EQA (Aug 2024)
Characterization of epipedons in soils of varying parent materials under cocoa plantation
Abstract
Epipedons type and thickness affect the properties and productivity of soils. Therefore, the study was carried out at the Obafemi Awolowo University Teaching and Research Farm, Nigeria, to assess the influence of vegetation on epipedon characteristics in soils of varying parent materials with a view to highlighting their salient properties for sustainable utilization of soils in the area. Three mini pits were established within each soil series supporting similar plantation. Morphological description of the soils was undertaken on the field, using the guidelines of FAO. Soil samples were taken from both the top- and sub-surface horizons of the mini pits for analyses, using standard procedures. The epipedons were fairly thick, ranging between 0-20 and 0-30 cm, brightly coloured with good internal drainage, except those of the Jago series, and varied from slightly sticky, slightly-plastic to very sticky, very plastic, suggesting higher clay content at lower depth and the ability of the soils to hold moisture for crop use after cessation of rains. The soils are devoid of gravel within the minipits. The soil’s pH was low and ranged between medium acid and slightly acid while the organic matter within the epipedons was relatively moderate. Total nitrogen content varied from medium to high within the soils of Oba and Egbeda series while it varied from low to medium in Iwo and Jago series, available P in the epipedons ranged from low to medium. Exchangeable Ca was lower than the critical value established for soils in southern Nigeria while exchangeable Mg and K values were adequate. Litter production was highest (7.50 t/ha) in Egbeda soil series and least (3.57 t/ha) in Jago series. Soils of Iwo and Oba series had 4.57 t/ha and 5.50 t/ha of litter production, respectively. Tissue phosphorus of litters in Egbeda soils series was high, while that of Iwo and Oba series formed from coarse-grained granite, and hill wash medium to fine material, respectively, was low. Soils of Iwo, Oba and Jago series need supplemental application of nitrogen, phosphorus and calcium fertilizers for optimal cacao production due to their lower values than the minimum required.
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