| THE NITROGEN BOMB IS STILL TICKING |
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The danish agriculture has almost exploded in the last fourty years. The complete loss of nitrogen can be estimated by a so called mass balance. The mass balance distinguishes two forms of nitrogen. The nitrogen bound in form of natural fertilizers, fodder an biological bound nitrogen in general. The other form of nitrogen is as inorganic fertilizer like nitrate.
In the period from 1950 to 1985 the sale of fertilizer products
increased by 100% from 18 kilo of N/ha to 36 kilo N/ha. This had a significant
influence on the total content of nitrogen. The total content of nitrogen
per ha. increased from 102 kilo N/ha up to 236 N/ha, that is 131 %.
The nitrogen that gets lost flows slowly into the groundwater, the
streams and lakes. It is even sometimes discharged directly into the lakes
and streams as liquid manure, which is nowadays prohibited. The rest can
be dissolved into the air as ammonia or as free nitrogen as a result of
the denitrification process.
Nitrogen can be washed out of the soil in the zone of the roots from the crops. This depends on the amount of rainwater that reaches the field and is predominantly occuring in the winterseason. The extent of nitrogen being washed out from the ´root zones´ depends on the content of nitrate in the ground and the type of the soil, that is, whether it is clayey or sandy.
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