This project aims to apply the outcomes of PN 9101 (and in particular information on visual symptoms of nutrient deficiency and toxicity) to the solution of sustainable production problems of sweet potato and taro. In north Queensland, nutrient management systems for sweet potatoes grown on old tobacco soils will be developed. Calcium deficiency and boron toxicity are threats on these very sandy soils. Knowledge of visual stress symptoms, along with appropriate chemical analysis of plant tissue, will be used to monitor the effectiveness of management systems developed. In Papua New Guinea, knowledge of visual nutrient stress systems will be used for two purposes: to monitor success of small amounts of fertilisers in preventing fertility decline after clearing (this work was started at Unitech farm in PN 9101, but delayed by security problems); to screen the PNG sweet potato germplasm collection for varieties well suited to acid soils and magnesium deficient soils.