Growth and nutrient uptake of some cocoa varieties grown on contrasting soils

Abstract

A comparative growth analysis and N, P and K contents of six cocoa varieties grown in two cocoa-growing soils of different fertility status under greenhouse conditions were carried out over a period of 12 months. The cocoa varieties studied were inter amazon crosses, namely: T85/ 799 x Amel, T79/50 I x T85/799, T85/799 x Pa7/808, APA 5 x Pa7/808, T60/887 x Pd 15, and T79/501 x ALPHA B 36. Tire experiment was a factor ial in randomised block designed with three replicates. Seedling h_eight, stem girth, root length, and total dry weight were recorded ·at 3-month intervals. N, P and K concentrations of the roots and shoots of the seedlings were determined. Seedling growth was better in the relatively fertile soil than in the relatively poor soil. The differences in growth rates among the varieties in both soils were not significant. T85/799 x Pa7/808 and T79/501 x ALPHA B 36 grew more vigorously and produced higher dry matter yields, whilst T79/50 I x T85/799 showed slower growth rates in both soil! Cocoa varieties grown in the relatively poorer soil had significantly longer roots than those grown in the relat ively fe rtile soil, with T60/887 x Pd 15 recording the longest root length in both soils. The differences in '/PK uptake among the varieties in each soil were not significan t. However, the absolute amounts of the nutrients in the plant tissues tended to be highest in T85/ 799 x Pa7/808 and T79/50 I x ALPHA B 36 for both soil~, The uptake of the nutrients by the cocoa varieties was in the order N>K>P. Although P was the least absorbed by the varieties, P concentrations in the plant tissues related positively with the dry matter yield of the varieties. Selection of cocoa varieties with higher root to shoot ratios and shorter root lengths for planting in suitable and marginal soils as well as top dressing of seedlings with P fertilizer may be recommended in the cocoa rehabilitation