Characteristics Of Water Consumption Of Different Cropping Patterns And Optimization Of Crop Plantation In The Upstream Of Baiyangdian Lake

As the largest freshwater lake wetland in the North China Plain,Baiyangdian Lake has outstanding ecological value,however,it is now facing a serious problem of water shortage.Under the background of the construction of Xiong’an,which is a "millennium plan",adjusting the planting structure and reducing the water consumption of planting industry in the upstream of the district are the key measures to optimize the use of water resources and alleviate the water resource shortage in the basin,which can better guarantee the sustainable development of Xiong’an.Previous studies on regional crop water-saving and planting structure optimization mainly focused on wheat water-saving extraction and different fallow patterns,but the water-saving effect of fallow was affected due to the failure to consider soil water retention during fallow period of wheat and other crops and the overgrowth of weeds.This study based on field experiment,combined with weighing lysimeter and soil moisture observation,by setting the different cropping systems and fallow period water-protecting measure(Plastic filmmulching,shallow tillage,weed control and straw mulching)experiment,the water consumption law of multiple planting systemshas been studiedsystematically,the water-saving effectofwater-protecting measures during the different fallow periods has been cleared;At the same time,to explore the optimized plan for the future planting structure of DianQu upstream plains and mountainsaround 14 kinds of planting systems,using non-dominated sorting genetic algorithm(NSGA-Ⅱ)and water resources,cultivated land and social needs as the basic constraint conditions,economic,ecological benefit maximum and irrigation water consumption minimumas the goals,proposed planting structure optimization schemesto the mountain and plain area upstream of Baiyangdian Lakeunder thelimitation water resources and labor.The main research results are as follows:(1)The annual water consumption of 9 cropping systems from high to low were summer potato-winter wheat(954 mm),summer corn-winter wheat(856 mm),spring potato(792 mm),summer soybean-winter wheat(760 mm),summer millet-winter wheat(757 mm),mung bean-fresh corn(755 mm),and fallow-winter wheat(707 mm)Mm),summer maize-fallow(647 mm),and spring maize(593 mm).Among them,except spring potato,the annual water consumption of two-cropping system was generally higher than that of one-cropping system.According to the different planting system of water consumption,food equivalent number,different scale of water use efficiency,anniversary of the use of field effect comprehensive evaluation,a year two cooked-winter wheat summer corn,the highest scores followed by potato-in the summer of winter wheat,the lowest scores are fallow-winter wheat,followed by the spring of potatoes and green beans-fresh corn.(2)The water conservation experiment during the fallow period of two wheat growing seasons from 2018 to 2020 showed that the water saving effect of straw mulching from 2018 to 2019 was the best,which was 71 mm higher than the control.The second was straw control and shallow tillage with water saving of 62 mm and 45 mm,respectively.The worst water-saving effect was film mulching(white film)treatment,saving only 8 mm.From 2019 to 2020,black film had the most significant effect on water conservation and grass control,saving water by 177 mm compared with the control.The other three treatments of straw mulch,grass control and shallow tillage were 65 mm,71 mm and 25 mm respectively.In the early stage of soil moisture conservation,the black film mulching treatment showed good water retention for shallow soil moisture.In the late stage of strong evapotranspiration,the black film mulching treatment showed good water retention for all soil depths,while other treatments showed no significant difference in water retention for different soil depths in different periods.(3)Based on the restriction of total water resources and the economic and ecological benefits,the optimization analysis of 14 planting systems showed that:in the plain area,under the situation that the current mechanization level is not limited to water,the economic benefits can be increased by 12.6%by increasing the planting area of vegetables and mung bean-fresh corn,but the ecological benefits and water saving benefits are reduced to some extent;Under the water restriction scenario,the economic benefit and water saving benefit can be improved by increasing the area of mung beanfresh corn,spring potato,vegetables and fruits,and increasing the reduction proportion of wheat to maize.Under the goal of saving 20%water,the planting area of all crops needs to be reduced,and the planting area of wheat-maize under the high water consumption planting system needs to be reduced by 21.5%,and both economic and ecological benefits are reduced.Under the scenario of increasing mechanization level and reducing labor input in the future,the economic benefit after adjustment and optimization will be improved compared with the current mechanization level.In mountainous areas.the planting area of wheat-maize decreased in all scenarios(no water limit,less than current water resources and 20%water saving),and the greater the water limit,the greater the reduction range.In order to ensure economic benefits,the planting area of fruit trees should be increased.