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The present study aimed to examine the relationship between canopy air temperature difference and vapor pressure deficit (VPD) in wheat crops under normal or nonstressfull conditions. The treatments were undertaken on five plots, having randomized block design (RBD), each maintained at different levels of soil moisture having full irrigation; no irrigation; and 10%, 30%, and 50% soil moisture. Then canopy air temperature difference was regressed against VPD to generate non-water stress and maximum water stress baselines, and the crop water stress index (CWSI) was computed using empirical approach-baseline methods at different soil moisture deficits. It was found that irrigation treatment at 30% soil moisture deficit yielded the maximum water use efficiency. The canopy air temperature difference and VPD resulted in linear relationships, and the slope (m) and intercept (c) for lower baseline of preheading and postheading stages of wheat crop were found as m=−2.371 , c=−1.659 ; and m=−1.8952 , c=−2.32 , for the crop season of 2018–2019. Similarly, the non-water stress baseline equation in the season of 2019–2020 had m=−1.7184 , c=−2.3009 ; and m=−1.8137 , c=−1.9176 for preflowering and postflowering stages of wheat, respectively. The CWSI was determined by using the developed empirical equations for three irrigation schedules of different maximum allowable depletion (MAD) of available soil water (ASW). The developed CWSI may have the potential to improve irrigation scheduling of wheat in India. The study shows practical applications for enhancing wheat cultivation under varying soil moisture conditions. First, it recommends irrigating at 30% soil moisture deficit to maximize water use efficiency, aiding farmers in balancing crop yield and water conservation. Second, established relationships between canopy air temperature difference and VPD allow for the assessment of water stress. By utilizing regression equations, farmers can estimate the CWSI across soil moisture levels, guiding irrigation scheduling during critical growth stages. Third, the developed empirical equations enable real-time prediction of water stress. Monitoring the canopy air temperature difference and VPD offers insights into plant health, helping with informed decisions on irrigation and fertilization. Last, the findings are relevant for water-scarce regions like India, where tailored CWSI equations can be integrated into irrigation systems, promoting sustainable practices under a changing climate. This study may help farmers with practical tools for water-efficient wheat cultivation, fostering informed choices for sustainable agriculture, particularly in water-scarce regions. [ABSTRACT FROM AUTHOR]

Tropospheric ozone (O3 ) has often formed in the emission of volatile organic compounds and nitrogen oxides from human activities. The elevated O3 concentration can seriously reduce the photosynthetic rate of wheat in the late grain-filling stage. The resulting loss of wheat yield can then threaten the food security and the carbon-water cycle of farmland ecosystems. Particularly, there is a closely coupled relationship between grain yield and field water use of wheat. Taking the Nongmai 88 variety as the research object, this study aims to investigate the impacts of elevated O3 on farmland water and heat flux in the wheat field. The response of wheat field transpiration to elevated O3 concentrations was also determined using free air ozone concentration enrichment system (O3 -FACE) simulation. The field microclimate was continuously monitored on AA (ambient air) and E-O3 (1.5 × ambient O3 concentration) in O3 -FACE. There was a great variation in the water and heat flux at different stages of wheat growth under elevated O3, according to the residual energy balance. The results show that latent heat flux was an important energy consumption item of wheat farmland ecosystem, accounting for 61.65%(AA) and 63.77%(E-O3 ) of energy expenditure, respectively. Sensible heat flux and soil heat flux accounted for 24.50%(AA), 21.07%(E-O3 ) and 13.95% (AA), 15.20%(E-O3 ), respectively.In terms of diurnal variation, net radiation, soil heat flux, both sensible and latent heat flux shared the "n" type unimodal trends, reaching the maximum at noon. The net radiation increased gradually during the wheat growing season. Whereas, the latent heat flux showed a trend of first increasing and then decreasing. The sensible heat flux was opposite to the latent one, indicating the trend of first decreasing and then increasing. The latent heat flux decreased in the senescent leaf, while the sensible heat flux increased rapidly. There was no significant effect of elevated O3 on the net radiation, soil heat flux, sensible and latent heat flux, as well as their energy distribution from the wheat jointing to the milk maturity stage. The elevated O3 also accelerated the senescence of wheat leaf in the period from milk ripening to ripening, leading to a reduction in the chlorophyll content. There was a great decrease in the mean and peak value of latent heat flux and evapotranspiration. However, the elevated O3 had no significant effect on evapotranspiration, grain yield and water use efficiency. As such, excellent O3 resistance was achieved to cultivate this variety under the elevated O3, especially for the high grain yield and water use efficiency in the wheat field. This finding can provide new evidence to evaluate the water and heat flux of winter wheat farmland, in order to simulate the farmland water use and grain yield under elevated O3 and variety replacement. [ABSTRACT FROM AUTHOR]

Background: Wheat is an important food crop of world. This crop has the wider adaptability due to its genetic makeup. The sowing environment and varieties interaction plays important role to enhance its productivity and optimum utilization of the resources. As this crop has wider adaptability so we planned our experiment to study the grain yield, heat use and water use efficiency of diverse wheat varieties which have been recommended in different wheat growing zones, sown at different environment in North-western India, to increase the varietal spectrum. Methods: The field experiment was conducted in 2017-18 and 2018-19 at the research farm of the Punjab Agricultural University, Ludhiana, India. The experiment was conducted with four sowing dates (November 5, November 25, December 15 and January 5) in main plot and six wheat varieties (HS 562, HD 2967, HD 3086, HI 1544, MACS 6222 and WR 544) in sub-plot of split plot design with three replications. Result: The wheat crop sown on November 5 recorded the highest emergence count, plant height, heat use efficiency, normalized difference vegetative index, yield attributes, grain yield and water use efficiency than later sowing dates. Among the wheat varieties, HS 562 recommended for northern hill zone recorded heat use efficiency, helio-thermal use efficiency, at leaf value, effective tillers, grains per earhead, grain yield and water use efficiency similar to HD 3086 recommended for North-western zone. The varieties recommended for other zones like HI 1544, MACS 6222 and WR 544 could not perform similar to the HD 3086. [ABSTRACT FROM AUTHOR]