Growth and Nutrient Uptake Response of Cocoa (<i>Theobroma cacao</i> (L.) Seedlings to Different Growth Media at the Nursery in Ghana

A. O.  Mornyuie; S. K.  Asomaning; A. K.  Quaye; R.  Asare; J. O.  Eduah; J. K.  Essibu

A. O. Mornyuie
S. K. Asomaning
A. K. Quaye
R. Asare
J. O. Eduah
J. K. Essibu

Keywords: Cocoa pod husk compost, rice husk biochar, topsoil, rice husk, sawdust, media and cocoa

Abstract

Cocoa (Theobroma cacao L.) seedlings are primarily grown in nurseries using topsoil as the main polybag medium. Some of these soils are acidic, highly weathered, and low in plant nutrients. The poor development of cocoa seedlings in nurseries has been attributed to the use of unsuitable potting media. This study aimed to assess the impact of incorporating rice husk biochar (RHB) and cocoa pod husk compost (CPHC) into soil, sawdust, and rice husk–based media on the growth and nutrient uptake of cocoa seedlings in the nursery. The experiment was laid out in a Completely Randomized Design (CRD) with three replicates. The experiment was carried out at the nursery site of Mabang Megakarya Selection programme at Mabang a substation of Cocoa Research Institute of Ghana. The treatments comprised three base-materials viz: Topsoil (TS), Rice husk (RH) and Sawdust (SD) amended with three rates of rice husk biochar (RHB) at 75%: 25%, 50%:50% and 25%:75% and two rates of cocoa pod husk-based compost (CPHC) at 90%:10% and 80%:20% (base-media: amendment on v/v). The respective amounts of media combinations were mixed thoroughly and filled into polybags with dimensions 18 cm wide x 25 cm high. Seedlings were raised from C.69 clone mixed hybrid cocoa and seedling growth was assessed at bi-monthly intervals for six months. Chemical analysis of soil and organic materials were carried out using standard laboratory procedures. At six months after sowing, results indicate that seedlings raised in TS50:RHB50 (60.3 cm) media mix were significantly (p<0.05) taller and had the highest number of leaves per plant, the highest chlorophyll content, larger leaf area and longer tap root length. Stem diameter of seedlings raised in TS90:CPHC10 media mix was bigger than in the TS100 and TS50:RHB50 mix. Cocoa seedlings grown in TS50:RHB50 media mix had the highest dry matter yield. Nitrogen uptake was significantly (p<0.05) higher in TS50:RHB50 potting media mix while P, K, Ca, and Mg were higher in TS90:CPHC10 potting media mix than in the TS50:RHB50 mix. The results indicate that the best potting mixture of soil and biochar for growing vigorous cocoa seedlings is 50% top soil mixed with 50% rice husk biochar.