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Luca Testi - One of the best experts on this subject based on the ideXlab platform.
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effects of canopy size and water stress over the Crop Coefficient of a tempranillo vineyard in south western spain
Irrigation Science, 2012Co-Authors: J Picontoro, Victoria Gonzalezdugo, David Uriarte, Luis Alberto Mancha, Luca TestiAbstract:This paper describes the assessment of the Crop Coefficient of an irrigated Tempranillo vineyard measured in a weighing lysimeter during 5 years in south-western Spain. During the first year of the study (2006), young vines displayed a different canopy growth compared to the subsequent years. From 2007 to 2010, vines experienced 2 years with no restriction in water supply, and two other years with short periods of Crop water stress. Basal Crop Coefficient (K cb) started from 0.2 at bud-break until 1.0 at full development in every year, being this maximum management-dependent. K cb showed a good correlation with canopy size indices, which allows to interpolate these results to a wide range of commercial vine systems that are usually managed with lower vegetation size. Moreover, a simple linear model of Crop evapotranspiration reduction with relative water content is presented, allowing the estimation of consumptive water use under deficit irrigation conditions.
Shaozhong Kang - One of the best experts on this subject based on the ideXlab platform.
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comparison of dual Crop Coefficient method and shuttleworth wallace model in evapotranspiration partitioning in a vineyard of northwest china
Agricultural Water Management, 2015Co-Authors: Peng Zhao, Ling Tong, Shaozhong KangAbstract:The objective of this study was to evaluate the potential use of dual Crop Coefficient method in FAO-56 (FAO dual-Kc) and Shuttleworth–Wallace (S–W) model in estimating evapotranspiration (ET) and its components (plant transpiration and soil evaporation) of a vineyard in arid region of northwest China. Continuous measurements of ET with eddy covariance, plant transpiration (T) with sap flow system and soil evaporation (E) with micro-lysimeter in 2013 and 2014, were used to validate the performance of two approaches. Results indicate that sap flow system and micro-lysimeter can provide accurate measurements of T and E at hourly and daily scales if compared to eddy covariance, respectively. The FAO dual-Kc method in partitioning ET was acceptable when using the site-specific basal Crop Coefficient obtained from sap flow, with the slope and intercept of linear regression of 0.96 and −0.13mmd−1 (R2=0.81) for ET, 0.92 and −0.07mmd−1 (R2=0.76) for E, 0.93 and 0.16mm d−1 (R2=0.80) for T, respectively. The S–W model can better estimate ET, but overestimated T and underestimated E when using site-specific soil surface resistance, with the slope and intercept of linear regression of 0.98 and 0.28mmd−1 (R2=0.79) for ET, 0.49 and 0.42mmd−1 (R2=0.46) for E, 1.10 and 0.38mmd−1 (R2=0.81) for T, respectively. Both approaches had obvious discrepancies of E after rainfall and irrigation, especially the S–W model, and overestimated T after a snowfall. Sensitivity analysis indicates that estimated ET and its components were sensitive to soil field capacity and wilting point in both approaches, and in the S–W model, predicted T was also sensitive to leaf area index (LAI) and minimum stomatal resistance and predicted E sensitive to soil surface resistance and LAI. Thus two approaches can estimate ET with good accuracy, but the FAO dual-Kc method had higher accuracy in estimating E and T.
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Crop Coefficient and ratio of transpiration to evapotranspiration of winter wheat and maize in a semi humid region
Agricultural Water Management, 2003Co-Authors: Shaozhong Kang, Binjie Gu, Taisheng Du, Jianhua ZhangAbstract:Crop Coefficient (Kc) is an important parameter for irrigation scheduling and water allocation. This study investigated and determined the Crop Coefficients and the ratio of transpiration to evapotranspiration (Tp/ETc) of winter wheat (Triticum aestivum L.) and maize (Zea Mays) based on lysimeter data for 10 years in a semi-arid region of northwest China (34°20'N, 108°24'E). Several relationships, Kc and days after sowing (DAS), Kc and leaf area index (LAI), and Tp/ETc and LAI, were also analyzed. The average seasonal ETc for winter wheat and maize were 443.6 and 424.0 mm, respectively, compared to their reference Crop evapotranspiration (ET0), 483.9 and 407.7 mm, respectively, for their seasons. The seasonal transpiration accounted for 67.0 and 74.0% of their evapotranspiration for winter wheat and maize, respectively. The average, maximum and minimum seasonal Kc were 0.92, 1.33 and 0.42, respectively, for winter wheat, and 1.04, 1.43 and 0.45, respectively, for the maize. The relationship between Kc and DAS was fitted to a fifth-order polynomial equation with significant correlation Coefficients, R2=0.960 and 0.980, respectively, for wheat and maize. The maximum Kc occurred at about 200 and 80 DAS for winter wheat and maize, respectively. Kc and LAI showed a saturation relationship, R2=0.861 and 0.952, respectively, for wheat and maize, and Kc exceeded 1.0 when LAI was larger than 2.5 for both Crops. The Tp/ETc and LAI also showed saturation relationship, R2=0.968 and 0.981, respectively, for wheat and maize. Tp/ETc started from 0 at sowing, and reached to its maximum, near 0.9, at the middle growth stage or when LAI reached to about 3.0 for both Crops. Tp/ETc maintained at its maximum when LAI was larger than 3.0. These results should help the precise planning and efficient management of irrigation for these Crops in this region. Author Keywords: Crop Coefficient; Evapotranspiration; Transpiration; Leaf area index; Wheat (Triticum aestivum); Maize (Zea Mays) Abbreviations: Kc, Crop Coefficients; DAS, days after sowing; ETp, evapotranspiration; LAI, leaf area index; ET0, reference Crop evapotranspiration; Es, soil evaporation; Tp transpiration
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effects of shallow water table on capillary contribution evapotranspiration and Crop Coefficient of maize and winter wheat in a semi arid region
Crop & Pasture Science, 2001Co-Authors: Shaozhong Kang, Fucang Zhang, P H Jerie, Lu ZhangAbstract:A lysimeter experiment was conducted during 19866—96 to study the impacts of groundwater tables on the capillary contribution, evapotranspiration, and Crop Coefficient of maize and winter wheat grown in a semi-arid region in loess loam soils. The depth of groundwater table was set to 0.5, 0.8, 1.0, 1.2, 1.5, 2.0, and 2.50 m, respectively. The results showed that the rate of capillary contribution from groundwater to Crop root-zone was influenced mainly by the depth of the water tables. The daily variation in capillary contribution was not the same as pan evaporation; the peak was delayed when the water table was >0.8 m, and the time of delay increased with the depth of water table. The Crop evapotranspiration was decreased with increasing groundwater table in the early growth period and harvest period. The maximum evapotranspiration occurred at 1.2 m groundwater table in the other periods. Values of Crop Coefficients (K c ) were estimated based on the measured evapotranspiration (ET) and reference Crop ET computed by the modified Penman method. The estimated K c was significantly different from the values computed and used in the region in the absence of groundwater table effects, and it varied markedly with groundwater tables. Relationships between the Crop Coefficient and the depth of groundwater table were developed using mean Crop Coefficients derived from multi-year data. It was found that linear model was better for the period Octobermp;mdash;February in the winter wheat growing season and June in the summer maize growing season. The polynomial model was suitable for the period March;mdahs;June in the winter wheat growing season and from July to October in the summer maize growing season.
Claudio O. Stöckle - One of the best experts on this subject based on the ideXlab platform.
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use of Cropsyst as a tool to predict water use and Crop Coefficient in japanese plum trees
Agricultural Water Management, 2014Co-Authors: Alberto Samperio, Maria Jose Monino, Jordi Marsal, M H Prieto, Claudio O. StöckleAbstract:The development of a method to estimate the seasonal Crop Coefficient (Kc) would be of great benefit to irrigated agriculture. We examined the simulation capacities of CropSyst for determining Crop water use of Japanese plum under varying growing conditions. These conditions involved weather changes occurring during a period of three years (2010–2012), different pruning intensities, and the use of two cultivars having different vigor and maturity time (Prunus salicina Lindl. ‘Angeleno’ and ‘Red Beaut’). Crop evapotranspiration (ETc) was determined using the soil water balance method. Midday stem water potential (Ψstem) was determined using a pressure chamber. Two parameters of the CropSyst Crop model: Crop Coefficient at full canopy (Kc,fc) and maximum plant hydraulic conductance (Cmax) were parameterized in 2010 season to predict Kc, while 2011 and 2012 were used for validation. In 2011 and 2012, ‘Angeleno’ trees were subjected to severe summer pruning so that tree size would be smaller than in 2010. The influence of the high vigor and early harvest of ‘Red Beaut’ was tested in 2011. The results of 2010 parameterization revealed that Kc,fc and Cmax had a distinctive seasonal pattern. This parameterization was adequate to simulate Kc and Ψstem for ‘Angeleno’ in other seasons and smaller trees than in 2010. The parameters adjusted in 2010 were not adequate to simulate the behavior of the more vigorous cultivar of ‘Red Beaut’. In ‘Red Beaut’, the factor that best explained the need to adapt CropSyst parameters was the difference in vigor but not the time of the removal of fruit sinks. To accurately simulate Kc and Ψstem in ‘Red Beaut’ it was required to use slightly higher values of Kc,fc and Cmax during a specific midsummer period.
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Crop Coefficient k c for apple comparison between measurements by a weighing lysimeter and prediction by Cropsyst
Irrigation Science, 2013Co-Authors: Jordi Marsal, Joan Girona, Jaume Casadesus, G Lopez, Claudio O. StöckleAbstract:Accurate prediction of Crop Coefficient (K c) is necessary for proper irrigation management. We explored CropSyst for determining irrigation requirements of apple trees and for accuracy of K c prediction. Values of K c were compared to those obtained, over 2002–2010, from lysimeter-grown trees. Over these years, trees had different ratios of height (H) to width (W). CropSyst predicted irrigation requirements using tree light interception and water uptake sub-model components. Parameters of the model were adjusted using data obtained from the lysimeter in 2010. Tree light interception sub-model was verified by 2007 data. After parameterization, good agreement was found between simulated and measured K c over different seasons. The porosity Coefficient of the canopy was related to changes in tree’s H/W ratio and leaf overlapping. Accordingly, different porosity values could be estimated for each year. When yearly changes in canopy porosity was considered, CropSyst improved K c prediction and generated relevant information for managing irrigation under changing canopy shape for apple trees.
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Revising Crop Coefficient for Washington Sate
2013 Kansas City Missouri July 21 - July 24 2013, 2013Co-Authors: Tina Karimi, Troy Peters, Claudio O. StöckleAbstract:Abstract. Water shortages are expected to increase in the future due to the need to grow Crops to feed a growing population, the increasing production of bio fuel Crops, the desire to protect and restore waterways for fish, the competition for water among different sectors, and water shortages due to climate change effects. Thus, it is important to accurately predict Crop water use to design efficient irrigation systems, to improve irrigation scheduling, and for hydrologic studies and equitable waterâ€right allocations. The Washington State evapotranspiration and consumptive irrigation water requirement guideline created in the 1980s uses now outdated ET methods applied with limited weather data. As part of this work, the water requirement guideline was updated by selecting and adapting Crop Coefficients (Kc) for use with ET calculations based on the ASCE standardized Penman-Monteith approach for Crops that are economically important in WA. Crop Coefficients were selected from AgriMet, FAO56, Wright 1982 and Allen 2006. Daily alfalfa reference ET based on the Kimberly 1982 and the ASCE standardized equations, and the daily grass reference ET based on FAO56 were determined for 211 weather stations across the state. Seasonal Crop Coefficient curves for use with the ASCE standardized reference ET equation based on weather data from east central Washington were developed, since the planting dates information for Crops of interest are available in this region. These curves were expressed as a function of cumulative growing degree days so as to make them applicable to all climatic regions of the state and to account for the yearâ€toâ€year climatic variability. A database of information on water use and Kc was developed for use with GIS spatial mapping software.
Richard G Allen - One of the best experts on this subject based on the ideXlab platform.
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fitting measured evapotranspiration data to the fao56 dual Crop Coefficient method
2015 ASABE IA Irrigation Symposium: Emerging Technologies for Sustainable Irrigation - A Tribute to the Career of Terry Howell Sr. Conference Proceedi, 2015Co-Authors: Richard G Allen, Ayse Kilic, Andrew E Suyker, Jane OkaleboAbstract:Abstract. The FAO-56 publication of the UN Food and Agriculture Organization contains guidelines on constructing and applying a ‘dual Crop Coefficient‘ method to characterize the behavior of evapotranspiration (ET) on a day to day basis. The dual Crop Coefficient (K c ) method substantially improves the ability to fit simulated with measured data, as compared to the ‘single‘ K c method, by partitioning evaporation from soil (Es) from transpiration from vegetation. This permits the separate estimation of Es when there are known wetting events from precipitation and irrigation and assists in explaining behavior of measured data. The application of the dual K c method is relatively straight forward, especially when applied using the straight-line segment method for the basal K c curve, K cb . Illustrations are given on fitting the dual K c method and K cb curve to daily ET data for irrigated and rainfed corn Crops near Mead, Nebraska measured by eddy covariance and sensitivity to various soil and root zone parameters. Assessment of transferring K cb curve parameters to other fields and years indicates that soil and root zone parameters are relatively transferrable with little modification, whereas lengths of the four Crop growth stages do vary from year to year due to differences in cultivar type and possibly differences in weather.
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implementing the dual Crop Coefficient approach in interactive software 1 background and computational strategy
Agricultural Water Management, 2012Co-Authors: Ricardo D Rosa, Paula Paredes, Goncalo C Rodrigues, I Alves, R M Fernando, L S Pereira, Richard G AllenAbstract:Abstract Irrigation planning and scheduling require the availability of modeling tools that are accurate, quick and easy to use. The Crop Coefficient ( K c )-reference evapotranspiration (ET) method is a traditional method for estimating ET, but has become relatively complicated with the introduction of the dual K c procedure. The dual Crop Coefficient approach ( K cb + K e ) gives a better estimation of daily Crop evapotranspiration because it separately considers soil evaporation and Crop transpiration. This approach allows one to plan irrigation schedules properly, especially in the case of Crops that do not completely cover the soil, where evaporation from the soil surface may be substantial. The SIMDualKc software application was developed with the purpose of simplifying implementation of the computation of the Crop Coefficient and Crop evapotranspiration using the dual Crop Coefficient approach over a range of cultural practices and to provide ET information for use in irrigation scheduling and hydrologic water balances. The model performs a soil water balance at the field level using a daily time step. It estimates Crop transpiration and soil evaporation as well as soil water dynamics to support irrigation scheduling for full and incomplete cover Crops. This paper is the first part of a two-part series, where the second part describes model testing and application for various Crops, locations and irrigation management issues.
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implementing the dual Crop Coefficient approach in interactive software 2 model testing
Agricultural Water Management, 2012Co-Authors: Ricardo D Rosa, Paula Paredes, Goncalo C Rodrigues, I Alves, R M Fernando, L S Pereira, Richard G AllenAbstract:Abstract This paper is the second of a two-part series, with the first part describing the SIMDualKc model, an irrigation scheduling simulation tool that employs the dual Crop Coefficient approach for calculating daily Crop ET and then performs a water balance for a Cropped soil. The model was applied, calibrated and validated for rainfed and basin irrigated maize (Coruche, Portugal), rainfed and surface irrigated wheat (Aleppo, Syria), and furrow irrigated cotton (Fergana, Central Asia). Results show good agreement between available soil water content observed in the field and that predicted by the model. Results indicate that the calibrated model does not tend to over- or underestimate available soil water over the course of a season, and that the model, prior to calibration, and using standard values for many parameters, also performed relatively well. After calibration, the average growing season maximum estimation errors were 10 mm for maize, 8 mm for winter wheat and 9 mm for cotton, i.e., respectively 3.6, 2.9 and 5.0% of total available water. Results indicate that the separation between evaporation and transpiration and the water balance calculation procedures are accurate enough for use in operational water management. The indicators used for assessing model performance show the model to accurately simulate the water balance of several Crops subjected to a variety of irrigation management practices and various climate conditions. In addition, the model was applied to alternative irrigation management scenarios and related results are discussed aiming at assessing the model's ability to support the development of alternative active water management strategies.
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estimating evaporation from bare soil and the Crop Coefficient for the initial period using common soils information
Journal of Irrigation and Drainage Engineering-asce, 2005Co-Authors: Richard G Allen, Dirk Raes, Martin Smith, William O Pruitt, L S PereiraAbstract:The Crop Coefficient during the initial period sKc inid varies with wetting frequency, evaporative demand, and water-holding capacity of the upper soil layer. It is possible to develop a semitheoretical integrated function to predict the average Kc ini representing the initial period of a growing season when the soil is mostly bare and that incorporates these three factors. The function is based on a two-stage evaporation function as used in the Food and Agriculture Organization Irrigation and Drainage Paper No. 56 (FAO-56) dual Crop Coefficient method. Parameters in the integrated equation are soil based and can be calculated a priori without field measurements. The procedure can be used to produce graphical figures similar to that introduced in FAO-24 for Kc ini. Similar to FAO-24, the function utilizes the mean time between wetting events and reference evapotranspiration. In this paper, the development of the procedure and figures for Kc ini are described. Comparisons with measured evaporation and Kc ini in southern California indicate relatively good perfor- mance by the function without calibration.
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FAO-56 Dual Crop Coefficient Method for Estimating Evaporation from Soil and Application Extensions
Journal of Irrigation and Drainage Engineering, 2005Co-Authors: Richard G Allen, Dirk Raes, Luis S. Pereira, Martin Smith, James L. WrightAbstract:Crop Coefficient curves provide simple, reproducible means to estimate Crop evapotranspiration (ET) from weather-based reference ET values. The dual Crop Coefficient sKcd method of the Food and Agricultural Organization of the United States (FAO) Irrigation and Drainage Paper No. 56 (FAO-56) is intended to improve daily simulation of Crop ET by considering separately the contribution of evaporation from soil. The dual method utilizes basal Crop Coefficients representing ET from Crops having a dry soil surface and separately predicts evaporation from bare soil based on a water balance of the soil surface layer. Three extensions to the evaporation calculation procedure are described here that are intended to improve accuracy when applications warrant the extra complexity. The first extension uses parallel water balances representing the portion of the soil surface wetted by irrigation and precipitation together and the portion wetted by precipitation alone. The second extension uses three stages for surface drying and provides for application to deep cracking soils. The third extension predicts the extraction of the transpiration component from the soil surface layer. Sensitivity and analyses and illustrations indicate moderate sensitivity of daily calculated ET to application of the extensions. The dual Kc procedure, although relatively simple computationally and structurally, estimates daily ET as measured by lysimeter relatively well for periods of bare soil and partial and full vegetation cover.
Yi Luo - One of the best experts on this subject based on the ideXlab platform.
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remote sensing of regional Crop transpiration of winter wheat based on modis data and fao 56 Crop Coefficient method
Intelligent Automation and Soft Computing, 2013Co-Authors: Yi Luo, Chunjiang Zhao, Guijun YangAbstract:Crop evapotranspiration is one of the most important parameters of farmland water cycle, which consists of Crop transpiration (T c) and soil evaporation. As the efficient component for Crop production, T c and its accurate determination, especially on a regional scale, is very critical for scientific design of irrigation scheduling and high-efficiency utilization of water resources. In this work, the T c of winter wheat over an irrigation area located in the lower Yellow River of China was estimated by combining MODIS data and FAO-56 Crop Coefficient method. Specifically, the relationships between the single Crop Coefficient (K c), basal Crop Coefficient (K cb) and canopy vegetation indices were investigated and compared based on field data. Then, the actual K cb map of winter wheat over the study area was estimated with MODIS-derived soil adjusted vegetation index (SAVI) using the relationship obtained from above field investigations. Finally, the T c of winter wheat over the area was determined as the p...
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a consolidated evaluation of the fao 56 dual Crop Coefficient approach using the lysimeter data in the north china plain
Agricultural Water Management, 2010Co-Authors: Yujie Liu, Yi LuoAbstract:The main purpose of this paper was to evaluate whether or not the dual Crop Coefficient (DCC) method proposed in FAO-56 was suitable for calculating the actual daily evapotranspiration of the main Crops (winter wheat and summer maize) in the North China Plain (NCP). The results were evaluated with the data measured by the large-scale weighing lysimeter at the Yucheng Comprehensive Experimental Station (YCES) of the Chinese Academy of Sciences (CAS) from 1998 to 2005 using the Nash-Sutcliffe efficiency (NSE), the root mean square error (RMSE) and the root mean square error to observations' standard deviation ratio (RSR). The evaluation results showed that the DCC method performed effective in simulating the quantity of seasonal evapotranspiration for winter wheat but was inaccurate in calculating the peak values. The RMSE value of the winter wheat during the total growing season was less than 0.9mm/d, the NSE and RSR values during the total growing stage were "Very Good", but the results for summer maize were "Unsatisfactory". The recommended basal Crop Coefficient values Kcbtab during the initial, mid-season and end stages for winter wheat and summer maize were modified and the variation scope of basal Crop Coefficient Kcb was analyzed. The Kc (compositive Crop Coefficient, Kc=ETc/ET0, ETc here is the observed values by lysimeter, ET0 is the reference evapotranspiration) values were estimated using observed weighing lysimeter data during the corresponding stages for winter wheat and summer maize were 0.80, 1.15, 1.25, 0.95; 0.90, 0.95, 1.25, 1.00, respectively. These can be a reference for irrigation planning.