Journal
AGRICULTURAL WATER MANAGEMENT
Volume 45, Issue 1, Pages 41-54Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/S0378-3774(99)00071-2
Keywords
rice; sunflower; crop ET; crop coefficients; lysimeter; reference ET
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Lysimeter experiments were conducted on rice during rainy season (July-October) and sunflower during summer seasons (March-June) in a set of two electronic weighing type lysimeters of 2 m x 2 m x 2 m size to measure the hourly evapotranspiration of these crops from 1994 to 1995 at Karnal, India. The average weekly ET of rice varied from <3 mm per day in the early growing period to >6.6 mm per day at milking stage. The peak ETc was 6.61 mm per day and it occurred 11 weeks after transplanting at reproductive stage when LAI was 3.4. In case of sunflower, ETc was <1.0 mm per day at the initial stage, achieved a peak value of 14.1 mm per day between 8 and 9 weeks after sowing (WAS) and it declined to 3 mm per day during maturity phase. Precise information on crop coefficients, which is required for regional scale irrigation planning is lacking in Asian countries. Crop coefficients (K-c) for rice and sunflower from ETc measurements and weather data have been developed. The estimated values of crop coefficient for rice at the four crop growth stages (initial, crop development, reproductive and maturity) were 1.15, 1.23, 1.14 and 1.02 and corresponding K-c values for sunflower were 0.52, 1.1, 1.32 and 0.41. The estimated K-c values of sunflower is 11.6-74.2% higher than the values suggested by FAO. Relationship between standard FAO-Penman-Monteith with other reference evapotranspiration methods has also been established (C) 2000 Elsevier Science B.V. All rights reserved.
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