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.
Citations
More filters
TL;DR: METRIC uses as its foundation the pioneering SEBAL energy balance process developed in The Netherlands by Bastiaanssen, where the near-surface temperature gradients are an indexed function of radiometric surface temperature, thereby eliminating the need for absolutely accurate surface temperature and theneed for air-temperature measurements.
Abstract: Mapping evapotranspiration at high resolution with internalized calibration (METRIC) is a satellite-based image-processing model for calculating evapotranspiration (ET) as a residual of the surface energy balance. METRIC uses as its foundation the pioneering SEBAL energy balance process developed in The Netherlands by Bastiaanssen, where the near-surface temperature gradients are an indexed function of radiometric surface temperature, thereby eliminating the need for absolutely accurate surface temperature and the need for air-temperature measurements. The surface energy balance is internally calibrated using ground-based reference ET to reduce computational biases inherent to remote sensing-based energy balance and to provide congruency with traditional methods for ET. Slope and aspect functions and temperature lapsing are used in applications in mountainous terrain. METRIC algorithms are designed for relatively routine application by trained engineers and other technical professionals who possess a fami...
1,570 citations
Cites background or methods from "Crop evapotranspiration : guideline..."
...Air density in the aerodynamic equation is calculated using standard equations for mean atmospheric pressure and the universal gas law and simplifying for the effect of vapor pressure virtual temperature is estimated as 1.01 Ts as done by Allen et al. 1998 ...
[...]
...where P = atmospheric pressure kPa; W = water in the atmosphere mm; and hor= solar zenith angle over a horizontal surface from Eq. 8. Kt = unitless turbidity coefficient 0Kt 1.0, where Kt = 1.0 for clean air and Kt = 0.5 for extremely turbid, dusty, or polluted air Allen 1996; Allen et al. 1998 ....
[...]
...The transmittance functions for in,b and out,b by Tasumi et al. 2007 follow a common format similar to the broad-band global transmittance function of Majumdar et al. 1972 that was adapted by FAO and EWRI standardizations for calculating evapotranspiration Allen et al. 1998; ASCE-EWRI 2005...
[...]
...Users need to recognize that what appear to be differences in ETr between weather stations may actually be caused by faulty and biased weather measurements Allen et al. 1998; ASCE-EWRI 2005....
[...]
...In METRIC, a similar approach and assumptions are made for determining dThot for the hot pixel, although a daily surface soil water balance such as that of the FAO56 publication Allen et al. 1998 is run for a bare soil condition to confirm that ET= 0 or to supply a nonzero value for ET if there is residual evaporation Suleiman and Ritchie 2003 from antecedent precipitation or other wetting event....
[...]
TL;DR: Several cases on the successful use of regulated deficit irrigation (RDI) in fruit trees and vines are reviewed, showing that RDI not only increases water productivity, but also farmers' profits.
Abstract: At present and more so in the future, irrigated agriculture will take place under water scarcity. Insufficient water supply for irrigation will be the norm rather than the exception, and irrigation management will shift from emphasizing production per unit area towards maximizing the production per unit of water consumed, the water productivity. To cope with scarce supplies, deficit irrigation, defined as the application of water below full crop-water requirements (evapotranspiration), is an important tool to achieve the goal of reducing irrigation water use. While deficit irrigation is widely practised over millions of hectares for a number of reasons—from inadequate network design to excessive irrigation expansion relative to catchment supplies—it has not received sufficient attention in research. Its use in reducing water consumption for biomass production, and for irrigation of annual and perennial crops is reviewed here. There is potential for improving water productivity in many field crops and there is sufficient information for defining the best deficit irrigation strategy for many situations. One conclusion is that the level of irrigation supply under deficit irrigation should be relatively high in most cases, one that permits achieving 60–100% of full evapotranspiration. Several cases on the successful use of regulated deficit irrigation (RDI) in fruit trees and vines are reviewed, showing that RDI not only increases water productivity, but also farmers’ profits. Research linking the physiological basis of these responses to the design of RDI strategies is likely to have a significant impact in increasing its adoption in water-limited areas.
1,540 citations
Cites methods from "Crop evapotranspiration : guideline..."
...At present, the Penman–Monteith equation (Monteith andUnsworth, 1990; Allen et al., 1998) is the established method for determining the ET of the major herbaceous crops with sufficient precision formanagement purposes....
[...]
...Penman–Monteith equation (Monteith andUnsworth, 1990; Allen et al., 1998) is the established method for determining the ET of the major herbaceous crops with sufficient...
[...]
TL;DR: The water footprint of a country is defined as the volume of water needed for the production of the goods and services consumed by the inhabitants of the country as mentioned in this paper, which shows the extent of water use in relation to consumption of people.
Abstract: The water footprint shows the extent of water use in relation to consumption of people. The water footprint of a country is defined as the volume of water needed for the production of the goods and services consumed by the inhabitants of the country. The internal water footprint is the volume of water used from domestic water resources; the external water footprint is the volume of water used in other countries to produce goods and services imported and consumed by the inhabitants of the country. The study calculates the water footprint for each nation of the world for the period 1997-2001. The USA appears to have an average water footprint of 2480 m 3 /cap/yr, while China has an average footprint of 700 m 3 /cap/yr. The global average water footprint is 1240 m 3 /cap/yr. The four major direct
1,398 citations
Cites methods from "Crop evapotranspiration : guideline..."
...Crop water requirement have been calculated per crop and per country using the methodology developed by FAO (Allen et al., 1998)....
[...]
...External water dependency...
[...]
...Databases on water use traditionally show three columns of water use: water withdrawals in the domestic, agricultural and industrial sector respectively (Gleick, 1993; Shiklomanov, 2000; FAO, 2003)....
[...]
...For the latter two sectors we have used data from AQUASTAT (FAO, 2003)....
[...]
TL;DR: Some of the lessons learned from the long-term investment in Free-Air CO(2) Enrichment experiments are described, where many of these lessons have been most clearly demonstrated in crop systems, and have important implications for natural systems.
Abstract: Plant responses to the projected future levels of CO2 were first characterized in short-term experiments lasting days to weeks. However, longer term acclimation responses to elevated CO2 were subsequently discovered to be very important in determining plant and ecosystem function. Free-Air CO2 Enrichment (FACE) experiments are the culmination of efforts to assess the impact of elevated CO2 on plants over multiple seasons and, in the case of crops, over their entire lifetime. FACE has been used to expose vegetation to elevated concentrations of atmospheric CO2 under completely open-air conditions for nearly two decades. This review describes some of the lessons learned from the long-term investment in these experiments. First, elevated CO2 stimulates photosynthetic carbon gain and net primary production over the long term despite down-regulation of Rubisco activity. Second, elevated CO2 improves nitrogen use efficiency and, third, decreases water use at both the leaf and canopy scale. Fourth, elevated CO2 stimulates dark respiration via a transcriptional reprogramming of metabolism. Fifth, elevated CO2 does not directly stimulate C4 photosynthesis, but can indirectly stimulate carbon gain in times and places of drought. Finally, the stimulation of yield by elevated CO2 in crop species is much smaller than expected. While many of these lessons have been most clearly demonstrated in crop systems, all of the lessons have important implications for natural systems.
1,377 citations
Cites background from "Crop evapotranspiration : guideline..."
...The deep rooting of maize, sorghum, and millet in the field (commonly 1–2 m; Allen et al., 1998; Carcova et al., 2000) provides water from a much larger soil volume than pots used in some enclosure experiments (e.g. 3.5 l in Ziska and Bunce, 1997; Ziska et al., 1999; 5.0 l in Wong, 1979; Maroco et…...
[...]
...The deep rooting of maize, sorghum, and millet in the field (commonly 1–2 m; Allen et al., 1998; Carcova et al., 2000) provides water from a much larger soil volume than pots used in some enclosure experiments (e....
[...]
TL;DR: In this article, the authors present a new global inventory on the extent of areas irrigated with groundwater, surface water or non-conventional sources, and determine the related consumptive water uses.
Abstract: . Irrigation is the most important water use sector accounting for about 70% of the global freshwater withdrawals and 90% of consumptive water uses. While the extent of irrigation and related water uses are reported in statistical databases or estimated by model simulations, information on the source of irrigation water is scarce and very scattered. Here we present a new global inventory on the extent of areas irrigated with groundwater, surface water or non-conventional sources, and we determine the related consumptive water uses. The inventory provides data for 15 038 national and sub-national administrative units. Irrigated area was provided by census-based statistics from international and national organizations. A global model was then applied to simulate consumptive water uses for irrigation by water source. Globally, area equipped for irrigation is currently about 301 million ha of which 38% are equipped for irrigation with groundwater. Total consumptive groundwater use for irrigation is estimated as 545 km3 yr−1, or 43% of the total consumptive irrigation water use of 1277 km3 yr−1. The countries with the largest extent of areas equipped for irrigation with groundwater, in absolute terms, are India (39 million ha), China (19 million ha) and the USA (17 million ha). Groundwater use in irrigation is increasing both in absolute terms and in percentage of total irrigation, leading in places to concentrations of users exploiting groundwater storage at rates above groundwater recharge. Despite the uncertainties associated with statistical data available to track patterns and growth of groundwater use for irrigation, the inventory presented here is a major step towards a more informed assessment of agricultural water use and its consequences for the global water cycle.
1,370 citations
Cites methods from "Crop evapotranspiration : guideline..."
...GCWM was applied using climate data for the period 1998–2002, and the FAO Penman-Monteith method (Allen et al., 1998) was used to compute reference evapotranspiration....
[...]
References
More filters
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