Soil fertility and sweet potato production on volcanic ash soils in the highlands of Papua New Guinea

摘要: Abstract Experiments are reported which examined the potential for increasing sweet potato yield in highlands of Papua New Guinea; first set experiments this was by rates traditional composting, and second applying phosphate potash fertilizers. were conducted on nine soils representing major soil types area derived predominantly from volcanic ash. Composting treatments 0, 20, 40, 60, 80 100 t fresh weight per ha grass Ischaemum polystachyum. Fertilizer 250, 500 1000 kg P/ha as triple super phosphate, 90, 180 360 K/ha sulphate potash. Yields varied with type responded significantly to all manuring methods. Response composting less higher inherent fertility, fertilizer response increased levels supplied nutrient decreased. Responses application asymptotic; maximum increase any a factor 3 ca. 20 tuber yield/ha. In organic experiments, responses compost linear; 4 17 t/ha. Improving productivity may have limited if it leads an unacceptable burden work women. Despite large increases application, only economic. The efficiency use P K applied greater than inorganic manuring, but advantage decreased influence resorted or limestone parent material formation increased. be particularly suitable ash because supplies nutrients directly plant, thereby overcoming fixation poor base nutrition these soils. Phosphate dominant affecting fertility regression analysis showed that affected indigenous mycorrhizal infection; infection associated reduced application.