Spectral estimates of the absorbed photosynthetically active radiation and light-use efficiency of a winter wheat crop subjected to nitrogen and water deficiencies†

Steinmetz, S.; Guérif, Martine; Delécolle, R.; Baret, Frédéric

doi:10.1080/01431169008955130

Cited by 47 publications

(24 citation statements)

References 25 publications

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“…These findings are in accordance with those of Liakatas (1998), who determined that because of lack of sufficient water from anthesis onwards, especially during the seed-filling duration (which usually occurs in central Greece during May-June (Dalezios et al, 2002)), the expected wheat yield may be up to 75% less than the maximum yield that would have been achieved on the Aegean Islands had there been no lack of water. Furthermore, the literature corroborates that water shortage seems to have a surprisingly small effect on the radiation use efficiencies of winter and durum wheat in the period before anthesis (Steinmetz et al, 1990). The seven growing season drought indices were used to develop a set of curvilinear regression-based wheat yield models for each region/drought index combination.…”

Section: Methodsmentioning

confidence: 99%

“…In the case of Orig-PDSI, the effects of climate change scenarios were 'absorbed' by the soil moisture anomaly Z. The monthly time series of Z for observed and perturbed climate followed the same pattern (not shown) since the two climates differed only by the temperature/precipitation change suggested by the climate model (section 'Control Simulation 1961-1990. The strong agreement of the two Orig-PDSI time series in Figure 6(a) is a result of the small contribution of Z(P DSI i = p · P DSI i−1 + q · Z i (1), where i is the current month and p = 0.897 and q = 1/3 are the duration factors) to the estimated PDSI values.…”

Section: Orig-pdsmentioning

confidence: 97%

“…Both the K-S two-sample test and the frequency histogram of drought severity levels confirmed the above-mentioned conclusion. At the southern location, on the other hand, when the projected climate series were supplied, the SC-PDSI scheme that was calibrated over the historical data set for 1950-2001 (as explained in the section 'Control Simulation 1961-1990 Figure 4(b)). In the case of Orig-PDSI, the effects of climate change scenarios were 'absorbed' by the soil moisture anomaly Z.…”

Section: Orig-pdsmentioning

confidence: 99%

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Drought index evaluation for assessing future wheat production in Greece

Mavromatis

2006

Intl Journal of Climatology

149

102

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Abstract:The main objectives of this study were (1) to evaluate the SPI, and three variations of the Palmer Drought Severity Index (PDSI) (the original PDSI (Orig-PDSI), a self-calibrated version (SC-PDSI) and a modified scheme employing Priestlay-Taylor's approach to compute potential evapotranspiration (PET) instead of Thornthwaite's method) and their respective moisture anomaly indices for assessing rainfed common wheat and durum wheat yield in two pilot crop regions in north and central Greece, and (2) to assess the vulnerability of wheat production to climate change, using the most appropriate drought index, with future scenarios provided by the Hadley Centre regional climate model HadRM3. The yield models that performed best at high-drought risk years (the Orig-PDSI index in the northern region and the SC-PDSI in the southern region, explaining 82.5 to 84.7% and 92% of the measured yield variability, respectively) were also the most effective at predicting the observed wheat yields when soil moisture was not an important yield-limiting factor. However, the strength of the relationship between the drought indices and the crop yields was much weaker. Improving the representation of PET in the PDSI algorithm did not improve the model's performance. The sensitivity of the two types of wheat to HadRM3 projections for the high-drought risk years differed dramatically between the two pilot districts, with extremely decreased yields of 3.14 tn ha −1 expected in the southern district and much smaller changes expected in the northern district (−4.6 vs +6.7% for durum wheat and common wheat, respectively). For the low-drought risk years, the yield models in the northern region predicted lower yields by 30 to 60 kg ha −1 . A positive yield response by 30 kg ha −1 was found for the southern district.

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Section: Methodsmentioning

confidence: 99%

Section: Orig-pdsmentioning

confidence: 97%

Section: Orig-pdsmentioning

confidence: 99%

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Drought index evaluation for assessing future wheat production in Greece

Mavromatis

2006

Intl Journal of Climatology

149

102

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“…(2), i.e., PAR absorbed by photosynthetic tissues, is usually within 10% of fI-PAR (Russell et al, 1989) but can differ significantly due to canopy and soil reflectance (Prince, 1991) and absorption by non-photosynthetic tissues (Asner et al, 1998), with the latter becoming very significant during senescence (e.g., Asrar et al, 1984). Remote sensing estimates of fAPAR (e.g., Asrar et al, 1984;Steinmetz et al, 1990;Wiegand et al, 1992) have their own uncertainties due to imperfect relationships between combinations of red and near-infrared (NIR) reflectance, called spectral vegetation indices (SVI), and fAPAR. Some commonly employed SVI include the simple ratio (SR) and normalized difference vegetation index (NDVI):…”

Section: Remote Sensing Of Yieldmentioning

confidence: 99%

Remote sensing of regional crop production in the Yaqui Valley, Mexico: estimates and uncertainties

Lobell

Asner

Ortiz‐Monasterio

et al. 2003

Agriculture, Ecosystems & Environment

276

156

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Quantifying crop production at regional scales is critical for a wide range of applications, including management and carbon cycle modeling. Remote sensing offers great potential for monitoring regional production, yet the uncertainties associated with large-scale yield estimates are rarely addressed. In this study, we estimated crop area, yield, and planting dates for 2 years of Landsat imagery in an intensive agricultural region in northwest Mexico. Knowledge of crop phenology was combined with multi-temporal imagery to estimate crop rotations throughout the region. Remotely sensed estimates of the fraction of absorbed photosynthetically active radiation (fAPAR) were then incorporated into a simple model based on crop light-use efficiency to predict yield and planting dates for wheat. Uncertainty analysis revealed that regional yield predictions varied up to 20% with the method used to determine fAPAR from satellite, but were relatively insensitive to modeled variability in crop phenology, light-use efficiency, and harvest index (the ratio of grain mass to aboveground biomass). Comparisons of satellite-based and field-based estimates indicated errors in regional wheat yields of less than 4% for both years of data. In contrast, planting date calculations exhibited uncertainties of up to 50% using a sparse, three-date sampling from satellite-based sensors. A simplified model was also developed to explore yield predictions using only one date of imagery, demonstrating high accuracies depending on the date of image acquisition. The spatial and temporal distributions of crop production derived here offer valuable information for agricultural management and biogeochemical modeling efforts, provided that their uncertainties are well understood.

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“…After flowering, it has been shown in the case of wheat crops that the spike water content is correlated to the total biomass and so to the final yield [17]. On the other hand, studies have shown that the efficiency of light conversion (ε c ), which is a key variable for estimating dry matter production from solar radiation [14,15], is influenced by the plant hydric status [2,19].…”

Section: Introductionmentioning

confidence: 99%

Estimation of the vertical profile of the wheat crop water content with an electrostatic multipole. An experimental study

Helbert¹,

Boissard

Buis³

2001

Agronomie

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-A new instrument, an electrostatic multipole, has been developed to assess in situ and non-destructive estimations of water content of horizontal layers of crops by dielectric measurements. A winter wheat crop was measured by using the multipole during the last month before harvesting. Results show that it is possible to detect the plant development stages, typically the end of the water plateau revealing the grain maturity. The electrostatic multipole was also used to estimate the total water content of the canopy aerial part. The average error on the water content is about 320 g·m -2 . Simultaneous estimations of spike and stem water contents can also be achieved; the root mean square errors (RMSE) are about 120 g·m -2 and 230 g·m -2 respectively. However the accuracy of these estimations decreases as the plant water content becomes spatially heterogeneous. On relatively homogeneous plots the RMSE of the spike and stem water contents are respectively 100 g·m -2 and 195 g·m -2 . These values correspond to a relative error of about 15% which is very close to the accuracy of the gravimetric technique considered as the reference method.water content / dielectric permittivity / non-destructive method / vegetation canopy / biomass Résumé -Estimation in situ du profil vertical du contenu en eau d'une culture de blé à l'aide d'un multipôle électrostatique. Étude expérimentale. Un nouvel instrument de mesure, un multipôle électrostatique, a été développé pour permettre l'estimation in situ et non destructive du contenu en eau des strates horizontales d'un couvert végétal grâce à la mesure de leur permittivité diélec-trique. Une culture de blé d'hiver a été suivie à l'aide de ce multipôle électrostatique pendant un mois jusqu'à la récolte. Les résultats montrent qu'il est possible de détecter les stades de développement des plantes, notamment la fin du palier hydrique révélatrice de la maturité des grains. Le multipôle électrostatique a également été utilisé pour estimer le contenu en eau des plantes. L'erreur moyenne commise sur le contenu en eau est de l'ordre de 320 g·m -2 . Les contenus en eau des épis et des tiges de blé peuvent par ailleurs être estimés simultanément avec une précision d'environ 120 g·m -2 pour les épis et 230 g·m -2 pour les tiges. Cependant, cette précision est limitée en présence de fortes hétérogénéités de contenu en eau. En évitant ces fortes hétérogénéités, les contenus en eau des épis et des tiges peuvent être estimés avec une meilleure précision, respectivement de l'ordre de 100 g·m -2 et de 195 g·m -2 . Ces valeurs correspondent respectivement à des précisions relatives de l'ordre de 15 %, précisions comparables à celle de la méthode pondérale de référence.

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Spectral estimates of the absorbed photosynthetically active radiation and light-use efficiency of a winter wheat crop subjected to nitrogen and water deficiencies†

Cited by 47 publications

References 25 publications

Drought index evaluation for assessing future wheat production in Greece

Drought index evaluation for assessing future wheat production in Greece

Remote sensing of regional crop production in the Yaqui Valley, Mexico: estimates and uncertainties

Estimation of the vertical profile of the wheat crop water content with an electrostatic multipole. An experimental study

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