Evapotranspiration from an Olive Orchard using Remote Sensing-Based Dual Crop Coefficient Approach

A remote sensing-based approach to estimate actual evapotranspiration (ET) was tested in an area covered by olive trees and characterized by Mediterranean climate. The methodology is a modified version of the standard FAO-56 dual crop coefficient procedure, in which the crop potential transpiration, Tp, is obtained by directly applying the Penman-Monteith (PM) equation with actual canopy characteristics (i.e., leaf area index, albedo and canopy height) derived from optical remote sensing data. Due to the minimum requirement of in-situ ancillary inputs, the methodology is suitable also for applications on large areas where the use of tabled crop coefficient values become problematic, due to the need of corrections for specific crop parameters, i.e., percentage of ground cover, crop height, phenological cycles, etc. The methodology was applied using seven airborne remote sensing images acquired during spring-autumn 2008. The estimates based on PM approach always outperforms the ones obtained using simple crop coefficient constant values. Additionally, the comparison of simulated daily evapotranspiration and transpiration with the values observed by eddy correlation and sap flow techniques, respectively, shows a substantial agreement during both dry and wet days with an accuracy in the order of 0.5 and 0.3 mm d−1, respectively. The obtained results suggest the capability of the proposed approach to correctly partition evaporation and transpiration components during both the irrigation season and rainy period also under conditions of significant reduction of actual ET from the potential one

Combining the FAO56 agrohydrological model and remote sensing data to assess water demand in a Sicilian irrigation district

Agricultural water use in irrigated areas plays a key role in the Mediterranean regions characterized by semi-arid climate and water shortage. In the face of optimizing irrigation water use, farmers must revise their irrigation practices to increase the drought resilience of agricultural systems and to avoid severe damages in agro-ecosystems. In this direction, during the last decades, the research has been focused on mathematical models to simulate the process of driving mass transport and energy exchanges in the Soil-Plant-Atmosphere system. The objective of the paper was to test the suitability of the combination of FAO56 agrohydrological model with remote sensing data retrieved from the Moderate Resolution Imaging Spectroradiometer (MODIS) platform, to assess the spatiotemporal distributions of crop water requirement and to schedule irrigation in an irrigation district of the south-west of Sicily, Italy. The proposed approach allowed obtaining the spatiotemporal distributions of soil and crop parameters used in the FAO56 model implemented in a GIS environment to simulate the water balance, as well as to assess the actual irrigation strategy. The GIS database was organized to include soil and crop parameters, as well as the irrigation volumes actually delivered to each farmer; the latter data can be used not only as input for water balance to evaluate the efficiency of the actual irrigation strategies but also to identify different irrigation scheduling scenario obtained by the FAO56 procedure. The first application was carried out for the period 2014-2017, to identify a combination of irrigation scheduling parameters to be implemented in the model aimed at reproducing the ordinary strategy adopted by the farmers, based on the spatiotemporal variability of soil and climate forcings. When the model outputs were aggregated for single crop types, a fairly good agreement was found between simulated and actual seasonal irrigation volumes delivered either at the level of district and secondary units. Alternative scenarios of irrigation water distribution were then identified and analyzed, to provide irrigation technicians and policymakers a decision support tool to improve the efficiency of irrigation systems and to optimize the distribution based on the availability of water resources

Comparison of SWAP and FAO Agro-Hydrological Models to Schedule Irrigation of Wine Grape

This paper compares two agro-hydrological models that are used to schedule irrigation of a typical Mediterranean crop. In particular, a comparison between the Food and Agriculture Organization (FAO) model, which uses a black box approach, and the soil-water-atmosphere-plant (SWAP) model, which is based on the numerical analysis of Richards' equation, are shown for wine grape. The comparison was carried out for the 2005 and 2006 irrigation seasons and focused on hydrological balance components and on soil water contents. Next, the ordinary scheduling parameters were identified so that the performance of the two models, which aimed to evaluate the seasonal water requirements and the irrigation times, could be assessed. In the validation phase, both of the models satisfactorily simulated the soil water content, and comparable values of cumulative evapotranspiration were obtained. With the goal of recognizing the crop water stress condition in the field, the original algorithm of the FAO model was modified. This research provided evidence of how the two agrohydrological models, although characterized by different approaches in modeling the phenomena, showed a similar behaviour when used for scheduling irrigation under soil water deficit conditions. © 2012 American Society of Civil Engineers

Detecting crop water status in mature olive groves using vegetation spectral measurements

Full spectral measurements (350-2500nm) at tree canopy and leaf levels and the corresponding leaf water potentials (LWP) were acquired in an olive grove of Sicily, at different hours of the day, during summer season 2011. The main objective of the work was to assess, on the basis of the experimental data-set, two different approaches to detect crop water status in terms of LWP. Specifically, using existing families of Vegetation Indices (VIs) and applying Partial Least Squares Regression (PLSR) were optimised and tested. The results indicated that a satisfactory estimation of LWP at tree canopy and leaf levels can be obtained using vegetation indices based on the near infrared-shortwave infrared (NIR-SWIR) domain requiring, however, a specific optimisation of the corresponding "centre-bands". At tree canopy level, a good prediction of LWP was obtained by using optimised indices working in the visible domain, like the Normalized Difference Greenness Vegetation Index (NDGI, RMSE=0.37 and R2=0.57), the Green Index (GI, RMSE=0.53 and R2=0.39) and the Moisture Spectral Index (MSI, RMSE=0.41 and R2=0.48). On the other hand, a satisfactory estimation of LWP at leaf level was obtained using indices combining SWIR and NIR wavelengths. The best prediction was specifically found by optimising the MSI (RMSE of 0.72 and R2=0.45) and the Normalized Difference Water Index (NDWI, RMSE=0.75 and R2=0.45). Even using the PLSR technique, a remarkable prediction of LWP at both tree canopy and leaf levels was obtained. However, this technique requires the availability of full spectra with high resolution, which can only be obtained with handheld spectroradiometers or hyper-spectral remote sensors

Evaluating the performance of reference evapotranspiration equations with scintillometer measurements under Mediterranean climate and effects on olive grove actual evapotranspiration estimated with FAO-56 water balance model

The concept of reference potranspiration is widely used to support water resource management in agriculture and for irrigation scheduling, especially under arid and semi-arid conditions. The Penman-Monteith standardized formulations, as suggested by ASCE and FAO-56 papers, are generally applied for accurate estimations of ETo, at hourly and daily scale. When detailed meteorological information are not available, several alternative and simplified equations, using a limited number of variables, have been proposed (Blaney-Criddle, HargreavesSamani, Turc, Makkinen and Pristley-Taylor). In this paper, scintillometer measurements collected for six month in 2005, on an experimental plot under “reference” conditions, were used to validate different ETo equations at hourly and daily scale. Experimental plot is located in a typical agricultural Mediterranean environment (Sicily, Italy), where olive groves is the dominant crop. As proved by other researches, the comparison confirmed the best agreement between estimated and measured fluxes corresponds to FAO-56 Penman-Monteith standardized equation, that was characterized by both the lowest average error and the minimum bias. However, the analysis also evidenced a quite good performance of Pristley-Taylor equation, that can be considered as a valid alternative to the more sophisticated PenmanMonteith method. The different ETo series, obtained by the considered simplified equations, were then used as input in the FAO-56 water balance model, in order to evaluate, for olive groves, the errors on estimated actual evapotranspiration ET. To this aim soil and crop model input parameters were settled by considering previous experimental researches already used to calibrate and validate the FAO-56 water balance model on olive groves, for the same study area. Also in this case, assuming as the true values of ET those obtained using the water balance coupled with Penman- Monteith ETo input values, the Priestley-Taylor equation, requiring a limited number of input meteorological data, was characterized by the best performance if compared to the other equations used to evaluate ETo. Under environments conditions similar to those considered therefore, according to the good performance associated to the Priestley-Tailor approach, FAO-56 model can allow realistic estimation of ET, even in absence of a full meteorological dataset

Drag Bingo - Lucy Diamonds and Ladda Nurv

Photograph of first Drag Bingo event at Bryant University held in the Stephen Bello Grand Hall. The event was sponsored by the Krupp Library, IDEI, the Pride Center, Bryant Pride, Queer @ Bryant, and Student Affairs. Drag hosts and performers were Ladda Nurv and Lucy Diamonds

Drag Bingo - First Image of Crowd

Photograph of first Drag Bingo event at Bryant University held in the Stephen Bello Grand Hall. The event was sponsored by the Krupp Library, IDEI, the Pride Center, Bryant Pride, Queer @ Bryant, and Student Affairs. Drag hosts and performers were Ladda Nurv and Lucy Diamonds

Drag Bingo - Third Image of Crowd

Photograph of first Drag Bingo event at Bryant University held in the Stephen Bello Grand Hall. The event was sponsored by the Krupp Library, IDEI, the Pride Center, Bryant Pride, Queer @ Bryant, and Student Affairs. Drag hosts and performers were Ladda Nurv and Lucy Diamonds

Drag Bingo - Fifth Image of Crowd

Photograph of first Drag Bingo event at Bryant University held in the Stephen Bello Grand Hall. The event was sponsored by the Krupp Library, IDEI, the Pride Center, Bryant Pride, Queer @ Bryant, and Student Affairs. Drag hosts and performers were Ladda Nurv and Lucy Diamonds

Drag Bingo - Sixth Image of Crowd

Photograph of first Drag Bingo event at Bryant University held in the Stephen Bello Grand Hall. The event was sponsored by the Krupp Library, IDEI, the Pride Center, Bryant Pride, Queer @ Bryant, and Student Affairs. Drag hosts and performers were Ladda Nurv and Lucy Diamonds