Use Of Crop Water Stress Index Research Articles

Combining proximal and remote sensing to assess 'Calatina' olive water status.

Developing an efficient and sustainable precision irrigation strategy is crucial in contemporary agriculture. This study aimed to combine proximal and remote sensing techniques to show the benefits of using both monitoring methods, simultaneously assessing the water status and response of 'Calatina' olive under two distinct irrigation levels: full irrigation (FI), and drought stress (DS, -3 to -4 MPa). Stem water potential (Ψstem) and stomatal conductance (gs) were monitored weekly as reference indicators of plant water status. Crop water stress index (CWSI) and stomatal conductance index (Ig) were calculated through ground-based infrared thermography. Fruit gauges were used to monitor continuously fruit growth and data were converted in fruit daily weight fluctuations (ΔW) and relative growth rate (RGR). Normalized difference vegetation index (NDVI), normalized difference RedEdge index (NDRE), green normalized difference vegetation index (GNDVI), chlorophyll vegetation index (CVI), modified soil-adjusted vegetation index (MSAVI), water index (WI), normalized difference greenness index (NDGI) and green index (GI) were calculated from data collected by UAV-mounted multispectral camera. Data obtained from proximal sensing were correlated with both Ψstem and gs, while remote sensing data were correlated only with Ψstem. Regression analysis showed that both CWSI and Ig proved to be reliable indicators of Ψstem and gs. Of the two fruit growth parameters, ΔW exhibited a stronger relationship, primarily with Ψstem. Finally, NDVI, GNDVI, WI and NDRE emerged as the vegetation indices that correlated most strongly with Ψstem, achieving high R2 values. Combining proximal and remote sensing indices suggested two valid approaches: a more simplified one involving the use of CWSI and either NDVI or WI, and a more comprehensive one involving CWSI and ΔW as proximal indices, along with WI as a multispectral index. Further studies on combining proximal and remote sensing data will be necessary in order to find strategic combinations of sensors and establish intervention thresholds.

Termografi Tekniği ile Biber Bitkisinde Su Stresinin ve Bazı Fizyolojik Özelliklerin Belirlenmesi

Çalışmada, termografi tekniği ile hesaplanan indeksler kullanılarak biberde su stresinin ve bu indeksler ile bazı fizyolojik özelliklerin belirlenmesi hedeflenmiştir. 2017 yılında Çanakkale’de dört farklı sulama konusundan (S100, S75, S50 ve S25) oluşan bir deneme yürütülmüştür. Çalışmadan elde edilen sonuçlara göre, uygulanan sulama konularından termal indeksler ve tüm fizyolojik özellikler etkilenmiştir. Termal kamera yardımıyla bitki düzeyindeki ölçümlerden ampirik olarak belirlenen bitki su stresi indeksi (CWSIe) verilen sulama suyundaki azalışa bağlı olarak artmış, stoma iletkenliği indeksi (IGe) ise azalmıştır. Sınıflama ve regresyon ağacı analizine göre, CWSIe’nin sulamaya başlama zamanını belirlemek amacıyla kullanımının yeterli olduğu söylenebilir. Bu durumda söz konusu indeksin eşik değeri 0.42 alınabilir. Termal indeksler ile fizyolojik özellikler arasında her bir büyüme dönemi için yapılan regresyon analizi sonuçlarına göre oldukça önemli ilişkiler elde edilmiştir. Söz konusu ilişkiler çiçeklenme döneminden sonra artış göstermiştir. Çalışmanın sonucu olarak su stresini ayırt etmedeki başarısı ve uygulamadaki kolaylığı nedeni ile biber bitkisinde uzaktan algılama tekniklerinden biri olan termografi tekniği ile elde edilen indekslerin kullanımı önerilebilir. Çalışma, termal görüntülerden yararlanarak biber bitkisinde su stresinin hızlı ve doğru bir şekilde belirlenebilme potansiyeli olduğunu göstermiştir.

Seasonal evolution of crop water stress index in grapevine varieties determined with high-resolution remote sensing thermal imagery

The seasonal characterization of spatial variability in water requirements across and within vineyards could assist the viticulturist to fine-tune irrigation management for quality optimization. Remotely sensed crop water stress index (CWSI) is related to crop water status, but it is not known how applicable it is to different grape varieties at different times of the season. This study focused on the determination of the lower and upper baselines for calculating CWSI for the Chardonnay, Pinot-noir, Syrah and Tempranillo varieties at different phenological stages. Baselines were determined based on canopy temperatures measured with infrared temperature sensors placed on top of well-watered grapevines in 2011. Results indicated that non-water-stressed baselines differed depending on variety and phenological stage. During 2011, an aircraft equipped with a thermal camera flew over the vineyards on six particular days throughout the season at 150 m altitude above ground level. At the same time, leaf water potential (Ψ L) was measured for each variety. Variety and phenological stage affected the relationship between remotely sensed CWSI and Ψ L, with phenology having greater influence on the observed measurements than on variety. For instance, the one-to-one relationship between estimated and measured Ψ L had R 2 of 0.634 and 0.729 for variety and phenology, respectively. The baselines and estimations of Ψ L were validated in different vineyards of the same region and in a different season (2013) using the same methodology as in 2011. Data obtained in 2013 were in agreement with observations during 2011. It is concluded that the use of CWSI for assessing vineyard water status requires calibration to account for the effects, primarily of phenological stage, but also, of variety. Once calibrated, this can be successfully applied to other vineyards and seasons.

Irrigation timing in maize by using the crop water stress index (CWSI)

The aim of the investigation was to determine if the CWSI could be used to determine when the irrigation water should be applied to maize under Hungarian changeable weather. Three water treatments were applied: “Ad libitum” watering in lysimeter’s growing chambers, irrigated treatment (use of CWSI), and rainfed control. The theoretical approximation of crop water stress index was applied in our long-term investigation. Among the 17 consecutive seasons between 1989 and 2005 included in the study there were seven arid and four humid seasons. The remaining summers had semi-humid character. To represent the influence of drought on water stress index of maize we chose the year of 2000, the driest and warmest season from the beginning of weather observations of Keszthely. As a counterpoint stress index results of 1997 served as an example of humid seasons. The degree of the deviation in CWSI as a result of different weather may vary, but the tendency in arid or humid seasons remained the same. The basic parameter of CWSI, the canopy temperatures were measured using a hand-held infrared thermometer. Relevant meteorological and plant data were collected locally. Our final conclusion was that there is no problem in use of CWSI during arid summers, where radiation is undisturbed and the cloudiness does not disturb the canopy temperature sampling. In arid seasons increases in assimilatory surface size and yield of maize in irrigated treatments were between 20–35% and 10–30%, respectively. The extra production seems to be enough to cover the irrigation costs. There is also no problem in humid seasons, where the sky is often covered by clouds, but there is no need to irrigate maize in Hungary. In semi-humid weather not only the environmental circumstances may disturb the plant temperature measurements and calculation of CWSI (doubtful results caused by changeable radiation and wind), but the probable yield surplus — below 5% — is also negligible. The irrigation costs are higher than the production gain during semi-humid seasons. In Hungary about one third of the seasons have characteristics of an arid weather where sampling of canopy temperatures provides reliable basis to calculate CWSI and plan irrigation timing.

Infrared Thermometry and the Crop Water Stress Index. II. Sampling Procedures and Interpretation

Infrared thermometry can be a valuable research and production tool for detecting and quantifying water stress in plants, as shown by a large volume of published research. Users of infrared thermometers (IRT) should be aware of the many equipment, environmental, and plant factors influencing canopy temperature measured by an IRT. The purpose of this paper is to describe factors influencing measured plant temperature, outline sampling procedures that will produce reliable Crop Water Stress Index (CWSI) values, and offer interpretations of CWSI and plant temperatures relative to crop production and other water stress parameters by reviewing previously conducted research. Factors that are considered are IRT condition, configuration, and position; psychrometer location; wind speed; solar radiation; time of day; leaf area and orientation; and appropriate non-water-stressed baseline equation. Standard sampling and CWSI calculation procedures are proposed. Use of CWSI with crops varying in type of response to water stress is described. Previously conducted research on plant temperatures or CWSI is tabulated by crop and water stress parameters measured. The paper provides valuable information to assist interested users of IRTs in making reliable water stress measurements.