Nutrient status of cocoa (Theobromae cacao) in Papua New Guinea: results from a survey

Abstract

Cocoa is the primary cash crop in most coastal areas of Papua New Guinea (PNG), supporting an estimated 150,000 households. Smallholders produce most of the crop, but their yields are low, at about 10% of the maximum. Low yields have been attributed to many factors, but the possibility of nutrition-related limitations to productivity has not been examined in detail. Here we report on a survey of 63 cocoa blocks across the country. Based on leaf analyses, N and Fe deficiencies appear to be very widespread, with 95 % of sampled blocks falling below the critical level for N and 89 % for Fe. P deficiencies were encountered in ~25% of the blocks sampled. Leaf Mg concentrations were adequate in most blocks in most provinces, except East New Britain, where 64 % of the blocks sampled were deficient. Deficiencies of K, Ca, Mn, B, Cu and Zn were encountered in 2 -15 % of sampled blocks. There were significant relationships between leaf and soil contents of K, Ca, Mg and P. There is a clear need to further examine nutrition-related limitations to productivity in PNG, including establishment of more reliable critical levels for leaf nutrient concentrations.