Analysis Of Crop Water Requirement And Optimization Of Irrigation Plan During Drought Period In The Case Of Jinan

The drought in China,coupled with the scarcity of water,has caused incalculable losses.Agriculture is a large water user and the agricultural development is more dependent on water resources.Drought and water shortage has become the main challenge of agriculture in China.On the one hand,due to the extensive mode of irrigation,irrigation water in China effective utilization degree is low,the irrigation water use efficiency is only about 0.5,far lower than developed countries,the level of 0.7-0.8,improve the water use efficiency of irrigation has great potential.On the other hand,because of drought,water shortage is becoming increasingly serious,how to try to ensure that food production is the basis of a small cut or compressed agricultural water,ensure the city life and rural drinking water has become an urgent need to solve the problem..At present,the research for the crop model become an important means of agricultural crop simulation and prediction,present a more important position.In the past,the method of research often only paid attention to the variation of the crops in different conditions,and the mechanism and precision are deficient.The use of crop models to formulate irrigation schedules is of great significance to the improvement of crop management measures.Based on the above problems for agricultural irrigation and water requirements,In this study,we chose to optimize the irrigation schedule of common crops in Jinan City,which is located in the North China Plain.On the basis of field survey data,collecting weather,soil,geology,crop types in the study area,production and agricultural management measures such as data,analysis of the historical drought occurrence in the study area.Select normal rain year,drought and severe drought years.Analysis of water requirement in common duration of common drought in typical drought period using APSIM crop model,Under the rated based on different quantity of irrigation,and set up to simulate irrigation schedules,discuss the different irrigation schedules for production and the influence of field water use efficiency,yield and water use efficiency(wue)field selected better irrigation schedules,provide the basis for the actual irrigation measures.The paper mainly draws the following conclusions:(1)The simulation results were validated and evaluated,and the parameters of the model were determined by using wheat yield data in 2001-2010,with RMSE = 344.0 kg/ha.NRMSE=5.8%;D = 0.82;R squared = 0.46.The model was verified by wheat yield of 2011-2013,with an error of 0.9%,8.8%and 6.8%respectively.Corn evaluation results,the RMSE = 580 kg/ha,NRMSE = 8.9%,squared R = 0.72,D = 0.61,with corn yield data from 2011 to 2014 to verify this model,the output of 2011-2014 error are 0.12%,7.49%,6.53%and 0.12%respectively.It is shown that the APSIM model can simulate common crops in Jinan area.(2)Using the APSIM model of winter wheat and summer corn,the process of water shortage in corn and wheat was analyzed,and the critical period of water requirement for corn and wheat was determined.The results showed that the critical period of water requirement was jointing,flowering and filling stage.The critical period of water requirement of maize is jointing,pumping and filling.Water stress during critical period of water requirement will result in huge yield reduction,and the water requirement of crop critical period should be given priority when irrigation amount is limited.Corn and wheat seedlings need less water,and the amount of water available can generally be met.Based on the analysis of water shortage,the water use efficiency,yield and water consumption of crops under different irrigation and irrigation conditions were analyzed.The analysis shows that,in the absence of irrigation with the extent of drought,the wheat production fell sharply,while water consumption will be reduced,field water use efficiency will be reduced,in irrigation,water consumption,reduce the yield gap.Among them,in normal years,Jinan city wheat water requirement maximum in mid-April,the maximum daily water demand reached 5.64mm,the maximum corn water requirement in late August,the maximum daily water demand is 10.77mm;in the typical drought years,wheat in Jinan city water demand maximum in mid-April,the daily maximum water requirement of maize reached 7.89mm.Water is the biggest in the middle of August,the daily maximum water requirement for 7.12mm;which,in the typical drought years,wheat in Jinan city water demand maximum in mid-April,the maximum daily water demand reached 8.09mm,the maximum corn water requirement in early August,the daily maximum water quantity is 8.05mm.(3)Wheat were set up 21 groups of irrigation schedules,corn set 26 groups of irrigation schedules.The optimal irrigation schedule was selected to determine the irrigation time and the amount of irrigation,and the irrigation plan was optimized to guide the actual irrigation measures.For winter wheat in Jinan city in the level of irrigation 100mm,should be selected for irrigation at jointing stage;irrigation in 200mm at yield and field water use efficiency changed little when the irrigation amount was 300mm,the water use efficiency decreased,the mean annual irrigation water 200mm can basically meet the water requirement of wheat.In drought years,when irrigation 100mm should consider the critical period of water requirement,the water requirement of jointing stage should be fully considered when irrigation 200mm.In severe drought,the winter wheat should be fully taken into consideration when jointing and flowering stage.For summer maize,the water requirement of 250mm should be fully taken into account during the irrigation period of 150mm,and the requirement of water requirement should be satisfied during the irrigation period.In dry years,the yield increased significantly after irrigation,and the yield and water use efficiency increased significantly in severe drought years.In the normal year,when rainfall was considered,100mm could basically ensure wheat yield during the jointing stage.100mm irrigation schedule is superior to corn for irrigation at jointing and pumping.In typical drought years,100mm can basically guarantee wheat yield when wheat is irrigated during flowering.For corn irrigation,150mm has basically met the requirement of corn water requirement,namely,irrigation 50mm and 100mm at jointing and pumping separately.In severe drought years,100mm irrigation schedule is superior to wheat for irrigation at jointing stage.For corn,100mm,50mm and 100mm were irrigated at jointing,pumping and grouting respectively.