| Abstract: | Abstract The effects of application of zinc fertilizer on dry matter yield, uptake and distribution of zinc and other nutrients by Amazon and Amelonado cocoa cultivars grown in a soil of low zinc content in the greenhouse were investigated. There was a differential response to zinc fertilization by the two cocoa cultivars. Maximum dry matter yields of Amazon and Amelonado were attained with 10 ppm Zn and 50 ppm Zn, respectively. Under similar experimental conditions Amelonado seedlings expressed zinc deficiency symptoms whereas Amazon did not. Zinc concentrations in the leaves, stem and roots of both cuitivars did not give a good index of the zinc status of the crops. This was because of the existence of the “Piper‐Steenbjerg”; effect in that nil zinc rates often gave higher leaf concentration of the zinc than next higher rate. In general, the relative content of zinc followed the pattern; leaves > roots > stem with the Amazon cultivar containing more zinc than the Amelonado. The distribution of absorbed Cu in the leaves, stem and roots did not differ in both varieties. Whereas Fe uptake was mostly concentrated in the roots, Mn absorbed was largely concentrated in the leaves of both varieties and only Mn uptake in the leaves of Amazon consistently increased with Zn application. The differences in the uptake and distribution of nutrients between the two cocoa cultivars was attributed to differences in their ability to extract nutrients from the soil and in their requirements for metabolic processes. |
