This study evaluated of irrigation deficit and NPK fertilization on growth and yield of onion grown in the semi arid area of Libya. A field experiment was conducted using onion grown in northeast Libya at Elbyda (البيضاء) in 2011 and 2012. Four irrigation deficits and four NPK fertilization rates were arranged in a randomized split-plot design. Irrigation treatments were a ratio of crop evapotranspiration (ET) as: 1.0 ET, 0.85 ET, 0.75 ET, and 0.65 ET. Fertilizer treatments were 100, 75, 50, and 0 % of the applied recommended rate of NPK. The results showed that the interaction between different water levels and NPK rates had no significant effects on growth and yield parameters when transit from 100 to 85% ET or when decreasing NPK rates from 100 to 75 %. The growth and yield parameters (fresh bulb weight, bulb diameter, bulb length, and bulb yield) where non significantly decreased (2.2 and 14.6 %), (3.2 and 13.8%), (3.7 and 1.9 %), and (2.1 and 14.6%) in 2011 and (0.12 and 9.6 %), (2.8 and 3.5 %), (0.27 and 2.6 %), and (0.12 and 9.6%) in 2012, respectively when compared to 100 % ET or 75 % NPK rate. An optimal treatment was statistically developed based on crop response in deficit irrigation and NPK fertilization rate to achieve maximum yield of onion.
This study evaluated of irrigation deficit and NPK fertilization on growth and yield of onion grown in the semi arid area of Libya. A field experiment was conducted using onion grown in northeast Libya at Elbyda (البيضاء) in 2011 and 2012. Four irrigation deficits and four NPK fertilization rates were arranged in a randomized split-plot design. Irrigation treatments were a ratio of crop evapotranspiration (ET) as: 1.0 ET, 0.85 ET, 0.75 ET, and 0.65 ET. Fertilizer treatments were 100, 75, 50, and 0 % of the applied recommended rate of NPK. The results showed that the interaction between different water levels and NPK rates had no significant effects on growth and yield parameters when transit from 100 to 85% ET or when decreasing NPK rates from 100 to 75 %. The growth and yield parameters (fresh bulb weight, bulb diameter, bulb length, and bulb yield) where non significantly decreased (2.2 and 14.6 %), (3.2 and 13.8%), (3.7 and 1.9 %), and (2.1 and 14.6%) in 2011 and (0.12 and 9.6 %), (2.8 and 3.5 %), (0.27 and 2.6 %), and (0.12 and 9.6%) in 2012, respectively when compared to 100 % ET or 75 % NPK rate. An optimal treatment was statistically developed based on crop response in deficit irrigation and NPK fertilization rate to achieve maximum yield of onion.