Properties and management of andisols in the highlands of Papua New Guinea.

Abstract

Research on coffee nutrition conducted in Papua New Guinea between 1954 to 1998 is reviewed and deals with arabica coffee with and without shade and under both smallholder and plantation conditions. Coffee leaf nutrient contents can respond within eight months to fertilizer applications but seasonal variation in leaf nutrient contents is large. Leaf nutrient contents are generally higher in shaded coffee. Unshaded coffee nearly always responds to N fertilizers although two or more years are required before the response occurs. Without N fertilizers, coffee will die within a few years when there is no shade. Large applications of N have, however, been shown to strongly acidify the soils which is accompanied by a decrease in exchangeable cations. The application of K fertilizers is beneficial in some soils although negative effects on the uptake of Ca and Mg have been found. In some soils positive responses to P fertilizers occur with young coffee but no significant response to Mg fertilizers have been recorded in Papua New Guinea. Shaded coffee rarely responds to N fertilizers and negative effects have also been found. Shaded coffee commonly responds to K fertilizers up to 400 kg K20/ha. Positive responses to Zn and B have also been recorded. Although substantial yield increases may be obtained with inorganic fertilizer applications, recycling of coffee litter, pruning and processing waste products, can reduce fertilizer applications by up to 20%.