Water Saving Irrigation Standard of Tomato in Greenhouse
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The Average daily PET (Potential evapotranspiration), evaluated based on the last 30 years meteorological data and the lysimeter experiment carried out by RDA during 11 years, of 9 regions in Korea for the tomato cultivated in greenhouse, was Keywords:
Lysimeter
DNS root zone
Four modified empirical methods viz. Blaney Criddle method, Radiation method, Modified Penman method and Pan evaporation methods of determining potential evapotranspiration were compared for Ludhiana conditions. The potential evapotranspiration values calculated by these methods were multiplied by crop coefficient to find the actual evapotranspiration and these actual ET values were compared with lysimeter data. The study suggested that Modified Penman method is best for cumulative evapotranspiration (CET) and radiation method is best for calculating the daily/fortnightly evapotranspiration.
Lysimeter
Pan evaporation
Crop coefficient
Penman–Monteith equation
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This report compares evapotranspiration estimated with the Bowen-ratio and eddy-correlation methods with evapotranspiration measured by weighing lysimeters for two sparse-canopy sites in eastern Washington. The sites are located in a grassland area (grass lysimeter site) and a sagbrush- covered area (sage lysimeter site) on the Arid Lands Ecology Reserve in Benton County, Washington. Lysimeter data were collected at the sites from August 1990 to November 1994. Bowen-ratio data were collected for varying periods from May 1993 to November 1994. Additional Bowen-ratio data without interchanging air- temperature and vapor-pressure sensors to remove sensor bias (fixed-sensor system) were collected from October 1993 to June 1994. Eddy-correlation data were collected at the grass lysimeter site from March to April 1994, and at the sage lysimeter site from April to May 1994. The comparisons of evapotranspiration determined by the various methods differed considerably, depending on the periods of record being compared and the sites being analyzed. The year 1993 was very wet, with about 50 percent more precipitation than average; 1994 was a very dry year, with only about half the average precipitation. The study showed that on an annual basis, at least in 1994, Bowen-ratio evapotranspiration closely matched lysimeter evapotranspiration. In 1993, Bowen-ratio and lysimeter evapotranspiration comparisons were variable. Evapotranspiration estimated with the Bowen-ratio method averaged 5 percent more than evapotranspiration measured by lysimeters at the grass lysimeter site from October 1993 to November 1994, and 3 percent less than lysimeters at the sage lysimeter site from November 1993 to October 1994. From March 24 to April 5, 1994, at the grass lysimeter site, the Bowen-ratio method estimated 11 percent less, the Bowen-ratio method utilizing the fixed sensor system about 7 percent more, and the eddy-correlation method about 28 percent less evapotranspiration than the lysimeters measured. From May 7 to June 18, 1993, however, the Bowen-ratio method estimated only 54 percent of the evapotranspiration measured by lysimeters at the grass lysimeter site. This large difference possibly may be attributed to Bowen-ratio instrument variability or error, to the density of grasses in the lysimeters being greater than in the surrounding area, or to heating effects on the lysimeters. From September 1 to October 31, 1993, the Bowen-ratio method estimated more than 450 percent more evapotranspiration than was measured by lysimeters at the sage lysimeter site. This difference may have been due to conditions in the lysimeters at the sage lysimeter site that were unrepresentative of natural conditions. The Bowen-ratio instruments measured evapotrans- piration over sagebrush plants outside the lysimeters, which were blooming very heavily, possibly using supplemental ground water or spring water from nearby upslope areas. The sagebrush plants contained by the lysimeters showed very little evapotranspiration, possibly because they were root-bound and had already used all available water. Also, plants in the lysimeters would not have been able to access any supplemental water available to plants outside the confines of the lysimeters. Earlier in 1993, from June 17 to July 12, the Bowen-ratio method estimated only 1 percent less evapotranspiration than determined for the lysimeters at the sage lysimeter site. On the basis of lysimeter measurements from August 1990 to November 1994, cumulative evapotrans- piration ranged from about 97 to 103 percent of the annual precipitation each year. The evapotranspiration measurements made at the grass and sage lysimeter sites, which were based on weight changes in the lysimeters, showed that storage changes became nearly zero each year some time between August and November as average surface soil moisture decreased to about 2 percent and evapotranspiration rates decreased to less than 0.1 millimeter per day.
Lysimeter
Bowen ratio
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Peak water requirements for crops in southern Idaho were determined from frequency distributions of evapotranspiration rates for 1-day, 3-day, 7-day, 15-day, and 30-day averag ing peri ods. Daily evapotranspiration for a well watered reference crop (alfalfa), measured with a precision weighing lysimeter, and meteorological data were used to verify the calculations of daily evapotranspiration.
Lysimeter
Crop coefficient
Water balance
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The lysimeter is an important instrument for measuring evapotranspiration (ET) of crops. It is widely used in the irrigation and drainage experimental stations in China. However, the areas of lysimeters are often quite different, thus, measured evapotranspiration values are often not the same. According to the experimental date, evapotranspiration measured by a lysimeter with an area of 6m 2 may represent field evapotranspiration. This paper discusses the relationship between evapotranspiration and area of lysimeters and presents a method for converting between them.
Lysimeter
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Hourly evapotranspiration in paddy field was observed directly by lysimeter and eddy covariance method(EC),and was simulated with using Penman-Monteith(PM)equation and Shuttleworth-Wallace(SW)model,respectively.The reliabilities of the two models were verified through comparing the observed and simulated evapotranspiration.The results showed that1 the measured evapotranspiration by EC were obvious lower compared with the lysimeter in each rice growth stage,and the reliability of measured evapotranspiration by lysimerter was higher.2The simulated effect of Shuttleworth-Wallace model was better than Penman-Monteith equation,and the simulated evapotranspiration was closer to the measured evapotranspiration by lysimeter,especially during the periods with sparse canopy.3Soil evaporation had a lower proportion in total evapotranspiration as well as a smaller resistance because of the water in the paddy,and the sensitivity of soil resistance was smaller than that in arid regions.
Lysimeter
Penman–Monteith equation
Potential evaporation
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Efficient planning of water resources requires accurate evaluation of all components in the water budget. Evapotranspiration is an essential component of the water budget and the correct estimation of evapotranspiration is vital for improved water resources management. This study discusses about estimation of evapotranspiration using a simple technology which is economically viable for developing countries. In this study, daily reference evapotranspiration (ETo) was estimated based on the measurements from a non-weighable drainage type lysimeter. ETo estimations by Blaney Criddle, Radiation and Penman methods were compared with ETo estimations by the lysimeter measurements. It is revealed that the lysimeter estimations were overestimating the ETo during the months of February, March and April in year 2008 by 24%, 12% and 11% respectively compared to ETo estimations by the Penman method. Reasons for the above overestimations were discussed and recommendations for reliable ETo estimations by lysimeters were presented in relation to lysimeter design, installation, operation and maintenance.
Lysimeter
Water balance
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The purpose of this research was to evaluate estimating method of standard evapotranspiration and crops evapotranspiration using lysimeter than be compared with estimation result of evaporimeter pan and Penman – Monteith model who recommendated by FAO. Standard evapotranspiration was estimated using reference crops and crops evapotranspiration was estimated using soybean Kaba varieties which planted in lysimeters. Rainfall data and standard evapotranspiration of evaporimeter pan be obtained from Agroclimate stations of Masgar in Pesawaran distric in Lampung, and evapotranspiration Penman – Monteith model was estimated by CROPWAT using climate data during 2007 – 2011 from Agroclimate stations of Masgar. The estimating result of standard evapotranspiration and crops evapotranspiration using lysimeter were higher than evaporimeter pan and model. The estimation results of standard evapotranspiration and crop evapotranspiration of Lysimeter was higher than the estimation evaporimeter pan and model. The average of standard evapotranspiration during nine dasarian is 6.14 mm/day, average of crop evapotranspiration is 7.54 mm/day, while the standard evapotranspiration of evaporimeter pan is 3.55 mm / day, and standard evapotranspiration estimation results with CROPWAT for November to February are 3.27; 3.20; 3.63; 3.51 mm/day. Crop coefficient (Kc) estimation results of each phase was 0.96 in the initial phase, 1.16 in the development phase, 1.67 in the mid season phase, and 1.18 at the end season phase. Crop coefficient (Kc) Soybean lysimeter estimation results are higher than FAO Crop coefficient recommendation. However observed from the growth and yield of soybean plants seen their best with 10.73 gr of 100 seeds of yield. So that suggested for further research with direct ET o measurement method can be applied with modification or regenerated of lysimeter specifications and construction to consider other parameters of water balance in lysimeter. keywords : standard evapotranspiration, crops evapotranspiration, lysimeter, soybean
Lysimeter
Crop coefficient
Growing season
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A new dynamic weighing lysimeter is described. Digital values of evapotranspiration, condensation or wet fog deposition are summed up during 1-2 minutes and are recorded automatically. The evapotranspiration from lichens and heather vegetation measured by means of the lysimeter and that calculated by the Bowen ratio energy balance method are compared. Some errors in evaluation of evapotranspiration by means of both methods are discussed.
Lysimeter
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Ratios of reference evapotranspiration for alfalfa (ET r) and for grass (ET0) are evaluated using
measured ETr and ET,, from lysimeter systems at Kimberly, Idaho and Bushland, Texas. In
addition, ratios are evaluated using estimates by the Kimberly Penman and ASCE Penman-Monteith
evapotranspiration methods. An ET reference conversion equation from FAO-56 is
also compared. The ASCE-PM and Kimberly Penman methods predict differently for both ET,
and ET0 so that ratios of ETr / ET° computed from both methods behave differently Ratios of
ETr / ET0 from lysimeter measurements averaged 1.15 at both locations.
Lysimeter
Penman–Monteith equation
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Citations (33)
Lysimeter
Potential evaporation
Growing season
Pan evaporation
Penman–Monteith equation
Bowen ratio
Water balance
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Citations (77)