Intensification of subsistence agriculture on the Nembi Plateau, Papua New Guinea 1. General information and inorganic fertilizer trials.

Abstract

A crop intensification programme was conducted in an area of high population density, extended periods of land use, low crop yields, and consequent high child malnutrition rates. Sweet potato (Tpomoea batatas (L.)Lam.) is grown in continuously cropped fields without fertilizers or crop rotation and supplementary crops are planted seasonally. In this first of three papers, the Nemhi Plateau environment is described and results are given from inorganic fertilizer trials undertaken to investigate nutrient imbalances and deficiencies. The first fertilizer trial included nitrogen (N), phosphate (P), potassium (K), minor elements, and boron (B). Sweet potato tubers and top growth showed a large response to K. P increased tuber yield, and minor elements increased top growth yield. B significantly depressed tuber yield whilst increasing top growth yield. A marked K deficiency was confirmed by sweet potato leaf analysis and soil analysis. A further small trial examined the effect of boron fertilizer on Casuarina oligodon Johnson. A very marked response to B was found. Another trial examined the effect of minor elements and B on peanuts (Arachis hypogaea h.), cowpea (Vigna unguiculata (L.) Walpers var. unguiculata) and winged bean (Psophooarpus tetragonolobus (L.) A.P. de Candolle). There were no significant responses.