Soil Properties and Cocoa (theobroma Cacao L.) Nutrient Uptake as Affected by Organic and Inorganic Based Fertilizers in Southwestern Nigeria

Low soil fertility is a major problem for cocoa establishment on the field; however, cocoa (Theobroma cacao L) is characterized by high nutrient demand particularly N, P, K, Ca and Mg during its early growth. In this study, the effects of organic and inorganic fertilizers on soil properties and nutrient uptake of cocoa in Ibadan and Owena soils of Southwestern Nigeria were investigated in 2011. The experiments were 4 x 4 factorial fitted into Randomized Complete Block Design (RCBD) with three replications. The fertilizers were: Goat Dung (GD), Sunshine Organic (OF) and Organo -Mineral Fertilizers (OMF) and NPK 15:15:15 and the rates of application were: 0, 200, 400 and 600 kg/ha. Four hundred and thirty two (432) plantain suckers were planted at 3 x 3 m spacing while 432 cocoa seedlings (F3 Amazon) were also transplanted at 3 x 3 m respectively at each experimental site. Top soil samples were collected randomly from each experimental sites using soil auger. The samples were bulked, air dried and subjected to routine laboratory analysis for physical (sand, silt, clay, bulk density, moisture) and chemical properties (SOM, pH, N, P, K, Mg, Ca, and Na). Two grammes (2g) each of the organic fertilizers used were also analyzed for their nutrients composition. The fertilizers were applied to treatment plots one month after cocoa seedlings were transplanted using ring method. Leaf samples (4tI leaf) which were collected from 4 tagged cocoa seedlings at 12 months after transplanting were analyzed in the laboratory for chemical compositions. The experiments were monitored for 36 months (144 weeks) after planting. Soil samples were collected from treatment plots processed and analyzed using standard procedures. Data collected were subjected to statistical analysis using Analysis of variance (ANOVA) and significant means separated by Tukey’s HSD (P < 0.05) test. Goat dung (GD), Organo-mineral fertilizer (OMF) and organic fertilizers (OF) had pH of 8.17, 7.00 and 7.30 respectively. They contained in similar order 2.86, 0.63 and 3.64 g/kg OC, 4.80, 1.09 and 6.27 OM, 1.26, 0.06 and 2.16% N, 113.24, 138.06 and 7.08 cmol/kg P, 2.60, 2.00, and 13.10 cmol/kg Ca, 0.38, 0.18, and 2.30 cmol/kg Na respectively. Application of 200 kg OMF, 600kg/ha GD and 400 kg/ha GD, 400 kg/ha OF significantly increased soil moisture contents in both Ibadan and Owena experiments. Application of GD, OMF and OF significantly reduced soil bulk density compared with NPK 15:15:15 and the control. In addition, these treatments enhanced soil and leaf chemical properties at 15 MAT at both locations.