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Northwest Agriculture and Forestry University (2019)

Modeling Water Productivity in Maize and Wheat under Arid and Semi-arid Condition

Qaisar Saddique

Titre : Modeling Water Productivity in Maize and Wheat under Arid and Semi-arid Condition

Auteur : Qaisar Saddique

Grade : Doctoral Dissertation 2019

Université : Northwest Agriculture and Forestry University

Résumé
The worldwide population is anticipated to increase from 7.5 billion to over 9 billion by the mid-century.To make sure the food security of growing population,about 65%more food will be required than current production which is projected to put environment and agricultural production systems under pressure.Physical water shortage,contest for the water between industrial and urban sector is also increasing that will bound the capacity of the land resources for crop production.The farmers will face the problems of water shortage for growing more crop production.The Intergovernmental Panel on Climate Change(IPCC)expected climate change scenarios is projected to extend the gap between food demand and supply.Similarly,changes in climate conditions(rainfall,temperature and solar radiation)also varying for food production in China.Crop production directly affected from these change climate conditions.However,due to the spatial and temporal variation in rainfall,the seasonal crop production varies substantially and occasionally is not economical for poor farmers to produce.The contest to maintain or improve crop water productivity(CWP)under sudden changing climatic conditions essentially needs greater inferring of the likely impacts of these changes on crop production/productivity before implementing adaptive strategies for short and long-term period.Therefore,this study finds out the possible ways or techniques to improve crop water productivity under available limited water resources.In addition,employing of Cropping System Model(CSM)to investigate the prospective increase in crop water productivity under irrigation conditions and proper implementation of supplementary irrigation treatment/strategy for rainfed cropping system.Moreover,the influence of future climate changes on maize and wheat production was carried out under IPCC scenarios.Main results and conclusion of the studies are stated below:1.CERES(Crop Estimation through Resource and Environment Synthesis)-maize model calibration process was carried out for full irrigation treatments of four growing seasons,(2012–2015).The calibration phase model showed good agreement between simulated and observed values,with normalized root mean square error(nRMSE)ranging from 4.51%to 14.5%.The performance of the model during evaluation was satisfactory with acceptable nRMSE error ranging from 7 to 10%.Appropriate simulated sowing dates for higher production and water productivity were from 14 to 24 June.The proper amount and timing of irrigation water application was 100 mm at the flowering stage,and 100 mm at the grain filling stage respectively.Summer maize yield can be improved by adjusting the sowing date and applying supplementary irrigation when precipitation cannot meet the crop water demand in the Guanzhong Plain.2.The ongoing global warming and perplexing patterns of precipitation have significant implications for crop production.In this context,the downscaled ensemble projections of 17 General Circulation Models(GCMs)under four representative concentration pathways(RCP 2.6,RCP 4.5,RCP 6.0,and RCP 8.5)were used as input for calibrated CERES-Maize model.Results showed a negative correlation between temperature and maize yield in the study area.It is expected that each 1°C rise in seasonal temperature would cause upto 9%decrease in the yield.However,influence of CO2 fertilization(390-900ppm)showed positive response as witnessed by increase in the crop production.With CO2fertilization,average increase in the maize crop yield per decade was 6%,5%,5.5%and4.5%under RCP2.6,RCP4.5,RCP6.0 and RCP8.5 scenarios,respectively.3.Future adaptations were evaluated by using the five crop models(APSIM,AquaCrop,DSSAT,EPIC and STICS)under future climate change scenarios.Future yield was projected to increase 1.1–23.2%,1.0–22.3%,and 2–31%under irrigation,delayed planting date,and double adaptation strategies,respectively,as compared with the baseline yield.Adaptation strategies were very effective for increasing the future average yield.We conclude that maize yield in the Guanzhong Plain can be improved under future climate change conditions if irrigation and planting adaptation strategies are used together in this region.4.APSIM and CERES models showed that no adaptation caused 4.6-30%decrease in winter wheat yield compared to baseline yield under future climate change.Under elevated CO2(380 ppm-886 ppm),yield was increased by 0.95-10%,and under irrigation adaptation(180 mm-380 mm irrigation over the growing season),yield increased by 5.6-25.5%.On an average water use efficiency(WUE)with irrigation adaptation strategies and elevated CO2concentration was improved by 26.5%relative to baseline WUE during 2020-2080 years.When CO2 concentration reached about 550-866 ppm,the WUE improved by 60%with third irrigation strategy relative to the baseline conditions

Mots clés : Multiple crop models; Irrigation; maize; wheat; climate change; CO2;

Présentation (CNKI)

Page publiée le 28 février 2020