Study On The Summer Maize Water Use Efficiency And Influencing Factors Based On Eddy Covariance Method And SIMDual Kc Model

Water use efficiency (WUE) is a common concept in agronomy, plant physiology, plant ecology and other fields, for different subject endowed with different meanings of water use efficiency. Water resources shortage is a serious problem facing most region of north China agricultural production. Study on crop water use efficiency, and improve crop water use efficiency is an effective way for a higher crop output with limited water resources.Crop evapotranspiration is the basic gist to determine the crop irrigation system, is the important basis for studying on farmland moisture change rule, irrigation and water conservancy project planning and design, analysis and calculation of irrigation water use and so on.Crop evapotranspiration including leaf transpiration and soil evaporation, separated the two parts of the leaf transpiration and soil evaporation effectively, reduce the crop of soil evaporation and reduce crop water consumption, in order to improve the crop water use efficiency, to realize double destinations of high output and water saving.Based on the Beijing daxing summer maize actual measurement data for continuous three years, analyzes carbon dioxide flux, latent heat flux and the distribution of water use efficiency during the summer maize growth period in the Beijing area, and discuss the total evapotranspiration rate, leaf transpiration and soil evaporation of proportional distribution in the whole growth period of summer maize and all growth periods in Beijing region that all applied technology developed at the university of Lisbon, Portugal dual crop coefficient model SIMDual_Kc model, as well the influence factors of affecting the crop water use efficiency are discussed. Through the above research, the main research contents and results are as follows:(1) The carbon dioxide flux of summer maize trend to first drop and rising after during the whole growing period,and have a very significant linear correlation with the latent heat flux, sensible heat flux, and the solar net radiation during the whole growth period, The diurnal variation of the carbon dioxide flux shows ChanGu type distribution, Among the ChanGu type curve distribution for the four growth periods of summer maize, the heading stage is minimum, postulation period second, again is the elongation stage, the last is the mature period. The diurnal variation of the latent heat flux shows Unimodal type distribution, compared with the four growth stage of summer maize, the heading stage still the maximum, followed by the postulation period, and at lase the elongation stage and the mature period, The correlation coefficient of the latent heat flux and solar radiation reaches nearly0.9, they have the same curve distributed situation for the seasonal change approximately during the whole growth period.(2) The water use efficiency of summer maize during the whole period is approximate distribution between0.004to0.008g/g, and trend to first rising and drop after during the whole growing period, the diurnal variation of the water use efficiency in all stages of growth period, roughly the same10:00-17:00, broadly in line with a trend of distribution, basic numerical stability, the overall value gradually decreases slightly.This decline phenomenon is from17:00when the performance is quite obvious, slow drop turn into falling fast, The water use efficiency decrease of mature period for the summer maize that happened earlier than the other three growth periods,reduced almost to zero at19:00roughly, the second grouting period a little bit later in the mature period of zero moment, and then the heading stage, finally the elongation stage.(3) The crop evapotranspiration of the summer maize is about between310mm and350mm during the whole growing period, wherein the soil evaporation takes up about130mm, the leaf transpiration takes up close to200mm thereby taking a leading role, the daily average soil evaporation is below1.5mm and the daily average leaf transpiration reaches close to1,9mm thereby taking a relatively leading role. For the whole summer maize growth stage, The evaporation proportion of the total evapotranspiration in proper order for seeding stage, elongation stage, heading period, postulation period, and the mature period is75%,30%-50%,15%,10%,10%-20%, The maximum evaporation of the four periods is the seedling stage, elongation stage second, We can make appropriate surface coated for improving the crop water use efficiency.