Effect of media type and compost mixtures on nutrient uptake and growth of cocoa (Theobroma cacao L.) seedling in the nursery

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Abstract

This experiment investigated the effect of four media types, viz: Sawdust (SD), Cocopeat (CP), Rice husk biochar (RH) and Topsoil (TS) and four rates of compost; viz: 0g (Comp0), 200g (Comp1), 400g (Comp2) and 600g (Comp3) polybag^-1 on nutrient uptake and growth of cocoa seedlings. The treatments were arranged in a completely randomized design with four replicates. Foliar and residual nutrients were analyzed as well as growth and biomass production at 42 weeks after sowing. Results indicated that leaf area was significantly (p<0.05) higher in RH (133.2 cm²) than in TS (98.1 cm²). Plant nutrients uptake (NPK), was significantly (p<0.05) higher in RH (10.0, 8.7 and 22.8 g plant^-1) than in SD (4.0, 3.3 and 8.5 g plant^-1). Seedlings raised in RH were significantly taller (38.5 cm) and bigger (6.6mm) than those grown in SD. Shoot and root biomass of seedlings in RH (9.3g and 3.5g) were higher than those in SD (4.2g and 2.3g). Seedling height and girth as well as shoot and root biomass were higher with higher rates of compost. Residual N, Mg and Ca in the potting media were highest in CP (5.5 g Kg^-1, 12.8 Cmol ₍₊₎ Kg^-1 and 28.5 Cmol ₍₊₎ Kg^-1) and lowest in TS (2.3 g Kg^-1, 3.3 Cmol ₍₊₎ Kg^-1 and 19.9 Cmol ₍₊₎ Kg^-1, respectively). The residual nutrients were significantly (p<0.05) higher with higher compost rate. The combined effect of RH with Comp3 significantly (p<0.05) increased pH and available P of the potting media. The results showed that rice husk biochar mixed with either 400g or 600g of the compost was the most suitable medium for raising cocoa seedlings as it produced seedlings with adequate foliar and residual nutrients which could support vigorous growth and plant survival after transplanting. Further evaluation of mixing TS, RH and compost at different ratios as a suitable potting media for raising cocoa seedling is recommended.