Simulation of Onion Response to Soil Moisture Stress at Different Growth Stages on Yield and Water Productivity Using Aquacrop

Abstract

The objective of this study is to select the most effective water-saving techniques and improve the water productivity of irrigated onion. The phenological growth of onion, the crop was subjected to moisture stress during one, two, or three of the growth stages. The highest yield attained was 21.157 tons/ha and the lowest was 7.177 tons/ha. Treatments T3 & T4 were water stressed during second and last growth stages produce yields that weren’t significantly different from the yield achieved under completely irrigated (T1). Compared to the maximum yield, 22.3% to 48.4% lower yields were recorded under treatments subjected to water deficiency during two growth stages. Treatments that were stressed during one growth stage had a 2.6 to 42.7% yield reduction relative to the maximum yield. The highest yield reduction was observed under treatment irrigated during the first growth stage (T8), followed by irrigated during first and second growth stages (T7), first and late stages (T5) and then treatment not irrigated during midseason (T2). This shows that a prolonged deficiency over three growing stages has more yield reduction (T8). Plots stressed during both third and fourth growth stages were producing lower yields indicating the severe effects of water stress during flowering and early bulb filling stages on yield. Water savings achieved under different treatments with no significant differences in yield from full irrigated plots range 11.8% to 21.7% (T4 & T3) respectively.