ISHS Acta Horticulturae 278: Symposium on Scheduling of Irrigation for Vegetable Crops under Field Condition
EVALUATION OF EVAPOTRANSPIRATION BY COMBINING PLANT CHARACTERISTICS AND METEOROLOGICAL INFORMATION |
| Authors: | M. Meron, M. Fuchs, I. Levin, R. Halel, R. Feuer |
| Abstract:
Three methods of Evapo-Transpiration measurements were tested at the Field Crops Experimental Farm of the Upper Galilee Regional Council at the Hula Valley of Israel, in 1987:
Radiation, windspeed, air temperature and relative humidity (RH) were measured with an automatic weather station at 2.0 m above ground. A USWB Class "A" evaporation pan was located nearby. Plant data were collected at a cotton field (cv. SJ-2), drip irrigated daily with 3 water amounts at 2 timings, creating 6 different canopy shapes and stress levels. Soil water balance, calculated from weekly neutron probe measurements, was used to estimate actual ET. Diurnal Penman ET was about 96.5 % of Pan ET. When summed over daylight hours only, it comprised 85.6% of Pan ET, similar to the crop coefficient recommended for drip irrigated cotton. Two models were used: LI (light interception) factored Penman ET, and the Fuchs model described 91.5 % of soil water balance ET when summed over full season. There was a considerable variation in matching the monthly data that was measured and modeled. For practical irrigation scheduling purposes, however, both models look equally adequate. A pilot regional irrigation scheduling information service, using LI corrected Penman model, was started in 1988 and was turned permanent this year, after positive evaluation. | |
Download Adobe Acrobat Reader (free software to read PDF files) | |
