In this study the degree of leaching of the nitrogen surplus to
groundwater and surface waters is calculated per soil type for arable
land and grassland. Leaching differs between soil types and forms of
land use. For arable land on well drained sandy soils about 90% of the
nitrogen surplus leaches from the root zone. For grassland on peat soils
this is only 5%.
A nitrogen surplus is the remainder of nitrogen supply, for example via
artificial fertiliser and manure, and nitrogen removal, for example via
harvest of crops. Of the three soil types considered leaching of
nitrogen decreases in the order: sand - clay - peat. For sandy soils
leaching is largest for well drained soils with relatively deep
groundwater levels and smallest for poor drained soils with shallow
groundwater. In addition leaching is larger for arable land than for
grassland.
This data is of importance to prevent too much leaching of nitrogen to
groundwater and surface waters due to fertilisation. The Nitrates
Directive obliges all Member States to prevent this. The Netherlands
have developed a system of nitrogen use standards that limits both total
nitrogen use and nitrogen use via animal manure. For arable and
horticultural crops grown on sandy soils or loess nitrogen use standards
are not yet available for 2008 and 2009.
This data will be used by an official working group to derive
environmentally safe use standards for total nitrogen use and use of
animal manure nitrogen. For this study data is used collected by the
National Mineral Policy Monitoring Programme (LMM) of RIVM and
LEI.