowest and highest grain yields of 1238 kg∙ha−1 and 2098 kg∙ha−1, respectively. Variety and nitrogen effects on partial factor productivity (PFPN), agronomic efficiency (AEN), net returns (NR), value cost ratio (VCR) and marginal return (MR) indicated that these parameters were significantly affected (p < 0.05) by these factors. The highest PFPN (41.3 kg grain kg−1∙N) and AEN (29.4 kg grain kg−1∙N) were obtained in the 30 kg∙N∙ha−1 plots, while the highest VCR (2.8) and MR (SLL 1.8 SLL−1 spent on N) were obtained in the 180 kg∙N∙ha−1. The significant influence of variety and nitrogen on traits suggests that increasing yields and maximizing profits require use of appropriate nitrogen fertilization and improved farming practices that could be exploited for increased productivity of maize.

Effect of Supplementary Irrigation on the Yield of Sorghum (Sorghum bicolor L. Moench) in the Context of Climate Change in the Dry Savannahs of Togo

Under the current context of climate change, supplementary irrigation may be needed for crop production resilience. We determined the effects of supplementary irrigation on sorghum grain yield in the dry Savannah region of Togo. A two-year trial was conducted in a controlled environment at AREJ, an agro-ecological center in Cinkassé. The plant material was sorghum variety Sorvato 28. The experimental design was a Completely Randomized Block with three replications and three treatments as follows: T0 control plot (rainfed conditions);T1 (supplementary irrigation from flowering to grain filling stage) and T2 (supplementary irrigation from planting to grain filling stage). Two irrigation techniques (furrow and Californian system) were used under each watering treatment. The results showed that irrigation technique significantly affected panicle length with no effect on 1000 grains mass. Panicle length and grain yields varied from 15.59 to 25.71 cm and 0.0 to 2.06 t∙h−1, respectively, with the highest values (25.66 cm and 2.06 t∙h−1, respectively) under the T2 treatment with the California system-based supplementary irrigation. The comparison of results obtained on treatment T0 and T2, shows that supplementary irrigation increased the yields by at least 68.62%. Supplementary irrigation during sowing and growing season (T2) improved sorghum yields in the dry savannahs of Togo, with a better performance of the California irrigation system.

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.