Sustainable Nitrogen Management in Agriculture: An Action Programme towards Protecting Water Resources in Walloon Region (Belgium) - Water and Agriculture: Sustainability, Markets and Policies - page 396

Figure 2. Application period of nitrogen fertilisers in the Walloon region

J F M A M J J A S O N D

Mineral
nitrogen

Slow-
acting
manure

Fast-
acting
manure

Spreading forbidden

Spreading forbidden unless followed by catch crop or winter crop

Spreading authorised provided maximal quantities are respected

Source: Walloon water code.

Mineral nitrogen
If one is only concerned about farm manure, the objective of reducing nitrate
pollution of both underground and surface waters is likely not to be met. One must also
focus on the total nitrogen applied by agricultural activities, and even also on the total
nitrogen released by domestic as well as industrial activities. The last two factors are
being taken care of by a very dense sewage and sewerage plants network. According to
other European regulations (Directive 2000/60: Water Framework Directive), medium
and high-capacity plants are currently being upgraded in order to substantially reduce the
nitrate loads at the outlet of the plant.
Regarding nitrogen directly linked to agricultural activities, the total quantity
(organic + mineral) applied in a field is also restricted by law. The upper limit depends on
the type of crop and ranges from 30 kg N.ha -1 .yr -1 for the common pea to
330 kg N.ha 1 .yr -1 for sugar beet with a restriction of 250 kg.ha -1 .yr -1 on the total arable
land surface of the farm. On grassland, the total nitrogen applied must not exceed
350 kg.ha -1 .yr -1 .
These amounts stand of course for legal upper limits. The aim is to sensitise farmers
to use only the appropriate quantity, strictly necessary to feed the plant. Today, the farmer
is advised to calculate this quantity for each of his field using a balance between the
nitrogen supplied by the soil (fertilisers, mineralisation of humus, nitrogen remaining
from last crop …) and the expected needs of the plant.

Water monitoring network
Of course, all those measures would not make sense without a performing water
monitoring network. In this regard, the Walloon region benefits from one of the most
dense networks with more than 950 measuring points for underground water and
300 points for surface water on such a small territory. Very detailed reports, measures and
maps can be obtained on line by visiting the site: http://environnement.wallonie.be .