| The North China Plain is an important food-producing region of China,and it is important to develop appropriate irrigation schedule to maintain stable food crop production in the context of water resource constraints.In this thesis,we chose Yongnian District,Handan Province,as the study area,and used the methods of survey,data collection and experimental monitoring to construct the Agricultural Policy Environmental e Xtender(APEX)model,the rationality of the irrigation schedule in the study area was analyzed from the angle of crop growth and water resources utilization,and the rigidity constraint of the total amount of irrigation water was considered,the irrigation schedule under different irrigation scenarios was simulated,screened and optimized.The results were as follows:(1)The space crop growth model in Yongnian District was constructed.By collecting relevant data,the geographic information of the study area was digitized,and the model parameters were adjusted according to the crop growth index,and the model validation was completed by using the annual yield data and measured soil moisture data.The results showed that the Nash efficiency coefficient of soil moisture simulation was above 0.7,and the root mean square error of unit yield of winter wheat was 0.42t/hm~2from 2011 to 2019,and the average relative error was 3.95%.The results show that APEX model has good applicability in the study area.(2)The temporal and spatial distribution characteristics of winter wheat growth and the change rule of growth index under the current irrigation schedule.Based on the simulation results of APEX model,the unit yield of winter wheat in 2019 will be higher in the east and lower in the west;During the whole growth period,the water use efficiency in the north was higher than that in the south,and gradually decreased from the east to the west.During the period from emergence to rejuvenation,leaf area index,biomass and daily evapotranspiration changed evenly,with small values and fluctuations.Leaf area index,biomass and daily evapotranspiration showed spatial difference and peak asynchrony from the beginning of the rejuvenation period.(3)Evaluation on the rationality of winter wheat irrigation schedule in Yongnian under the current irrigation schedule.The results show that the current irrigation schedule has good applicability to the east and middle of Yongnian.(4)Under the rigid constraint of water resources,the optimal irrigation schedule for the whole year was screened,that is,under the condition of 240 mm of total irrigation amount in the rise maturity period,three times of normal node irrigation were conducted at the rise jointing,jointing heading and heading flowering stages,and the irrigation water volume was 90 mm,60 mm and 90 mm respectively.Through single factor analysis,the regional irrigation law is obtained.Properly increasing the amount of irrigation before the starting period(before April 1)will help increase production,while excessive irrigation will lead to production reduction;Increasing irrigation once at booting stage(before or after April 20)can increase yield;Increasing irrigation water volume during the rising grouting period(before May 20)can achieve yield increase effect;In the middle and late stage of grouting(around May 25),increasing the amount of irrigation did not significantly promote the yield increase.The research results are of great significance for improving regional agricultural water resources management.. |
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