|Evett, Steven - Steve|
Submitted to: Agricultural Water Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/9/2007
Publication Date: 5/24/2007
Citation: Ibragimov, N., Evett, S.R., Esanbekov, Y., Kamilov, B.S., Mirzaev, L., Lamers, J. 2007. Water use efficiency of irrigated cotton in Uzbekistan under drip and furrow irrigation. Agricultural Water Management. 90(1-2):112-120. Interpretive Summary: The amount of crop produced per unit of water used is called the water use efficiency (WUE). In water-short regions of the world, including the U.S. Great Plains and the central Asian Republic of Uzbekistan, increasing WUE in irrigated agriculture is critical. Research on irrigation methods, deficit irrigation, and crops is key to improving WUE and reducing irrigation water use. We grew cotton under conventional furrow irrigation and drip irrigation for three years and at two irrigation rates near Tashkent, Uzbekistan. Under drip irrigation, seed-cotton yield was increased 7 to 13% relative to that for furrow irrigated cotton; and 18 to 42% of the irrigation water was saved using drip irrigation rather than furrow. Irrigation water use efficiency increased by 34 to 104% under drip irrigation compared with that of furrow irrigation. The more deficit irrigation rate provided both larger yields and larger water use efficiencies. These results, and the similarity between WUE increases in Uzbekistan and the High Plains of Texas under deficit irrigation, lend credibility to results obtained in both countries. Important outcomes in both countries are that both WUE and yield can be improved by moderate deficit irrigation and conversion to drip irrigation.
Technical Abstract: Cotton water use and water use efficiency as related to irrigation method and irrigation scheduling parameters are inadequately understood in the central Asian Republic of Uzbekistan. The main goal of this research was to measure cotton water use, and to determine irrigation water scheduling parameters associated with optimal seed-lint yield and irrigation water use efficiency. A cotton (Gossypium hirsutum L.) field experiment with drip irrigation in comparison to furrow (conventional) irrigation was carried out on a deep silt loam soil (Calcic Xerosol) at the Central Experiment Station of the Uzbekistan National Cotton Growing Research Institute at Tashkent in 2003, 2004 and 2005. As a starting point for investigations of irrigation scheduling, the field capacity (FC) index was adopted, which was 0.30 m**3 m**-3 in this soil. Irrigations were scheduled when soil water in the root zone was depleted by the crop to specific fractions of FC, e.g., irrigation at 70% of FC, for each of three main plant growth periods (germination - squaring; squaring - flowering; beginning of maturation - maturation). Water content and use were determined by the soil water balance approach on a weekly basis using a neutron moisture meter (NMM), which was field calibrated. Under drip irrigation and the optimal mode (70-70-60% of FC) of irrigation scheduling, 18 to 42% of the irrigation water was saved in comparison with furrow irrigated cotton grown under the same condition; and irrigation water use efficiency increased by 34 to 104% compared with that of furrow irrigation. Seed-cotton yield was increased 7 to 13% relative to that for furrow irrigated cotton. The irrigation scheduling rule developed here is applicable to irrigated Calcic Xerosols of Uzbekistan.