Analysis of Geometrical Relationships and Friction Losses in Small-Diameter Lay-Flat Polyethylene Pipes
[EN] The use of lay-flat polyethylene pipes to irrigate horticultural crops has been receiving widespread attention in the last decade, due to the significant improvements in their hydraulic performance, their potentially high application efficiency, and their limited installation costs. However, even if hydraulic design procedures for conventional microirrigation systems are fairly well established, there is still the need to know how different pipe-wall thicknesses of lay-flat pipes can affect the pipe geometry under different operating pressures as well as the related consequences on friction losses. This paper, after comparing two different procedures (caliper and photographic) to asses…
Assessing agro-hydrological models to schedule irrigation for crops of Mediterranean Environment
Analytical Approach Determining the Optimal Length of Paired Drip Laterals in Uniformly Sloped Fields
Microirrigation plants, if properly designed, allow for water use efficiency to be optimized and high values of emission uniformity to be obtained in the field. Disposing paired laterals, for which two distribution pipes extend in opposite directions from a common manifold, can contribute to reducing the initial investment cost that represents a limiting factor for small-scale farmers of developing countries where in the last decade, the diffusion of such irrigation systems has been increasing. The objective of this paper is to propose an analytical approach to evaluate the maximum lengths of paired drip laterals for any uniform ground slope, respecting the criteria to maintain emitter flow…
INDAGINE SPERIMENTALE SULLA DISTRIBUZIONE SPAZIALE DELLA DENSITÀ RADICALE DI PIANTE DI OLIVO (OLEA EUROPEA, L.) IRRIGATE A GOCCIA
Modellazione in continuo dell’umidità del suolo e dell’evapotraspirazione effettiva mediante l’uso di un modello accoppiato energetico/idrologico
Actual evapotranspiration assessment by means of a coupled energy/hydrologic balance model: Validation over an olive grove by means of scintillometry and measurements of soil water contents
Summary A coupled energy/hydrologic model was applied to simulate the exchange of energy and water in the soil–plant-atmosphere system (SPA). The model, which uses a “two-source” approach to estimate the energy fluxes, and the “force-restore” approach to represent the water balance, was validated by means of evapotranspiration measurements collected via scintillometry and soil moisture measurements collected via time domain reflectometry (TDR) in a Sicilian olive grove. The comparison between measured and estimated fluxes values at an hourly scale showed good agreement. Additional comparisons on a daily timescale confirmed the model’s applicability for quantifying crop water requirements. A…
Eddy covariance and sap flow measurement of energy and mass exchange of woody crops in a Mediterranean environment
Evapotranspiration estimation by micrometeorological techniques through the assessment of mass and energy exchanges in the soil-plant-atmosphere continuum (SPAC) is a very active research area, involving both well-known and novel measurement techniques. A crucial aspect in validating experimental results is the integration of independent measurements of mass and energy exchanges in the SPAC. To this aim, the development and validation of an integrated approach in major tree crop species, involving different independent techniques, are presented. Eddy covariance estimates of ET fluxes were compared to up-scaled sap flow measurements in olive, orange and grapevine, three important Mediterrane…
Mass and surface energy balance approaches for monitoring water stress in vineyards
Abstract Tree crops are representing one of most widespread agricultural systems in Mediterranean regions, thus contributing in a substantial way to the economy and productivity of primary sectors of the countries interested. Besides the aspects concerning their economical relevance, tree crops like vineyards, olive and orange orchards are also typical elements of the Mediterranean landscape, and their ecological role has been recently revitalised in consideration of their function as carbon sinks for the Kyoto agreement. The environmental and economical sustainability of these agricultural systems in arid and semi-arid zones has to cope with the availability and management of water resourc…
Assessing HYDRUS-2D model to simulate water content and salt accumulation in a soil irrigated with a subsurface drip system: Application in a semiarid area of central Tunisia
In this paper, the suitability of HYDRUS-2D model to predict the average soil water content in the root zone of potato crop irrigated with subsurface drip irrigation plant, is initially assessed on the basis of a field study. Then, the model is tested to predict the salt distribution around a buried emitter, when two different water qualities (i.e. electrical conductivity of 1.0 dS m-1 and 4.0 dS m-1), are used during the growing season (treatments T1 and T2). Finally, the soil volume in which salts accumulates, as well as the effects on crop yield is recognized for both the considered treatments.The results evidenced that predicted values of average soil water content in the root zone were…
Assessing Field and Laboratory Calibration Protocols for the Diviner 2000 Probe in a Range of Soils with Different Textures
Frequency domain reflectometry (FDR) downhole sensors have been increasingly used for soil moisture field monitoring because they allow measurement, even continuously, along a soil profile. Moreover, they can also be installed with minimal soil disturbance around the access tube. The objectives of the paper were to assess the field and laboratory calibration protocols for a FDR capacitance probe (Diviner 2000) for a range of soils characterized by different particle size distributions and shrink/swell potential and to propose a practical and effective protocol on the basis of undisturbed soil samples, accounting for soil shrinkage/swelling processes characterizing swelling clay soils. The e…
Micrometeorological and sap flow measurement of energy and mass exchanges of woody crops in a Mediterranean environment
Assessing Hydrus-2D to Simulate Soil Water Content (SWC) and Salt Accumulation Under an SDI System: Application to a Potato Crop in a Semi-Arid Area of Central Tunisia
In this paper the suitability of the HYDRUS-2D model to simulate volumetric soil water content in the root zone of a potato crop under subsurface drip irrigation (SDI) is initially assessed on the basis of a field study. Then, considering that the crop is moderately sensitive to soil salinity, the model is tested to predict the salt distribution around a buried emitter, when two different water qualities (i.e. electrical conductivity of 1.0 and 4.0 dS m-1) are used during the growing season (treatments T1 and T2). Finally, the soil volume in which salt accumulates is distinguished by the model for the two treatments, for which the respective yields are not significantly different. The resul…
Monitoraggio e modellazione agro-idrologica in ambiente mediterraneo:Applicazione ed indagini sperimentali.
Uso di modelli agro-idrologici per la gestione dell'irrigazione di colture arboree mediterranee
Modellistica agro-idrologica per la stima dei consumi traspirativi di colture Mediterranee e schematizzazione della funzione di stress idrico
I modelli di simulazione agro-idrologica permettono la schematizzazione dei fenomeni che si manifestano nel sistema suolo-vegetazione-atmosfera (SVA) su un ampio range di scale spaziali e temporali. Ogni singolo comparto del sistema è caratterizzato da comportamenti complessi dovuti, ad esempio, alle strategie adattative della pianta in risposta a condizioni di deficit idrico del suolo. Con riferimento a quest’ultimo aspetto, nella stima degli attingimenti radicali e quindi dei consumi traspirativi effettivi, di cruciale importanza risulta la corretta schematizzazione della funzione di stress idrico, descritta in generale utilizzando coefficienti riduttivi della traspirazione potenziale in …
Misura e Modellazione degli Scambi Idrici nel Sistema Continuo SPA e approfondimenti sulle Funzioni di Stress Idrico: Applicazione alla coltura dell’Olivo
Gli effetti negativi dovuti ai periodi di aridità che caratterizzano i Paesi del bacino del Mediterraneo (Rebetez et al. 2006) determinano nel suolo una ridotta disponibilità di acqua per le piante e quindi l’insorgenza inevitabile di una forma importante di stress abiotico (Nielsen et al., 1996). In particolare, nel bacino del Mediterraneo l'aridità ambientale viene ancor più accentuata da fattori climatici poiché, in corrispondenza del periodo estivo, alle scarse o assenti precipitazioni sono associate elevate temperature che si traducono in un aumento della domanda evapotraspirativa dell’atmosfera. Tali effetti sono più marcati nelle regioni semiaride del bacino del Mediterraneo e più in…
Using scintillometry to assess reference evapotranspiration methods and their impact on the water balance of olive groves
Abstract Reference evapotranspiration (ET 0 ) is widely used for irrigation scheduling, to promote an efficient use of water resources for a sustainable agro-ecosystem productivity, as well as to manage water quality and to face other environmental concerns. As suggested by ASCE-EWRI and FAO, standard Penman–Monteith methods are generally applied for an accurate estimation of ET 0 from hourly to daily scale. In absence of detailed meteorological information several simplified equations, using a limited number of variables, have been proposed as alternative. In this paper, the performance of different reference evapotranspiration methods, at hourly (Penman–Monteith, Pristley–Taylor, Makkink …
Effects of Saline and Deficit Irrigation on Soil-Plant Water Status and Potato Crop Yield under the Semiarid Climate of Tunisia
Water supplies have been decreasing in several semi-arid regions, and it is therefore necessary to adopt irrigation strategies aimed at maximizing water use efficiency. In this paper, the effects of saline and deficit irrigation on water use efficiency and on potato crop response, based on observations of soil and plant water status, were investigated. Experiments were carried out in Central Tunisia, by monitoring potato crop growth during two seasons in four distinct treatments (T1&ndash
USO DELLA TECNICA SCINTILLOMETRICA A SUPPORTO DELLA STIMA DEI CONSUMI EVAPOTRASPIRATIVI DELL’OLIVO
L’uso razionale della risorsa idrica in agricoltura richiede, unitamente all’adozione di tecniche irrigue avanzate che assicurino la migliore efficienza degli interventi irrigui, l’individuazione dei tempi e dell’entità dei singoli interventi. Perché questi ultimi obiettivi siano raggiunti è necessario stimare con precisione i consumi di evapotraspirazione delle colture che, nell’ambiente mediterraneo, caratterizzato da un periodo vegetativo tipicamente non in fase con quello piovoso, si manifestano sotto condizioni di stress idrico. Nel presente lavoro è descritta un’applicazione a una piantagione di oliveto della tecnica scintillometrica, che permette una stima indiretta del flusso di cal…
Assessing the performance of thermal inertia and Hydrus models to estimate surface soil water content
The knowledge of soil water content (SWC) dynamics in the upper soil layer is important for several hydrological processes. Due to the difficulty of assessing the spatial and temporal SWC dynamics in the field, some model-based approaches have been proposed during the last decade. The main objective of this work was to assess the performance of two approaches to estimate SWC in the upper soil layer under field conditions: the physically-based thermal inertia and the Hydrus model. Their validity was firstly assessed under controlled laboratory conditions. Thermal inertia was firstly validated in laboratory conditions using the transient line heat source (TLHS) method. Then, it was applied in…
Assessing daily actual evapotranspiration through energy balance: an experiment to evaluate the selfpreservation hypothesis with acquisition time
An operational use of the actual evapotranspiration estimates requires the integration from instantaneous to daily values. This can commonly be achieved under the hypothesis of daytime self-preservation of the evaporative fraction. In this study, it has been evaluated the effect of this assumption on the assessment of daily evapotranspiration from proximity sensing images acquired at hourly intervals over a homogeneous olive groove. Results have been validated by comparison with observations made by a micrometeorological (EC-flux tower) and an eco-physiological (sap flux) sensor. SEBAL model has been applied to thermal and multispectral images acquired during a clear day on August 2009 trou…
Analisi delle relazioni tra indici di stato idrico e firme spettrali in piante adulte di olivo (Olea europea L.)
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 “re…
Improvement of FAO-56 Model to Estimate Transpiration Fluxes of Drought Tolerant Crops under Soil Water Deficit: Application for Olive Groves
[EN] Agro-hydrological models are considered an economic and simple tool for quantifying crop water requirements. In the last two decades, agro-hydrological physically based models have been developed to simulate mass and energy exchange processes in the soil-plant-atmosphere system. Although very reliable, because of the high number of required variables, simplified models have been proposed to quantify crop water consumes. The main aim of this paper is to propose an amendment of the Food and Agricultural Organization (FAO) of the United Nations FAO-56 spreadsheet program to introduce a more realistic shape of the stress function, valid for mature olive orchards (Olea europaea L.). The mod…
Assessment of actual transpiration rate in olive tree field combining sap-flow, leaf area index and scintillometer measurements
TESTING APPROACH TO ESTIMATE HOURLY REFERENCE EVAPOTRANSPIRATION WITH SCINTILLOMETER MEASUREMENTS UNDER MEDITERRANEAN CLIMATE
Discussion on "Modeling Approaches for Determining Appropriate Depth of Subsurface Drip Irrigation Tubing in Alfalfa"
The discussed paper deals with the quite interesting topic of design and management of subsurface drip irrigation (SDI), with the aim to identify the appropriate depth at which to install driplines to avoid wetting the soil surface. The study proposes the results of simulations, obtained with the well-known HYDRUS 2D/3D model version 2.x, and considering three different irrigation management strategies applied on alfalfa crop cultivated in two different soil types in Holtville, California.
Using HYDRUS-2D model to assess the optimal drip lateral depth for eggplant crop in a sandy loam soil of central Tunisia
The main objective of the work is to assess the optimal drip lateral depth for Eggplant crop (Solanum melongena L.) irrigated with a drip system in a sandy loam soil by means of field measurements and simulation models. Initially, the performance of Hydrus-2D was assessed based on the comparison between simulated soil water contents (SWC) and the corresponding measured in two plots, in which laterals with co-extruded emitters were laid on the soil surface (drip irrigation, DI-0) and at 20 cm depth (subsurface drip irrigation, SDI-20), respectively. In order to identify the optimal position of the lateral, the results of different scenarios, obtained by changing the installation depth of the…
Updated single and dual crop coefficients for tree and vine fruit crops
Abstract The present study reviews the research on the FAO56 crop coefficients of fruit trees and vines performed over the past twenty years. The main objective was to update information and extend tabulated single (K c ) and basal (K cb ) standard crop coefficients. The selection and analysis of the literature for this review have been done to consider only studies that adhere to FAO56 method, computing the reference ET with the FAO Penman–Monteith ET o equation and field measuring crop ET with proved accuracy. The crops considered refer to vine fruit crops, berries and hops, temperate climate evergreen fruit trees, temperate climate deciduous fruit trees and, tropical and subtropical fru…
Transpiration and Water Use of an Irrigated Traditional Olive Grove with Sap-Flow Observations and the FAO56 Dual Crop Coefficient Approach
The SIMDualKc model was applied to evaluate the crop water use and the crop coefficient (Kc) of an irrigated olive grove (Olea europaea L.) located in Sicily, Italy, using experimental data collected from two crop seasons. The model applies the FAO56 dual Kc approach to compute the actual crop evapotranspiration (ETc act) and its components, i.e., the actual tree transpiration (Tc act), obtained through the basal crop coefficient (Kcb), and soil evaporation according to an evaporation coefficient (Ke). Model calibration was performed by minimizing the difference between the predicted Tc act and the observed daily tree transpiration measured with sap flow instrumentation (TSF field) acquired…
Irrigation water saving strategies in Citrus orchards: Analysis of the combined effects of timing and severity of soil water deficit
[EN] The knowledge of the crop response to soil water deficit is essential to predict the actual crop water requirements under limited soil water conditions. The mathematical schematization of the crop response under RDI can allow identifying the exact irrigation timing. The threshold of soil water status below which crop transpiration decreases represents a key parameter for the water stress functions. The main objective of this paper was to investigate the effects of several RDI treatments, applied during the three stages of fruit growth, on soil-plant-water relations of drip-irrigated mandarin trees. Experiments were carried out in seven irrigation treatments: a control, irrigated at 125…
Agro-hydrological models to schedule irrigation of Mediterranean tree crops
In this paper a comparison between two agro-hydrological models, used to schedule irrigation of typical Mediterranean tree crops, is assessed. In particular the comparison between the model proposed by FAO, using a black box processes schematization, and the SWAP model based on the numerical analysis of Richards’ equation is initially presented for two irrigation seasons, 2005 and 2006, and two Mediterranean tree crops, i.e. grapevine (Vitis vinifera, L.) and olive oil (Olea europea, L.). The comparison mainly focuses on hydrological balance components and on soil water contents. After investigating and setting the scheduling parameters ordinarily practiced by the framers in the area (i.e o…
On the Use of the Eddy Covariance Latent Heat Flux and Sap Flow Transpiration for the Validation of a Surface Energy Balance Model
Actual evapotranspiration is assessed via surface energy balance at an hourly rate. However, a robust estimation of daily evapotranspiration from hourly values is required. Outcomes of surface energy balance are frequently determined via measures of eddy covariance latent heat flux. Surface energy balance can be applied on images acquired at different times and spatial resolutions. In addition, hourly actual evapotranspiration needs to be integrated at a daily rate for operational uses. Questions arise whether the validation of surface energy balance models can benefit from complementary in situ measures of latent heat flux and sap flow transpiration. Here, validation was driven by image ac…
Estimation of actual evapotranspiration of Mediterranean perennial crops by means of remote-sensing based surface energy balance models
Abstract. Actual evapotranspiration from typical Mediterranean crops has been assessed in a Sicilian study area by using surface energy balance (SEB) and soil-water balance models. Both modelling approaches use remotely sensed data to estimate evapotranspiration fluxes in a spatially distributed way. The first approach exploits visible (VIS), near-infrared (NIR) and thermal (TIR) observations to solve the surface energy balance equation whereas the soil-water balance model uses only VIS-NIR data to detect the spatial variability of crop parameters. Considering that the study area is characterized by typical spatially sparse Mediterranean vegetation, i.e. olive, citrus and vineyards, alterna…
Assessing the agro hydrological SWAP model to simulate soil water balance in typical Mediterranean crops
Estimation of Mediterranean crops evapotranspiration by means of remote-sensing based models
Abstract. Actual evapotranspiration from typical Mediterranean crops has been assessed in a Sicilian study area by using Surface Energy Balance and Agro-Hydrological models. Both modelling approaches require remotely sensed data to estimate evapotranspiration fluxes in a spatially distributed way. The first approach exploits visible (VIS), near-infrared (NIR) and thermal (TIR) observations to solve the surface energy balance equation. To this end two different schemes have been tested: the two-sources TSEB model, where soil and vegetation components of the surface energy balance are treated separately, and the widely used one-source SEBAL model, where soil and vegetation are considered as a…
Using Hydrus 2-D to assess the emitters optimal position for Eggplants under surface and subsurface drip irrigation
The main objective of the work is to assess the emitters optimal position for Eggplant crop (Solanum melongena L.) in a sandy loam soil irrigated with surface or subsurface drip irrigation systems, by means of field measurements and simulations carried out with Hydrus-2D model. Initially, the performance of the model is evaluated on the basis of the comparison between simulated soil water contents (SWC) and the corresponding measured in two plots, in which laterals with coextruded emitters are laid on the soil surface (T0) and at 20 cm depth (T20), respectively. In order to choose the best position of the lateral, the results of different simulation runs, carried out by changing the install…
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, T p, 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…
Modelling eco-physiological response of table olive trees (Olea europaea L.) to soil water deficit conditions
Abstract The knowledge of crop response to water stress is crucial to predict transpiration reductions under limited soil water conditions and for a rational scheduling of irrigation. In order to assess whatever water stress model, it is necessary to estimate critical thresholds of soil water status, below which plant transpiration starts to decrease. The main objective of the work is to identify the shape and to determine the parameters of table olive orchards (Olea europaea, var. Nocellara del Belice) water stress function, assessed according to relative transpiration or leaf/stem water potential. In order to assess different water stress functions describing the eco-physiological field r…
Adapting FAO-56 Spreadsheet Program to estimate olive orchard transpiration fluxes under soil water stress condition
Assessing AQUACROP water stress function to evaluate the transpiration reductions of olive tree.
Quantitative evaluation of the drought adaptation processes of crops is an important prerequisite for efficient irrigation management. Modeling the plant response under water stress conditions is crucial to identify the exact irrigation timing. Assessment of any water stress function requires the knowledge of its shape and then the estimation of critical thresholds of the soil water status, below which a strong reduction of plant transpiration occurs. In this work, the macroscopic approach is used to assess the water stress function implemented in AQUACROP for mature olive tree. In particular, after discussing about the function shape, the critical thresholds of soil water status are propos…
Assessing Hydrus-2D model to investigate the effects of different on-farm irrigation strategies on potato crop under subsurface drip irrigation
The objective of this paper was to assess the performance of Hydrus-2D model to simulate the effects of different on-farm irrigation strategies applied on potato crop. The ability of the model to simulate the stress coefficient (Ks), obtained as the ratio between actual and maximum transpiration, and to define the productive function of potato crop under the semi-arid conditions of central Tunisia were also evaluated. Experiments were carried out on potato crop under full (FI) and deficit irrigation (DI) and two different water qualities supplied by means of a subsurface drip irrigation system. Results evidenced that the model, despite some discrepancies locally observed, can fairly accurat…
Comparison of SWAP and FAO Agro-Hydrological Models to Schedule Irrigation of Wine Grapes
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 irrigatio…
Gestione dell’irrigazione del vigneto attraverso l’uso di modelli di simulazione e misure di campo.
In the paper the applicability of a numerical model, i.e. SWAP (Soil Water Atmosphere Plant), and a functional model, i.e. FAO 56, for irrigation scheduling is assessed. Model validation was initially carried out through the comparison between simulated and measured water content of a soil profile. The two models were then used in order to verify the possibility to simulate the typical irrigation management of the study area. In particular, the attitude of the two models to simulate the number and the distribution of watering, as well as the seasonal water consumption found in the ordinary management irrigation was assessed. Different scenarios of irrigation management allowed the analysis …
Sviluppi recenti e nuove tecnologie per la stima dei fabbisogni irrigui in ambiente mediterraneo
DINAMICA DEI FLUSSI EVAPOTRASPIRATIVI IN SISTEMI ARBOREI ETEROGENEI
Assessing the performance of different model-based techniques to estimate water content in the upper soil layer
he knowledge of soil water content (SWC) of the upper soil layer is important for most hydrological processes occurring over vegetated areas and under dry climate. Because direct field measurements of SWC are difficult, the use of different type of sensors and model-based approaches have been proposed and extensively used during the last decade. The main objective of this work is to assess the performance of two models estimating SWC of the upper soil layer: the transient line heat source method and the physically based Hydrus-1D model. The models' performance is assessed using field measurements acquired through a Time Domain Reflectometer (TDR). The experiment was carried out on an olive …
Valutazione della performance di impianti per la microirrigazione mediante misure di efficienza ed uniformità della distribuzione
Predicting soil and plant water status dynamic in olive orchards under different irrigation systems with Hydrus-2D: Model performance and scenario analysis
The paper analyzes the performance of Hydrus-2D model to simulate the dynamic of soil water contents and transpiration fluxes in an olive orchard in which two different irrigation systems were used in 2011 and 2012. The relationship between measured midday stem water potential, MSWP, and simulated relative transpiration (ratio between simulated actual and maximum crop transpiration), Ks, was also identified with the aim to use the model for crop water status predictions. Finally, a scenario analysis was carried out for irrigation management purposes, by considering the level of crop water stress achieved in the different phases of the vegetative growth. The results evidenced that active roo…
ASSESSING FAO-56 MODEL TO ESTIMATE TABLE OLIVE WATER CONSUME UNDER SOIL WATER DEFICIT CONDITIONS
Agro-hydrological models can be considered an economic and simple tool to quantify crop water requirements. In the last two decades, agro-hydrological physically based models have been developed to simulate mass and energy exchange processes in the soil-plant-atmosphere system. Although very reliable, due to the high number of required variables, simplified models have been proposed as simple tools to quantify crop water consumes. The main aim of the paper is to assess, for a Sicilian orchard of table olive, the suitability of FAO-56 agro-hydrological model to estimate the crop transpiration under soil water deficit conditions. The model validation is carried out by means of measurements of…
Closure to “Laboratory and Field Calibration of the Diviner 2000 Probe in Two Types of Soil” by J. Haberland, R. Gálvez, C. Kremer, and C. Carter
The authors deal with the quite interesting and actual problem of Diviner 2000 capacitance probe calibration and present some field and laboratory data obtained on two different layers (0–0.26 and 0.26–0.50 cm) of the same soil profile, characterized by different textural class. The importance of site-specific calibration of sensors used to monitor soil or plant water status assumes a particular relevance in semiarid environments where the application of precision irrigation represents an appropriate management strategy aimed to achieve high values of water use efficiency (Cammalleri et al. 2013). Moreover, in clay soils, physical properties are strongly influenced by soil water content (Pr…
Discussion of “Laboratory and field calibration of the Diviner 2000 probe in two types of soil” by J. Haberland, PhD, R. Galvez, C. Kremer, PhD, and C. Carter.
The authors deal with the quite interesting and actual problem of Diviner 2000 capacitance probe calibration and present some field and laboratory data obtained on two different layers (0-0.26 cm and 0.26-0.50 cm) of the same soil profile, characterized by different textural class. The importance of site-specific calibration of sensors used to monitor soil or plant water status assumes a particular relevance in semi-arid environments where the application of precision irrigation represents an appropriate management strategy aimed to achieve high values of water use efficiency (Cammalleri et al., 2013). Moreover in clay soils, physical properties are strongly influenced by soil water content…
Application of EMI and FDR Sensors to Assess the Fraction of Transpirable Soil Water over an Olive Grove
Accurate soil water status measurements across spatial and temporal scales are still a challenging task, specifically at intermediate spatial (0.1–10 ha) and temporal (minutes to days) scales. Consequently, a gap in knowledge limits our understanding of the reliability of the spatial measurements and its practical applicability in agricultural water management. This paper compares the cumulative EM38 (Geonics Ltd., Mississauga, ON, Canada) response collected by placing the sensor above ground with the corresponding soil water content obtained by integrating the values measured with an FDR (frequency domain reflectometry) sensor. In two field areas, characterized by different soil clay conte…
Assessment of a calibration procedure to estimate soil water content with Sentek Diviner 2000 capacitance probe
A New Calibration Equation for Diviner2000 Capacitance Probe Accounting for Soil Shrinkage Characteristic Curve and Estimation of Parameters on the Basis of Soil Physical Properties
Real-time measurements of soil water status are quite often used for irrigation scheduling and particularly in precision irrigation, in order to identify the exact timing and amount to supply to crops according to their water requirements. Diviner2000 capacitance probes, measuring the apparent soil dielectric permittivity, have been extensively used in the last decade. Several studies have shown that, for different soils, there is a relationship between the volumetric soil water content (SWC) and the scaled frequency (SF) measured by the sensor. However, for swelling/shrinking clay soils, for which bulk density changes with soil water content, there is a lack of knowledge on how these varia…
Combined use of eddy covariance and sap flow techniques for partition of ET fluxes and water stress assessment in an irrigated olive orchard
Correct estimation of crop actual transpiration plays a key-role in precision irrigation scheduling, since crop growth and yield are associated to the water passing through the crop. Objective of the work was to assess how the combined use of micro-meteorological techniques (eddy covariance, EC) and physiological measurements (sap flow, SF) allows a better comprehension of the processes involving in the Soil–Plant–Atmosphere continuum. To this aim, an experimental dataset of actual evapotranspiration, plant transpiration, and soil water content measurements was collected in an olive orchard during the midseason phenological period of 2009 and 2010. It was demonstrated that the joint use of …
Using field measurements and FAO-56 model to assess the eco-physiological response of citrus orchards under regulated deficit irrigation
[EN] Micro-irrigation is considered one of the most efficient water distribution systems and allows increasing water use efficiency if coupled with effective water-saving irrigation management strategies as regulated deficit irrigation (RDI) or partial root-zone drying (PRD) techniques. However, application of these strategies makes it crucial the real-time monitoring of soil and crop water status, in order to identify appropriate irrigation scheduling parameters (irrigation timing and doses) and to prevent irreversible damage of plant system and/or crop yield reductions. Even if midday stem water potential (MSWP) is considered one of the most affordable indicator for direct determinations …
Optimizing subsurface dripline installation depth with Hydrus 2D/3D to improve irrigation water use efficiency in the central Tunisia
The main objective of the work is to optimize drip installation depth for Eggplant crop irrigated with surface or subsurface drip irrigation systems to improve irrigation Water Use Effeciency (WUE), by means of field measurements and simulations carried out with Hydrus-2D model. Initially, a comparison between simulated Soil Water Contents (SWC) and the corresponding measured in two plots, in which laterals with coextruded emitters are laid on the soil surface (T0) and at 20 cm depth (T20), respectively. In order to choose the best position of the lateral, the results of different simulation run, carried out by choosing a deeper installation (T45) depth. Simulated SWC’s resulted fairly clos…
Detecting crop water status in mature olive orchards using vegetation spectral measurements.
Full spectral measurements (350–2500 nm) 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 in…