Density Affects Plant Development and Yield of Bulb Onion (Allium cepa L.) in Northern Ghana

ABSTRACT The current spatial arrangement and density of onion plants adopted by producers in Northern Ghana was found to limit onion production. A study was carried out at two onion-growing locations in Northern Ghana, during the 1996–97 and 1997–98 onion growing seasons, to evaluate the response of onion cv. Bawku Red to eight spacings, i.e., 0.18 × 0.15, 0.15 × 0.15, 0.18 × 0.10, 0.15 × 0.13, 0.15 × 0.10, 0.13 × 0.10, 0.10 × 0.10, and 0.8 × 0.8 m, which gave the following plant densities: 37.04; 44.44; 51.28; 55.56; 66.67; 76.92; 100 and 156.25 plants/m2, respectively. The experimental variables measured were plant height, number of leaves, number of marketable bulbs, number of culls, neck diameter, mean bulb weight, bulbing index and bulb yield. Plant population density significantly (P < 0.05) affected bulb yields and yield components of onion. Bulb neck diameter, mean bulb weight and plant height decreased as population density increased. Total bulb yield increased significantly (P < 0.05) as population density increased. Number of marketable bulbs increased significantly (P < 0.05) with higher planting density. Onion bulb yield in the study ranged between 20.9 and 33.1 t·ha−1. It was concluded that sowing onion at densities above 76.92 plants/m2 increased marketable onion bulb yields.