Phosphorus losses through transfer, soil erosion and runoff : processes and implications

Phosphate rock is a strategic material upon which pastoral agriculture and all New Zealanders depend. Phosphate fertilizer has no close substitute, and is, therefore an important limiting factor to agricultural productivity. The future wellbeing of the country depends on its efficient acquisition, manufacture, distribution and use. This report is part of a larger cross-disciplinary study carried out by Centre staff on the multiple dimensions of phosphate management in New Zealand. The report presents an examination of phosphorus losses from the production system and the attendant consequences on environmental quality. Special emphasis is given to hill country loss mechanism, where it is known that significant amounts of phosphate fertilizer are picked up in surface runoff and/or are displaced by grazing animals. The longer term consequences of nutrient loading on downstream water bodies are discussed, and the policy and management implications for maintaining current water quality levels are highlighted