Book•
Crop evapotranspiration : guidelines for computing crop water requirements
01 Jan 1998-Iss: 1
TL;DR: In this paper, an updated procedure for calculating reference and crop evapotranspiration from meteorological data and crop coefficients is presented, based on the FAO Penman-Monteith method.
Abstract: (First edition: 1998, this reprint: 2004). This publication presents an updated procedure for calculating reference and crop evapotranspiration from meteorological data and crop coefficients. The procedure, first presented in FAO Irrigation and Drainage Paper No. 24, Crop water requirements, in 1977, allows estimation of the amount of water used by a crop, taking into account the effect of the climate and the crop characteristics. The publication incorporates advances in research and more accurate procedures for determining crop water use as recommended by a panel of high-level experts organised by FAO in May 1990. The first part of the guidelines includes procedures for determining reference crop evapotranspiration according to the FAO Penman-Monteith method. These are followed by updated procedures for estimating the evapotranspiration of different crops for different growth stages and ecological conditions.
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TL;DR: In this article, a three-year study (2003-2005) was conducted with two large drainage lysimeters (length = 4.87 m, width = 3.65 m, and depth = 1.37 m) to quantify ET c and K c for seepage-irrigated watermelon under plastic mulch in sub-tropical Florida.
Abstract: . The crop coefficient (K c ) method is the most widely used method for computing crop evapotranspiration (ET c ) and relies on selecting a representative K c value for a specific production system, soil, and climate. Literature-based (e.g., FAO-56) K c values, used in the absence of local K c , can lead to erroneous ET c estimates. This error becomes considerably high when the standard K c values from the open-field production systems are applied to plastic mulch production systems with seepage irrigation that results in shallow water table conditions. A three-year study (2003-2005) was conducted with two large drainage lysimeters (length = 4.87 m, width = 3.65 m, and depth = 1.37 m) to quantify ET c and K c for seepage-irrigated watermelon under plastic mulch in sub-tropical Florida. The seasonal ET c varied from 344 to 422 mm, with an average of 373 mm. The K c values for initial, development, mid-season, and late stages were 0.64, 1.00, 1.28, and 1.15, respectively, and were statistically higher than the values reported in the literature, including FAO-56. The initial K c especially was greater than the literature values due to low plant cover and high surface soil moisture in the row-middle areas at the beginning of the season resulting from frequent rainfall and shallow water table. To adjust K c for the effect of variable rainfall wetting on evaporation during the initial stage, a multivariate regression model (r 2 = 0.74) was developed as a function of rainfall and solar radiation. Use of literature-based K c values resulted in underestimation of seepage-irrigated ET c by 26% to 43%; the 26% underestimation was from a comparison using the same lysimeter setup and seasons but with drip (surface) irrigation. Such large differences, not reported earlier, highlight the importance of developing local K c for a specific irrigation method, climate, and production system. Regression models (r 2 = 0.96) were developed for predicting K c as functions of time and growing degree days. With approximately 65,000 ha of vegetables grown under seepage irrigation in Florida, there is a need for developing local K c values for irrigation management and water allocations. Scaling up the errors in water use from literature-based K c values to Florida’s seepage-irrigated vegetable lands for one season per year showed errors of 25 to 42 million m 3 of water. This error accounts for 15% to 25% of annual rainfall and is likely to be much higher for dual cropping systems within a year. The extent of errors and related effects on watershed water balances highlight the need for similar studies for other seepage-irrigated mulched crops.
13 citations
TL;DR: In this paper, the authors developed a simple two-parameter (specific yield, Sy, and pore-size distribution index, λ), one-dimensional unsaturated flow model from simplifications of the Richards equation (using the Brooks-Corey relationships) to determine lag times from agricultural deep drainage associated with the irrigation of alfalfa hay and various row crops in the Antelope Valley of California, USA Model-predicted lag times to depths of 85 m bgs (below ground surface) were similar to that measured in a 2-year ponded
Abstract: Estimates of groundwater volumes available in semiarid regions that rely on water balance calculations require the determination of both surface to groundwater lag times and volumes from irrigation or rainfall initiated recharge Subsurface geologic material hydraulic properties (eg hydraulic conductivities, water retention functions) necessary for unsaturated flow modelling are rarely available as are the instrumented field tests that might determine such lag times Here we develop a simple two-parameter (specific yield, Sy, and pore-size distribution index, λ), one-dimensional unsaturated flow model from simplifications of the Richards equation (using the Brooks-Corey relationships) to determine lag times from agricultural deep drainage associated with the irrigation of alfalfa hay and various row crops in the Antelope Valley of California, USA Model-predicted lag times to depths of 85 m bgs (below ground surface) were similar to that measured in a 2-year ponded recharge field trial, slightly overestimating that measured by approximately 15% (051 vs 044 years) Lag time estimates were most sensitive to estimated deep percolation rates and roughly equally sensitive to the model hydraulic parameters Generally, as subsurface material textures coarsen towards larger Sy and λ values for all Sy >10%, lag times progressively increase; however, at Sy <10%, lag times decrease substantially suggesting that particular combinations of Sy and λ values that may be associated with similarly textured materials can result in the prediction of different lag times for Sy approximately 10% Overall, lag times of 1–3 years to a depth of 69 m bgs were estimated from deep drainage of agricultural irrigation across a variety of irrigation schedules and subsurface materials Copyright © 2012 John Wiley & Sons, Ltd
13 citations
Cites methods from "Crop evapotranspiration : guideline..."
...Here, daily DP, or recharge below the alfalfa root zone (1.5m thick soil profile), was determined from daily SWB calculations presuming full stand establishment and crop coefficients as described in FAO-56 (1998)....
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TL;DR: In this article, the authors examined how much on-farm reservoirs can increase groundwater quantity and improve surface water quality using a spatial-dynamic model of farm profit maximization in the Arkansas Delta.
Abstract: We examine how much on-farm reservoirs can increase groundwater quantity and improve surface water quality using a spatial-dynamic model of farm profit maximization in the Arkansas Delta. Sensitivity analysis of the farm profit objective by including the value of surface water quality and the groundwater buffer value evaluates how accounting for environmental value affects the optimal crop mix, water use, and farm profits. The best policy for a critical water resource area is to have the government cost share construction of on-farm reservoirs because groundwater conservation and surface water quality goals are achieved efficiently for a modest redistribution of income.
13 citations
TL;DR: A Python programming language script was developed for implementing monthly FAO Penman-Monteith evapotranspiration equation in ESRI's ArcMap environment, which has the advantage of being independent of the type of geospatial data and can be applied in point, line and polygon data while at the same time being flexible and time saving without loss of accuracy.
13 citations
TL;DR: In this paper, the authors assess for Minas Gerais the cokriging methodology, in order to characterize the spatial variability of Thornthwaite annual moisture index, annual rainfall, and average annual air temperature, based on geographical coordinates, altitude, latitude, and longitude.
Abstract: The objective of the present study was to assess for Minas Gerais the cokriging methodology, in order to characterize the spatial variability of Thornthwaite annual moisture index, annual rainfall, and average annual air temperature, based on geographical coordinates, altitude, latitude, and longitude The climatic element data referred to 39 INMET climatic stations located in the state of Minas Gerais and in nearby areas and the covariables altitude, latitude, and longitude to the SRTM digital elevation model Spatial dependence of data was observed through spherical cross semivariograms and cross covariance models Box–Cox and log transformation were applied to the positive variables In these situations, kriged predictions were back-transformed and returned to the same scale as the original data Trend was removed using global polynomial interpolation Universal simple cokriging best characterized the climate variables without tendentiousness and with high accuracy and precision when compared to simple cokriging Considering the satisfactory implementation of universal simple cokriging for the monitoring of climatic elements, this methodology presents enormous potential for the characterization of climate change impact in Minas Gerais state
13 citations
Cites background or methods from "Crop evapotranspiration : guideline..."
...This procedure was adopted because the method of Penman–Monteith–FAO ( Allen et al. 1998 ) is considered, internationally, the most accurate for ETo or ETp estimation in several places, when compared with the Thornthwaite method....
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...Penman–Monteith–FAO estimates of ETo or ETp were defined by ( Allen et al. 1998 ):...
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...In conceptual terms, the Penman–Monteith–FAO method was considered as a reference evapotranspiration (ETo) estimator, in accordance to Allen et al. (1998) ....
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...In this method, the best ETo estimates are obtained in the function of their physic–mathematic formulation of the evapotranspiration process and by the greatest number of variables considered, increasing the accuracy of the estimates ( Allen et al. 1998 )....
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...All these parameters were calculated by models presented in full detail by Allen et al. (1998) ....
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References
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TL;DR: It is shown that a satisfactory account can be given of open water evaporation at four widely spaced sites in America and Europe, the results for bare soil receive a reasonable check in India, and application of theresults for turf shows good agreement with estimates of evapolation from catchment areas in the British Isles.
Abstract: Two theoretical approaches to evaporation from saturated surfaces are outlined, the first being on an aerodynamic basis in which evaporation is regarded as due to turbulent transport of vapour by a process of eddy diffusion, and the second being on an energy basis in which evaporation is regarded as one of the ways of degrading incoming radiation. Neither approach is new, but a combination is suggested that eliminates the parameter measured with most difficulty—surface temperature—and provides for the first time an opportunity to make theoretical estimates of evaporation rates from standard meteorological data, estimates that can be retrospective. Experimental work to test these theories shows that the aerodynamic approach is not adequate and an empirical expression, previously obtained in America, is a better description of evaporation from open water. The energy balance is found to be quite successful. Evaporation rates from wet bare soil and from turf with an adequate supply of water are obtained as fractions of that from open water, the fraction for turf showing a seasonal change attributed to the annual cycle of length of daylight. Finally, the experimental results are applied to data published elsewhere and it is shown that a satisfactory account can be given of open water evaporation at four widely spaced sites in America and Europe, the results for bare soil receive a reasonable check in India, and application of the results for turf shows good agreement with estimates of evaporation from catchment areas in the British Isles.
6,711 citations
TL;DR: In this article, the large-scale parameterization of the surface fluxes of sensible and latent heat is properly expressed in terms of energetic considerations over land while formulas of the bulk aerodynamic type are most suitahle over the sea.
Abstract: In an introductory review it is reemphasized that the large-scale parameterization of the surface fluxes of sensible and latent heat is properly expressed in terms of energetic considerations over land while formulas of the bulk aerodynamic type are most suitahle over the sea. A general framework is suggested. Data from a number of saturated land sites and open water sites in the absence of advection suggest a widely applicable formula for the relationship between sensible and latent heat fluxes. For drying land surfaces, we assume that the evaporation rate is given by the same formula for evaporation multiplied by a factor. This factor is found to remain at unity while an amount of water, varying from one site to another, is evaporated. Following this a linear decrease sets in, reducing the evaporation rate to zero after a further 5 cm of evaporation, the same at several sites examined.
5,918 citations
Book•
01 Jan 1976
TL;DR: Water quality for agriculture, water quality in agriculture for agriculture as mentioned in this paper, water quality of agriculture, Water quality of water for agriculture in agriculture, مرکز فناوری اطلاعات و اسلاز رسانی
Abstract: Water quality for agriculture , Water quality for agriculture , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی
3,518 citations
TL;DR: In this paper, the stomatal conductance of illuminated leaves is a function of current levels of temperature, vapour pressure deficit, leaf water potential (really turgor pressure) and ambient CO $_2$ concentration and when plotted against any one of these variables a scatter diagram results.
Abstract: Attempts to correlate values of stomatal conductance and leaf water potential with particular environmental variables in the field are generally of only limited success because they are simultaneously affected by a number of environmental variables. For example, correlations between leaf water potential and either flux of radiant energy or vapour pressure deficit show a diurnal hysteresis which leads to a scatter diagram if many values are plotted. However, a simple model may be adequate to relate leaf water potential to the flow of water through the plant. The stomatal conductance of illuminated leaves is a function of current levels of temperature, vapour pressure deficit, leaf water potential (really turgor pressure) and ambient CO $_2$ concentration. Consequently, when plotted against any one of these variables a scatter diagram results. Physiological knowledge of stomatal functioning is not adequate to provide a mechanistic model linking stomatal conductance to all these variables. None the less, the parameters describing the relationships with the variables can be conveniently estimated from field data by a technique of non-linear least squares, for predictive purposes and to describe variations in response from season to season and plant to plant.
2,897 citations
01 Jan 1986
TL;DR: In this paper, a methodology to quantify yield response to water through aggregate components which form the "handles" to assess crop yields under both adequate and limited water supply is presented, which takes into account maximum and actual crop yields as influenced by water deficits using yield response functions relating relative yield decrease and evapotranspiration deficits.
Abstract: This publication presents a methodology to quantify yield response to water through aggregate components which form the "handles" to assess crop yields under both adequate and limited water supply. The method presented in part A takes into account maximum and actual crop yields as influenced by water deficits using yield response functions relating relative yield decrease and evapotranspiration deficits. Part B gives an account of water-related crop yield and quality information for 26 crops
2,680 citations