Identification Of Lettuce Water Indicator Using Infrared Thermography

Crop canopy temperature is a indicator to reflect the available soil moisture and crop water status.With the development of temperature measurement technology, the infrared thermal imager are used timely and nondestructively monitoring canopy temperature, with short time, low cost, simple operation, high degree of automation to overcome the complexity of traditional measurement methods for crop water and delay. Using infrared thermal image technology to predict crop water deficit information has become a hot field, which has important significance for crop precision irrigation and water saving production.In order to make a more comprehensive diagnosis about the crop water requirement,We put the lettuce as the experimental object in this study,dividing the whole growth period of lettuce into seedling stage,growth stage and mature stage to monitor canopy surface Temperature and other conventional physiological indexes.etc by some high precision instruments such as infrared thermal imaging system and optical instrument,etc.The analysis results are as follows:(1) The linear relationship between transpiration rate and stomatal conductance was Tr= 0.812+0.07Gs;R2=0.877;The relationship between photosynthetic efficiency and stomatal conductance was Pn=-10.243+2.311ln(Gs) Correlation coefficient R2=0.825.It is wrong to restrain transpiration by the one-sided emphasis on water conservation,because The method of increasing stomatal resistance to restrain transpiration can not only increase the efficiency of water use,but also increase the yield of photosynthesis when the stomatal conductance was greater than 450mmol/m2s-1.(2) Soil Water is the main source of water for crop evapotranspiration;The transpiration rate, photosynthetic rate,stomatal conductance and soil water content had significant positive or negative correlation; Canopy temperature is the result of the interaction between the internal and external environment and the energy conservation,and it was positively correlated with stomatal conductance and transpiration;Therefore, the canopy temperature can be used as a reflection of the status of the crop water deficit index.(3) we used The simulation method of the leaf to Simplify empirical formula in The research project;The analysis results of Water stress index CWSI empirical model show that The transpiration rate,photosynthetic rate and CWSI value linear empirical model;The soil moisture content and CWSI value showed a negative linear correlation;These show that the CWSI model can be used to monitor the experience of lettuce under water stress;According to CWSI in different growth stages of the diurnal variation of the determination of the best time of water stress in lettuce 15:00～17:00;According to the regression equation of different soil moisture and CWSI,we calculate the critical irrigation index of CWSI,which is about 0.65.