ABSTRACT

An experiment was carried out at the Crop Farm, Eastern University, Chenkalady, Sri Lanka during the period May-July 2013 to investigate the effect of different plant densities and nitrogen on growth and economic yield of onion (cv. Vethalan). Three densities viz. 156, 100 and 83 plants/m2 and three levels of nitrogen namely 120, 150 and180 kg N/ha were used. This experiment was carried out using a 3 x 2 Factorial Randomized Complete Block Design (RCBD) replicated three times. All other agronomic practices were adopted as recommended by the Department of Agriculture. The dry weight of leaves/ha, total plant weight/ha and bulb yield/ha were the highest at the density of 1,560,000 plants/ha (8 x 8 cm) with 150 kg N/ha.

The results suggest that at the plant density of 1,560,000 plants/ha, the application of nitrogen at the rate of 150 kg N/ha could increase the bulb yield by 22%. Further increase in nitrogen level to 180 kg N/ha could decrease the yield by 34%.