Analysis of diurnal cycles of interferometric coherence and backscattering coefficient measured on an irrigated wheat field in Morocco

2021 ◽  
Author(s):  
Nadia Ouaadi ◽  
Ludovic Villard ◽  
Jamal Ezzahar ◽  
Pierre-louis Frison ◽  
Saïd Khabba ◽  
...  
Keyword(s):  
Water Movement ◽  
Water Status ◽  
Physiological Activity ◽  
High Sensitivity ◽  
Eddy Correlation ◽  
Backscattering Coefficient ◽  
Time Step ◽  
Area Index ◽  
Wheat Field ◽  
Irrigated Wheat

<p>C-band radar observations have shown a high sensitivity to the water status of vegetation, including forests and crops. Several studies conducted mainly on forests have observed daily changes of the backscattering coefficients between ascending and descending orbits and have suggested that these differences are related to the diurnal cycle of vegetation water content. Likewise, the water movement within annual crops could be associated to change of the phase centre locations leading to a daily cycle of the interferometric coherence as well that has already been observed on tropical forest using C-band in situ acquisitions. In this context, an experimental setup composed of 4C-band antennas targeting an irrigated wheat field was installed at the top of a 20 m tower near Chichaoua (Morocco) from January to June 2020. The collected data includes measurements of the backscattering coefficient at both cross- and parallel polarizations and the interferometric coherence with a 15 mns time step. The field is also equipped with an eddy-correlation station for half hourly measurements of convective fluxes, soil moisture and temperature profiles. Simultaneously, measurement of above-ground biomass, leaf area index, canopy height and surface roughness are also carried out every 15-daysduring the agricultural season.  The preliminary results of the experiment reveal the existence of strong correlation between the daily evolution of interferometric coherence and the physiological activity of wheat at dawn while the changes observed in the afternoon are ratherrelated to the wind peaks. For the backscattering coefficient, a good agreement is observed between the evolution of its daily average and the evolution of evapotranspiration. These open insights for the monitoring of the crops water status using radar dataacquired at sub-daily timescale.</p>

scholarly journals Vegetative nitrogen stress decreases lodging risk and increases yield of irrigated spring wheat in the subtropics

2016 ◽  
Vol 67 (9) ◽  
pp. 907 ◽  
Author(s):  
A. S. Peake ◽  
K. L. Bell ◽  
P. S. Carberry ◽  
N. Poole ◽  
S. R. Raine
Keyword(s):  
Spring Wheat ◽  
Growth Phase ◽  
Vegetative Growth ◽  
Yield Potential ◽  
N Application ◽  
Area Index ◽  
Wheat Production ◽  
Small Plot ◽  
Management Techniques ◽  
Irrigated Wheat

In-crop nitrogen (N) application is used widely in rainfed winter wheat production to reduce lodging risk; however, uncertainty exists as to its ability to reduce lodging risk in subtropical irrigated wheat production without simultaneously reducing yield potential. The objective of this study was therefore to determine whether in-crop N application reduces lodging risk without reducing yield of irrigated spring wheat in a subtropical environment. Irrigated small-plot experiments were conducted to compare the effect of alternative N timing on lodging and yield in two cultivars. Variable N regimes were imposed during the vegetative growth phase, after which additional N was applied to ensure that total season N application was uniform across N-timing treatments. Treatments with low N at sowing had significantly less lodging and were the highest yielding, exhibiting yield increases of up to 0.8 t ha–1 compared to treatments with high N at sowing. Increased leaf area index, biomass and tiller count at the end of the vegetative growth phase were correlated with increased lodging in both cultivars, although the strength of the correlation varied with cultivar and season. We conclude that canopy-management techniques can be used to simultaneously increase yield and decrease lodging in irrigated spring wheat in the subtropics, but require different implementation from techniques used in temperate regions of Australia.

Deployment, calibration, and efficiency of SHUD model in cold and arid watersheds

2021 ◽  
Author(s):  
Lele Shu ◽  
Hao Chen ◽  
Xianhong Meng
Keyword(s):  
Water Movement ◽  
Yellow River ◽  
Hydrologic Model ◽  
Data Availability ◽  
Heihe River ◽  
Time Step ◽  
Subsurface Hydrology ◽  
The Usa ◽  
The One ◽  
Global Datasets

<p>The hydrologic model is ideal for experimenting and understanding the water movement and storage in a watershed from the upper mountain to the river outlet. Nevertheless, the model's performance, suitability, and data availability are the primary challenge for a modeler. This study introduces the Simulator for Hydrologic Unstructured Domains (SHUD), a surface-subsurface integrated hydrological model using the semi-discrete Finite Volume Method. Though the SHUD applies a fine time-step (in minutes) and flexible spatial domain decomposition (m to km) to simulate the fully coupled surface-subsurface hydrology, the model can solve the watershed-scale problem efficiently and dependably. Plenty of applications in the USA proved the SHUD model's performance and suitability in the humid and data-rich watersheds.  </p><p>In this research, we demonstrate the SHUD model deployment in two data-scarce watersheds in the northwest of China with global datasets, validate the simulations against local observational data, and assess the SHUD model's efficiency and suitability.  The one is the Upstream Heihe River (UHR), which is a typical semi-arid mountainous watershed.  The other is Yellow River Source (YRS), the upstream of Yellow River, contributing more than 50% of total discharge. The results, figures, and analysis based on SHUD simulations under global datasets highlight the model's suitability and efficiency in data-limited watersheds, even ungaged ones. The SHUD model is a useful modeling platform for hydrology and water-related coupling studies.</p>

scholarly journals Evaluation of the Effect of Irrigation on Biometric Growth, Physiological Response, and Essential Oil of Mentha spicata (L.)

Water ◽  
2019 ◽  
Vol 11 (11) ◽  
pp. 2264 ◽  
Author(s):  
Marino ◽  
Ahmad ◽  
Ferreira ◽  
Alvino
Keyword(s):  
Water Stress ◽  
Essential Oil ◽  
Water Status ◽  
Stomatal Closure ◽  
Critical Role ◽  
Net Photosynthesis ◽  
Leaf Biomass ◽  
Water Losses ◽  
Mentha Spicata ◽  
Area Index

A field experiment was performed on spearmint (Mentha spicata L.) under different irrigation regimes in a hilly area of Southern Italy. Objectives of the study include evaluating the physiological and biometrical response of mint from plant establishment up to its complete maturation, as well as the yield composition in essential oil at two different dates. Increasing levels of water stress affected later developing leaves and plant’s water status and net photosynthesis (from the beginning of stress (DAT 63), while affecting negatively the biometric response very soon and significantly from 35 DAT. Photosynthesis limitation played a critical role from DAT 53 on, namely later, in the harvest period (DAT 35–70). Under severe water stress, crop restricted water losses by modulating stomatal closure and, at harvest, showing lowered mesophyll conductance. Irrigation treatments did not affect the concentration of organic compounds, while the yield of essential oils was negatively affected by water stress due to reduced crop growth, in terms of total and leaf biomass, leaf area index (LAI) and crop height.

Development and use of a variable-speed lateral boom irrigation system to define water requirements of 11 turfgrass genotypes under field conditions

2007 ◽  
Vol 47 (1) ◽  
pp. 86 ◽  
Author(s):  
D. C. Short ◽  
T. D. Colmer
Keyword(s):  
Water Conservation ◽  
Irrigation System ◽  
Water Status ◽  
Irrigation Scheduling ◽  
Variable Speed ◽  
Leaf Water Status ◽  
Area Index ◽  
Class A ◽  
Irrigation Requirements ◽  
Class A Pan

Improved irrigation scheduling is one strategy by which water management can be improved in turfgrass systems. The development and testing of a variable-speed lateral boom irrigation system for use in field-based irrigation trials is reported. Christiansen’s coefficient of uniformity was greater than 92% and the efficiency of irrigator discharge was greater than 90% for application depths (mm/unit land area) of 0.5–13 mm. The minimum irrigation requirements were determined for 11 turfgrass genotypes from a summer irrigation dose–response field trial that applied daily treatments of 100 (control), 80, 60, 40 and 20% of the previous day’s net evaporation measured using a US Class A pan. Responses of several shoot parameters, including clipping production, green leaf area index, leaf chlorophyll and leaf water status were evaluated to define minimum irrigation requirements for the turfgrasses. Minimum irrigation requirements (as defined by declines of 10% in several shoot responses) for C3 and C4 turfgrasses were 64–94% and 32–78% of US Class A pan, respectively. Variability in irrigation requirements within C3 or C4 types was due mainly to variations in estimates based on the different shoot parameters. The results demonstrate the opportunity for water conservation by using C4 rather than C3 turfgrasses in locations with hot dry summers (and mild winters) typical of a Mediterranean-type climate.

scholarly journals Determining Evapotranspiration by Using Combination Equation Models with Sentinel-2 Data and Comparison with Thermal-Based Energy Balance in a California Irrigated Vineyard

2021 ◽  
Vol 13 (18) ◽  
pp. 3720
Author(s):  
Guido D’Urso ◽  
Salvatore Falanga Bolognesi ◽  
William P. Kustas ◽  
Kyle R. Knipper ◽  
Martha C. Anderson ◽  
...  
Keyword(s):  
Energy Balance ◽  
Meteorological Data ◽  
Water Status ◽  
Pixel Resolution ◽  
Meteorological Forcing ◽  
Area Index ◽  
Surface Parameters ◽  
Landsat 7 ◽  
Shortwave Infrared ◽  
Sentinel 2

A new approach is proposed to derive evapotranspiration (E) and irrigation requirements by implementing the combination equation models of Penman–Monteith and Shuttleworth and Wallace with surface parameters and resistances derived from Sentinel-2 data. Surface parameters are derived from Sentinel-2 and used as an input in these models; namely: the hemispherical shortwave albedo, leaf area index and water status of the soil and canopy ensemble evaluated by using a shortwave infrared-based index. The proposed approach has been validated with data acquired during the GRAPEX (Grape Remote-sensing Atmospheric Profile and Evapotranspiration eXperiment) in California irrigated vineyards. The E products obtained with the combination equation models are evaluated by using eddy covariance flux tower measurements and are additionally compared with surface energy balance models with Landsat-7 and -8 thermal infrared data. The Shuttleworth and Wallace (S-W S-2) model provides an accuracy comparable to thermal-based methods when using local meteorological data, with daily E errors < 1 mm/day, which increased from 1 to 1.5 mm/day using meteorological forcing data from atmospheric models. The advantage of using the S-W S-2 modeling approach for monitoring ET is the high temporal revisit time of the Sentinel-2 satellites and the finer pixel resolution. These results suggest that, by integrating the thermal-based data fusion approach with the S-W S-2 modeling scheme, there is the potential to increase the frequency and reliability of satellite-based daily evapotranspiration products.

Time- and Energy-Resolved Emission Spectroscopy Using a Step-Scan FT Spectrometer Combined with Correlational Analysis Techniques

1997 ◽  
Vol 51 (4) ◽  
pp. 548-551 ◽  
Author(s):  
K. Thonke ◽  
T. Baier ◽  
J. Hamann ◽  
O. Scheerer ◽  
R. Sauer
Keyword(s):  
Emission Intensity ◽  
Continuous Wave ◽  
Signal To Noise Ratio ◽  
High Sensitivity ◽  
Visible Spectral Range ◽  
Binary Sequences ◽  
Pseudorandom Sequence ◽  
Time Step ◽  
Time Resolved ◽  
Time And Energy

The decay of photoluminescence emission signals on the time scale from microseconds to seconds can be measured with superior dynamics and signal-to-noise ratio by a new method which makes use of correlation analysis with pseudorandom binary sequences. Instead of excitation of the sample by one short laser pulse for each decay cycle (which results in low average emission intensity), the sample is pumped with a continuous-wave laser modulated by a pseudorandom sequence with δ-function-like autocorrelation properties. Therefore, on the time average half of the exciting laser power pumps the sample, and the resulting high emission intensity allows recording of photoluminescence decays over as many as four orders of magnitude within measurement times of 10 min. When this technique is combined with a step-scan Fourier transform spectrometer, both time and energy resolution can be obtained simultaneously. For each interferometer step, the sample response to the excitation sequence is recorded, later autocorrelated digitally, and combined to interferograms for each time step, and finally Fourier transformed. With this technique, time-resolved high-sensitivity spectra can be recorded in the NIR, where only detectors with relatively poor detectivity ( D) are available, and in the visible spectral range. Preliminary results obtained from relatively slow emission processes at defects in semiconductors are presented, which show decay constants on microsecond to millisecond scales.

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