Nutrient status and fertilizer responses of oil palms on different soils in the forest zone of Ghana
1970
Van Der Vossen, H.A.M., Oil Palm Research Centre, Crops Research Institute, P.O. Box 43, Kade, Ghana
Climatic requirements and topography restrict economic oil palm production in Ghana mainly to the Forest Oxysols and Forest Ochrosol-Oxysol Intergrades developed over granites, LowerBirrimian rocks (phyllites) and a relatively inextensive area (520 km2) in the extreme south-western part of the country of Oxysols over Tertiary sands. 8-12 years' yield records of seven 25 and 24 factorial fertilizer trials (planted in 1954-57), together with foliar analysis data taken from these trials and other experimental fields, have shown P and K deficiencies in oil palms on soils of all three geological formations. Consistent and highly significant yield responses of 30-35% to phosphate fertilizer applications were found in an experiment on soils over Tertiary sands (Aiyinasi) and in one trial on soils over granites (Assin-Foso), while both experiments also showed a significant K effect in some years. A PK interaction by which responses to potash fertilizers became highly significant (20% yield increase) in presence of added P was found in another trial on soils over granites (Pretsea). Incidental N effects, KMg and other interactions in various trials are discussed. The sharp yield decline after the 5th-6th year of production in the experiments at Aiyinasi (Tertiary sands), in contrast to more stable yield levels at Bunso (11-15 t/ha) and other stations, indicates that under conditions of light soils, and excessively high rainfall special precautions have to be taken to preserve a satisfactory fertility status of these soils. Tentative recommendations on type, rate and frequency, time and method of fertilizer application are given.
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