EVALUATION OF LATENT EVAPORATION ESTIMATES AND THEIR CONVERSION TO POTENTIAL EVAPORATION

1971 ◽  
Vol 51 (4) ◽  
pp. 255-266 ◽  
Author(s):  
W. BAIER
Keyword(s):  
Water Use ◽  
Irrigation Scheduling ◽  
Type Model ◽  
Climatic Data ◽  
Crop Water ◽  
Crop Water Use ◽  
Air Temperatures ◽  
Crop Development ◽  
Irrigated Crops ◽  
Consumptive Water

Daily and monthly latent evaporation (LE) estimates obtained from an earlier-described regression-type model are compared with estimates from Penman’s (PE) and Thornthwaite’s (PET) techniques. Penman’s PE was selected as a control. Daily PE estimates were more closely related to LE than to PET estimates, as seen from the coefficients of determination (100 CD) of 52 and 21%, respectively. Similarly, variations of monthly PE means were more closely associated with variations of monthly LE means (65%) than with PET means (45%). Both the LE and PET models use the same standard climatic data as input. The improvement of 31% for the daily values and 20% for the monthly means results from using maximum and minimum air temperatures separately in the LE model, instead of mean air temperature as in the PET technique. The least bias in PE as derived from converted LE estimates was obtained by a factor of 0.0094 cm/cm3 (0.0037 in./cm3). However, a review of literature on ratios of consumptive water use by irrigated crops to LE measurements suggested a factor in the order of 0.0086 cm/cm3 (0.0034 in./cm3). This factor has been successfully employed in irrigation scheduling and water budgeting experiments. The discrepancy could result from the consumptive crop water use for part of the growing season being less than Penman’s PE as computed in this study. Although eventually seasonally adjusted conversion factors based on crop development phases are preferred, the findings warrant the use of the LE model in various climates for estimating either PE, by applying 0.0094 cm/cm3 (0.0037 in./cm3), or seasonal consumptive crop water use, by applying 0.0086 cm/cm3 (0.0034 in./cm3).

scholarly journals Evaluation of Evapotranspiration from Eddy Covariance Using Large Weighing Lysimeters

Agronomy ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 99 ◽  
Author(s):  
Jerry Moorhead ◽  
Gary Marek ◽  
Prasanna Gowda ◽  
Xiaomao Lin ◽  
Paul Colaizzi ◽  
...  
Keyword(s):  
Energy Balance ◽  
Eddy Covariance ◽  
Water Use ◽  
Growing Season ◽  
Irrigation Scheduling ◽  
Error Rates ◽  
Energy Balance Closure ◽  
Crop Water ◽  
Crop Water Use ◽  
Hourly Data

Evapotranspiration (ET) is an important component in the water budget and used extensively in water resources management such as water planning and irrigation scheduling. In semi-arid regions, irrigation is used to supplement limited and erratic growing season rainfall to meet crop water demand. Although lysimetery is considered the most accurate method for crop water use measurements, high-precision weighing lysimeters are expensive to build and operate. Alternatively, other measurement systems such as eddy covariance (EC) are being used to estimate crop water use. However, due to numerous explicit and implicit assumptions in the EC method, an energy balance closure problem is widely acknowledged. In this study, three EC systems were installed in a field containing a large weighing lysimeter at heights of 2.5, 4.5, and 8.5 m. Sensible heat flux (H) and ET from each EC system were evaluated against the lysimeter. Energy balance closure ranged from 64% to 67% for the three sensor heights. Results showed that all three EC systems underestimated H and consequently overestimated ET; however, the underestimation of H was greater in magnitude than the overestimation of ET. Analysis showed accuracy of ET was greater than energy balance closure with error rates of 20%–30% for half-hourly values. Further analysis of error rates throughout the growing season showed that energy balance closure and ET accuracy were greatest early in the season and larger error was found after plants reached their maximum height. Therefore, large errors associated with increased biomass may indicate unaccounted-for energy stored in the plant canopy as one source of error. Summing the half-hourly data to a daily time-step drastically reduced error in ET to 10%–15%, indicating that EC has potential for use in agricultural water management.

scholarly journals Crop Water Use and Irrigation Scheduling Guide for North Florida

EDIS ◽  
2020 ◽  
Vol 2020 (6) ◽  
Author(s):  
Vivek Sharma ◽  
Charles Barrett ◽  
De Broughton ◽  
Thomas Obreza
Keyword(s):  
Water Use ◽  
Irrigation Schedule ◽  
Irrigation Scheduling ◽  
Growth Stages ◽  
Crop Water ◽  
Leaching Potential ◽  
Crop Water Use ◽  
Crop Water Demand ◽  
Crop Growth Stages ◽  
The Right

Effective irrigation scheduling enables the irrigator to apply the right amount of water at the right time to meet the crop water demand. This 19-page guide presents information on average daily and weekly crop water use and crop growth stages for twelve north Florida crops that can be used to help schedule irrigation. This will allow a grower to develop a realistic irrigation schedule that minimizes plant water stress, saves water, and reduces nutrient leaching potential. Written by Vivek Sharma, Charles Barrett, De Broughton, and Thomas Obreza, and published by the UF/IFAS Department of Soil and Water Sciences, revised December 2020.

scholarly journals EFFECT OF IRRIGATION REGIMES ON YIELD AND WATER USE EFFICIENCY OF EXTRA-EARLY MAIZE VARIETY IN KANO RIVER IRRIGATION PROJECT

2020 ◽  
Vol 4 (3) ◽  
pp. 292-299
Author(s):  
Mubarak Lawal ◽  
Muyideen Abubakar Oyebode ◽  
Jamilu Suleiman
Keyword(s):  
Water Use Efficiency ◽  
Water Use ◽  
Irrigation Water ◽  
Block Design ◽  
Irrigation Scheduling ◽  
Yield Reduction ◽  
Crop Water ◽  
Crop Water Use ◽  
Irrigation Regimes ◽  
Use Efficiency

A field experiment was conducted to evaluate the effect of irrigation regimes on yield and water use efficiency of maize crop (Zea Mays L.; SAMMAZ 29) under different irrigation scheduling. Randomized Complete Block Design (RCBD) was used and the experiment consisted of three levels of irrigation water application depth of 100%, 75% and 50% replacement of Total Available Water Capacity (TAWC) and three irrigation intervals of 7, 10 and 13 days replicated three times. Irrigation water was applied into each of 0.75 m × 90 m furrow using siphon tube of 7.5 cm diameter and 200 cm length. The results showed that the highest average irrigation water use efficiency was at I10D75% with 0.71 kg/m3 while the least was at I13D50% with 0.41 kg/m3. The highest average crop water use efficiency (CWUE) was at I10D75% with 0.79 kg/m3 while the least was at I13D75% with 0.56 kg/m3. The highest average maize yield was at I7D100% with 3580 kg/ha while the least was at I13D50% with 1200 kg/ha. The study established that irrigation after every 10 days interval with 75% replacement of TAWC using furrow irrigation of 90 m lengths produced the highest crop water use efficiency, thus saving about 48.3% of irrigation water (amounting to 329 mm) with reference to control (I7D100%) which causes a yield reduction of about 19% (amounting to 680 kg/ha). This efficient water usage saved cost and also helps to address the problem of high water table of the study area.

scholarly journals Crop Water Use and Irrigation Scheduling Guide for North Florida

EDIS ◽  
2009 ◽  
Vol 2009 (1) ◽  
Author(s):  
Thomas Obreza
Keyword(s):  
Water Use ◽  
Irrigation Scheduling ◽  
Crop Water ◽  
Crop Water Use ◽  
Daily Water ◽  
Water Science ◽  
Soil And Water

Revised! SL-278, an 18-page illustrated guide by Thomas Obreza, presents average daily water use for 13 North Florida crops that can be used to help schedule irrigation. Published by the UF Department of Soil and Water Science, December 2008. Revised January 2009. SL 278/SS491: Crop Water Use and Irrigation Scheduling Guide for North Florida (ufl.edu)

scholarly journals Crop Simulation and Crop Evapotranspiration for Irrigation Management of Spinach

HortScience ◽  
2006 ◽  
Vol 41 (4) ◽  
pp. 971B-971
Author(s):  
Giovanni Piccinni ◽  
Thomas Gerik ◽  
Evelyn Steglich ◽  
Daniel Leskovar ◽  
Jonghan Ko ◽  
...  
Keyword(s):  
Water Use ◽  
Irrigation Water ◽  
Crop Production ◽  
Meteorological Data ◽  
Irrigation Management ◽  
Irrigation Scheduling ◽  
South Texas ◽  
Crop Evapotranspiration ◽  
Crop Water ◽  
Crop Water Use

Improving irrigation water management for crop production is becoming increasingly important in South Texas as the water supplies shrink and competition with urban centers in the region grows. Crop simulators and crop evapotranspiration (ET) are appealing methods for estimating crop water use and irrigation requirements because of the low investment in time and dollars required by on-site (in-field) measurement of soil and/or crop water status. We compared the effectiveness of the Crop.m.an/EPIC crop simulator and Crop-ET approaches estimating the crop water use for irrigation scheduling of spinach. In-ground weighing lysimeters were used to measure real-time spinach water use during the growing season. We related the water use of the spinach crop to a well-watered reference grass crop to determine crop coefficients (Kc) to assist in predicting accurate crop needs using available meteorological data. In addition, we ran several simulations of CropMan to evaluate the best management for growing spinach under limited water availability. Results show the possibility of saving about 61 to 74 million m3 of water per year in the 36,500 ha of irrigated farms of the Edwards aquifer region if proper irrigation management techniques are implemented in conjunction with the newly developed decision support systems. We discuss the implications of the use of these technologies for improving the effectiveness of irrigation and for reducing irrigation water requirements in South Texas.

A parametric crop water use model

1981 ◽  
Vol 17 (4) ◽  
pp. 1095-1108 ◽  
Author(s):  
J. E. Burt ◽  
J. T. Hayes ◽  
P. A. O'Rourke ◽  
W. H. Terjung ◽  
P. E. Todhunter
Keyword(s):  
Water Use ◽  
Crop Water ◽  
Crop Water Use

Response of four grain legumes to water stress in south-eastern Queensland. IV. Interaction with sowing arrangement

1983 ◽  
Vol 34 (6) ◽  
pp. 661 ◽  
Author(s):  
RJ Lawn
Keyword(s):  
Water Stress ◽  
Population Density ◽  
Water Use ◽  
Spatial Arrangement ◽  
Crop Growth ◽  
Yield Response ◽  
Crop Water ◽  
Area Index ◽  
Crop Water Use ◽  
South Eastern

The effect of spatial arrangement and population density on growth, dry matter production, yield and water use of black gram (Vigna mungo cv. Regur), green gram (V. radiata cv. Berken), cowpea (V. unguiculata CPI 28215) and soybean (Glycine rnax CP126671), under irrigated, rain-fed fallowed and rain-fed double-cropped culture was evaluated at Dalby in south-eastern Queensland. Equidistant spacings increased initial rates of leaf area index (LAI) development and crop water use compared with 1-m rows at the same population densities. In the irrigated and rain-fed fallowed treatments, where more water was available for crop growth, both seed yields and total crop water use were higher in the equidistant spacings. However, in the double-cropped treatment, where water availability was limited, there was no yield difference between rows and equidistant spacings, primarily because initially faster growth in the latter was offset by more severe water stress later in the season. Higher population density also increased initial crop growth rate and water use, particularly in the equidistant spacings. However, there was no significant yield response to density, presumably because subsequent competition for light/ water offset initial effects on growth. Although absolute yield differences existed between legume cultivars within cultural treatments, there were no significant differential responses to either spatial arrangement or population density among these four cultivars.

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