Assessing crop water stress of winter wheat by thermography under different irrigation regimes in North China Plain

Thermal imaging can be used as an indicator of water stress due to the closure of stomatal aperture.In this paper,we analyzed the robustness and sensitivity of thermography of winter wheat in the North China Plain.The seasonal and diurnal variations of Crop Water Stress Index(CWSI)were evaluated.Five treatments were applied by means of irrigation,with plots receiving 100%of ETo(DI),50%(D50),16%(D16)and no irrigation(NI).A high correlation was found between stomatal conductance(gs)and CWSI,depending on the phenological stage of the crop with R2=0.44 at pre-heading stage and R2=0.77 at post-heading stage.In addition,a high correlation between yield and CWSI at different growth stages indicates that thermography can predict yield.Hourly measurements of canopy temperature were taken to study the effect of the time of day on image acquisition and it was found that midday was the most appropriate time.These results should assist in designing precision irrigation scheduling for setting the threshold values.

Monitoring physiological responses to water stress in two maize varieties by infrared thermography

Water stress is one of the main causes of yield reductions in crops,especially in arid and semi-arid regions where the water supply is limited.Plant water status is frequently assessed by pre-dawn leaf water potential(ΨPD)or leaf stomata conductance(gL)measurements,in support of advanced irrigation scheduling.However,both methods are time and labour consuming.A non-invasive approach to water status detection is the use of infrared thermography(IRT).This experiment was conducted in a greenhouse on two potted maize varieties under irrigated and non-irrigated conditions,and the measurements began when the crop had reached its twelve leaf stage.In order to establish the IRT measurements for detecting the water status of maize,an IRT-based crop water stress index(CWSI)was calculated and compared with simultaneously measuredΨPD and gL data.Good correlations were found between CWSI and gL data(r2=0.71&0.81),as well between CWSI andΨPD data(r2=0.53&0.81).These results highlight the appropriateness of infrared thermal imagery to detect and differentiate between the crop water statuses of different genotypes.

Non-invasive water status detection in grapevine(Vitis vinifera L.)by thermography

Grapevines are preferentially grown under mild to moderate water stress conditions to achieve the best compromise between wine quality and quantity.Water status detection for advanced irrigation scheduling is frequently done by predawn leaf water potential(ΨPD)or leaf stomata conductance(gL)measurements.However,these measurements are time and labor consuming.Therefore,the use of infrared thermography(IRT)opens up the possibility to study large population of leaves and to give an overview on the stomatal variation and their dynamics.In the present study IRT was used to identify water stress of potted grapevines.In order to define the sensitivity of IRT measurements to water stress,the IRT-based water status information were compared with simultaneously measuredΨPD and gL data.Correlations between IRT-based CWSI data on the one hand and gL andΨPD on the other showed the potential of IRT for water stress detection.However,the CWSI calculation procedure is laborious and the sensitivity of CWSI for water stress detection still needs to be improved.Therefore,further improvements are necessary in order to apply remote IRT-based systems for irrigation scheduling in the field.