Agriculture is the foundation for our food production.
Farmers use fertilisers because crops need nutrients such as nitrogen and phosphorus.
But the nutrients not absorbed by the crops accumulate in the soil.
Or they end up in the groundwater or surface water.
This is called 'leaching'.
Starting in the 1950s, the Dutch agricultural sector began to intensify its operations.
More animals, higher yields, more fertilisers and more leaching.
The consequences?
Rare plants and animals disappear,
cyanobacteria contaminate swimming water,
and excess amounts of nitrates
a soluble form of nitrogen
make groundwater less suitable for use as drinking water.
In the 1980s, people began to realise that the environment had to be protected.
So in 1991 the European Nitrates Directive went into effect.
The European nitrate standard is based on the drinking water standard of 50 mg/l.
The Netherlands also implemented its own quality standards
for nitrogen and phosphorus concentrations in surface water.
To comply with these standards,
limits were imposed on the use of animal manure and artificial fertilisers.
Starting in 1992, the independent Minerals Policy Monitoring Programme
has monitored the effects of these measures.
We collect water samples and data,
for instance on the use and production of fertilisers
at approximately 450 farms throughout the Netherlands.
The results?
In the 1990s,
the use of fertilisers and the leaching levels reduced dramatically.
Nitrate leaching levels are lowest in areas with peat or clay soils.
But in areas with sand and loess soils,
nitrate concentrations occasionally still exceed the standard of 50 mg/l.
Nutrients are less prone to leaching in grasslands than in ploughed fields.
Dairy farms therefore have a lower average nitrate concentration
in the groundwater than crop farms.
Phosphorus binds easily to soil,
so we observe less leaching into groundwater.
However, the soil can gradually become saturated.
This may cause problems in the future.
We are gradually achieving a better balance between
intensive agriculture, nature and water quality.
In the coming years,
the Netherlands will try to improve that balance even further
through its minerals policy.
The results of the Minerals Policy Monitoring Programme
will be vital to achieve this goal.