evapotranspiration (ET a )] and deficit irrigation (0.3 × ET a ). ET a was determined by weighing and calculating the mean mass change of three fully watered (1.0 × ET a ) lysimeters within each of the three water source treatments. Irrigation was then supplied at
Reagan W. Hejl, Benjamin G. Wherley, James C. Thomas and Richard H. White
Jack D. Fry, Steven C. Wiest and Ward S. Upham
Evapotranspiration from tall fescue, perennial ryegrass and zoysiagrass turfs during the summers of 1992-3 was compared to evapotranspiration estimates from an evaporation pan, a black Bellani plate, and several empirical combination models, Actual measurement of turf water use was made with small weighing lysimeters. Soil was maintained at field capacity. Data were collected on 51 dates between June and September. Tall fescue was clipped weekly at 7.6 cm whereas ryegrass and zoysiagrass were clipped 3 times weekly at 2.5 cm, Although differences between the grass species existed, in general the rankings of estimate precision were Bellani plate > evaporation pan > empirical models when compared with measured evapotranspiration rates.
Tim R. Pannkuk
(ASABE) has recently defined mixed-species landscape water use normalized to reference evapotranspiration as plant factors, rather than crop coefficients ( ASABE, 2012 ; Beeson et al., 2014 ; Sun et al., 2012a ). The new S623 Standard attempts to define
Janet S. Hartin, David W. Fujino, Lorence R. Oki, S. Karrie Reid, Charles A. Ingels and Darren Haver
al., 2017 ). A summary and brief review of these UC-led studies follows. Evapotranspiration adjustment factor (ETAF) study . California implemented water conservation legislation that required reductions in urban and agricultural water usage ( CDWR
Toshio Shibuya, Yoshiaki Kitaya, Toyoki Kozai and Masaichi Nakahara
Net photosynthetic and evapotranspiration rates of tomato (LAI = 2.3) and lettuce (LAI = 6.6) plug sheets were estimated based on measurements of the weight of plug sheets and vertical profiles of CO2 concentration above the plug sheets. The measurements were continued in situ for several days in a greenhouse when plugs were at transplant stage. The maximum net photosynthetic rates of tomato and lettuce plug sheets were 0.8 and 2.0 mg CO2/m2 per sec on a plug sheet area basis, respectively. The maximum evapotranspiration rates of those sheets were 100 mg·m–2·s–1. Net photosynthetic and evapotranspiration rates of tomato and lettuce plug sheets increased linearly with an increase in solar radiation flux, with a correlation coefficient of 0.9.
Julián Miralles-Crespo, María J. Sánchez-Blanco, Alejandra Navarro G., Juan J. Martínez-Sánchez, Jose A. Franco L. and Sebastián Bañón A.
) followed by a fourth one during which the plants died (August). To confirm plant death, it was irrigated for 2 weeks and when it was seen that the leaves remained dry and produced no new shoots, it was considered dead. Evapotranspiration determination. The
Daniel I. Leskovar, Shinsuke Agehara, Kilsun Yoo and Nuria Pascual-Seva
strategies on quercetin content of onion remains largely unknown. Previous investigations have not evaluated the interactive effects of PD and deficit irrigation rates using specific growth-stage crop coefficients as a tool for evapotranspiration
at 70% of ET c . Rainfall in both experiments was comparable. Table 1. Precipitation, evapotranspiration (ET), depth of applied water, and total volume of applied water per tree in ‘Pacific Gala’ apple from 2004 to 2007. Effects of rootstock on leaf
Rolston St. Hilaire, Cathleen F. Feser, Theodore W. Sammis and Anderson S. St. Hilaire
Accurate measurement of evapotranspiration (ET) is difficult and expensive for large, in-ground container (pot-in-pot) plants. We engineered and used a simple and inexpensive system to determine evapotranspiration of in-ground container trees. The system was shop-assembled and used a block and tackle system attached to a collapsible tripod. A unique container harness system attached to the block and tackle system was used to lift containers that were sunken in the ground. Containers were weighed with a battery-operated balance that was accurate to 1 g (0.04 oz) at its maximum load capacity of 60 kg (132.3 lb). One person operated the system, and the weight of the system exclusive of the balance was 17.5 kg (38.50 lb). Gravimetric water use data obtained with the system werecombined with meteorological data to compute crop coefficients (Kc) of mexican elder (Sambucus mexicana). The system detected small changes in daily water use of mexican elder trees grown in 76-L (20-gal) in-ground containers. Crop coefficients ranged from 0.17 to 0.71. The acquisition of evapotranspiration data from relatively large, containerized landscape plants may be facilitated because the system is simple, inexpensive, and accurate.
Fabián Robles-Contreras, Raul Leonel Grijalva-Contreras, Manuel de Jesus Valenzuela-Ruiz and Rubén Macias-Duarte
The main crops in Caborca, Sonora, Mexico, in the Sonoran Desert, are grapes, asparagus, olive, and vegetables, such as melons and green beans. The growers in this area normally do not use methods to calculate water requirements of the crops, although in a desert region water use management needs to be as efficient as possible. A reason for using some of the models is the need to fit water requirements to regional conditions, or some stress could be caused in the crops. Recently, studies have been made in northwestern Mexico that indicate it is feasible to adapt the use of the Makkink model. Three models for estimated potential evapotranspiration (Eto) were evaluated: Penman-Monteith, Hargreaves, and Makkink, and were compared with the Class A pan method (control). Measured variables were the correlation coefficient (R 2) between the models and the control; and the daily average difference between the models and the control. The results indicate that a low R 2 exists between the three evaluated models and the control (0.55, 0.67, and 0.54 for Hargreaves, Penman-Monteith, and Makkink, respectively). The average difference of the daily Eto in the course of 75 days of evaluation was of 0.62, 0.5, and 0.81 mm/day for Hargreaves, Penman-Monteith, and Makkink, respectively. This represents almost 6–10 cm less of potential evapotranspiration with the models, for a cycle crop of 120–130 days.