How can we Reduce Small Phosphorus Losses from Agricultural Fields?.

Eutrophication of the Baltic Sea is considered to be a major environmental problem today. The former opinion that nitrogen is the limiting element in the Baltic Sea was recently revised based on an international evaluation. In all countries bordering the Baltic Sea, agriculture is estimated to be responsible for the greatest contribution of phosphorus. Of all anthropogenic P-loads in Sweden, 46% originate from farmland. However, this contribution is estimated to be, on average, only 0.4 kg P ha^-1. The question is how can we reduce such small losses further to meet the Swedish environmental quality goals triggered by the regulations in the EU Water Framework Directive? In this presentation, we outline some best management practices (BMPs) to reduce small P losses further and how we follow water quality changes over time. We examine measures such as removal of dissolved P from tile-drainage through the use of precipitation traps; application of lime close to existing tile-drains; construction of simple sedimentation traps; and design of efficient buffer strips. Detection of small changes in P-loadings over time due to implementation of BMP practices requires long monitoring periods. Other factors such as weather conditions, soil type etc. also have a profound effect on P losses, which can mask the effects of BMPs. We still believe that even small losses can be reduced substantially through development and implementation of proper BMPs.