SOIL-LANDSCAPE MODELS AND SOILS OF EASTERN HIGHLANDS, PAPUA-NEW-GUINEA

Soil-landscape models of three landscapes representative of the Eastern Highlands, Papua New Guinea, have been developed and validated in a study area east of Kainantu. Soils were classified according to Soil Taxonomy. Validation of a model in a strongly dissected landscape predicted soils 88% correctly at Order level, 94% at Suborder and 88% at Great Group and Subgroup level. Soils in weakly dissected landscapes were predicted 96% correctly at Order level, 92% at Suborder and Great Group level, and 88% at Subgroup level. Soils on a simple alluvial terrace system were predicted 100% correctly at Order and Suborder level and 89% correctly at Great Group and Subgroup level. Soils of the strongly dissected landscape are formed from an irregular cover of weathered tephra overlying weathered schist. They are mostly well drained Hapludolls or Argiudolls on steep slopes with Troporthents on slipped slopes. Soils of the weakly dissected landscape are formed from thick weathered tephra. Broad ridges and sideslopes are dominated by Argiaquolls, Argiudolls, Hapludalfs, Hapludolls and Humitropepts with dense concretionary layers of iron and manganese. Soils of the terrace landscape are formed from alluvium and vary from Fluvaquents and Endoaquolls to Hapludolls. General nutrient trends of the soils of the strongly and weakly dissected landscapes show low levels of exchangeable cations, plant available phosphorus and zinc. Profile readily available water is low and clay mineralogy is dominated by kaolinite. Volcanic glass occurs in upper horizons of stable sites. Alluvial soils of the terrace landscape have higher nutrient values, particularly exchangeable magnesium.