Abstract:
Onion is second most important crop after tomato in the world. Due to shallow root system, absence of root hairs and reduced leaf water potential, onion is considered a drought sensitive crop. Pakistan is ranked 8th in onion production. Water availability in Pakistan is continuously declining due to population explosion and limited water storability facilities in the country. Increasing water productivity seems to be the best possible option which should be adopted for better future. Keeping in view above aspects, a study was conducted to improve water use efficiency of onion. Three different experiments were executed in the field under RCBD factorial arrangements. In the first experiment, three irrigation methods (furrow irrigation, alternate furrow irrigation and fixed furrow irrigation) were tested with or without mulching. In the second experiment, onion crop was subjected to 50% water stress at different growth stages, vegetative, bulbing and bulb maturation (individually as well as in all possible combinations),to find out critical crop growth stage. A third experiment was conducted to determine the optimum irrigation interval and quantity needed for quality onion bulb production. All three experiments were conducted during 2012 and 2013. Results indicated that alternate furrow irrigation method with mulching gave similar results as normal furrow irrigation without mulching. Among growth stages, water stress at vegetative and bulbing stage was found most destructive. Water stress at these growth stages significantly reduced plant height, leaf diameter, number of leaves, leaf area, leaf area index, bulb diameter, bulb weight, number of bulbs per plant, and total and marketable yield per hectare. However, significant increase in percent dry matter contents, bolting, acidity and soluble solid contents was observed under water stress. Mulching significantly improved the water use efficiency of the plant and benefit cost ratio. Results showed that under drip irrigation system, application of 3mm and 6mm water at 2 day irrigation interval is suitable for onion crop under mulched and non-mulched conditions respectively.
