Written Paper

Water Requirement of Irrigated Garlic  [2008]

Ayars, J.E.

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A replicated field trial was conducted on the west side of the San Joaquin Valley to determine the crop coefficient and water requirements of irrigated garlic. Irrigation systems used included simulated furrow irrigation, subsurface drip irrigation, and surface drip irrigation. Irrigation levels were set at 50%, 75%, 100%, and 125% of crop evapotranspiration (ET(c)) measured with a weighing lysimeter. Field plots consisted of four beds 80 m long and a 1 m wide, with the two inside beds used for experimental purposes and the outside beds as buffers. Irrigation scheduling was controlled by the crop lysimeter using ET(c) threshold values: 1 mm for the subsurface drip irrigation, 2 mm for the surface drip irrigation, and a weekly irrigation equal to the accumulated ET(c) for the simulated furrow irrigation treatment. The crop water use at 100% ET(c) for the interval 1 March to 21 May 2006 was 426 mm, including 108 mm of rainfall. The irrigation schedule was modified to reflect the rainfall contribution during the experimental period. An asymptote was used to relate yield to the applied water and the total water use. Maximum yield occurred at 100% ET(c), and irrigation in excess of 100% ET(c) did not provide any additional yield. Statistically, there was very little difference in the yield parameters and quality parameters when compared across irrigation system types. Statistical differences occurred between the irrigation levels. Peak crop coefficient values w
ere estimated in the range of 1.3 to 1.4. The K(c) was linearly related to the day of the year. This represents the development segment of the crop coefficient curve as described in FAO Irrigation and Drainage Paper 56.

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