Effect of Oil Palm Bunch Refuse Ash in Sustainable Production of Egusi-Melon (Colocynthis citrullus) in an Ultisol

Soil fertility management is a major challenge in high humid tropical regions of Nigeria. Field experiment were conducted at National Cereals Research Institute, Uyo Out-Station in 2011 and 2012 to investigate the response of egusi melon (Colocynthis citrullus) to different rates of OBRA (1,2,3,4, 5 and 6 t/ha) and 200kg/haNPK as recommended rate of inorganic fertilizer for egusi in the study area. The experiment was laid out in a randomized complete block design, replicated three times. Data collected on growth and yield of egusi-melon were subjected to analysis of variance. Significant means were compared using least significant difference at 5% probability level. Application of 6 t/ha OBRA produced significant seed yield of 243.40 and 253.10 kg/ha in 2011 and 2012. Treatment of 200kg/ha NPK produced seed yield of 193.60 and 201.75 kg/ha respectively. The control (no soil amendment) produced the least seed yield of 125.33 and 128.11 kg/ha in 2011 and 2012, respectively. Comparing with recommended rate of NPK (200kg/ha), treatment of 6t/ha OBRA had seed yield of 21 and 20% greater than the recommended rate of NPK. Soil chemical properties at harvest indicated high soil pH (7.80 and 7.90) and organic matter (3.50 and 3.55%) respectively compared with low soil pH (5.00 and 4.90) and organic matter (2.08 and 20.1%) observed in NPK treatment. The study therefore concluded that application of 4t/h OBRA could be cheap alternative means of sustainable production of egusi melon in acid coastal plain soils of Nigeria.