Effect of Compost Combination and Chemical Fertilizers on Yield and Yield Components of Onion (Allium cepa L.)

In order to find suitable ratio of chemical fertilizer and compost, to increase economic yield of onion, a study was carried out at the Malekan Agricultural Farm and Natural Resources Research and Education Station in 2013. The experiment was done in split plot using RCBD with three replications. Fertilizers (A) were asseigned to main plots with six levels (recommended dosage of chemical fertilizers as control (a1), ¾ of the control + 4 ton ha-1 of compost (a2), ½ of the control + 8 ton ha-1 compost (a3), ¼ of the control + 12 ton ha-1 compost (a4) and the compost alone (16 and 20 ton ha-1) (a5 and a6)) and cultivars to subplots with five levels , (B) (Zanjan Qoli Qissa (b1) and Red Azarshahr (b2)). Red Azarshahr was superior to Qoli Qissa in all traits. Fertilizer levels had significant effects on all traits, except number of edible layers, and a1 was highest amount in these traits compared to other fertilizer rates. The interaction of fertilizer × cultivar was not significant in all traits. Combined use of chemical fertilizers and compost had significant positive effect on vegetative traits, bulb diameter, yield per plant and total yield as compared to that of using compost alone. Using ¾ a1 and ½ a1 along with the rate of 4 and 8 t.ha-1 (a2 anda3) of compost had no significant decreasing effect on bulb weight per plant and yield as compared with chemical fertilizer application alone (a1). Thus use of ¾ the control treatment + 4 ton ha-1 of compost (a2) and ½ of the control treatment + 8 ton ha-1 of compost (a3) can be recommended to the region.