Canopy-air Temperature Difference Research Articles

Utilizing Infrared Thermometry to Assess the Crop Water Stress Index of Wheat Genotypes in Arid Regions under Varying Irrigation Regimes

Researchers are depending more than ever on remote sensing techniques to monitor and assess the agricultural water status, as well as to estimate crop water usage or crop actual evapotranspiration. In the current work, normal and stressed baselines for irrigated wheat genotypes were developed in an arid part of the Sohag governorate, Egypt, using infrared thermometry in conjunction with weather parameters. The experiment was carried out in a randomized complete block design in the normal and drought stress conditions based on three replicates using ten bread wheat genotypes (G1–G10), including five accessions, under drought stress. A standard Class-A-Pan in the experimental field provided the daily evaporation measurements (mm/day), which was multiplied by a pan factor of 0.8 and 0.4 for normal and stressed conditions, respectively. The relationship between the vapor pressure deficit (VPD) and canopy-air temperature differences (Tc − Ta) was plotted under upper (fully stressed) and lower baseline (normal) equations. Accordingly, the crop water stress indexes (CWSIs) for the stressed and normal baselines for wheat genotypes were developed. Additionally, the intercept (b) and the slope (a) of the lower baseline equation were computed for different genotypes. The results indicate that, before applying irrigation water, the CWSI values were high in both growing seasons and under all irrigation regimes. After that, the CWSI values declined. G10 underwent stress treatment, which produced the greatest CWSI (0.975). Conversely, the G6 condition that received well-watered irrigation yielded the lowest result (−0.007). When compared to a well-watered one, the CWSI values indicated a trend toward rising stress. There existed an inverse link between the CWSI and grain yield (GY); that is, a lower CWSI resulted in better plant water conditions and a higher GY. Under standard conditions, the wheat’s highest GY was recorded in G2, 8.36 Ton/ha and a WCSI of 0.481. In contrast, the CWSI result for the stress treatment was 0.883, indicating a minimum GY of 5.25 Ton/ha. The Water Use Efficiency (WUE) results demonstrated that the stress irrigation regime produced a greater WUE value than the usual one. This study makes a significant contribution by investigating the techniques that would allow CWSI to be used to estimate irrigation requirements, in addition to determining the irrigation time.

Determination of threshold crop water stress index for sub-surface drip irrigated maize-wheat cropping sequence in semi-arid region of Punjab

A thorough understanding of how crops respond to water stress is essential for effective irrigation management under changing climate conditions and declining water resources. Amongst the various methods of irrigation, crop water stress index (CWSI)-based irrigation is popular due to its non-invasive techniques that require less data and can precisely indicate the severity of crop water deficiency. The present study focuses on establishing the upper- and lower-baselines of canopy-air temperature difference (Tc-Ta) for the estimation of the CWSI and to determine the CWSI threshold for maize and wheat crops. The upper- and lower-baseline of (Tc-Ta) was established using the relationship between (Tc-Ta) and vapor pressure deficit (VPD) for different irrigation treatments such as 60 %ETc, 70 %ETc, 80 %ETc, 90 %ETc, and 100 %ETc with irrigation interval of 1-day, 2-days, and 3-days. The study showed that the baselines varied with the growth stages of the crop and with irrigation treatments and reached the maximum in Anthesis and Silking growth stage for wheat and maize, respectively. The threshold of CWSI was estimated by developing a relationship between the normalized values of grain yield (GY) and irrigation water productivity (WPI). For the Rabi wheat, a quadratic correlation was identified between CWSI and WPI (r2 = 0.89), and GY (r2 = 0.93). Similarly, for Kharif maize, a quadratic relationship was noted between CWSI and both WPI (r2 = 0.75) and GY (r2 = 0.85). From the study, it was found that the CWSI thresholds of Rabi wheat and Kharif maize are 0.29 and 0.31, respectively. Based on the study, it can be concluded that by utilizing the thresholds for a winter wheat-summer maize cropping system, high GY and WPI can be achieved.

Infrared thermometry-based stress indices as indicators of yield performance and seasonal evapotranspiration in potato plants grown under different moisture and potassium regimes

As the demand for food continues to rise and water availability challenges intensify, the delicate equilibrium between efficient water usage and sustainable agricultural production has become increasingly pivotal. Recognizing the significance of water stress monitoring and nutrient management in the country's agricultural landscape, two years of field trials (2018–2019 and 2019–2020) were conducted at the Regional Research Station, Bidhan Chandra Krishi Viswavidyalaya, Gayeshpur, Nadia, to demonstrate the efficiency of canopy temperature-based indices for monitoring crop water stress in potato (cv. Kufri Jyoti) under varied irrigation (IW:CPE = 0.4, 0.8, 1.2 and 1.6) and potassium doses (K2O @ 100, 150 and 200 kg ha−1). The seasonal evapotranspiration of potato plants ranged from 121.0 mm to 320.9 mm during the crop growth period, and it exhibited a quadratic relationship with both the total dry biomass and the tuber yield. In 2019–2020, the highest water use efficiency (WUE) of 12.74 kg m−3 was obtained from the application of IW; CPE= 1.20 with the application of K2O @ 200 kg ha−1. In the following year, the highest WUE of 9.78 kg m−3 was obtained from irrigation at IW:CPE= 1.60, along with K2O application @ 200 kg ha−1. During a major part of the growth period, the canopy air temperature difference (CATD) was greater in the treatments in which irrigation was applied at IW:CPE = 0.4 and 0.8 than in those in which irrigation was applied at higher levels, i.e., IW:CPE = 1.2 and 1.6, implying the effectiveness of CATD as a stress indicator. The stress indices, stress degree days (SDD) and crop water stress index (CWSI) accumulated over the crop growing season showed decreasing trends with increasing irrigation and potassium doses. Both the accumulated SDD and accumulated CWSI showed a strong inverse relationship with tuber yield. The significant linear relationship between tuber yield and the seasonal accumulation of both infrared thermometry-based stress indices (i.e., SDD and CWSI) may help to predict crop yield in response to seasonal moisture stress and thus aid in strategic crop planning under the limited availability of irrigation.

Precise Drought Threshold Monitoring in Winter Wheat Using the Unmanned Aerial Vehicle Thermal Method

Accurate monitoring of crop drought thresholds at different growth periods is crucial for drought monitoring. In this study, the canopy temperature (Tc) of winter wheat (‘Weilong 169’ variety) during the three main growth periods was extracted from high-resolution thermal and multispectral images taken by a complete unmanned aerial vehicle (UAV) system. Canopy-air temperature difference (ΔT) and statistic Crop Water Stress Index (CWSIsi) indicators were constructed based on Tc. Combined experiment data from the field and drought thresholds for the ΔT and CWSIsi indicators for different drought levels at three main growth periods were monitored. The results showed a strong correlation between the Tc extracted using the NDVI-OTSU method and ground-truth temperature, with an R2 value of 0.94. The CWSIsi was more stable than the ΔT index in monitoring the drought level affecting winter wheat. The threshold ranges of the CWSIsi for different drought levels of winter wheat at three main growth periods were as follows: the jointing–heading period, where the threshold ranges for normal, mild drought, moderate drought, and severe drought are <0.30, 0.30–0.42, 0.42–0.48, and >0.48, respectively; the heading–filling period, where the threshold ranges for normal, and mild, moderate, and severe drought are <0.33, 0.33–0.47, 0.44–0.53, and >0.53, respectively; and the filling–maturation period, where the threshold ranges for normal, mild drought, moderate drought, and severe drought are <0.41, 0.41–0.54, 0.54–0.59, and >0.59, respectively. The UAV thermal threshold method system can improve the accuracy of crop drought monitoring and has considerable potential in crop drought disaster identification.

Exogenous application of spermidine and methyl jasmonate can mitigate salt stress in fenugreek (Trigonella foenum-graecum L.)

Fenugreek (Trigonella foenum-graecum L.) has long been cultivated as both culinary and medicinal plant. The objective of this study was to investigate the effect of plant growth regulators such as spermidine (Spd) and methyl jasmonate (MeJA) on morpho-physiological and biochemical properties of fenugreek under saline conditions. A replicated greenhouse experiment in completely randomized block design was conducted with two levels of salinity (0.5 dS/m as control and 6 dS/m), three levels of spermidine (0, 1, 2 mM) and methyl jasmonate (0, 100, 200 µM), respectively. The results showed that salinity elevation reduced the leaf relative water content, leaf water potential, canopy-air temperature difference, photochemistry efficiency of photosystem II, and water-use efficiency of fenugreek. In contrast, salinity increased leaf thickness,greenness index, canopy temperature, leaf Na+, ash contents, malondialdehyde, other aldehydes, and electrolyte leakage. Moreover, Salinity stress reduced the amount of photosynthetic pigments, chlorophyll a/b ratio, total soluble protein, K+, maximum fluorescence, and K+/Na+ ratio in leaves. Elevation of water salinity, however, resulted in an increase in the activity of antioxidant enzymes (except superoxide dismutase), proline, and minimum fluorescence. When fenugreek was treated with 1 mM spermidine and/or 100 µM methyl jasmonate, the adverse effects of salinity stress were significantly mitigated, while the effects of these plant growth regulators on mitigating salinity stress were less pronounced at higher concentrations (2 mM spermidine and/or 200 µM methyl jasmonate). The current study suggests the application of 1 mM spermidine and/or 100 µM methyl jasmonate during the vegetative growth stage mitigating the adverse effects of salinity with an associated improvement in plant growth under moderate salinity (about 6 dS/m) when used for irrigation.

Physiological and Canopy Temperature Responses to Drought of Four Penstemon Species

Available water for urban landscape irrigation is likely to become more limited because of inadequate precipitation and the ever-increasing water demand of a growing population. Recent droughts in the western United States have also increased the demand for low-water-use landscapes in urban areas. Penstemon species (beardtongues) are ornamental perennials commonly grown in low-water-use landscapes, but their drought tolerance has not been widely investigated. The objectives of this study were to determine the effects of water availability on the morphology, physiology, and canopy temperature of Penstemon barbatus (Cav.) Roth ‘Novapenblu’ (Rock Candy Blue® penstemon), P. digitalis Nutt. ex Sims ‘TNPENDB’ (Dakota™ Burgundy beardtongue), P. ×mexicali Mitch. ‘P007S’ (Pikes Peak Purple® penstemon), and P. strictus Benth. (Rocky Mountain penstemon). Twenty-four plants of each penstemon species were randomly assigned to blocks in an automated irrigation system, and the substrate volumetric water content was maintained at 0.15 or 0.35 m3⋅m−3 for 50 days. The decreased substrate volumetric water content resulted in a decreased aesthetic appearance of the four penstemon species because of the increased numbers of visibly wilted leaves and chlorosis. Plant growth index [(height + (width 1 + width 2)/2)/2], shoot number, shoot dry weight, leaf size, and total leaf area also decreased as the substrate volumetric water content decreased, but the root-to-shoot ratio and leaf thickness increased. Photosynthesis decreased, stomatal resistance increased, and warmer canopy temperatures were observed when plants were dehydrated. Additionally, as substrate volumetric water content decreased, the leaf reflectance of P. barbatus and P. strictus increased. Penstemon digitalis, which had the highest canopy–air temperature difference, was sensitive to drought stress, exhibiting a large proportion of visibly wilted leaves. Penstemon ×mexicali, which had the lowest root-to-shoot ratio, had the lowest shoot water content of the species studied and more than 65% of leaves visibly wilted when experiencing drought stress. Penstemon barbatus and P. strictus, native to arid regions, exhibited lower canopy–air temperature differences and better aesthetic quality than the other two species. Under the conditions of this study, Penstemon barbatus and P. strictus exhibited better drought tolerance than P. digitalis and P. ×mexicali.

Applicability of the crop water stress index based on canopy–air temperature differences for monitoring water status in a cork oak plantation, northern China

The crop water stress index based on canopy–air temperature differences (CWSIdT) is an appropriate index for monitoring the water status of croplands but is rarely used to evaluate the water status of forest ecosystems. In this study, we selected a cork oak plantation in the lithoid mountain area of northern China as the research object and observed the canopy temperature (Tc), actual evapotranspiration (ETa), and meteorological factors of the plantation continuously and synchronously during the period of canopy closure (May–September) in 2020 and 2021. Taking the crop water stress index based on the ratio of ETa to potential evapotranspiration (CWSIet) as a standard, the applicability of CWSIdT for detecting water status in the plantation was evaluated. The results showed that, under well-watered conditions, the canopy–air temperature differences (dT) and the canopy surface transpiration rate were both controlled by the net radiation received by the canopy surface (Rnc), and the warming effect of Rnc masked the cooling effect of latent heat on dT, resulting in a failure establishment of the non-water-stressed baseline in the plantation. Therefore, the empirical CWSIdT (CWSIdTe) is not suitable for evaluating the water status in this plantation. However, the theoretical CWSIdT (CWSIdTt), based on the energy balance and Penman–Monteith equation, captured daily variations in the water status in our plantation and showed a significant linear correlation with the measured relative available water content in the root zone (R2 = 0.59, P < 0.01) and CWSIet (R2 = 0.75, P < 0.01). The CWSIdTt showed an upward trend during the day, and midday (13:00−14:00) was the optimal time to measure dT for detecting the daily water status of the plantation. The CWSIdTt provides an effective, sensitive, and non-contact method of assessing daily water status changes in the cork oak plantation.

Quantifying water stress of safflower (Carthamus tinctorius L.) cultivars by crop water stress index under different irrigation regimes

Infrared thermometry allows evaluating water status of the crop by measuring crop water stress index (CWSI), without the need of physical contact to leaves. In order to quantify water stress by CWSI and finding the best irrigation regime a two-year field experiment was conducted in safflower during 2017 and 2018 growing seasons at Darab, Fars province, Iran. Two safflower cultivars (Goldasht and Local Isfahan) and four irrigation regimes consisted of well-watered [Irrigation based on 100% field capacity (FC)], mild (75% FC), severe (50% FC), and most severe (25% FC) water stress were arranged as split plot according to randomized completely block design with four replicates. The relationship between vapor pressure deficit (VPD) and canopy-air temperature differences (Tc-Ta) was plotted under upper (fully stressed) and lower baselines (non-stressed) equations. In two cultivars, by VPD increment, the distance between upper and lower base lines increased. In Goldasht, the upper baseline (Tc-Ta)ul, was 7.8 °C in 2017 and 8.9 °C in 2018. From April to July when air warmed, Tc-Ta differential was increased up to July and the highest seasonal CWSI (0.72–0.77) were obtained in Local Isfahan under most severe water stress. In 2017, under water stress, the highest relative water content (RWC; 55%), color quality (6–7) and water use efficiency (WUE; 2.69 g m−2 mm−1) was observed in Goldasht under mild water stress which was more than 2018 and Local Isfahan. It might be attributed the more tolerance of Goldasht to water stress and lower air temperature and evaporation in the first year. CWSI with total water consumed (R2 = 0.88∗∗), RWC (R2 = 0.87∗∗), color quality (R2 = 0.75∗) and seed yield (R2 = 0.83∗∗) related, negatively. Overall, a mild water stress (75% FC) with 0.28–0.33 seasonal CWSI had higher RWC, color quality, WUE, with an acceptable yield, which could be the best irrigation regime under water deficit conditions for safflower.

Susceptibility and tolerance of fenugreek (Trigonella foenum-graceum L.) to salt stress: Physiological and biochemical inspections

Greenhouse experiments were conducted to evaluate the effects of soil salinity on some physiological and biochemical attributes of fenugreek (Trigonella foenum-graecum L.) and its tolerance for salt using some empirical models. The treatments included different salinity levels of irrigation water (0.5, 2, 4, 6, 8, 10 and 12 dS/m) which were arranged in the form of a randomized complete block design with three replicates. Some physiological and biochemical properties were measured at the vegetative stage and trigonelline at seed ripening. As the results showed, salinity reduced leaf area, relative water content, water use efficiency, and leaf water potential, but it increased leaf thickness, greenness index, canopy temperature, sodium, ash, electrolyte leakage, malondialdehyde (MDA) and the other aldehydes. Salt stress also reduced photosynthetic pigments, chlorophyll a/b ratio, leaf soluble protein, potassium, K+/Na+ ratio, photochemical efficiency of photosystem II (PSII) and canopy air temperature difference (CATD) index. Like catalase (CAT) and ascorbate peroxidase (APX) activities, the activity of superoxide dismutase (SOD) was increased up to 6 dS/m and then decreased. Furthermore, proline concentration was increased up to 8 dS/m and decreased at higher salinities. The increased salinity enhanced seed trigonelline up to 6 dS/m and then decreased it. According to a linear model, the salinity threshold tolerance and the yield reduction slope were 1.28 dS/m and 4.9%, respectively. Nonlinear models, however, showed a yield reduction of 10%, 25% and 50% at the soil salinity of 3.38, 6.28 and 11.67 dS/m, respectively. The salinity tolerance index was found to be 12.24. Therefore, fenugreeks can be considered moderately sensitive to salinity at the vegetative growth stage. It may also be grown on slightly to moderately saline lands. Some characteristics may be considered as selective criteria to identify the cultivars of fenugreek that tolerate salt stress.

Influence of meteorological parameters on wheat yield under different sowing conditions

Field experiments were conducted on the research farm of IARI, New Delhi during Rabi 2016-17 and 2017-18. Three varieties of wheat (PBW-723, HD-2967 and HD-3086) were sown on three different dates for generating different weather condition during various phenological stages of crop. Results showed that during early crop growth stages soil moisture had higher value and soil temperature had lower value and with progress of crop growth stage, the moisture in the upper layer decreased and soil temperature increased significantly as compared to the bottom layers. During tillering and jointing stage, air temperature within canopy was more and relative humidity was less while during flowering and grain filling stage, air temperature within canopy was less and relative humidity was more in timely sown crop as compared to late and very late sown crop. Radiation use efficiency and relative leaf water content had significantly higher value while leaf water potential had lower value in timely sown crop followed by late and very late sown crop. Yield had higher value in HD-3086 followed by HD-2967 and PBW-723 in all weather conditions. Canopy air temperature difference had positive value in very late sown crop particularly during flowering and grain-filling stages. This reflects in the yield. Yield was more in timely sown crop as compared to late and very late sown crop.&#x0D;

Applicability of the Crop Water Stress Index Based on Canopy–Air Temperature Differences for Water Diagnosis in a Cork Oak Plantation, Northern China

Applicability of the Crop Water Stress Index Based on Canopy–Air Temperature Differences for Water Diagnosis in a Cork Oak Plantation, Northern China

Detection of the 3D temperature characteristics of maize under water stress using thermal and RGB-D cameras

Global warming and water resource shortage greatly influence the crop growth and negatively affect the crop yield. Breeding water–stress resistant crop varieties is one of the effective ways to handle this problem. The surface temperatures of the crop are essential for assessing their water stress resistance. Thermal imaging has been widely used to acquire the crop surface temperatures. However, most studies focus on 2D measurement. A 3D thermal imaging system is designed, and a method is developed by using the thermal and RGB-D data to acquire 3D thermal information of maize under water stress conditions. First, thermal and RGB-D cameras were used to collect the thermal and color images, and depth data of maize at the jointing stage and the thermal and color images were processed to extract the edge images of maize. Second, the KAZE feature was selected to register the edge images. Testing results showed that the KAZE feature has better performance than the SURF and BRISK features in the thermal and color image registration of maize. On the basis of the thermal and color image registration, the depth data of maize were assigned with temperature values. Third, the depth data of maize were further processed with denoising, maize extraction, amplification, smoothing, and temperature correction steps to improve the data qualities. Finally, the crop water stress index and canopy–air temperature difference values of each point were calculated. The results demonstrated that the system and the proposed method can effectively detect the water stress characteristics of maize in 3D, which can be combined with the morphological traits of leaves to synthetically analyze the water stress resistance of the crop.

Study of energy balance components at different growth stages of green gram grown in new alluvial zone of West Bengal

An experiment was conducted in the experimental farm of Bidhan Chandra KrishiViswavidyalaya, Nadia, West Bengal to study the radiation pattern and its balance over green gram (Vignaradiata var. Samrat). The BREB method was used to determine the sensible heat flux and latent energy. The net radiation was measured through net radiometer and the ground heat flux was measured using Fourier's law. Both the diurnal and seasonal variation of net radiation were studied. Similarly, the energy balance components were studied regularly for different crop growth stages as well as on diurnal basis. It is observed that the net radiation varies from 6.32 Wm-2 to 606.43 Wm-2. The latent heat flux constitutes more than 50% of the net radiation for all growth stages as depicted by energy balance partitioning. The sensible heat flux is partitioned into 10% to 20% of total net radiation throughout the growth stages of green gram, which is the lowest in magnitude among all three energy fluxes. The relationship between Bowen ratio and Vapour pressure deficit (VPD), Bowen ratio and Canopy air temperature difference (CATD) was studied. It was found that Bowen ratio is negatively correlated with VPD but positively correlated with CATD. This study enables to monitor ET pattern through latent heat flux and microclimatic characteristics through sensible and ground heat flux.

Assessment of sunflower water stress using infrared thermometry and computer vision analysis

Abstract The objectives of the current study were to implement affordable and non-invasive measurements of infrared thermometry, leaf relative water content (RWC), crop water stress index (CWSI), leaf area index (LAI) from computer vision analysis and seed yield of sunflowers. The experiment was designed as split-plot based on randomized complete blocks with three replications. Treatments were four different levels of deficit irrigation as the main plots and three fertilization treatments were applied as sub-plots. Results showed a significant effect (P ≤ 0.01) of water stress and fertilizer on CWSI during different stages of sunflower growth. Changes in fertilizer amount and type resulted in a change in lower (dTLL) and upper (dTUL) limits of canopy-air temperature difference. A combination of chemical fertilizer with biofertilizer could help to decrease CWSI. From computer vision analysis, the normalized difference red blue index (NDRBI) had a strong linear relationship with RWC and CWSI for sunflowers (R2 of 0.87 and 0.93, respectively) and the normalized difference green blue index (NDGBI) had a linear relationship with seed yield (R2 = 0.79). Therefore, analysis of digital RGB images and CWSI were efficient, non-destructive and low-cost methods to assess crop water status for sunflowers under different irrigation and fertilizer treatments.

Soil Moisture Monitoring of the Plant Root Zone by Using Phenology as Context in Remote Sensing

In this study, the phenological behavior and energy balance of plants are used as a sensory mechanism for root-zone soil moisture monitoring using both in-situ and satellite remote sensing data. The commonly used in-situ measurements are not feasible for mapping soil moisture at large-scale agricultural areas. Local direct root-zone soil moisture measurements cannot be reliably interpolated owing to the high spatial variability of soil structure and the vegetative content. Remote sensing methods are negatively affected by vegetation coverage and density regarding penetration and backscattering characteristics. In order to overcome these limitations, we propose a root-zone soil moisture estimation method utilizing a context-aware data clustering process, which can be applied prior to any statistical analysis, for empirical evaluation of data. In this aspect, the crops’ phenological stages and soil–air temperature differences are defined as the two contexts for data clustering. Parameters such as canopy–air temperature difference, land surface temperature, and solar radiation with respect to plant energy and water processes are used for the analysis. The proposed model is utilized using piecewise linear regression of data obtained from 16 rainfed wheat parcels distributed across Turkey, under different climatic and topographic conditions. It is shown that the proposed context-aware data clustering process enables the nonlinear plant behavior to be analyzed linearly. The correlation value of the whole season increased from 21% to a range between 78% and 95% for different clusters. The outliers became relevant and the parameters became significant after the proposed context-aware data clustering.

Assessment of the Crop Water Stress Index and Color Quality of Bur Clover (Medicago polymorpha L.) Under Different Irrigation Regimes

ABSTRACTRelationship between canopy temperature and soil moisture is important for using the potential of canopy temperature as an indicator of crop water stress. A two-year field experiment was carried out during June to September 2016 and 2017 at the Research Station of College of Agriculture, Darab, Shiraz University, Iran, to determine crop water stress index (CWSI) for bur clover. Irrigation regimes including well-watered [Irrigation according to 100% field capacity (FC)], mild water stress (75% FC), severe water stress (50% FC), and most severe water stress (25% FC) were arranged in a randomized complete block design with four replications. In 2016, CWSI values showed an increasing trend from June (0.066 in well-watered) to August (0.821 in most severe water stress) as a result of higher vapor pressure deficit (VPD) and depression in canopy-air temperature differences (Tc-Ta). A similar trend was observed in the second year. In both years, by increase in mean temperature from June to August, Tc-Ta differential increased and the highest monthly average value of CWSI for all treatments was obtained in August. By enhancing water stress, the color grading score decreased sharply (from 6 to 3) and stayed constant (2) for August and September. Also, a negative relationship was observed between CWSI and dry matter production (R2 = 0.88**) and color quality (R2 = 0.94**). It was concluded that mild water stress (75% FC) with mean seasonal CWSI being ranged about 0.198 to 0.294, without any loss in visual color quality might be the best irrigation regime for bur clover production.

Quantifying water stress in canola (Brassica napus L.) using crop water stress index

The relationship between canopy temperature and soil moisture is particularly important because of using canopy temperature as an indicator of crop water stress. A field experiment was conducted to calculate crop water stress index (CWSI) of two canola cultivars including RGS and Sarigol at College of Agriculture and Natural Resources of Darab, Shiraz University, Iran during 2013-2014 growing season. Irrigation regimes consisted of well watered [Irrigation equal to 100% field capacity (FC)], light drought (75% FC), moderate drought (50% FC), and severe drought (25% FC) stresses which were arranged in a randomized complete block design (RCBD) with three replications. In RGS and Sarigol, CWSI values showed an increasing trend from March (0.066 and 0.093 in well watered) to June (0.711 and 0.821 in severe drought) respectively, as a result of higher vapor pressure deficit (VPD) and increase in canopy-air temperature differences (Tc-Ta).In both cultivars, when the air temperature increased from March to June, Tc-Ta increased. The highest monthly average value of CWSI for all treatments was obtained in June. By increasing the drought stress, the color grading score decreased from 6 to 2 sharply in May and June. An acceptable color quality (6 -5) was sustained in May, under light drought condition. Also, a negative relationship was observed between CWSI with color quality (R2=0.94**) and grain yield (R2=0.97**). It could be concluded that in semi-arid areas, light drought is the best option for canola production while mean seasonal CWSI being ranged about 0.198 to 0.294 without any loss in visual color quality of canola.

水分亏缺冬小麦近等基因系冠气温差与群体总耗水量的关系

PDF HTML阅读 XML下载 导出引用 引用提醒 水分亏缺冬小麦近等基因系冠气温差与群体总耗水量的关系 DOI: 10.5846/stxb201712212292 作者: 作者单位: 中国农业科学院农业环境与可持续发展研究所,中国农业科学院农业环境与可持续发展研究所,中国农业科学院农业环境与可持续发展研究所,中国农业科学院农业环境与可持续发展研究所,中国农业科学院农业环境与可持续发展研究所,中国农业科学院农业环境与可持续发展研究所,中国农业科学院农业环境与可持续发展研究所,中国农业科学院农业环境与可持续发展研究所,中国农业科学院农业环境与可持续发展研究所 作者简介: 通讯作者: 中图分类号: 基金项目: 国家"十二五""863"计划课题（2011AA100501） Canopy-air temperature difference of winter wheat near-isogenic lines and its relationship with total water consumption by winter wheat grown under water deficit conditions Author: Affiliation: Institute of Environment and Sustainable Development in Agriculture, Chinese Academy of Agricultural Sciences,,,,,,,,Institute of Environment and Sustainable Development in Agriculture, Chinese Academy of Agricultural Sciences Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:研究品种之间群体耗水特性的差异及其关键影响因素，为品种耗水特性评价与低耗水品种鉴选方法提供依据。选用水分亏缺条件下产量差异不显著，但耗水量差异极显著的冬小麦品种晋麦47和京411及其15个近等基因系为实验材料。利用防雨池和防雨棚开展实验，模拟水分亏缺条件。监测全生育期土壤水分含量，计算总耗水量，收获后测定籽粒产量，计算水分利用效率（WUE）。同时，分别在拔节-孕穗期、抽穗-开花期和灌浆期3个不同生育期监测冠层-大气温度差值（CTD）、叶片蒸腾速率和气孔导度。结果表明，3个不同生育期，15个近等基因系及其亲本之间，CTD均达到显著差异。CTD的方差分析表明，基因型和年份均对不同生育期的CTD有显著影响，但是二者之间仅在抽穗-开花期存在互作（P=0.0002）。15个近等基因系及其亲本之间耗水量存在显著差异，产量没有显著差异。源于耗水量的差异，部分品种/系之间WUE达显著差异。3个不同生育期，15个近等基因系及其亲本之间，CTD与总耗水量均呈极显著负相关关系。抽穗-开花期最高，2012-2013年度和2016-2017年度分别达到0.7042和0.6095。叶片蒸腾速率和气孔导度与群体总耗水量之间相关性很弱，3个生育期均未达到显著水平。对该组近等基因系材料，影响群体总耗水量的关键因素不是叶片蒸腾生理特性，而是群体冠层生长特性。表明构建合理的群体冠层结构不仅是获得高产的途经，而且是调控群体总耗水量，提高品种水分利用效率的重要途径。 Abstract:This study explored the key factors that lead to differences in water consumption among different populations with different genotypes, to evaluate genotype-specific water consumption traits and select ideal varieties with low water requirements. Fifteen near-isogenic lines (NILs), along with their donor parent Jing 411 and recurrent parent Jinmai 47, were used as materials in this experiment. The materials tested have significantly different water consumptions, but there are no significant differences in their yields under water deficit conditions. Automatic rain-shelter and rain-proof pools that can prevent water seepage were used for the simulated water deficit treatment. The soil water content of all the genotypes were monitored over the whole experimental period and the total water consumption was calculated using the water balance equation. Grain yield was measured after harvest and then the water use efficiency (WUE) was calculated. The canopy-air temperature difference (CTD), leaf transpiration rate, and stomatal conductance were also monitored at the jointing-booting, heading-flowering, and grain-filling stages. The results indicated that the 15 NILs, along with their parents, had significantly different CTDs during all three growth periods. Analysis of variance for the CTD differences indicated that genotype, and growth and development year significantly affected CTD, but there was an interaction between the two factors only at the heading-flowering stage (P=0.0002). There were significant differences in water consumption among the 15 NILs and their parents. However, there were no significant differences in yield. The differences in water assumption meant that there were significant differences in WUE among some genotypes. The CTDs at all three growth and development stages negatively correlated with water consumption. The R2 value was the highest at the heading-flowering stage, and was 0.7042 and 0.6095 during 2012-2013 and 2016-2017, respectively. The correlations between leaf transpiration rate, and stomatal conductance and water consumption were very weak among the 15 NILs and their parents. The correlations were not significant for any of the three growth and development stages. The results for the near-isogenic lines tentatively indicate that under water deficit conditions, the canopy structure traits, rather than leaf gas exchange properties such as leaf transpiration rate and stomatal conductance, significantly affect population-specific water consumption. The results also show that establishing a suitable population canopy structure increases yields and can control water consumption, which leads to an improvement in WUE. 参考文献 相似文献 引证文献

Diurnal Response of Sun-Induced Fluorescence and PRI to Water Stress in Maize Using a Near-Surface Remote Sensing Platform

Sun-induced Fluorescence (SIF) and Photochemical Reflectance Index (PRI) data were collected in the field over maize to study their diurnal responses to different water stresses at the canopy scale. An automated field spectroscopy system was used to obtain continuous and long-term measurements of maize canopy in four field plots with different irrigation treatments. This system collects visible to near-infrared spectra with a spectrometer, which provides a sub-nanometer spectral resolution in the spectral range of 480~850 nm. The red SIF (FR) and far red SIF (FFR) data were retrieved by Spectral Fitting Methods (SFM) in the O 2 -A band and O 2 -B band, respectively. In addition to PRI, Δ PRI values were derived from PRI by subtracting an early morning PRI value. Photosynthetic active radiation (PAR) data, the canopy fraction of absorbed PAR (fPAR), and the air/canopy temperature and photosystem II operating efficiency (YII) at the leaf scale were collected concurrently. In this paper, the diurnal dynamics of each parameter before and after watering at the jointing stage were compared. The results showed that (i) both FR and FFR decreased under water stress, but FR always peaked at noon, and the peak of FFR advanced with the increase in stress. Leaf folding and the increase in Non-photochemical Quenching (NPQ) are the main reasons for this trend. Leaf YII gradually decreased from 8:00 to 14:00 and then recovered. In drought, leaf YII was smaller and decreased more rapidly. Therefore, the fluorescence yield at both the leaf and canopy scale responded to water stress. (ii) As good indicators of changes in NPQ, diurnal PRI and Δ PRI data also showed specific decreases due to water stress. Δ PRI can eliminate the impact of canopy structure. Under water stress, Δ PRI decreased rapidly from 8:00 to 13:00, and the maximum range of this decrease was approximately 0.05. After 13:00, their values started to increase but could not recover to their morning level. (iii) Higher canopy-air temperature differences ( Δ T ) indicate that stomatal closure leads to an increase in leaf temperature, which maintains a higher state in the afternoon. In summary, to cope with water stress, both leaf folding and changes in physiology are activated. To monitor drought, SIF performs best around midday, and PRI is better after noon.

Leaf phenology paradox: Why warming matters most where it is already warm

Interactions between climate and ecosystem properties that control phenological responses to climate warming and drought are poorly understood. To determine contributions from these interactions, we used space-borne remotely sensed vegetation indices to monitor leaf development across climate gradients and ecoregions in the southeastern United States. We quantified how air temperature, drought severity, and canopy thermal stress contribute to changes in leaf flushing from mountainous to coastal plain regions by developing a hierarchical state-space Bayesian model. We synthesized daily field climate data with daily vegetation indices and canopy surface temperature during spring green-up season at 59 sites in the southeastern United States between 2001 and 2012. Our results demonstrated strong interaction effects between ecosystem properties and climate variables across ecoregions. We found spring green-up is faster in the mountains, while coastal forests express a larger sensitivity to inter-annual temperature anomalies. Despite our detection of a decreasing trend in sensitivity to warming with temperature in all regions, we identified an ecosystem interaction: Deciduous dominated forests are less sensitive to warming than are those with fewer deciduous trees, likely due to the continuous presence of leaves in evergreen species throughout the season. Mountainous forest green-up is more susceptible to intensifying drought and moisture deficit, while coastal areas are relatively resilient. We found that with increasing canopy thermal stress, defined as canopy-air temperature difference, leaf development slows following dry years, and accelerates following wet years.