ISSN: 0041-3216

ISSN: 0041-3216 (Online), 0041-3216 (Print)
Volume 66 Number 2
Research Papers
Response of onion to lime and fertilizer N in a tropical Ultisol
J.E. Asiegbu
Two experiments conducted in 1938 and 1984 are reported in which the responses of onions (Allium cepa L.) to lime and fertilizer N treatments were studied in a tropical Ultisol. Liming in the range of 1.5-3.0 t CaO ha-1 brought the soil pH to 5.5-5.9 (CaCl2) and proved optimum for onion production. Application of 150 kg N ha-1 was sufficient to produce high bulb yields. The premium bulb grades (I and II) were mostly obtained when lime at 1.5 or 3.0 t CaO ha-1 was combined with N at 150 kg N ha-1. Higher rates of lime and N did not result in further grade improvement. Apparent recovery of applied N in the bulb was low when lime was not applied and also when high rates of lime and fertilizer N were applied. N recovery was best when a moderate rate of 100 kg N ha-1 was used.
Keywords: Onion; Allium cepa; Tropical Utisol; Optimum N and lime; Bulb grades; N recovery