EVALUATION OF LOW COST IRRIGATION METHODS FOR ENHANCED ONION PRODUCTIVITY UNDER SEMI ARID CLIMATE OF PAKISTAN
Onion (Allium cepa L. is second most important horticultural crop in the world after tomato (Black et al. 2006) Onion is grown on an area of 44.4 Mha with total production of 85 MT. Annual onion productivity of the world is 19.3 t/ha (FAO, 2013) It is an important vegetable for its flavor (Kopsell and Randle, 1997; Javaid and Rauf, 2015) and medicinal value (Griffiths et al. 2002) Statistical data revealed significant differences in mean onion productivity of developed countries like USA (i.e. 54.5 t/ha) and developing countries like Pakistan (13.1 t/ha) (FAO, 2013).Use of inferior management techniques is major reason of low productivity in developing countries (Masood et al. 2012) The situation is further exacerbated in semiarid regions due to high temperature and erratic rainfall (Hudson, 1987) At present irrigation water availability is becoming a serious issue (Hussain, 2011) More efficient water management practices are needed (Chiplunkar et al. 2012; Irfan et al. 2014) Scientists reported improved crop water productivity by the use of regulated deficit irrigation (English, 1990; Goodwin and Jerie, 1992; Pereira et al. 2002; Fereres and Soriano, 2007) partial root zone drying (Kang et al. 1997, 1998, 2000a, 2002b; Kang and Zhang, 2004; Zegbe et al. 2004) or alternative furrow irrigation (Mitchell et al. 1993; Mitchell and Yang, 1998) Due to shallow root system (Shock et al. 1998) absence of root hairs and lower leaf water potential (Brewster, 2008) onion is considered very sensitive to water stress (Singh and Alderfer, 1966) Onion crop showed significant reduction when subjected to deficit irrigation (Al Jamal et al. 2001; Shock et al. 1998) So, in order to maximize water productivity without losing onion profitability there is a need to improve irrigation methods (Playan and Mateos, 2004) Since, irrigation efficiency of system is affected by the different types of water losses (Walker, 1989) therefore, the efficiency of the system can easily be increased by limiting these losses. In literature, alternate furrow irrigation method was reported more efficient as compare to furrow irrigation method (Khan et al. 1999; Mitchell et al. 1993; Mitchell and Yang, 1998) Another modification of alternate furrow irrigation method is fixed furrow method. El Sharkawy et al. (2006) evaluated alternate furrow irrigation method and reported it suitable for onion cultivation under Gemmeiza, South Sudan. However, the fixed furrow irrigation method had not been tested. Keeping in view constraints in future water availability and the sensitivity of onion to water stress, the Pak. J. Agri. Sci. Vol. 53(4) 947 953; 2016 ISSN (Print) 0552 9034, ISSN (Online) 2076 0906 DOI: 10.21162/PAKJAS/16.5025 http:/www.pakjas.com.pk