Legumes are a key source of nitrogen (N) in organic production systems. However, there is evidence that reduced inputs may be leading to deficient soil phosphorus (P) on some organic dairy farms (Roberts et. al. 2008). This may affect crop performance and N fixation in forage legumes. This study aims to gauge the relationship between soil P dynamics in organic dairy systems and legume biological nitrogen fixation (BNF). The study has two main sub-projects:
1. A field survey of soil-test P and legume forage productivity and N fixation on dairy farms in Ontario and Nova Scotia, Canada.
2. Growth chamber and greenhouse studies examining:
a) The role of P nutrition in legume growth and N fixation, and
b) The P-supplying power of composts, struvite, and a rock P source.
Field data was commenced in the 2008 season, and was completed in 2009. Growth chamber and greenhouse studies were conducted in 2009. Analyses of 2009 samples are not complete at the report date
