The EU's Water Framework Directive (WFD) will limit growers' ability to discharge water from glasshouses, Wageningen University senior researcher Ellen Beerling warned at the conference.
"The Dutch government and growers are aware there is a problem. Areas around Dutch glasshouses have higher nutrient levels in the water, sometimes exceeding good water standards fivefold, and there is also a problem with pesticides," she said.
"Currently, each crop has its own emission standards based on what is feasible, but there is a huge range of emission levels, which shows that growers can learn from each other," she added. "We could be wasting resources by flushing them away."