Regulated Deficit Irrigation and Onion (Allium cepa L.) Yield Response on Water Productivity

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Irrigation is the only solution to improve crop production and productivity thereby contributing towards food security, self-sufficiency and export market. The efficient use of water by irrigation system is becoming increasingly important in arid and semi-arid regions with limited water resources. The Experiment was conducted in Debre Zeit Agricultural Research Center with the Regulated Deficit Irrigation and Onion (Allium cepa L.) Yield Response on Water Productivity in Ethiopia during 2017/2018 cropping season. The objective of the experiment was identify the pin point of water stress threshold value of onion under deficit irrigation and investigate the effect of alternate, fixed and conventional furrow irrigation methods on crop yield and water productivity under deficit irrigation. The experimental treatments had three furrow irrigation methods, (alternate furrow irrigation (AFI), fixed furrow irrigation (FFI) and conventional furrow irrigation (CFI)) and two deficit irrigation levels of application, viz., 85 % ETc, and70 % ETc and a control irrigation of 100%ETc. The design of the experimental plot was split plot in RCBD arrangement and replicated three times. The three furrow irrigation methods were arranged as main plots and the deficit levels as sub plots a total of nine (9) treatment combinations. All collected data, were statistically analyzed using SAS 9.1 statistical software. The experimental study result showed that bulb diameter, unmarketable bulb yield and total bulb yield of onion were highly significance difference (p<0.001) both in furrow irrigation methods and irrigation levels. Likewise diameter of onion also gave highest on CFI and 100%ETc irrigation water application level which is 6.69cm and 6.94cm respectively. According to the results obtained, the highest total yield was recorded for the treatment of 100%ETc irrigation water application and AFI of the furrow irrigation method 38947kgha -1 and 35920kgha -1 respectively however, the lowest total bulb yield of 30253kg ha -1 and 29135kg ha -1 were recorded when FFI system was applied and in 70%ETc of water applied. Bulb height of onion was highly significance difference (p<0.001) only on deficit irrigation levels. On the other hand, marketable bulb yield, irrigation water use efficiency and crop water use efficiency were significance difference (P ≤ 0.05) by the interaction of furrow irrigation methods and deficit irrigation levels. The highest average marketable bulb yield of onion was obtained 42219kgha -1 on CFI with the combination of 100%ETc irrigation level in addition to this IWUE and CWUE both are recorded highest result on 70%ETc and AFI furrow irrigation method. Generally, among all irrigation treatments 70%ETc deficit irrigation level applied under AFI method was efficient in conserving significant irrigation water. Therefore, it could be concluded that, AFI can save a substantial amount of water and labor without highly reduction of onion yield and the lowest CWUE and IWUE was gave FFI followed by CFI. Keywords: Alternate furrow irrigation, Conventional furrow irrigation, Deficit irrigation, fixed furrow irrigation, Onion DOI: 10.7176/JRDM/71-02 Publication date: November 30 th 2020