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.
Giovanni Piccinni, Thomas Gerik, Evelyn Steglich, Daniel Leskovar, Jonghan Ko, Thomas Marek, and Terry Howell
David R. Bryla, Thomas J. Trout, and James E. Ayars
crops are needed. A dependable method to estimate crop water requirements is a simple procedure whereby water lost by soil evaporation and plant transpiration, referred to collectively as crop evapotranspiration (ET c ), is calculated by multiplying
Esmaeil Fallahi, Bahar Fallahi, and Michael J. Kiester
this treatment, the trees were irrigated once a week at the full rate of evapotranspiration (ETc) for apple starting in 2002. During the period of this study (2008–11), ETc values for fully mature trees were used. Method for ETc calculation is described
Reagan W. Hejl, Benjamin G. Wherley, James C. Thomas, and Richard H. White
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
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