Phosphorus nutrition in organic vegetable production

Abstract

While the economic prospects for organic food and fibre products in the Australian and overseas markets are promising, Australian organic growers face several production constraints. Most of the investigations in Australian broad-acre (extensive arable) organic farming systems indicate a decline in soil available P over time, raising questions about the long term sustainability of organic farming in Australia. However, the sparse literature on vegetable production in NSW has indicated an excess of extractable P due to the use of manures and compost to meet N demand. With this in view, field and glasshouse investigations were carried out with the following objectives: 1. to assess the nutrient status (especially extractable soil P) of organic and conventional vegetable farms in a range of contrasting soil types and climatic conditions, to test the general validity of previous findings concerning organic vegetable production. 2. to examine the plant based P management techniques such as choice of cultivars and crop rotation using legumes to overcome P limitations in low fertility soil in order to develop effective phosphorus management strategies for vegetable growing during conversion to organic production.