VVM - N-tab fra rodzonen

tion between the root zone and ground water. For quantification of nitrate reduction in water
courses and lakes simple models are proposed as the most suitable estimating methods.
Limitations and alternatives
The turnover and losses of N in agricultural soils are extremely complex and are affected by a
number of factors such as soil type, livestock density, climate, crop rotations and use of manure
and fertilizer. The factors vary in time and space both at field, farm and regional level
causing uncertainties in the estimates of leaching irrespective of model used. Dynamic and
complicated models are able to take these factors into account, but they are time consuming in
use and operator dependent. Although simple, empirical models have their limitations they are
easy to use and therefore more suitable in the authorities management of environment impact
assessment. The selected model for estimating nitrate leaching is calibrated with Danish recordings
of nitrate leaching both from controlled field experiments and on-farm monitoring
programmes.
As the conditions for agriculture change in years due to market and legislations, the environmental
impact assessment may have a time frame of 5-10 years. Particularly for the changes
in the soil N pool it is important to consider an extended time frame as mineralization of organic
matter applied in manures occur during decades.
The further process
The FarmNTool programme is based on the proposed model-concept and has been selected
by the Danish Forest and Nature Agency (part of the Ministry of the Environment) as the tool
most suitable for the environmental impact assessment of nitrate leaching from the root zone.
The Danish Institute of Agricultural Sciences will further develop the FarmNTool programme.
To automate the updating of norms, and utilize the data from fertilizer accounts, its
coordination with the IT systems within the Ministry of Food, Agriculture and Fisheries responsible
for farm data reporting should be investigated. An internet version of the
FarmNTool will be operational by 1 January 2007 when the new structural reform comes into
force.
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