| Drought stress has been a great challenge for the sustainability of maize(Zea mays L.)production in arid and semi-arid regions.The utilization of drought-tolerant hybrids and proper irrigation regimes represent a management strategy in stabilizing maize production under water-limited conditions.A two-year(2017 and 2018)field experiments were conducted to assess the leaf gas exchange,plant growth,grain yield and water use efficiency of maize in two cultivars and under three irrigation treatments.Two maize cultivars were Zhengdan 958(H1)and Zhongdan 909(H2).Three irrigation treatments were full irrigation(FI),reproductive irrigation(RI)and no-irrigation(rain-fed,RF).The main objectives of this study were:(i)to investigate drought effects during flowering on maize grain yield and the yield gap between rainfed and full irrigation;(ii)to compare the effects of flowering irrigation between both hybrids;and(iii)to examine the interaction between three irrigation applications and two maize hybrids on maize growth and grain yield.1.The results elucidated that H1 acquired significantly higher biomass accumulation compared with H2 at the big flare stage.In contrast,at this stage,the dry biomass accumulation in RF was significantly decreased by 16.1%(H1)and 18.0%(H2)in 2017;and18.6%(H1)and 18.4%(H2)in 2018,compared with FI.At the flowering stage,the dry biomass accumulation under RF was significantly reduced by 23.9%(H1)and 25.3%(H2)in2017;and 25.0%(H1)and 25.8%(H2)in 2018,compared to FI.However,the dry biomass accumulation was also significantly declined in RF by 19.9%(H1)and 15.0%(H2)in 2017;and 21.5%(H1)and 15.7%(H2)in 2018,compared with RI.The grain yield in RF was significantly reduced by 30.4%(H1)and 31.1%(H2);and water use efficiency(WUE)by 8.5%(H1)and 9.3%(H2)compared to FI.On the other hand,irrigation application at the flowering stage was shown to significantly boost the grain yield by 40.3%(H1)and 25.5%(H2);and WUE by 27.6%(H1)and 14.1%(H2)compared to RF.H1 has benefited more from irrigation use compared to H2.The improved grain yield through reproductive irrigation was due to the greater soil plant analysis development(SPAD),net photosynthesis,and biomass production when compared to zero irrigation.Zhengdan 958was shown to be relatively more resistant to drought stress during flowering compared to Zhongdan 909.2.A field trial in 2019 was conducted to assess the effects of water stress and sowing time on growth and development,yield and yield components on maize hybrids.The main objective of this research was to find the best sowing time with good hybrid.This study consisted on three different sowing dates(SD1,June 12;SD2,June 17;SD3,June 22)as a main plot,two maize hybrids of Zhengdan 958(H1),and Zhongdan 909(H2)and two water treatments of fully irrigated,(FI)and Rainfed(RF).The above ground dry matter accumulation was significantly varied among sowing times and hybrids from jointing to physiological maturity,and FI significantly increased from flowering to physiological maturity as compared with RF while the highest value was noted in SD1H1FI treatment.SD1significantly increased dry matter accumulation by 3.79%,6.48%,1.48%,3.07%compared to SD2 and SD3,and H1 gained 5.22%and 4.21%higher contrast to H2 while FI enhanced by12.69%and 52.64 related with RF at flowering and maturity stages,respectively.We found that SD1 produced more grain yield by increasing the number of days from sowing to physiological maturity,leaf area index,dry biomass,leaf chlorophyll contents,photosynthesis rate and water use efficiency compared with SD2 and SD3.The H1 perform very well under optimum irrigation and rainfed conditions as compared with H2.3.Agricultural Production Systems Simulator(APSIM)is used worldwide as a modern tool to assess crop productivity in dryland farming.In this study,previous results of two-year field experiments about two maize hybrids under different irrigation regimes were used by APSIM-Maize.The APSIM-Maize model was calibrated for crop traits of the two hybrids for local soil characteristic under full irrigation,and then used to testify the simulations under RI and RF treatments.Predicted results confirmed the accuracy of the model,which was validating with skill scores like R~2,RMSE,d-stat values.Zhengdan 958 was shown to be relatively more resistant to water stress during flowering period compared to Zhongdan 909.Overall,Zhengdan 958 combined with RI should be recommended for sustaining maize grain yield and improving the efficiency of resource utilization in Huaibei plain or in similar conditions.The APSIM-maize model was successfully calibrated and effectively testified in the experimental region. |
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